Polymeric Biomaterials for Management of Pathological Scarring

Subscriber access provided by WEBSTER UNIV

Review

Polymeric Biomaterials for Management of Pathological Scarring David Yeo, Sharon Chew, and Chenjie Xu ACS Appl. Polym. Mater., Just Accepted Manuscript • DOI: 10.1021/acsapm.8b00203 • Publication Date (Web): 08 Feb 2019 Downloaded from http://pubs.acs.org on February 8, 2019

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Applied Polymer Materials

Polymeric Biomaterials for Management of Pathological Scarring David C. Yeoa, Sharon W. T. Chewa, Chenjie Xua,b,c* a

School of Chemical and Biomedical Engineering, Nanyang Technological University, 62

Nanyang Drive, 637459, Singapore b NTU-Northwestern

Institute for Nanomedicine, Nanyang Technological University, 50

Nanyang Avenue, 639798, Singapore c

National Dental Centre of Singapore, 5 Second Hospital Ave, 168938, Singapore

*

E-mail: [email protected]

Keywords: wound healing; pathological scarring; skin; polymer; biomaterials Abstract: Polymeric biomaterials play a significant role in wound care. This article reviews the latest advances in polymeric biomaterials for the care of wound pathologies (i.e. chronic wounds and abnormal scarring). After discussing the development of three categories of polymers (i.e. biodegradable, stimuli-responsive, and bioinspired polymers), we focus on the prevention and treatment of abnormal scarring using polymeric biomaterials. Specific attention is paid to their roles in scar prevention, early detection of abnormal scarring, and anti-scarring drug identification.

ACS Paragon Plus Environment

1

ACS Applied Polymer Materials 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 28

1. Introduction to pathological wound healing Following the rupture of skin, physiological processes attempt to restore the skin function through homeostasis. The normal healing process can be divided into 3 distinct phases (i.e. inflammation, proliferation and remodelling)1 and lasts in the order of weeks.2 However, this process sometimes becomes dysfunctional, resulting in pathologically insufficient or excess wound healing. Insufficient wound healing or chronic wounds refer to wounds that do not close for 12 weeks and recur.3 They are observed in pathological situations like arterial/venous deficiency, diabetes, presence of a foreign body and infection.4-6 In USA alone, chronic wounds affect 2.5-4.5 million people annually.4 On the other hand, excessive wound healing activity post-surgery, traumas, burns, and other skin injury results in abnormal scarring such as hypertrophic and keloid scars.7 These scars have the appearance of protruding skin lesions or nodules comprising appendageless (free from glands) dermal tissue.8,9 Whereas hypertrophic scars are confined to the site of the original injury, keloid scars typically overgrow the borders of the original wound site (Figure 1A).10 The overgrowth of the granulation tissue is believed to be closely related with the abnormal behaviours of skin fibroblasts in the wound healing process including increased proliferation, excessive collagen formation, and abnormal collagen turnover by matrix degrading enzymes. Furthermore, patients with keloid scars experience pain and itch which causes physical discomfort in addition to psychological trauma. Annually, ~100 million people in the developed world (approximately 1.2 billion) suffer from abnormal scarring.9 Both chronic wounds and abnormal scarring, wound healing insufficiency and excessiveness respectively, exert the significant burden on global healthcare. Fortunately, significant efforts have been made to mitigate chronic wounds by preventing infection, promoting cell migration, or improving angiogenesis. The related technical approaches include dressings, negative pressure therapy, advanced and adjuvant topically-applied therapeutics.4 It usually begins with standard wound care principles involving debridement for wound bed preparation. Subsequently, adjunctive therapies such as dressing and negative pressure therapy are used to improve the wound healing process.4, 11 Compared with chronic wound caring, abnormal scar management is dissatisfactory. Existing management typically involves the combination of (but not limited to) dressings, injections (steroids, chemotherapeutics, immunomodulatory drugs etc), laser, radiotherapy, cryotherapy and surgery etc. Multi-modal schemes require repeat visits to clinicians, e.g. up to 6 weekly visits.14 Hypodermic needle injections often cause significant pain to keloid lesions.9 Surgical removal risks recurrence as well as complications like infections. 15-16 Therapeutics relying on instruments such as lasers and radiotherapy are capital-intensive and may not be readily-available to patients.17 Dressings are often ineffective and have poor patient adherence rates.18 In addition, scar management is mostly based on the dermatologist’s experience that evolves into clinical ‘best-practice’.


2

Page 3 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Due to the relative maturation of chronic wound care, there are already a significant number of review articles documenting chronic wound management and therapy of polymers. 11-13 Therefore, this article focuses on the innovative management of abnormal scarring with polymeric biomaterials, which has been overlooked. 1.1. Identification of pathological or abnormal scarring: Conventionally, pathological or abnormal scarring is identified by dermatologists through the morphology and grade lesions based on qualitative measures, i.e. Vancouver scale (vascularity, pigmentation, pliability). This is a points-based system tabulated from the scores assessed by board-certified dermatologists.19 Other qualitative scales such as the Patient and Observer Scar Assessment Scale (POSAS) include the patient’s perception of pain and itch.20-22 Although the risk of scarring exists, biopsies are performed under certain circumstances to confirm abnormal scarring and exclude the possibility of malignancy. Tissue sections are typically mounted for histology to observe dermal tissue morphology.23 Morphology observation allows discrimination between keloid and hypertrophic scars. Hypertrophic and keloid scars can be readily distinguished by differences in dermal morphology. For example, the presence of α-SMA (smooth muscle actin) can be found in hypertrophic scars, whereas keloid scars comprise large, thick, fibrillar collagen bundles.24 Recent biological understanding about pathological wound healing and abnormal scarring have given rise to more precise methods to identify abnormal scarring. For example, pathological scarring overexpresses connective tissue growth factor (CTGF) and other downstream genes (e.g. fibronectin, Col1a1, α-SMA, TGF-β receptor etc), while Keloid and hypertrophic scars can be differentiated from each other using biomarkers like CGRP, Hsp27, MMP-19, PAI-2, and α2β1integrin.25 1.2. Treatment of abnormal scarring: Whereas mild lesions at earlier stages are managed with silicone dressings, pressure therapy, larger lesions at late stages combine these with injections (steroids, chemotherapeutics etc). In poorly responding scar lesions, surgery is typically utilized before cryotherapy and/or localized radiotherapy.26 Unlike hypertrophic scars that have the option of surgical revision and management with dressings, keloid scars often recur, requiring greater medical attention (Figure 1B). Updated guidelines for treating abnormal (hypertrophic, keloid) scars can be found elsewhere.27 Therapeutic strategies can be broadly categorized into: prophylaxis, routine and emerging. Prophylactic methods include pressure, silicone gel sheeting, silicone gel and flavonoids. However, these are often less effective due to lower adherence rates due to patient discomfort. Often, they also exhibit limited therapeutic efficacy. Routine treatments include corticosteroid injection, cryotherapy, scar revision, radiotherapy and lasers. Steroid injection gives rise to resistance and exhibits adverse skin symptoms. Cryotherapy can be painful, blistering and limited to smaller scars. Scar revision often gives rise to recurrence in 45 -100% of cases of keloid scars. Radiotherapy and laser therapeutics are


3


Page 4 of 28

equipment intensive with the potential for malignant transformation. Emerging therapeutics like interferon and 5-fluorouracil injections give rise to adverse bodily symptoms and are contraindicated for conditions like anemia and pregnancy.9 Detailed limitations and comments of some common treatments for abnormal scars can be found in reference 9.

Figure 1. Current Management Guidelines for Abnormal Scarring: (A) Representative images of Keloid scar (left) located on the ear and Hypertrophic scar (right) located on the wrist. (B) Current management guidelines for minor and major (high-risk) keloid scars. (Reproduced with permission from 28 Copyright 2014 Wolters Kluwer)

All these suggest the need for the ground-breaking technologies in scarring management. These involve early and accurate diagnosis, patient-friendly treatment, and timely monitoring of treatment outcomes. Therefore, this article summarizes the role of polymeric biomaterials in managing (diagnosis and treatment) pathological wound healing, with a focus on abnormal scarring. Polymeric biomaterials with a wide range of properties are used for delivering drugs to prevent infection, to promote healthy wound healing, and monitor the healing process. Future directions may involve


4

Page 5 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


integrating sensors with dressings and other external devices as a means of monitoring molecular biomarkers related to pathological scarring in a precise and quantitative manner.

2. Advances in Polymer Biomaterials Polymeric biomaterials are ubiquitous in the drug delivery system development. They play an integral role by providing controlled release of therapeutics and optimal microenvironment at the targeted site, thereby improving therapeutic efficacy.29 Thus, they are widely used for managing wound pathologies due to their ready availability, ease of manipulation to achieve specific chemical properties, potential to be degraded and importantly, the relative lack of severe immune-response.20 The degradation or swelling kinetics of polymeric biomaterials can be tuned to suit the need of different stages of wound healing.30 Currently, the polymeric biomaterials for the management of wound healing can be classified into biodegradable polymeric biomaterials, stimuli-responsive polymeric biomaterials, and bioinspired polymeric biomaterials (Figures 2 and 3). 2.1. Biodegradable polymeric biomaterials Biodegradable polymeric biomaterials are comprised of natural and/or synthetic polymers. They are degraded by enzymatic or non-enzymatic reactions, generating by-products that are safe and usually do not invoke immune-response.31-33 The non-enzymatic degradation reactions involve cues such as changes in pH, temperature or presence of water (Figure 2A), which are like that of physiological cues. This permits the control of the release kinetics of the encapsulated drugs through manipulating the polymeric network’s sensitivity to the physiological conditions.34-35 In addition, some of the degraded by-products could function as a wound healing agent to improve chronic wound healing. 36 Biodegradable polymers are depicted in Figure 2. Natural polymeric biomaterials such as hyaluronic acid (HA) are widely employed for drug delivery because it plays a vital role in various stages of wound healing.37 High HA concentration in skin creates porous scaffold network that allows selective cells and protein diffusion crucial for wound healing.37 For example, Park et al. utilized HA based microneedle skin patch to deliver Green tea extract (GT) as an antimicrobial agent to prevent infections.38 HA was mixed with 70% GT in a deionized water and loaded into a microneedle press mold using drop casting. The HA based microneedles incorporated with GT showed significant antimicrobial activity, inhibiting ~95% growth of gram-positive and gram-negative bacteria thereby improving wound healing.38 Besides natural polymeric biomaterial, poly(lactic-co-glycolic) acid (PLGA), a synthetic biodegradable polymer, is prevalent in drug delivery systems targeting chronic wound because of its high safety profile, tune-able biodegradability and most importantly, its approval by Food and Drug Administration (FDA) and the European Medicines Agency (EMA) as a drug delivery excipient (Figure 2B). The release kinetics from PLGA can be tuned by adjusting the ratio of PLA with PGA.39


5


Page 6 of 28

Lactate (PLGA by-product) has been reported to influence wound healing by promoting angiogenesis and thereby increasing the rate of wound healing. 36 Leveraging this, Chereddy et al studied synergism of PLGA and curcumin.40 Curcumin, a potential wound healing agent was encapsulated in PLGA nanoparticles for sustained wound site delivery. Versatility of release kinetics of PLGA allowed the sustained release of curcumin into the wound site over 8 days. This led to faster wound closure compared to other wound healing dressings. Full wound closure was attained 1.25 times faster than the employment of curcumin alone and PLGA nanoparticles alone. (Figure 2C) These results demonstrate the potential of PLGA platforms in improving the wound healing process.40 Further details can be found in the literature. 41 Using both synthetic and natural polymers, Alibolandi et al incorporated dextran hydrogel with PEG-PLA nano-micelles containing curcumin for treatment of full thickness wound. 42 The application of curcumin-loaded biodegradable hydrogel in mice model resulted in early closure of wound by day 15 compared to 21 days for normal wound closure by application of saline. Wound healing process was accelerated by hydrogel application with hair regeneration and complete skin observed after 21 days. Furthermore, histology analysis revealed that the hydrogel improved reepithelialization of epidermis and collagen deposition in the wound area. Biodegradable polymers allow the tuning of the release kinetics through adjusting polymer chemical composition. However, as wound healing is a dynamic and complex process, immediate or slow release of drugs from the polymeric biomaterials into the wound upon application might not be efficient for wound healing. One favoured approach involves the use of reconstituted natural materials in a nanofibrous material (e.g. cellulose, chitosan) to restore tissue dermis following wounding.43 Efficient wound closure would prevent infiltration of pathogens. 44 Being able to respond to different cues from the different stages of wound healing process is essential to facilitate improved wound healing process. Researchers have turned to incorporating functional groups to the polymeric biomaterials for better control of the release rate and interaction with the tissues in the wound site. 45This leads to the emergence of stimuli-responsive polymeric biomaterials.


6

Page 7 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 2. Biodegradable Polymer Biomaterials for Wound Healing: (A) Illustration of degradation mechanism of biodegradable polymers by biological cues (e.g. water). (B) Illustration of drug-loaded PLGA nanoparticles’ roles (e.g. inflammation, cell migration/proliferation, angiogenesis, re-epithelialization, granulation tissue formation etc.) for the management of the wound healing. (Reproduced with permission from 36

Copyright 2016 Wiley.); (C) Wound morphology evaluation following curcumin-containing PLGA

nanoparticle (PLGA-CC NPs) treatment on wound healing. (Reproduced with permission from 40 Copyright 2013 Elsevier.)

2.2 Stimuli-responsive polymeric biomaterials Stimuli-responsive polymeric biomaterials or smart/intelligent biomaterials respond to a variety of triggers including pH, temperature, mechanical force, small molecules and biomolecules, electric/magnetic fields etc. 45-46 They undergo rapid changes in microstructure upon the stimuli. These changes are often reversible upon the removal of external or internally-induced stimuli.47 This design permits the correlated drug delivery systems to sense physiological changes and respond accordingly. 45, 47 Smart biomaterials also include the incorporation of sensors, biosensors and chemomechanical actuators. 47 Representative work is depicted in Figure 3A and 3B. The most intuitive application of stimuli-responsive polymers is to protect the wound and to facilitate wound healing. Veld et al developed a thermosensitive hydrogel as wound dressing based on polyisocyanopeptide (PIC). 48The low LCST of PIC-based hydrogel allowed gelation of the PICbased hydrogel on the wound site upon contact with the body heat, ensuring easy application. This


7


Page 8 of 28

PIC-based hydrogel was able to stay adherent to the wound site without additional support as well as keep the wound site clean from infection. In addition, PIC-based hydrogel mimicked the extracellular microenvironment as its mechanical property resembled that of collagen and fibrin, thereby facilitating healing without provoking inflammatory responses. Additionally, it acted as a barrier preventing entry of pathogens into the wound site. pH-responsive polymeric biomaterials are explored as well. pH at the wound site plays an integral role in wound healing. The pH of the wound microenvironment is affected by the type of wound, the stage of healing process, and other factors like infection. Making use of the slightly acidic pH (pH 5.5) of the skin, polymeric biomaterials for wound dressing can be designed to release therapeutics at acidic pH.49-51 For example, Ninan et al developed a pH-responsive polymeric biomaterial from zinc ions-crosslinked carboxylated agarose/tannic acid hydrogel scaffold. 49 In this hydrogel scaffold, the carboxylic groups on carboxylated agarose were responsible for pH-induced swelling and release properties. Low pHs, above the pKa of the carboxylic acid groups led to ionising and resulted in charge repulsion, hydration and eventually hydrogel swelling. This polymer could be tuned to achieve the release of tannic acid, which is an antioxidant, antimicrobial and antiinflammatory agent.49 (Figure 3B) The antibacterial property of this hydrogel wound dressing was demonstrated by agar diffusion assay with E. Coli, showing similar efficacy to the topically applied gentamicin with similar zone of infection diameter (8mm for the hydrogel, 9mm for gentamicin). Conditioned media obtained from the incubation of cells and hydrogel was used to treat lipopolysaccharide (LPS) activated monocytes to assess the anti-inflammatory activity. Interestingly, this media attenuated the activation of the monocytes by the LPS, demonstrating the potential of antiinflammatory activity of the hydrogel. The researchers expect that this wound dressing is able to achieve both antibacterial and anti-inflammatory activities. 2.3. Bioinspired polymeric biomaterials Bioinspired polymeric biomaterials are synthetic materials designed to mimic those of the natural materials or living matter.52 Through studying the mechanisms behind the complex wound healing process, researchers hope to gain new insights for designing bioinspired polymeric materials for wound healing. An example is shown in Figure 3C. Mimicking the adhesive properties of a mucus secreted by a carnivorous Sundew plant, Li et al envisioned a hydrogel to deliver recombinant human MG53 protein (rhMG53) to treat chronic wounds.53 MG53, a tripartite motif (TRIM) family protein has been showed to improve wound healing by facilitating wound closure. This hydrogel was prepared by crosslinking sodium alginate with gum Arabic in the presence of calcium ions. Topical application of the rhMG53 hydrogel on the mouse model significantly improved the wound healing in days 5 and 7 compared with treatment with saline and rhMG53 only. The wound size in Sundew-inspired hydrogel + rhMG53 was half of that in mice treated with Saline. The wound closed completely by day 11, which could not be achieved with


8

Page 9 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Saline treatment. Chen et al proposed another multifunctional hybrid hydrogel that was inspired by the spontaneous injury healing process of the organism that uses coordinated multiple mechanisms for body recovery.54 It was synthesized by mixing benzaldehyde-terminated polyethylene glycol (BAPEG) with dodecyl-modified chitosan (DCS). This hybrid polymer showed excellent tissue adhesion and antibacterial properties due to the anchoring ability of dodecyl tail into lipid membranes as well as the antibacterial abilities of chitosan. This hybrid polymer facilitated every stage of the wound healing processes including blood cell coagulation, cell migration, and angiogenesis. It also exhibited effective antibacterial property and kept foreign bacteria away from the wound site.54 The application of vascular endothelial growth factor (VEGF) loaded hydrogel on the wound of S. aureus infected full-thickness skin defect mice models increased the wound closure rate (reduction of ~95% wound area by day 7) and higher granular wound thickness (2.5mm). The development of this bioinspired polymeric biomaterials is expected to lead a universal wound dressing for all types of wound. It is evident that the progress of polymeric biomaterials for wound management has transit from simply providing sustained release of therapeutic agents to facilitating the wound healing process with biological feedback systems. This is the outcome of our deepening understanding about the complex and dynamic nature of wound healing processes.


9


Page 10 of 28

Figure 3. Stimuli-responsive and Bioinspired Polymer Biomaterials for Wound Healing: (A) Illustration of the stimuli-responsive polymer’s roles for the management of the wound healing. Various stimuli include: pH, electricity, magnetic, temperature, mechanical, solvent/ions etc, whereas the biomaterial response could be: mechanical, phase separation, shape changes, permeability and optical. (B) pH-sensitive hydrogel with antibacterial property (CTZ2) improves wound healing due to antibacterial effects. (Reproduced with permission from 49 Copyright 2016 American Chemical Society.); (C) Schematic diagram of Sundew mucilage inspired adhesive hydrogel for wound healing management. Hydrogels immobilize proteins for sustained release (Reproduced with permission from 53 Copyright 2017 American Chemical Society.)


10

Page 11 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


3. Abnormal scar management with polymeric biomaterials 3.1. Drug delivery Polymeric biomaterials can be exploited to deliver therapeutics and modulate the wound healing process to improve wound outcomes by resolving abnormal scarring. These anti-scarring agents include Tumor necrosis factor, alpha-stimulated gene-6 (TSG-6) protein55, a Cx43 mimetic peptide56, and siRNA against transforming growth factor (TGF) β type I receptor. To enhance the delivery in preclinical animal models, siRNA was combined with cell penetrating peptides (PepMute transfection agent) and injected into granulation wound tissue. This reduced expression levels of transforming growth factor β type I receptor TGFBRI, CTGF, α-SMA, improved appearance based on Vancouver scar scale (VSS) and visual analog scale (VAS) and reduced the extent of scar elevation.57 A novel biomaterial containing collagen-binding peptides, mussel-adhesive protein and dermatan sulfate was used to manipulate wound healing in rat models. Inspired by collagenmodulating activity of Decorin, this biomaterial was designed as a means to prevent pathological collagen assembly (aligned versus randomly oriented fibres). In ‘scar-free’ wound healing, Decorin blocks TGFβ signalling to prevent excessive scarring.58 A similar approach was used to identify a peptide (i.e. the CARSKNKDC-peptide: CAR) and fuse it with decorin for scar suppression.59 This collagen-binding biomaterial significantly accelerated wound closure (keratinocytes and fibroblasts in vitro culture), decreased wound surface width, epidermal thickness and the length of the epithelial tongue (Figure 4A). Furthermore, inflammatory cells and cytokine levels were significantly attenuated, collagen extracellular matrix (ECM) normalized (closer to normal skin morphology) and TGF-1 signalling activity significantly suppressed.60 The flexibility of polymers allowed Hammond et al to utilize silk sutures (a naturally-occurring polymer) to deliver CTGF siRNA for improved wound healing. Therapeutic siRNA was loaded onto the sutures by the layer-by-layer (LBL) deposition method. Several biomarkers including CTGF, αSMA, tissue inhibitor of metalloproteinases 1 (TIMP1) and Collagen Type I, Alpha 1 (Col1α1) were significantly down-regulated in a 3rd-degree rat burn model. In turn, this led to reduced wound contraction, the emergence of papillary structures at the epidermis-dermis junction (indicating improved skin appendage regeneration) and randomly oriented collagen fibres (increased ECM normality). This suture modality integrated and effectively delivered anti-scarring therapeutics to decrease fibrotic response. Importantly, it integrated therapeutic nucleic acids with suturing - which is routinely used in elective surgeries. This allows ease of integrating anti-scarring therapy with existing medical practice.61 Our team utilized polyethylene glycol diacrylate (PEGDA) to deliver the anti-cancer drug 5fluorouracil (5-FU) to impede the proliferation of abnormal fibroblasts derived from abnormal scars. The patch was shaped into microneedle morphology through photolithography to deliver the drugs into the dermis layer of this skin.62 These significantly curbed keloid fibroblast cell proliferation to the same extent as the soluble drug which illustrated the concept of drug-release microneedle was


11


Page 12 of 28

feasible. To evaluate microneedle application, it was found to be sufficiently strong to penetrate pig skin yet flexible enough to conform to non-planar anatomy like the elbow. Finally, a realistic scenario was developed to examine the efficacy of 12 hr cycles of administration and rest for soluble versus microneedle delivered 5-FU. Crucially, microneedle delivered 5-FU outperformed soluble 5-FU over a period of 10 days keloid fibroblast culture.62 Besides 5-FU, PEGDA microneedles can also be loaded with Gap26 (a connexin-mimicking peptide that inhibits inter-cellular communications) for delivery into keloid tissue models.63 Although peptide therapeutics have shown significant promise recently, it experiences stability, loading and delivery issues. On the other hand, the authors introduced a gentle swelling strategy without UV exposure, to load peptides into PEGDA microneedles. Crucially, this facilitates multi-drug loading, by encapsulating hydrophobic drugs before loading hydrophilic peptides thereafter. Using 2 different drugs potentially increases antiscarring efficacy by inhibiting different independent signalling pathways. Delivery of Gap26 through microneedles reduced collagen expression in human keloid tissue models. This demonstrated successful delivery of therapeutics through the hydrogel-swelling strategy for loading microneedles.63 3.2. Scar prevention Compared with treatment post the formation of scars, a better approach is to prevent the process of abnormal scarring during the wound healing process. To date, the most popular means to do so is the use of silicone sheeting to occlude abnormal scars. In a study involving >200 patients, all cases experienced changes in color, thickness, and elasticity when silicone sheeting was applied for at least 4 hrs a day.64 Despite being a first-line therapy, the exact mechanism of silicone sheeting is considered uncertain todate.65 Recently, Weng et al discovered that aligned carbon nanotubes (ACNTs) suppressed fibroblast cell overproliferation, directed their growth and inhibited collagen expression.66 Further evaluation in a rabbit ear wound model showed that ACNTs relieved hypertrophic scar formation and even inhibited TGF- signalling to alter extracellular matrix, cell proliferation, cell cytoskeleton and cell motility. By employing chemical vapor deposition, the authors generated a means of costeffectively producing ACNTs. Thus, ACNTs applied following wound closure could replace silicone sheeting as a means of preventing abnormal scarring.66 Our group showed that microneedle mechanical contact can suppress abnormal scarring (Figure 4B). Microneedles without active ingredients were first used as a negative control and found to suppress keloid fibroblast proliferation.62 This suppressive activity was shown not to have come from any dissolvable toxic byproduct from the microneedles but occurred as a result of the microstructure contact with the cells in culture. In a rabbit ear wound model, drug-free microneedles were secured using 3M Tegaderm® dressing which significantly reduced the extent of abnormal scarring. Being drug-free, these microneedles were readily translated for


12

Page 13 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


clinical use on hypertrophic and keloid scar patients. A portion of the lesion was treated with microneedles while the remainder was left untreated before surgical revision.67 From the excised scar tissue, histology analysis showed that microneedle-treated scar tissue appeared to have an ECM morphology considered to be more ‘normal’ and fewer infiltrated immune cells. In further work, drug-free microneedles were similarly trialled on a 27-person clinical trial.68 The mechanical contact-based modality was highly appropriate for patients who grew resistant to steroid injections. Following a duration of 1 month of continuous (daily) application, keloid lesion volumes diminished by 10% with significant less pain and itch experienced. Being suitable for self-application also made the patients strongly favour it over painful steroid injections;68 although self-applied modalities may suffer from low rates of patient adherence. These results suggest that drug-free microneedles may be suitable alternatives for (silicon) dressing-based methods to prevent abnormal scar emergence when applied during early stages of wound remodelling. Thus, building upon the foundation of decades of silicon dressing usage, novel wound dressing technology, incorporating nano/micro-structural features may significantly improve wound outcome by suppressing the extent of abnormal scarring.


13


Page 14 of 28

Figure 4. Polymeric Biomaterial Innovations for Prevention, Treatment and Diagnosis of Abnormal Scarring: (A) Collagen-binding biomaterials to regulate collagen assembly in remodelling wounds to reduce abnormal scarring (Reproduced with permission from 60 Copyright 2017 Elsevier); (B) Drug-free microneedles to prevent abnormal scars affixed by dressings over the scar lesion (Reproduced from 67 , Open Access, 2017 Springer Nature); (C) DNA/FRET (fluorescent resonance energy transfer)-based sensors (e.g. NanoFlares) integrated in wound dressings for monitoring abnormal scarring (Reproduced with permission from 71 Copyright 2017 United States National Academy of Sciences).

3.3. Diagnosis and monitoring While the above-mentioned novel nano-/micro-structural features have great potential in preventing scar formation, the real-time monitoring of healing process still remains a significant unmet challenge. To date, the monitoring process largely relies on naked eye observation in a clinical setting, which remains largely qualitative.21 In chronic wounds, this is related with the trajectory of the wound (i.e. healing or suffering from infection).69 However, repeated changing of dressings to examine the wound can disrupt wound healing, exacerbating the chronic wound. Thus it is highly desired to have non-invasive and real-time strategies for the early identification of pathological


14

Page 15 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


scarring before its maturation (Figure 4C). Through identifying and quantifying related biomarkers, the above-mentioned drugs, devices and biomaterials can be used to minimize the extent of pathological scarring or to confirm treatment efficacy. One such effort is related with detecting CTGF mRNA, a downstream factor in the TGF signaling pathway. Wang et al bound hairpin-structured probes containing fluorophores to a graphene oxide base (nano-GO) which specifically hybridized CTGF mRNA (Figure 5A). When brought into close proximity with nano-GO sensors, the probes detached from the GO surface and bound to the mRNA species. This resulted in de-quenching behavior that restored fluorophore signal to indicate the presence of CTGF mRNA. These nano-GO sensors successfully detected and monitored CTGF expression in human fibroblast cells.70 Spherical nucleic acids (SNAs) is a class of 3D nanostructures with tremendous biomedical potential, particularly for gene detection and silencing.71 We demonstrated that NanoFlares detected CTGF mRNA expression non-invasively in cells, tissue and pre-clinical models (Figure 5C). A unique property of SNAs was its transdermal penetration properties, allowing it to cross intact skin. This was particularly evident for metabolically-active human skin tissue models and a rabbit ear wound model. Following skin barrier penetration, NanoFlares retained its functionality, detecting intracellular CTGF mRNA. Crucially, CTGF NanoFlare signal specifically tracked the extent of scarring in a rabbit model, correlating well with a functional measure of abnormal scarring (Figure 5C).72 This study demonstrated the possibility of using DNA-based nanoparticle sensors to image gene expression for abnormal scar detection/monitoring. A further study generated theranostic vehicles with gene-silencing and genereporting properties (Figure 5B).73 This dual function probe discriminated normal from hypertrophic scar fibroblasts (with overexpressed CTGF) in 2D and 3D microenvironments, facilitated the screening of anti-scarring drugs and monitored the role of TGF inhibition on the CTGF target. Apart from CTGF mRNA, fibroblast activation protein (FAP) -  is overexpressed by 75-fold in abnormal scar tissue compared to undiseased tissue.74 This makes it a suitable biomarker to discriminate cells of fibrotic from non-fibrotic origin. Interestingly, FAP- is also overexpressed in 90% of epithelial tumors especially those with high malignancy potential. A near infrared (NIR) molecular probe (FNP1) was developed by linking a dye (CyOH) with a linker and an FAP- substrate.77 In the presence of FAP-, FNP1 would generate significant fluorescence at 710nm. The FNP1 molecular probe discriminated between non-fibrotic (normal fibroblasts, keratinocytes) and fibrotic cells (keloid fibroblasts, fibroblasts treated with TGF-) and generated a similar trend to polymerase chain reaction (PCR)-based gene expression analysis.75 Furthermore, we used microneedles to assist FNP1 probe delivery to detect keloid cells in a metabolically-active human skin model. FNP1 was sufficiently sensitive to identify as few as 20,000 cells - equivalent to 2% of the cells in a scar lesion of 1 cm radius. FNP1 was then exploited for drug screening, which rapidly (16-fold (>US$800 Million84) and 5 – 10 years for development. Devices may take 3 general paths to clinic: 1) Pre-market approval (PMA), 2) premarket notification (510k) or 3) exempt devices (that do not require PMA or 510K). These paths are taken according to the level of risk posed to the patient. For PMA devices, they may lead to an unreasonable risk of illness or injury, whereas 510k devices need to demonstrate equivalent safety and efficacy compared to a legally marketed device. On the other hand, exempt devices need to demonstrate that they meet the safety and marketing requirements of regulators.85 Being cognizant of these issues, we developed a medical device based on a serendipitous laboratory discovery.62, 63, 67, 68 Observing that drug-free microneedles inhibited keloid cell and rabbit ear wound tissue proliferation, we collaborated with clinicians to develop microneedle devices to suppress keloid scars through physical contact. 62, 63, 67, 68 Because the therapeutic effect of these device was not achieved through chemical means, the regulators promptly approved its clinical adoption. In addition, this topically-applied device is not invasive. These attributes facilitated its rapid and costeffective clinical translation for suppressing and potentially preventing abnormal scarring.


17


Page 18 of 28

4.2 Manufacturing and Translation Transferring a scientific idea from the laboratory to the commercial market is the only route to ensure widespread public dissemination. Achieving this is a non-trivial matter as the drug and/or device (product) needs to be manufactured to achieve the required scale. The most challenging aspect from an academic perspective is to meet this scale, with minimal product quality deviation, in a costeffective manner. Cost is critical because of the commercial nature of enterprises. Developing and testing a prototype product (in academic or small-scale settings), may only constitute up to 2 of 8 steps in typical medicinal product development.85 Following feasibility (in vitro and in vivo), safety and efficacy testing (long-term monitoring and benchmarking of efficacy), a number of steps to reach the marketplace are still required. These include: pilot scale manufacturing, product scale-up, regulatory approval before product marketing and its launch.85-86 Such issues have significant ramifications on the eventual commercialization route. Commercialization options include: technology licensing or sale, partnering with industry for technology/product development and establishing stand-alone commercial enterprises.85 The decision to choose the most appropriate strategy is dependent on the type of technology, extent of technology development achieved by the inventors and the strength of the intellectual property (IP). Prior to clinical testing, the product needs to undergo complete characterization as detailed under the U.S. Food and Drug Administration (or respective regulators). For medical devices, the evaluation process involves: screening raw materials, biocompatibility of device components, safety and efficacy product testing, and testing during product release (followed by postmarketing/audit testing). Depending on the nature and duration of contact, regulators recommend evaluation of shortand long-term biological effects. These include, but are not limited to: cytotoxicity, sensitization, irritation, systemic toxicity (acute and subchronic), genotoxicity and hemocompatibility. On the basis that wounds are superficial by nature that do not require in vivo implantation, the full suite of regulatory requirements may not be necessary during device development for wound healing.85, 87 Certain common challenges are encountered in academic settings: material sourcing, biomaterial quality (ensure highest quality pre- and post-processing), material/process incompatibilities and other biocompatibility issues. Given the focus on polymeric biomaterial wound innovation, such manufacturing issues may be encountered during scale-up. Adapting production to achieve requisite scale can result in a number of challenges including: incremental scaling of production (to industrially-relevant quantities), sterile processes and endotoxin management.85, 86 To minimize supply chain disruption, incremental production scale-up reduces issues relating to supplier quantities, material and equipment efficiencies; and facilitates cost-benefit analysis to make strategic decisions. These considerations include determining whether to develop the manufacturing process inhouse or subcontract process development to contract manufacturing organizations (CMOs). Standardization is yet another manufacturing issue. It involves establishing a document by consensus


18

Page 19 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


and approval by a recognized body. Certain commonly used standards include: raw materials, contamination detection, and sterilization and packaging (ISO 10993/7). Quality management systems (ISO 134885) are also frequently used.85 4.3 Advanced Dressings with Integrated Sensors for Chronic Wound Monitoring Currently, a wide variety of dressings are available in the market for chronic wounds with varying wound conditions like superficial or deep, or clean or infected, and being dry or exuding.89 However, these dressings cannot respond actively to changes in the wound environment. Some of the advanced dressings can release drugs in response to cues such as pH changes in the wound environment. 51 Despite these advancements in wound care technologies, wound management remains extremely challenging due to the complexity of wound healing process. Integration of sensors into the dressings for management of chronic wounds have the potential to shed light on the wound status by detecting real-time changes in biomarker expression. Advanced dressings with integrated sensors potentially tackle many challenges associated with chronic wounds.90 They may be able to provide information on the wound condition, wound healing rate, treat infection and facilitate effective healing chronic wounds by actively responding to changes in the wound site. Assessment of wound status is critical for its management and is often performed by qualitative clinical assessments.90 The key wound parameters detected by the sensors integrated in the dressings potentially improve and add objectivity in assessing its status. These may improve wound management and minimize dressing changes, thus reducing healthcare costs for patients, hospitals, and insurance providers. Our experience has demonstrated that nanoparticles can be readily integrated with dressings to create smart biomaterials. This is one possibility to embed sensors into dressing or restorative matrices. For example, migrating and newly proliferating skin cells may readily uptake sub-cellular sensor particles. Previously, we demonstrated how adherent cells uptake sub-micron particles embedded in the culture substrate whereas suspension cells do not exhibit this behavior.91 This illustrates how fluorescent sensors may detect migrating cells (keratinocytes, fibroblasts, immune cells) in the chronic wound. These sensors may consist of either sub-micron polymer particles loaded with sensors for intracellular gene biomarker detection,92-93 or using nucleic acid nanoparticle technology for imaging the expression of gene biomarkers.94-95 Currently, there is ongoing research to identify suitable biomarkers for wound assessment. For instance, sensors are being explored to measure decreases in albumin levels, increases in interleukin1(IL-1) and interleukin-6 (IL-6) levels as they are associated with wound healing impairment.96-97 Apart from these, diagnostic biomarkers such as metalloproteinases (MMPs) are also used for predicting wound outcomes in clinical trials.98 For example, the MMP-9/MMP-1 expression ratio is a potential indicator since it is found to decrease significantly in healing wounds.99 These findings have led to the development of point-of-care tools to measure MMPs levels (MMP-8, MMP-9) through


19


Page 20 of 28

wound swabbing.100 Various cytokines and growth factors have also shown potential for wound status assessment such as TIMP1101, ADAM12 and K15.102 Despite this, these biomarkers are not completely specific.103 Biomarkers such as albumin, IL-1, and IL-6 levels are also related to inflammation which makes them less definitive to monitor wound healing. 4.4 Advanced Dressings Combining Wound Healing and Scar Resolution Both wound pathologies – chronic wounds and abnormal scars have significant differences between each other. Whereas chronic wounds are characterized by insufficiency, abnormal scars generate excessive fibrotic dermal tissue. During early wound healing stages (i.e. inflammation, proliferation), inflammation is necessary to prevent opportunistic infections102, whereas proliferation generates tissue mass (epidermal and dermal cell layers) to fill the wound. Yet, it is highly advantageous to have a single technology that caters to different requirements of the wound healing stages. This is because, a single dressing will mean less wound interference, facilitating prompt recovery.103 For example, the initial stages of wound healing may involve regulating wound inflammation and proliferation, whereas the latter stages serve to suppress scar formation. Given such disparate requirements, dressings need to incorporate an appropriate drug release schedule for the corresponding wound stage. For example, anti-inflammatory drugs have been incorporated into dressings to improve wound healing outcomes (e.g. Curcumin, Doxycycline, Neurotensin3, 104). While anti-inflammatory drugs have a positive effect on wound healing outcome initially, they are less likely to be critical later on. To promote proliferation, several mitogenic factors like platelet-derived growth factor (PDGF), fibroblast growth factor 2 (FGF2), nerve growth factor (NGF) etc. can be incorporated. A comprehensive list of growth factors and their different roles in wound healing can be found in previous review articles.105 Some of these reportedly influence the following: neutrophil infiltration, macrophage infiltration, angiogenesis, matrix deposition, scarring and reepithelialisation.105-107 To suppress abnormal scarring during wound remodelling109, a number of anti-scarring strategies (see above – section 3.1) have been employed. Many of them are based on inhibiting excessive TGF-β signalling. Whereas TGF-β1 facilitates cell proliferation, it is notably abundant in hypertrophic and keloid scars. Not only are soluble factors such as TGF-β1 chiefly responsible for abnormal scarring pathologies, recent studies have uncovered cell population(s) with intrinsic profibrotic behaviour.110 This subpopulation of fibroblasts have positive Engrailed-1 gene expression: a biomarker related to central nervous system development.111 This subpopulation was found to be the primary contributor to connective tissue secretion and organization in embryonic development, cutaneous wounding, radiation fibrosis, and cancer stroma formation.110 Thus, they developed an antifibrotic strategy by inhibiting CD26/DPP4 – (dipeptidyl peptidase-4) in fibrotic cells using diprotin A, the small molecule drug. Overall, wound healing was delayed by 5 days and achieved significant reduction in scar size (~4×).


20

Page 21 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Since different types of drugs/therapeutics correspond to different stages of wound healing (inflammatory, proliferation, scarring), delivering drugs to suit the appropriate wound healing stage is necessary. This may involve integrating polymeric biomaterials designed to release distinct packages of drugs at different periods of time. To mimic antigen release at discrete pulses to match vaccination schedules, a microfabrication method – StampEd Assembly of polymer Layers (SEAL) was used to deliver fluorescent dyes (model drug) to be released at 3 discrete timepoints in vivo. This was later used to deliver Ovalbumin (OVA). SEAL generated core-shell particles either matched, or outperformed dual-bolus OVA titer.112 For example, a potential combination could incorporate any combination of anti-inflammatory (e.g. Doxycycline), proliferative (e.g. PDGF) and anti-scarring (e.g. siRNA against TGF-β receptor I) released during appropriate wound recovery stages. Similarly, these microfabrication techniques incorporate a range of drugs and/or sensors to enable simultaneous treatment and diagnosis. For example, we demonstrated the development of an ‘oligonucleotide sprinkler’ for simultaneous knockdown of TGF-β signalling and detection of its downstream biomarker – CTGF.73 Conflict of Interests. The authors declare no conflict of interest. Acknowledgment. This work was supported by Singapore A*STAR Biomedical Research Council (IAF-PP grant to XCJ) and MOE Tier 1 grant (RG131/15 to XCJ)

References: 1. Falanga, V., Wound Healing and its Impairment in the Diabetic Foot. Lancet 2005, 366, 17361743. 2. Sheehan, P.; Jones, P.; Caselli, A.; Giurini, J. M.; Veves, A., Percent Change in Wound Area of Diabetic Foot Ulcers Over a 4-Week Period Is a Robust Predictor of Complete Healing in a 12-Week Prospective Trial. Diabetes Care 2003, 26, 1879-1882. 3. Boateng, J. S.; Matthews, K. H.; Stevens, H. N. E.; Eccleston, G. M., Wound Healing Dressings and Drug Delivery Systems: A Review. J. Pharm. Sci. 2008, 97, 2892-2923. 4. Frykberg, R. G.; Banks, J., Challenges in the Treatment of Chronic Wounds. Adv. Wound Care 2015, 4, 560-582. 5. Sen, C. K.; Gordillo, G. M.; Roy, S.; Kirsner, R.; Lambert, L.; Hunt, T. K.; Gottrup, F.; Gurtner, G. C.; Longaker, M. T., Human Skin Wounds: A Major and Snowballing Threat to Public Health and the Economy. Wound Repair Regen. 2009, 17, 763-771. 6. Brown, M. S.; Ashley, B.; Koh, A., Wearable Technology for Chronic Wound Monitoring: Current Dressings, Advancements, and Future Prospects. Front. Bioeng. Biotechnol. 2018, 6 , 47. 7. Fabbrocini, G.; Annunziata, M. C.; D'Arco, V.; De Vita, V.; Lodi, G.; Mauriello, M. C.; Pastore, F.; Monfrecola, G., Acne Scars: Pathogenesis, Classification and Treatment. Dermatol. Res. Pract. 2010, 893080. 8. Zhu, Z.; Ding, J.; Shankowsky, H. A.; Tredget, E. E., The Molecular Mechanism of Hypertrophic Scar. J. Cell. Commun. Signal 2013, 7, 239-252. 9. Gauglitz, G. G.; Korting, H. C.; Pavicic, T.; Ruzicka, T.; Jeschke, M. G., Hypertrophic Scarring and Keloids: Pathomechanisms and Current and Emerging Treatment Strategies. Mol. Med. 2011, 17, 113-125.


21


Page 22 of 28

10. Verhaegen, P. D. H. M.; Van Zuijlen, P. P. M.; Pennings, N. M.; Van Marle, J.; Niessen, F. B.; Van Der Horst, C. M. A. M.; Middelkoop, E., Differences in Collagen Architecture Between Keloid, Hypertrophic Scar, Normotrophic Scar, and Normal Skin: An Objective Histopathological Analysis. Wound Repair Regen. 2009, 17, 649-656. 11. Jones, R.; Foster, D. S.; Longaker, M. T., Management of Chronic Wounds—2018. JAMA 2018, 320, 1481-1482. 12. Han, G.; Ceilley, R., Chronic Wound Healing: A Review of Current Management and Treatments. Adv. Ther. 2018, 34, 599-610 13. Bekara, F.; Vitse, J.; Fluieraru, S.; Masson, R.; Runz, A. D.; Georgescu, V.; Bressy, G.; Labbé, J. L.; Chaput, B.; Herlin, C., New Techniques for Wound Management: A Systematic Review of Their Role in the Management of Chronic Wounds. Arch Plast Surg 2018, 45, 102-110. 14. Saray, Y.; Güleç, A. T., Treatment of Keloids and Hypertrophic Scars with Dermojet Injections of Bleomycin: a Preliminary Study. Int. J. Dermatol. 2005, 44, 777-784. 15. Juckett, G.; Hartman-Adams, H., Management of Keloids and Hypertrophic Scars. Am. Fam. Physician 2009, 80, 253-60. 16. Mangram, A. J.; Horan, T. C.; Pearson, M. L.; Silver, L. C.; Jarvis, W. R., Guideline for Prevention of Surgical Site Infection, 1999. Infect. Control Hosp. Epidemiol. 2015, 20, 247-280. 17. Chike-Obi, C. J.; Cole, P. D.; Brissett, A. E., Keloids: Pathogenesis, Clinical Features, and Management. Semin. Plast. Surg. 2009, 23, 178-184. 18. Arno, A. I.; Gauglitz, G. G.; Barret, J. P.; Jeschke, M. G., Up-to-date Approach to Manage Keloids and Hypertrophic Scars: A Useful Guide. Burns 2014, 40, 1255-1266. 19. Perez, J. L.; Rohrich, R. J., Optimizing Postsurgical Scars: A Systematic Review on Best Practices in Preventative Scar Management. Plast. Reconstr. Surg. 2017, 140, 782e-793e. 20. Finnerty, C. C.; Jeschke, M. G.; Branski, L. K.; Barret, J. P.; Dziewulski, P.; Herndon, D. N., Hypertrophic Scarring: the Greatest Unmet Challenge After Burn Injury. Lancet 2016, 388, 1427-1436. 21. Fearmonti, R.; Bond, J.; Erdmann, D.; Levinson, H., A Review of Scar Scales and Scar Measuring Devices. Eplasty 2010, 10, e43-e43. 22. Ud-Din, S.; Bayat, A., Non-Invasive Objective Devices for Monitoring the Inflammatory, Proliferative and Remodelling Phases of Cutaneous Wound Healing and Skin Scarring. Exp. Dermatol. 2016, 25, 579-585. 23. Lee, J. Y.-Y.; Yang, C.-C.; Chao, S.-C.; Wong, T.-W., Histopathological Differential Diagnosis of Keloid and Hypertrophic Scar. Am. J. Dermatopathol. 2004, 26, 379-384. 24. Ehrlich, H. P.; Desmoulière, A.; Diegelmann, R. F.; Cohen, I. K.; Compton, C. C.; Garner, W. L.; Kapanci, Y.; Gabbiani, G., Morphological and Immunochemical Differences Between Keloid and Hypertrophic Scar. Am. J. Pathol. 1994, 145, 105-113. 25. Suarez, E.; Syed, F.; Alonso-Rasgado, T.; Bayat, A., Identification of Biomarkers Involved in Differential Profiling of Hypertrophic and Keloid Scars Versus Normal Skin. Arch. Dermatol. Res. 2015, 307, 115-133. 26. Ogawa, R., The Most Current Algorithms for the Treatment and Prevention of Hypertrophic Scars and Keloids. Plast. Reconstr. Surg. 2010, 125, 557-568. 27. Monstrey, S.; Middelkoop, E.; Vranckx, J. J.; Bassetto, F.; Ziegler, U. E.; Meaume, S.; Téot, L., Updated Scar Management Practical Guidelines: Non-Invasive and Invasive Measures. J. Plast. Reconstr. Aesthet. Surg. 2014, 67, 1017-1025. 28. Gold, M. H.; McGuire, M.; Mustoe, T. A.; Pusic, A.; Sachdev, M.; Waibel, J.; Murcia, C.; International Advisory Panel on Scar Management: Part 2--algorithms for Scar Prevention and Treatment. Dermatol. Surg. 2014, 40, 825-831. 29. Gupta, P.; Vermani, K.; Garg, S., Hydrogels: From Controlled Release to pH-Responsive Drug Delivery. Drug Discov. Today 2002, 7, 569-579. 30. Pillai, O.; Panchagnula, R., Polymers in Drug Delivery. Curr. Opin. Chem. Biol. 2001, 5, 447451. 31. Tian, H.; Tang, Z.; Zhuang, X.; Chen, X.; Jing, X., Biodegradable Synthetic Polymers: Preparation, Functionalization and Biomedical Application. Prog. Polym. Sci. 2012, 37, 237-280. 32. Zeng, S. H.; Duan, P. P.; Shen, M. X.; Xue, Y. J.; Wang, Z. Y., Preparation and Degradation Mechanisms of Biodegradable Polymer: a Review. IOP Conf. Ser. Mater. Sci. Eng. 2016, 137, 012003.


22

Page 23 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


33. Danti, S.; D'Alessandro, D.; Mota, C.; Bruschini, L.; Berrettini, S., Applications of Bioresorbable Polymers in Skin and Eardrum. In Bioresorbable Polymers for Biomedical Applications: From Fundamentals to Translational Medicine; Perale, G., Hilborn, J., Eds.; Woodhead Publishing 2017, 423-444. 34. Kamoun, E. A.; Kenawy, E. S.; Chen, X., A Review on Polymeric Hydrogel Membranes for Wound Dressing Applications: PVA-Based Hydrogel Dressings. J. Adv. Res. 2017, 8, 217-233. 35. Turner, N. J.; Badylak, S. F., The Use of Biologic Scaffolds in the Treatment of Chronic Nonhealing Wounds. Adv Wound Care (New Rochelle) 2015, 4, 490-500. 36. Chereddy, K. K.; Vandermeulen, G.; Preat, V., PLGA Based Drug Delivery Systems: Promising Carriers for Wound Healing Activity. Wound Repair. Regen. 2016, 24, 223-36. 37. Frenkel, J. S., The Role of Hyaluronan in Wound Healing. Int. Wound J. 2014, 11, 159-63. 38. Park, S. Y.; Lee, H. U.; Lee, Y. C.; Kim, G. H.; Park, E. C.; Han, S. H.; Lee, J. G.; Choi, S.; Heo, N. S.; Kim, D. L.; Huh, Y. S.; Lee, J., Wound Healing Potential of Antibacterial Microneedles Loaded with Green Tea Extracts. Mater. Sci. Eng. C Mater. Biol. Appl. 2014, 42, 757-62. 39. Makadia, H. K.; Siegel, S. J., Poly Lactic-co-Glycolic Acid (PLGA) as Biodegradable Controlled Drug Delivery Carrier. Polymers 2011, 3, 1377-1397. 40. Chereddy, K. K.; Coco, R.; Memvanga, P. B.; Ucakar, B.; des Rieux, A.; Vandermeulen, G.; Preat, V., Combined Effect of PLGA and Curcumin on Wound Healing Activity. J Control. Release 2013, 171, 208-15. 41. Carter, P.; Narasimhan, B.; Wang, Q., Biocompatible Nanoparticles and Vesicular Systems in Transdermal Drug Delivery for Various Skin Diseases. Int. J. Pharm. 2019, 555, 49-62. 42. Alibolandi, M.; Mohammadi, M.; Taghdisi, S. M.; Abnous, K.; Ramezani, M., Synthesis and Preparation of Biodegradable Hybrid Dextran Hydrogel Incorporated with Biodegradable Curcumin Nanomicelles for Full Thickness Wound Healing. Int. J. Pharm. 2017, 532, 466-477. 43. Xin, S.; Li, X.; Wang, Q.; Huang, R.; Xu, X.; Lei, Z.; Deng, H., Novel Layer-by-Layer Structured Nanofibrous Mats Coated by Protein Films for Dermal Regeneration. J. Biomed. Nanotechnol. 2014, 10, 803-810. 44. Zhan, Y.; Zeng, W.; Jiang, G.; Wang, Q.; Shi, X.; Zhou, Z.; Deng, H.; Du, Y., Construction of Lysozyme Exfoliated Rectorite-Based Electrospun Nanofibrous Membranes for Bacterial Inhibition. Journal of Applied Polymer Science 2015, 132, 41496 45. Bawa, P.; Pillay, V.; Choonara, Y. E.; du Toit, L. C., Stimuli-Responsive Polymers and Their Applications in Drug Delivery. Biomed. Mater. 2009, 4, 022001. 46. Shi, Z.; Gao, X.; Ullah, M. W.; Li, S.; Wang, Q.; Yang, G., Electroconductive Natural PolymerBased Hydrogels. Biomaterials 2016, 111, 40-54. 47. Wei, M.; Gao, Y.; Li, X.; Serpe, M. J., Stimuli-Responsive Polymers and Their Applications. Polym. Chem. 2017, 8, 127-143. 48. Op 't Veld, R. C.; van den Boomen, O. I.; Lundvig, D. M. S.; Bronkhorst, E. M.; Kouwer, P. H. J.; Jansen, J. A.; Middelkoop, E.; Von den Hoff, J. W.; Rowan, A. E.; Wagener, F., Thermosensitive Biomimetic Polyisocyanopeptide Hydrogels may Facilitate Wound Repair. Biomaterials 2018, 181, 392-401. 49. Ninan, N.; Forget, A.; Shastri, V. P.; Voelcker, N. H.; Blencowe, A., Antibacterial and AntiInflammatory pH-Responsive Tannic Acid-Carboxylated Agarose Composite Hydrogels for Wound Healing. ACS Appl. Mater. Interfaces 2016, 8, 28511-28521. 50. Liu, L.; Li, X.; Nagao, M.; Elias, A.; Narain, R.; Chung, H.-J., A pH-Indicating Colorimetric Tough Hydrogel Patch towards Applications in a Substrate for Smart Wound Dressings. Polymers 2017, 9, 558. 51. Piva, R. H.; Rocha, M. C.; Piva, D. H.; Imasato, H.; Malavazi, I.; Rodrigues-Filho, U. P., Acidic Dressing Based on Agarose/Cs2.5H0.5PW12O40 Nanocomposite for Infection Control in Wound Care. ACS Appl Mater Interfaces 2018, 10, 30963-30972. 52. Barron, A. E.; Zuckerman, R. N., Bioinspired Polymeric Materials: in-between Proteins and Plastics. Curr. Opin. Chem. Biol. 1999, 3, 681-687 53. Li, M.; Li, H.; Li, X.; Zhu, H.; Xu, Z.; Liu, L.; Ma, J.; Zhang, M., A Bioinspired Alginate-Gum Arabic Hydrogel with Micro-/Nanoscale Structures for Controlled Drug Release in Chronic Wound Healing. ACS Appl Mater Interfaces 2017, 9, 22160-22175.


23


Page 24 of 28

54. Chen, G.; Yu, Y.; Wu, X.; Wang, G.; Ren, J.; Zhao, Y., Bioinspired Multifunctional Hybrid Hydrogel Promotes Wound Healing. Adv. Funct. Mater. 2018, 28, 1801386. 55. Wang, H.; Chen, Z.; Li, X.-J.; Ma, L.; Tang, Y.-L., Anti-Inflammatory Cytokine TSG-6 Inhibits Hypertrophic Scar Formation in a Rabbit Ear Model. Eur. J. Pharmacol. 2015, 751, 42-49. 56. Grek, C. L.; Montgomery, J.; Sharma, M.; Ravi, A.; Rajkumar, J. S.; Moyer, K. E.; Gourdie, R. G.; Ghatnekar, G. S., A Multicenter Randomized Controlled Trial Evaluating a Cx43-Mimetic Peptide in Cutaneous Scarring. J. Invest. Dermatol. 2017, 137, 620-630. 57. Wang, Y.-W.; Liou, N.-H.; Cherng, J.-H.; Chang, S.-J.; Ma, K.-H.; Fu, E.; Liu, J.-C.; Dai, N.T., siRNA-Targeting Transforming Growth Factor-β Type I Receptor Reduces Wound Scarring and Extracellular Matrix Deposition of Scar Tissue. J. Invest. Dermatol. 2014, 134, 2016-2025. 58. Järvinen, T. A. H.; Ruoslahti, E., Targeted Antiscarring Therapy for Tissue Injuries. Adv Wound Care 2013, 2, 50-54. 59. Järvinen, T. A. H.; Ruoslahti, E., Target-Seeking Antifibrotic Compound Enhances Wound Healing and Suppresses Scar Formation in Mice. Proc. Natl. Acad. Sci. U.S.A. 2010, 107, 21671-21676. 60. Jeon, E. Y.; Choi, B.-H.; Jung, D.; Hwang, B. H.; Cha, H. J., Natural Healing-Inspired Collagen-Targeting Surgical Protein Glue for Accelerated Scarless Skin Regeneration. Biomaterials 2017, 134, 154-165. 61. Castleberry, S. A.; Golberg, A.; Sharkh, M. A.; Khan, S.; Almquist, B. D.; Austen, W. G.; Yarmush, M. L.; Hammond, P. T., Nanolayered siRNA delivery platforms for local silencing of CTGF reduce cutaneous scar contraction in third-degree burns. Biomaterials 2016, 95, 22-34. 62. Xue, P.; Yeo, D. C. L.; Chuah, Y. J.; Tey, H. L.; Kang, Y.; Xu, C., Drug-Eluting Microneedles for Self-Administered Treatment of Keloids. TECHNOLOGY 2014, 02, 144-152. 63. Liu, S.; Yeo, D. C.; Wiraja, C.; Tey, H. L.; Mrksich, M.; Xu, C., Peptide Delivery with Poly(ethylene glycol) Diacrylate Microneedles through Swelling Effect. Bioeng Transl Med 2017, 2, 258-267. 64. Westra, I.; Pham, H.; Niessen, F. B., Topical Silicone Sheet Application in the Treatment of Hypertrophic Scars and Keloids. J Clin Aesthet Dermatol 2016, 9, 28-35. 65. Benjamin, B.; Simon, F.; Kathyryn, M.; Sean, K.; L., P. S., The Use of Silicone Adhesives for Scar Reduction. Adv Wound Care 2015, 4, 422-430. 66. Weng, W.; He, S.; Song, H.; Li, X.; Cao, L.; Hu, Y.; Cui, J.; Zhou, Q.; Peng, H.; Su, J., Aligned Carbon Nanotubes Reduce Hypertrophic Scar via Regulating Cell Behavior. ACS Nano 2018, 12, 76017612. 67. Yeo, D. C.; Balmayor, E. R.; Schantz, J.-T.; Xu, C., Microneedle Physical Contact as a Therapeutic for Abnormal Scars. Eur. J. Med. Res. 2017, 22, 28. 68. Tan, C.; Yeo Chen Long, D.; Cao, T.; Tan Wei Ding, V.; Srivastava, R.; Yow, A. P.; Tan, W. P.; Wong Wing Kee, D.; Xu, C.; Tey, H. L., Drug-free Microneedles in the Treatment of Keloids: a Single-Blinded Intraindividual Controlled Clinical Trial. Br. J. Dermatol. 2018, 179, 1418 – 1419. 69. Jennifer, H.; Kara, C.; Karen, L.; Laura, B.; Daniel, M.; Phil, B., Clinical Biofilms: A Challenging Frontier in Wound Care. Adv Wound Care 2015, 4, 295-301. 70. Wang, M.; Wiraja, C.; Wee, M.; Yeo, D.; Hu, L.; Xu, C., Hairpin-Structured Probe Conjugated Nano-Graphene Oxide for the Cellular Detection of Connective Tissue Growth Factor mRNA. Anal. Chim. Acta 2018, 1038, 140-147. 71. Halo, T. L.; McMahon, K. M.; Angeloni, N. L.; Xu, Y.; Wang, W.; Chinen, A. B.; Malin, D.; Strekalova, E.; Cryns, V. L.; Cheng, C.; Mirkin, C. A.; Thaxton, C. S., NanoFlares for the Detection, Isolation, and Culture of Live Tumor Cells from Human Blood. Proc. Natl. Acad. Sci. U.S.A. 2014, 111, 17104 – 17109. 72. Yeo, D. C.; Wiraja, C.; Paller, A. S.; Mirkin, C. A.; Xu, C., Abnormal Scar Identification with Spherical-Nucleic-Acid Technology. Nat. Biomed. Eng. 2018, 2, 227-238. 73. Zheng, M.; Wiraja, C.; Yeo, D. C.; Chang, H.; Lio, D. C. S.; Shi, W.; Pu, K.; Paller, A. S.; Xu, C., Oligonucleotide Molecular Sprinkler for Intracellular Detection and Spontaneous Regulation of mRNA for Theranostics of Scar Fibroblasts. Small 2018, 14, 1802546. 74. Canady, J.; Arndt, S.; Karrer, S.; Bosserhoff, A. K., Increased KGF Expression Promotes Fibroblast Activation in a Double Paracrine Manner Resulting in Cutaneous Fibrosis. J Invest Dermatol 2013, 133, 647-657.


24

Page 25 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


75. Miao, Q.; Yeo, D. C.; Wiraja, C.; Zhang, J.; Ning, X.; Xu, C.; Pu, K., Near-Infrared Fluorescent Molecular Probe for Sensitive Imaging of Keloid. Angew. Chem. Int. Ed. 2018, 130, 1270-1274. 76. Yeo, D. C.; Wiraja, C.; Miao, Q.; Ning, X.; Pu, K.; Xu, C., Anti-Scarring Drug Screening with Near-Infrared Molecular Probes Targeting Fibroblast Activation Protein-α. ACS Appl. Bio Mater. 2018, 1, 2054 - 2061 77. Cheng, P.; Zhang, J.; Huang, J.; Miao, Q.; Xu, C.; Pu, K., Near-infrared fluorescence probes to detect reactive oxygen species for keloid diagnosis. Chem. Sci. 2018, 9, 6340-6347 78. Mak, I. W.; Evaniew, N.; Ghert, M., Lost in Translation: Animal Models and Clinical Trials in Cancer Treatment. Am. J. Transl. Res. 2014, 6, 114-118. 79. Gintant, G.; Sager, P. T.; Stockbridge, N., Evolution of Strategies to Improve Preclinical Cardiac Safety Testing. Nat Rev Drug Discov. 2016, 15, 457. 80. Viera, M. H.; Amini, S.; Valins, W.; Berman, B., Innovative Therapies in the Treatment of Keloids and Hypertrophic Scars. J Clin Aesthet Dermatol. 2010, 3, 20-26. 81. Bertolini, F.; Sukhatme, V. P.; Bouche, G., Drug Repurposing in Oncology—Patient and Health Systems Opportunities. Nat. Rev. Clin. Oncol. 2015, 12, 732. 82. DiMasi, J. A.; Grabowski, H. G., The Cost of Biopharmaceutical R&D: is Biotech Different? MDE Manage Decis Econ. 2007, 28, 469-479. 83. Pashuck, E. T.; Stevens, M. M., Designing Regenerative Biomaterial Therapies for the Clinic. Sci. Transl. Med. 2012, 4, 160sr4-160sr4. 84. Rawlins, M. D., Cutting the Cost of Drug Development? Nat Rev Drug Discov. 2004, 3, 360. 85. Chandra, P.; Yoo, J. J.; Lee, S. J., Chapter 13 - Biomaterials in Regenerative Medicine: Challenges in Technology Transfer from Science to Process Development. In Translational Regenerative Medicine, Atala, A.; Allickson, J. G., Eds. Academic Press: Boston, 2015; pp 151-167. 86. Rathore, A. S.; Winkle, H., Quality by Design for Biopharmaceuticals. Nature Biotechnol 2009, 27, 26. 87. Reeve, L.; Baldrick, P., Biocompatibility Assessments for Medical Devices – Evolving Regulatory Considerations. Expert Rev. Med. Devices 2017, 14, 161-167. 88. Williams, D. J.; Thomas, R. J.; Hourd, P. C.; Chandra, A.; Ratcliffe, E.; Liu, Y.; Rayment, E. A.; Archer, J. R., Precision Manufacturing for Clinical-Quality Regenerative Medicines. Philos. Trans. Royal Soc. A 2012, 370, 3924-3949. 89. Dabiri, G.; Damstetter, E.; Phillips, T., Choosing a Wound Dressing Based on Common Wound Characteristics. Adv Wound Care 2016, 5, 32-41. 90. Dargaville, T. R.; Farrugia, B. L.; Broadbent, J. A.; Pace, S.; Upton, Z.; Voelcker, N. H., Sensors and Imaging for Wound Healing: a Review. Biosens Bioelectron 2013, 41, 30-42. 91. Gao, Y.; Lim, J.; Yeo, D. C. L.; Liao, S.; Lans, M.; Wang, Y.; Teoh, S.-H.; Goh, B. T.; Xu, C., A Selective and Purification-Free Strategy for Labeling Adherent Cells with Inorganic Nanoparticles. ACS Appl. Mater. Interfaces 2016, 8, 6336-6343. 92. Yeo, D. C.; Wiraja, C.; Mantalaris, A.; Xu, C., Nanosensors for Regenerative Medicine. J Biomed Nanotechnol. 2014, 10, 2722-2746. 93. Yeo, D.; Wiraja, C.; Chuah, Y. J.; Gao, Y.; Xu, C., A Nanoparticle-based Sensor Platform for Cell Tracking and Status/Function Assessment. Sci. Rep 2015, 5, 14768. 94. Wiraja, C.; Yeo, D.; Lio, D.; Labanieh, L.; Lu, M.; Zhao, W.; Xu, C., Aptamer Technology for Tracking Cells’ Status & Function. Mol Cell Ther. 2014, 2, 33. 95. Lio, D. C. S.; Liu, C.; Wiraja, C.; Qiu, B.; Fhu, C. W.; Wang, X.; Xu, C., Molecular Beacon Gold Nanosensors for Leucine-Rich Alpha-2-Glycoprotein-1 Detection in Pathological Angiogenesis. ACS Sensors 2018, 3, 1647-1655. 96. James, T. J.; Hughes, M. A.; Cherry, G. W.; Taylor, R. P., Simple Biochemical Markers to Assess Chronic Wounds. Wound Repair Regen 2001, 8, 264-269. 97. Trengove, N. J.; Bielefeldt-Ohmann, H.; Stacey, M. C., Mitogenic Activity and Cytokine Levels in Non-Healing and Healing Chronic Leg Ulcers. Wound Repair Regen 2001, 8, 13-25. 98. Ayuk, S. M.; Abrahamse, H.; Houreld, N. N., The Role of Matrix Metalloproteinases in Diabetic Wound Healing in Relation to Photobiomodulation. J Diabetes Res. 2016, 2016, 9. 99. Ladwig, G. P.; Robson, M. C.; Liu, R. A. N.; Kuhn, M. A.; Muir, D. F.; Schultz, G. S., Ratios of Activated Matrix Metalloproteinase-9 to Tissue Inhibitor of Matrix Metalloproteinase-1 in Wound Fluids are Inversely Correlated with Healing of Pressure Ulcers. Wound Repair Regen 2002, 10, 26-37.


25


Page 26 of 28

100. Serena, T. E., Development of a Novel Technique to Collect Proteases from Chronic Wounds. Adv. Wound care 2014, 3, 729-732. 101. Bullen, E. C.; Longaker, M. T.; Updike, D. L.; Benton, R.; Ladin, D.; Hou, Z., Howard, E. W., Tissue Inhibitor of Metalloproteinases-1 Is Decreased and Activated Gelatinases Are Increased in Chronic Wounds. J Invest Dermatol. 1995, 104, 236 -240 102. Harsha, A.; Stojadinovic, O.; Brem, H.; Sehara-Fujisawa, A.; Wewer, U.; Loomis, C. A.; Blobel, C. P.; Tomic-Canic, M., ADAM12: a Potential Target for the Treatment of Chronic Wounds. J. Mol. Med. 2008, 86, 961-969. 103. Derakhshandeh, H.; Kashaf, S. S.; Aghabaglou, F.; Ghanavati, I. O.; Tamayol, A., Smart Bandages: The Future of Wound Care. Trends Biotechnol 2018, 36, 1259-1274. 104. Dinarello, C. A., Therapeutic Strategies to Reduce IL-1 Activity in Treating Local and Systemic Inflammation. Curr Opin Pharmacol. 2004, 4, 378-385. 105. Moura, L. I. F.; Dias, A. M. A.; Carvalho, E.; de Sousa, H. C., Recent Advances on the Development of Wound Dressings for Diabetic Foot Ulcer Treatment—A Review. Acta Biomater. 2013, 9, 7093-7114. 106. Rosique, R. G.; Rosique, M. J.; Farina Junior, J. A., Curbing Inflammation in Skin Wound Healing: A Review. Int J Inflam. 2015, 2015, 9. 107. WERNER, S.; GROSE, R., Regulation of Wound Healing by Growth Factors and Cytokines. Physiol Rev 2003, 83, 835-870. 108. Landén, N. X.; Li, D.; Ståhle, M., Transition From Inflammation to Proliferation: a Critical Step During Wound Healing. Cell Mol Life Sci 2016, 73, 3861-3885. 109. Meilang, X.; J., J. C., Extracellular Matrix Reorganization During Wound Healing and Its Impact on Abnormal Scarring. Adv. Wound Care 2015, 4, 119-136. 110. Rinkevich, Y.; Walmsley, G. G.; Hu, M. S.; Maan, Z. N.; Newman, A. M.; Drukker, M.; Januszyk, M.; Krampitz, G. W.; Gurtner, G. C.; Lorenz, H. P.; Weissman, I. L.; Longaker, M. T., Identification and Isolation of a Dermal Lineage with Intrinsic Fibrogenic Potential. Science 2015, 348 (6232). 111. Beltran, A. S.; Graves, L. M.; Blancafort, P., Novel Role of Engrailed 1 as a Prosurvival Transcription Factor in Basal-like Breast Cancer and Engineering of Interference Peptides to Block its Oncogenic Function. Oncogene 2013, 33, 4767. 112. McHugh, K. J.; Nguyen, T. D.; Linehan, A. R.; Yang, D.; Behrens, A. M.; Rose, S.; Tochka, Z. L.; Tzeng, S. Y.; Norman, J. J.; Anselmo, A. C.; Xu, X.; Tomasic, S.; Taylor, M. A.; Lu, J.; Guarecuco, R.; Langer, R.; Jaklenec, A., Fabrication of Fillable Microparticles and other Complex 3D Microstructures. Science 2017, 357, 1138-1142.


26

Page 27 of 28


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


27


Biomaterials 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43

Abnormal Scars

Page 28 of 28

Therapeutics & Diagnostics NanoFlares

Drug-release

Protein-immobilized gels

Collagen-remodeling biomaterials


Microneedles

Polymeric Biomaterials for Management of Pathological Scarring

Recommend Documents