Poly(N,N-diethylacrylamide) Semi-IPN

Subscriber access provided by University of Sussex Library

Article

Smart macro-porous salecan/poly(N,N-diethylacrylamide) semi-IPN hydrogel for anti-inflammatory drug delivery Wei Wei, Xiaoliang Qi, Junjian Li, Gancheng Zuo, Wei Sheng, Jianfa Zhang, and Wei Dong ACS Biomater. Sci. Eng., Just Accepted Manuscript • DOI: 10.1021/acsbiomaterials.6b00318 • Publication Date (Web): 06 Jul 2016 Downloaded from http://pubs.acs.org on July 7, 2016

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 free 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 accessible to all readers and 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.

ACS Biomaterials Science & Engineering 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 35

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 Biomaterials Science & Engineering

Smart macro-porous salecan/poly(N,N-diethylacrylamide) semi-IPN hydrogel for anti-inflammatory drug delivery

Wei Wei, Xiaoliang Qi, Junjian Li, Gancheng Zuo, Wei Sheng, Jianfa Zhang, Wei Dong* Center for Molecular Metabolism, Nanjing University of Science & Technology, Nanjing 210094, China

* Corresponding author.

Fax: +86-25-84318533. Telephone: +86-25-84318533. E-mail: [email protected]

ABSTRACT: Poly(N,N-diethylacrylamide) is not only a thermo-sensitive polymer, but a good hydrogen bond acceptor as well. Therefore, drugs with carboxyl groups can serve as hydrogen bond donors and form interactions with the tertiary amide groups in N,N-diethylacrylamide. Herein, we report a novel drug delivery system for anionic drugs comprised of poly(N,N-diethylacrylamide) and salecan. Salecan was used to improve the hydrophilicity and accelerate the responsive rate of this system. As expected, salecan-enriched hydrogels exhibited higher swelling ratios and were more sensitive to temperature. Moreover, scanning electron microscopy images showed that the hydrogels are superporous structures, with pore sizes that increase with salecan concentration. The swelling ratios decreased continuously with the 1

ACS Paragon Plus Environment


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

increase of temperature in the range of 25 – 37 °C. MTT assay for cell viability and cell adhesion studies confirm the cell compatibility of the system. Delivery tests using diclofenac sodium, an anti-inflammatory drug, indicate that the thermo-sensitive property of this system is favorable for anionic drug delivery. Interestingly, the release rates of diclofenac sodium from the hydrogels were temperature dependent, with higher temperatures contributing toward faster release rate.

KEYWORDS: Salecan, Polysaccharidic hydrogel, Smart device, Cell compatible, Drug delivery.

1. Introduction Hydrogels are three-dimensional hydrophilic networks which are capable to absorb a large amount of water while maintaining their integrity 1-3. Because of the high water content, hydrogels can act as extracellular matrix mimics, and therefore, have been widely used in tissue engineering 4, 5. Meanwhile, hydrogels also provide versatile and viable platforms for drug delivery system

6-8

. In this case, they can be designed into

desired pore-sizes for different dimensional drugs range from protein, peptide to small molecular drugs

9-12

. Smart hydrogels can serve as promising drug delivery vehicles

for therapeutic healing because of their responsiveness to various environmental stimuli such as temperature, pH, and enzymes

13

. Among these smart devices,

thermo-responsive hydrogel is one of the most popular type for its easy temperature control and feasibility 14. Generally, hydrogels are fabricated via polymer chains crosslinking by chemical 2


Page 2 of 35

Page 3 of 35

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


binding and/or physical interaction

15-17

. Interpenetrating polymer networks (IPN)

technique is one of the most useful methods for hydrogel fabrication 18. IPN hydrogels are formed by interlacing, fully or partially, two or more networks without covalent binding

19

. Similarly, a semi-IPN hydrogel is a material comprising of crosslinked

polymer networks and linear polymer chains

20

. The polymer networks retain their

own properties because there is no chemical bonding between each other 21. Therefore, semi-IPNs technique is able to combine the superiority of both natural macromolecules (biocompatible) and synthetic polymers (consistent) natural

polymers,

polysaccharides

are

investigated

22, 23

extremely

. Among

for

their

biocompatibility, biodegradability, hydrophilicity, biomimetic physicochemical properties and nontoxicity

24

. IPN-polysaccharide hydrogels have emerged as

innovative biomaterials for tissue engineering and drug delivery 25. Salecan (CAS. no. 1439905-58-4) is an extracellular polysaccharide (EPS) produced by a salt-tolerant strain Agrobacterium sp. ZX09. This strain was isolated from a soil sample from the ocean coast of Shandong province by our laboratory and the 16S rDNA sequence was deposited in the GenBank database under the accession number GU810841. The excellent biological activities such as antioxidation and non-toxicity (edible safety) make it a great candidate in the field of food and medicine 26-29

. The structure exhibits a backbone built up by a linear (1→3)-β-D-glucan

consisted of β-1-3-linked glucopyranosyls with a small quantity of α-1-3-linked (Figure 1). Most glucans consisted of β-1-3 linkages were water-insoluble but salecan, the EPS from ZX09, displayed a water-soluble property even with a high molecular 3



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 4 of 35

mass 30. These special properties paved the way for its application in biomaterials. It is well known that a large variety of polysaccharides (e.g. chitosan, hyaluronic acid, xanthan Gum and carrageenans) have been used to fabricate hydrogels for various applications 31-35. Recent studies show both salecan and its derivatives can be used to provide hydrogels as well

36, 37

. In the system of salecan based hydrogels, properties

such as pore-size, strength and water content could be tuned easily by changing the content of salecan. Particularly, the swelling ratios of hydrogels were improved 38

significantly by interpenetrating salecan chains into some polymer networks

. It

makes an easy way to fabricate materials with superabsorbent property. Poly(N,N-diethylacrylamide) (PDE) is a temperature-sensitive water soluble polymer whose lower critical solution temperature (LCST) is about 31 °C

39, 40

. The

tertiary amide group in N,N-diethylacrylamide make it a hydrogen bond acceptor that can form hydrogen bond with hydrogen bond donor

41

. Crosslinked PDEA exhibits

volume phase transition in water at LCST as the balance between hydrogen bonds and hydrophobic interactions changes along with the temperature. Therefore, drugs which can act as hydrogen bond donor are ideal for this thermo-sensitive system. Diclofenac sodium (DS) is anti-inflammatory drug with well-established biological action in reducing pain and inflammations 42. The structure of DS is shown in Figure 1. The carboxyl group of DS was expected to form hydrogen bond with tertiary amide group of N,N-diethylacrylamide. For this reason, DS was chosen as a model drug in this work. Herein, we report a novel anionic drug delivery system by interpenetrating salecan 4


Page 5 of 35

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


chains into crosslinked poly(N,N-diethylacrylamide) networks. Our previous work was focused on synthesis method of salecan-based hydrogels 43. This is the first time to use a thermo-responsive semi-IPN hydrogel with entrapped salecan for anionic drug delivery. We choose DS as a model drug and expect to establish a platform for anionic drug delivery with our salecan.

2. Materials and methods 2.1 Materials Salecan (CAS: 1439905-58-4) was supplied by Center for Molecular Metabolism, Nanjing University of Science & Technology. N,N-diethylacrylamide (DEA) was purchased from Tokyo Chemical Industry (TCI) Co. Ltd., Shanghai, China. N,N'-Methylenebis(acrylamide)

(BIS),

ammonium

persulfate

(APS)

and

N,N,N',N'-tetramethylethylenediamine (TEMED) was obtained from Aladdin Reagent Co. Ltd., Shanghai, China. MTT cell proliferation and cytotoxicity detection kit was purchased from Nanjing KeyGen Biotech Co., LTD, China. Fluorescein Diacetate (FDA) was purchased from Sigma–Aldrich. Diclofenac sodium (DS) was purchased from Energy Chemical Technology (Shanghai) Co. Ltd.

2.2 Preparation of Salecan/PDE semi-IPN hydrogels The semi-IPN hydrogels were synthesized by free-radical polymerization of DEA and crosslinker BIS in the presence of salecan. The preparation process used in this work was referenced to our previous literature

24, 43

. Briefly, DEA monomer and BIS

5



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 6 of 35

solution (20 mg/mL) were added to salecan solution (2% w/v) according to the desired ratios (Table 1). The mixture was stirred under argon atmosphere until a uniform solution was obtained. Followed TEMED and APS, act as accelerator and initiator respectively, were added dropwise into the system to initiate the polymerization. The solution was thoroughly stirred for a while and then immediately poured into a mold and sealed. The reaction was allowed to proceed for 24 h at room temperature. After that, the hydrogels were immersed in deionized water to eliminate unreacted reagents. Note that deionized water should be refreshed several times every day and this process was proceeding for a week. Finally, the hydrogels were freeze-dried and stored for further use. Table 1 Feed ratios for salecan/PDE hydrogel samples Sample

Salecana

DEA

BISb

APS

TEMED

Water

codes

(mL)

(µL)

(µL)

(mg)

(mL)

(mL)

PDE

0

600

400

8

25

10

SPD1

3

600

400

8

25

7

SPD2

4

600

400

8

25

6

SPD3

5

600

400

8

25

5

SPD4

6

600

400

8

25

4

a: Salecan was used as a 2 wt% aqueous solution. b: The concentration of BIS was 20 mg/ml. 2.3 Characterization FT-IR spectra were recorded with a Nicolet iS10 FTIR instrument (Thermo Fisher 6


Page 7 of 35

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


Scientific, USA), resolution 4 cm-1, in the range of 4000 - 500 cm-1 by attenuated total reflectance (ATR) technique with lyophilized gels. Background measurements were performed prior to samples and auto subtracted from the readings. 1

H-NMR spectra of the hydrogels were obtained by a Bruker Avance III 500MHz

NMR spectrometer (1H at 500 MHz). The hydrogels were freeze-dried and rehydrated with deuterated water (D2O) for 24 h. Essays for the hydrogels were carried out at six different temperatures (25, 28, 30, 32, 34 and 37 °C), below and above the transition temperature. The spectra were analyzed by Topspin 3.0 software. Mechanical properties of the hydrogels were investigated by a rheometer (MCR 101, Anton Paar) with a parallel-plate (diameter 50 mm). To confirm the linear viscoelasticity region, dynamic strain sweep was performed prior to the test. Dynamic frequency sweep measurement (0.01% strain) was carried out on the hydrogels at 25 °C as a function of frequency in the range 0.1-10 Hz. The morphology of hydrogels was studied using a Scanning Electron Microscopy (SEM) (JEOLJSM-6380LV), operating at 30 kV. Lyophilized hydrogels were sputter-coated with gold before the observation. Average diameter of the pores was determined by Nano Measurer 1.2.5 software. To determine the swelling kinetics, freeze-dried samples were immersed in deionized water at 25 °C. The swelling hydrogels were weighed by an electronic balance, at predetermined intervals of time, after wiping off excess water at hydrogel surface by moistened filter paper. The swelling ratio (SR) for each hydrogel was calculated by the following equation: 7



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

SR = (Wt–Wd)/Wd

Page 8 of 35

(1)

where Wd is the weight of dried sample and Wt is the weight of the swelling sample at time t. For swelling ratio, and equilibrium swelling ratio see eq. 1 and eq. 2, respectively, in ref. 8. According to this protocol, temperature dependence, deswelling and reswelling kinetics were evaluated. Temperature dependence test was monitored by recording equilibrium swelling ratio (ESR) of the hydrogels as a function of temperature, in the range of 25 – 37 °C. Deswelling process was determined by transferring equilibrium swollen hydrogels at 25 °C to deionized water of 37 °C, while the reswelling process was the other way around (transferring the samples from 37 °C to 25 °C in deionized water). The weights at different time points were recorded. All the measurements were done in triplicate. 2.4 Cell culture Human lung adenocarcinoma epithelial cells (A549) and HEK 293T cells were used to study the cytotoxicity. The cells were cultured in tissue culture polystyrene (TCPS) dishes under 5% CO2 atmosphere at 37 °C and harvested after treating with 0.25% trypsin-EDTA solution. The culture medium used in this work was the Dulbecco's Modified Eagle's Medium (DMEM), supplemented with 10% fetal bovine serum (FBS), 2 mg/mL sodium bicarbonate and 100 µg/mL penicillin/streptomycin. Cytotoxicity of the hydrogels was evaluated according to MTT assay. Briefly, the hydrogels were sterilized with 70% ethanol and then washed with sterile PBS. After that, the sterilized gels were immersed in DMEM to get extracting liquid. Meanwhile, 8


Page 9 of 35

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


A549 cells and HEK 293T cells were cultured in a 96-well cell culture plate for 24 h. The cells were then divided into 6 groups and the culture medium was replaced by aforementioned hydrogel extracting liquid, while the negative control was DMEM medium without the extract of hydrogels. The cells were incubated sequentially for 24 h. Then each well was added by 50 µL of MTT solution and incubated for another 4 h. Finally, 150 µL of dimethyl sulfoxide (DMSO) was added to each well to form MTT formazan solution. The optical density was measured by a microplate reader at 570 nm. A further cell adhesion study was conducted as well. Sterilized hydrogel films (SPD4) were placed in cell culture dishes with DMEM and incubated at 37 °C for 2 days. Then the gels were seeded with A549 cells at a density of 1×104 cells/cm2, incubated in 5% CO2 atmosphere at 37 °C. The cell-culture process was lasting for 2 days and the culture medium was refreshed every day. Ultimately, the cells were stained with fluorescein diacetate (5µg/mL) and cell adhesion images were obtained using a phase-contrast optical microscope (OLYMPUS, Japan). 2.5 Drug delivery Diclofenac sodium (DS) was chosen as a model drug since its carboxyl group could form hydrogen bond with tertiary amide group of DEA

42

. To load DS into the

hydrogels, 40 mg xerogel was immersed in 20 mL DS solution (1 mg/mL) for 24 h. Prior to drug release procedure, the drug-loaded hydrogel was washed with 2 mL deionized water to remove the drug on its surface. The loading amount (mDS) was calculated through the followed equation： 9



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

mDS = c0v0 – c1v1

Page 10 of 35

(2)

where c0 and v0 were original concentration (1 mg/mL) and volume (20 mL) of DS solution. c1 and v1 were the concentration and volume of DS solution after drug loading and washing. The concentrations were detected by a UV-Vis spectroscopy at 275 nm with a standard calibration curve (Supporting information). For in vitro release procedure, drug-loaded hydrogels were immersed in 20 mL PBS buffer (pH = 7.4) at 37 °C with shaking (150 rpm). At determined intervals, 2 mL released medium was taken out and 2 mL fresh PBS buffer was added to keep the volume. The cumulative percent drug release (DS%) was calculated as follows: % =

∑

(3)

where V0 is the volume of release medium (20 mL), Cn represents the concentration of release medium after nth taken. For cumulative release, %, see eq. 5, in the same ref. 8, and eq. 6 in ref. 42.

3. Results and discussion 3.1 Formation of semi-IPN hydrogel The fabrication of semi-IPN hydrogels consisted of salecan and PDE, crosslinked with BIS, was conducted as shown in Figure 1. The semi-IPN system was composed of linear salecan chains physically entangled with crosslinked PDE networks. Each polymer could retain its inherent properties because there is no chemical binding between these two components 44. In this study, monomer N,N-diethylacrylamide was crosslinked with BIS through free-radical polymerization, in the presence of salecan solution. The reaction was initiated by sulfate free radicals produced by APS via a 10


Page 11 of 35

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


redox process, which can be accelerated by TEMED 45. The obtained hydrogels were differentiating by salecan content.

Figure 1 Schematic representation of preparation of salecan/PDE semi-IPNs hydrogel and

structures

of

chemicals:

salecan,

N,N-diethylacrylamide,

N,N'-Methylenebis(acrylamide), Diclofenac sodium.

3.2 Characterization of salecan/PDE semi-IPN hydrogels The FTIR spectra of salecan, crosslinked PDE and semi-IPNs were presented in Figure 2 (a). In the case of salecan, the absorption band at 3281 cm−1 corresponds to -OH stretching vibration. The typical peak at 1065 cm−1 is ascribed to C-O-C stretching vibration of glucopyranose ring. The two small peaks at 893 cm−1 and 814 cm−1 indicate the D-glucopyranose in salecan contains β-configuration and a little amount of α-glucopyranose 30. In the spectrum of crosslinked PDE, the peaks at 2971 cm-1 and 2933 cm-1 correspond to C−H stretching vibration of −CH3 and −CH2− in PDE side groups. The 11



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

characteristic peak found at 1624 cm-1 is assigned to C=O stretching vibrations (amide I). The peaks in the range of 1500-1350 cm-1 were associated with C−H deformation bands 46. The spectrum of salecan/PDE semi-IPNs shows a mixture of salecan and PDE signals, similar with crosslinked PDE but with some differences consisting in the intensity of the peaks. The peaks of salecan were obviously weakened but the peak at 1071 cm-1 was enhanced, indicating the presence of salecan. The peak at 1626 cm–1, shift from 1624 cm-1, is the characteristic absorption band of C=O in PDE. The absorption bands of −CH3 and −CH2− are observed as well: 2971 cm-1 and 2932 cm-1 are resulting from C–H stretching vibrations and 1447 cm-1 and 1380 cm-1 are corresponding to symmetrical C–H bending

47

. In short, the ATR-FTIR data clearly

show that the target semi-IPN hydrogel was synthesized successfully.

12


Page 12 of 35

Page 13 of 35

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 (a) FTIR spectra of salecan, PDE and salecan/PDE semi-IPNs; (b) 1H-NMR spectra of salecan/PDE (SPD4) hydrogel at different temperatures. 1

H-NMR tests were also carried out to characterize the formulations of the

hydrogels and the spectra of salecan/PDE and pure PDE hydrogel were shown in Figure S2 (Supporting Information). In the spectrum of pure PDE, peak 1 (the peaks were numbered from right to left) at 1.13 ppm was corresponding to the methyl group –CH3 present on the ethyl group; peak 2 at 1.72 ppm was the protons of –CH2– group on the backbone; peak 3 at 2.63 ppm was the proton of –CH– located on the backbone; peak 4 at 3.33 ppm was corresponding to the –CH2– group present on the ethyl group 48

. In addition, the integration ratio of peaks 1, 2, 3, and 4 approximate 6:2:1:4 13



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

confirms the structure of PDE. The peaks corresponding to BIS did not show up in the spectrum because they were overlapped by the peaks of water and PDE which has similar chemical shifts 49. The peak of NH was also disappeared because this type of protons could exchange with D2O easily. Besides, the amount of BIS used in this work was too low to be detected when compared to PDE. In the spectra of salecan/PDE hydrogels, only peaks corresponding to the protons of PDE were observed. The reasons for this phenomenon are presented below: 1. Main peaks corresponding to salecan have a similar chemical shift with D2O at 4.8 ppm, which could be overlapped with each other

30

. Nonetheless, small peaks were

found at 4.89 and 4.69 ppm, indicating the presence of salecan. 2. Signals corresponding to the protons of salecan are not so significant when compared to those of PDE, because the content of salecan is much lower. Similar results could be found in the literature 50. Variable-temperature 1H-NMR spectra obtained at different temperatures (25, 28, 30, 32, 34, and 37 °C) were used to study the structural changes resulting from the temperature (Figure 2 (b)). It is well known that PDE gel (or chains) in water exhibits a macroscopic volume phase (or coil-to-globule) transition at a temperature around 30-32 °C

41, 51

. The spectra of salecan/PDE semi-IPNs shows that the peaks become

broader with the rise of temperature, and even cannot be detected at 37 °C. The same trend was found in the spectra of PDE (Figure S3, Supporting Information). The results suggested that there is a reduction in molecular mobility of the polymer 14


Page 14 of 35

Page 15 of 35

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


segments when temperature exceed the lower critical solution temperature (LCST) of PDE. The mechanical properties were investigated by rheology tests. Frequency-sweep test was used to measure the values of G’ (storage modulus) and G’’ (loss modulus), which represents viscoelastic properties of the hydrogel. Generally, G’>G’’ demonstrates elastic behavior while G’’>G’ suggests viscous behavior

52

. Figure S4

shows the G’ and G’’ of hydrogels as a function of frequency at 25 °C. In the frequency range of 0.1-10 Hz, the values of G’ are greater than G’’ and have no dependence on the frequency which indicates the salecan/PDE semi-IPNs are solid-elastic materials. Furthermore, the G’ values of these hydrogels decreased with the increasing of salecan content. As shown in Figure S4, the storage modulus reduced from 300 Pa for PDE to 70 Pa for SPD5 by adding salecan. With higher salecan content, the swelling ratio of the hydrogel was enhanced (discussed in detail below) which means more free water in the network. It was reported water in hydrogels could act as a plasticizer that increase flexibility of the polymer chains and reduce the storage modulus

50

. This result clearly shows salecan plays an important

role in the hydrogel network strength formation. Rheological data suggests that mechanical characteristics of the hydrogel are remarkably related to salecan content which can be tailored conveniently. The SEM images presented in Figure 3 exhibit the morphology of lyophilized hydrogels. All the samples showed a sponge-like porous structure and the pores are open ended with continuous boundaries. The average pore-sizes were listed as follows: 15



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

112 ± 6 µm for PDE, 158 ± 11 µm for SPD1, 209 ± 10 µm for SPD2, 234 ± 6 µm for SPD3 and 344 ± 9 µm for SPD4. The pore-sizes enlarged with the rise of salecan content. In other words, higher amount of salecan led to larger pores. This phenomenon was related to the swelling behavior (discussed in detail below) of the hydrogel. Because the salecan/PDE hydrogels possess higher swelling ratios, larger ice crystal aggregates were formed and eventually sublimated to generate pores during the lyophilization. Thus, the average pore-sizes for salecan based hydrogels were enhanced in comparison to the neat PDE gel.

Figure 3 (a) Photograph of the prepared hydrogels at room temperature and 37 °C; (b) SEM micrographs of the morphology of freeze-dried hydrogels: (b) PDE, (c) SPD1, (d) SPD2, (e) SPD3, (f) SPD4.

3.3 Swelling properties The ability of absorbing and retaining water, evaluated as the swelling ratio, is one 16


Page 16 of 35

Page 17 of 35

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


of the most important features for hydrogels 53. The swelling kinetics of salecan/PDE hydrogels in deionized water at 25 °C are depicted in Figure 4 (a). As Figure 4 (a) shows, the maximal SR of the hydrogels was attained in 48 h, and the time was shortened by introduction of salecan. For example, SPD4 (with the highest salecan content) reached equilibrium in less than 24 h, which was much faster than neat PDE hydrogel. The maximum swelling ratios of salecan based hydrogels were found higher than that of PDE hydrogel. These swelling phenomenon can be explained by the high hydrophilicity of salecan chains. As published in previous work

54

, the extent of

swelling is determined by the hydrophilicity and crosslinking density of the system. In this work, the crosslinking density was constant because the amounts of DEA and BIS were the same for each hydrogel. Thus, the explanation for the swelling behavior described above could be that the whole hydrophilicity of the semi-IPNs was enhanced by the entanglement of salecan chains. In conclusion, the ability of absorbing and retaining water can be improved by the addition of salecan, due to its high hydrophilicity, without decreasing the crosslinking density. The thermo-sensitivity of salecan/PDE semi-IPNs, which is essential for thermal responsive applications, was investigated by measuring equilibrium swelling ratios (ESRs) of the hydrogels as a function of temperature. The ESRs changes with the temperature were depicted in Figure 4 (b). At 25 °C, the SPD5 gel swelled at a higher level than pure PDE gel due to the higher hydrophilicity of salecan. As the temperature was increased, the ESRs of all samples declined continuously. The dehydration of hydrogels was due to the collapse of the hydrophilic segments of PDE 17



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

when temperature is around its phase transition temperature (about 31 °C) result match the presentation in literature

41

Page 18 of 35

55

. The

that the macroscopic volume phase

transition of PDE hydrogels in water occurs in a broad temperature interval (∼15 °C). When the temperature reached 37 °C, all the hydrogels showed low ESRs without obvious difference, indicating they collapsed to a similar structure. The results demonstrate salecan/PDE hydrogels are thermo-sensitive as pure PDE gels. The deswelling kinetics of the hydrogels at 37 °C is presented in Figure 4 (c). The deswelling process was fast that all hydrogels were dehydrated within 15 min. It is interesting that the deswelling curves of salecan/PDE semi-IPNs are beneath that of pure PDE hydrogel, suggesting that the response rate can be improved by incorporating salecan into the networks. This observation indicates that salecan/PDE hydrogels possess much less stability of water retention than that of conventional PDE hydrogel

56

. The formation of semi-IPNs structures by introducing hydrophilic

polymers to enhance deswelling has been described before 57. In this work, semi-IPNs were formed by interpenetrating hydrophilic salecan chains into PDE networks, which could act as water-releasing channels during deswelling process. Obviously, more salecan chains means more water-releasing channels. Therefore, the deswelling rate increases as salecan content increases. To demonstrate the reversible swelling/deswelling property of these hydrogels, reswelling test was performed. The reswelling degree was depicted in Figure 4 (d) as a function of time. At 25 °C, the collapsed gels became hydrophilic and began to absorb water again

58

. As shown in Figure 4 (d), salecan-riched samples exhibited 18


Page 19 of 35

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


faster reswelling rate than the neat PDE gel. For example, SPD4 recovered to equilibrium swollen state within 24 h while PDE gel needed 48h. This suggested that salecan made a quicker reversible swelling/deswelling property for the hydrogels, which might be more favorable for certain applications.

Figure 4 Swelling behavior of the hydrogels: (a) Swelling kinetic curves in deionized water at 25 °C; (b) Equilibrium swelling ratio values in deionized water at 25 – 37 °C; (c) Deswelling kinetic curves in deionized water at 37 °C; (d) Reswelling kinetic curves in deionized water at 25 °C.

3.4 Cell compatibility Cytotoxicity of hydrogels was determined by MTT assay and the results are shown 19



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

in Figure 5 (a). A549 and HEK 293T cells were cultured on tissue culture polystyrene (TCPS) dishes. Results show that the activities of cells cultured with hydrogel extraction medium were comparable with those of DMEM medium. In other words, there was no significant difference in cell activity between salecan/PDE hydrogels and the negative control, indicating non-cytotoxicity of salecan/PDE semi-IPNs. Cell adhesion property is also important to a variety of biomedical applications. Figure 5 (b) and (c) shows the fluorescence images of A549 cells cultured on tissue culture polystyrene (TCPS) dishes and the hydrogels surface after 2 days. A large number of living cells were observed and the cells exhibited bipolar and flattened morphology, similar to that of cultured on TCPS dishes as the negative control. This further demonstrated the cell compatibility of these hydrogels for biomedical applications.

Figure 5 (a) (a) Cell viability of A549 cells and HEK 293T cells after treatment with hydrogel extracts; Phase-contrast micrographs (100×) of: (b) and (c) Fluorescence images of A549 cells cultured on the tissue culture polystyrene (TCPS) dishes and SPD4 hydrogel surface after 2 days.

20


Page 20 of 35

Page 21 of 35

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


3.5 Drug delivery Figure 6 (a) shows the drug loading amount per milligram of hydrogel. As shown in Figure 6 (a), SPD4 exhibit the highest loading efficiency of 58.9 µg DS/mg hydrogel while the pure PDE showed a loading efficiency of 25 µg DS/mg hydrogel. The loading efficiency increased with the increase of salecan content. It seems that the loading efficiency is associate with the swelling ratio talked above. The trend of loading efficiency is the same as that of swelling ratio for these hydrogels. Because of the same concentration of drug solution for loading, the hydrogel with stronger swelling ability can absorb more drug solution. As a result, the loading efficiency improved with the increase of salecan content. The release profiles of DS from different hydrogels at 37 °C are depicted in Figure 6 (b). SPD4 showed the fasted release rate among these hydrogels that it released more than 70 % of loaded drugs in half a day. The fast release rate was contributed to the fast response rate of salecan-based hydrogel as described above. As most of DS molecules were dissolved in the solution, the swelling response rate can be a predominant factor for the releasing of water soluble drugs. Thus, salecan chains accelerated the thermo-response rate first and the drug release rate further. On the other hand, the larger pores of hydrogel could lead to a faster diffusion of drug molecules. Besides that, we found the percentage cumulative DS release was also salecan dependent (Figure 6(c)). The percentage cumulative DS release for SPD4, SPD3, SPD2, SPD1 and PDE were 83%, 73%, 67%, 60% and 50% respectively. This can be explained by swelling property as well. The more water loss at 37 °C, the more 21



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

drug solution could be squeezed out of the hydrogel. This is important for drug delivery system, especially from the perspective of reducing cost. Because drug not loaded can be recycled for loading into other device, but drug not released is forever lost 9. Therefore, these results indicate salecan/PDE hydrogels is a good candidate for drug delivery system. The release profiles of DS in the temperature changed systems are depicted in Figure 6 (d). As Figure 6 (d) shows, the release rate of DS from PDE and SPD4 at 25 °C was very small in the first two hours. The release in such a temperature is mainly attributed to the physical diffusion of DS molecules. Changing the release environment to 37 °C, there was an initial rapid release (up to about 35% for PDE and 70% for SPD4) followed by a slow release. Finally, the cumulative release up to 60% in the case of PDE and 90% in the case of SPD4 after 24 h.

22


Page 22 of 35

Page 23 of 35

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 6 (a) Loading efficiency of the hydrogels; (b) Cumulative DS release profiles of hydrogels with different salecan content at 37 °C; (c) Cumulative DS release amount after 3 days; (d) Cumulative DS release profiles of hydrogels at 25 °C and 37 °C.

Drug denaturation may take place during the preparation, storage and release periods. It is important to compare the activity of released DS with that of pristine DS. Figure S6 shows the UV–vis absorption spectra of pristine and released DS. Both spectra showed a maximum absorption at 275-276 nm and no new peaks appeared. The results indicate DS was released in its original form and no detectable impurities were produced by this system. Consequently, DS kept its structure during loading and 23



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 24 of 35

releasing periods, suggesting our strategy of incorporating DS was effective. Similar method was used in other literature 59,60. 4. Conclusion In this paper, we report a novel drug delivery system - thermo-responsive hydrogels fabricated

by

a

polysaccharide

of

salecan

and

a

polymer network

of

poly(N,N-diethylacrylamide). The hydrogels were thermo-responsive, solid-elastic, macro-porous and cell compatible. Moreover, the porosity, mechanical strength and water content can be tuned by varying the content of salecan. The thermo-sensitive property was confirmed by both NMR spectrum and swelling ratio as a function of temperature.

Specifically,

we

explored

the

possibilities

of

salecan/poly(N,N-diethylacrylamide) hydrogels as anionic drug delivery matrices using diclofenac sodium (DS) as a model drug. The DS molecules were absorbed into the hydrogel at 25 °C and the loading efficiency increased with the increasing of salecan content. For drug release profiles, hydrogels with bigger pores possessed a higher cumulative percent drug release. Moreover, the cumulative percent drug release (DS%) in PBS (pH = 7.4) was increased with the increase of temperature from 25 °C (below the VPTT) up to 37 °C (above the VPTT). The ability of these hydrogels to load and release anionic drugs upon changing the temperature pave the way for their application of novel controlled drug delivery systems.

Supporting Information Weight percentage of hydrogel samples; Standard calibration curve of Diclofenac 24


Page 25 of 35

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


sodium (DS) solution; 1H-NMR spectra of salecan/PDE and pure PDE hydrogel; 1H-NMR spectra of PDE hydrogel at different temperatures; The storage modulus) and loss modulus of hydrogels as a function of frequency at 25 °C; The structure of salecan; UV–vis absorption spectra of pristine and released DS. This material is available free of charge via the Internet at http://pubs.acs.org. Notes The authors declare no competing financial interest. Acknowledgements This work was supported by National Natural Science Foundation of China under the Grant 51573078 and Priority Academic Program Development of Jiangsu Higher Education Institutions.

References 1.

Ladegaard Skov, A. Materials science: Like cartilage, but simpler. Nature 2015,

517, 25-6. 2.

Spoljaric, S.; Salminen, A.; Luong, N. D.; Seppälä, J. Stable, self-healing

hydrogels from nanofibrillated cellulose, poly(vinyl alcohol) and borax via reversible crosslinking. European Polymer Journal 2014, 56, 105-117. 3.

Memic, A.; Alhadrami, H. A.; Hussain, M. A.; Aldhahri, M.; Al Nowaiser, F.;

Al-Hazmi, F.; Oklu, R.; Khademhosseini, A. Hydrogels 2.0: improved properties with nanomaterial composites for biomedical applications. Biomedical materials 2015, 11, 014104. 25



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

4.

Wu, J.; Ding, Q.; Dutta, A.; Wang, Y.; Huang, Y. H.; Weng, H.; Tang, L.; Hong, Y.

An injectable extracellular matrix derived hydrogel for meniscus repair and regeneration. Acta biomaterialia 2015, 16, 49-59. 5.

Liu, Z. Q.; Wei, Z.; Zhu, X. L.; Huang, G. Y.; Xu, F.; Yang, J. H.; Osada, Y.;

Zrinyi, M.; Li, J. H.; Chen, Y. M. Dextran-based hydrogel formed by thiol-Michael addition reaction for 3D cell encapsulation. Colloids and surfaces. B, Biointerfaces 2015, 128C, 140-148. 6.

Jiang, Y.; Chen, J.; Deng, C.; Suuronen, E. J.; Zhong, Z. Click hydrogels,

microgels and nanogels: Emerging platforms for drug delivery and tissue engineering.

Biomaterials 2014, 35, 4969-4985. 7.

Chen, Y. Y.; Wu, H. C.; Sun, J. S.; Dong, G. C.; Wang, T. W. Injectable and

thermoresponsive self-assembled nanocomposite hydrogel for long-term anticancer drug delivery. Langmuir : the ACS journal of surfaces and colloids 2013, 29, 3721-9. 8. Qi, X. L.; Wei, W.; Li, J. J.; Liu, Y. C.; Hu, X. Y.; Zhang, J. F.; Bi, L. R.; Dong, W. Fabrication and Characterization of a Novel Anticancer Drug Delivery System: Salecan/Poly(methacrylic acid) Semi-interpenetrating Polymer Network Hydrogel.

Acs Biomater-Sci Eng 2015, 1, 1287-1299. 9.

Koetting, M. C.; Guido, J. F.; Gupta, M.; Zhang, A.; Peppas, N. A. pH-responsive

and enzymatically-responsive hydrogel microparticles for the oral delivery of therapeutic proteins: Effects of protein size, crosslinking density, and hydrogel degradation on protein delivery. Journal of controlled release : official journal of the

Controlled Release Society 2016, 221, 18-25. 26


Page 26 of 35

Page 27 of 35

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


10. Ron, E. S.; Bromberg, L. E. Temperature-responsive gels and thermogelling polymer matrices for protein and peptide delivery. Advanced drug delivery reviews 1998, 31, 197-221. 11. Yan, H.; Tsujii, K. Potential application of poly(N-isopropylacrylamide) gel containing polymeric micelles to drug delivery systems. Colloids and surfaces. B,

Biointerfaces 2005, 46, 142-6. 12. Nie, L.; Zhang, G.; Hou, R.; Xu, H.; Li, Y.; Fu, J. Controllable promotion of chondrocyte adhesion and growth on PVA hydrogels by controlled release of TGF-beta1 from porous PLGA microspheres. Colloids and surfaces. B, Biointerfaces 2015, 125, 51-7. 13. Tseng, T. C.; Tao, L.; Hsieh, F. Y.; Wei, Y.; Chiu, I. M.; Hsu, S. H. An Injectable, Self-Healing Hydrogel to Repair the Central Nervous System. Advanced materials 2015, 27, 3518-24. 14. Wei, J.; Cai, J.; Li, Y.; Wu, B.; Gong, X.; Ngai, T. Investigation of cell behaviors on thermo-responsive PNIPAM microgel films. Colloids and surfaces. B,

Biointerfaces 2015, 132, 202-7. 15. Wieduwild, R.; Krishnan, S.; Chwalek, K.; Boden, A.; Nowak, M.; Drechsel, D.; Werner, C.; Zhang, Y. Noncovalent hydrogel beads as microcarriers for cell culture.

Angewandte Chemie 2015, 54, 3962-6. 16. Selvam, S.; Pithapuram, M. V.; Victor, S. P.; Muthu, J. Injectable in situ forming xylitol-PEG-based hydrogels for cell encapsulation and delivery. Colloids and

surfaces. B, Biointerfaces 2015, 126, 35-43. 27



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

17. Nakagawa, Y.; Amano, Y.; Nakasako, S.; Ohta, S.; Ito, T. Biocompatible Star Block Copolymer Hydrogel Cross-linked with Calcium Ions. ACS Biomaterials

Science & Engineering 2015, 1, 914-918. 18. Dragan, E. S. Design and applications of interpenetrating polymer network hydrogels. A review. Chemical Engineering Journal 2014, 243, 572-590. 19. Gupta, N.; Srivastava, A. K. Interpenetrating Polymer Networks: A Review on Synthesis and Properties. Polymer International 1994, 35, 109-118. 20. Wang, T.; Liu, D.; Lian, C.; Zheng, S.; Liu, X.; Wang, C.; Tong, Z. Rapid cell sheet detachment from alginate semi-interpenetrating nanocomposite hydrogels of PNIPAm and hectorite clay. Reactive and Functional Polymers 2011, 71, 447-454. 21. Liu, Y.-Y.; Shao, Y.-H.; Jian, L. Preparation, properties and controlled release behaviors of pH-induced thermosensitive amphiphilic gels. Biomaterials 2006, 27, 4016-4024. 22. Loessner, D.; Meinert, C.; Kaemmerer, E.; Martine, L. C.; Yue, K.; Levett, P. A.; Klein, T. J.; Melchels, F. P.; Khademhosseini, A.; Hutmacher, D. W. Functionalization, preparation and use of cell-laden gelatin methacryloyl-based hydrogels as modular tissue culture platforms. Nature protocols 2016, 11, 727-46. 23. Dragan, E. S.; Cocarta, A. I.; Gierszewska, M. Designing novel macroporous composite hydrogels based on methacrylic acid copolymers and chitosan and in vitro assessment of lysozyme controlled delivery. Colloids and Surfaces B: Biointerfaces 2016, 139, 33-41. 24. Hu, X. Y.; Feng, L. D.; Xie, A. M.; Wei, W.; Wang, S. M.; Zhang, J. F.; Dong, W. 28


Page 28 of 35

Page 29 of 35

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


Synthesis and characterization of a novel hydrogel: salecan/polyacrylamide semi-IPN hydrogel with a desirable pore structure. Journal of Materials Chemistry B 2014, 2, 3646-3658. 25. Matricardi, P.; Di Meo, C.; Coviello, T.; Hennink, W. E.; Alhaique, F. Interpenetrating Polymer Networks polysaccharide hydrogels for drug delivery and tissue engineering. Advanced drug delivery reviews 2013, 65, 1172-87. 26. Zhou, M.; Wang, Z.; Chen, J.; Zhan, Y.; Wang, T.; Xia, L.; Wang, S.; Hua, Z.; Zhang, J. Supplementation of the diet with Salecan attenuates the symptoms of colitis induced by dextran sulphate sodium in mice. Br J Nutr 2014, 111, 1822-9. 27. Zhou, M.; Pu, C.; Xia, L.; Yu, X.; Zhu, B.; Cheng, R.; Xu, L.; Zhang, J. Salecan diet increases short chain fatty acids and enriches beneficial microbiota in the mouse cecum. Carbohydr Polym 2014, 102, 772-9. 28. Zhou, M.; Jia, P.; Chen, J.; Xiu, A.; Zhao, Y.; Zhan, Y.; Chen, P.; Zhang, J. Laxative effects of Salecan on normal and two models of experimental constipated mice. BMC Gastroenterology 2013, 13, 52-57. 29. Xiu, A.; Zhan, Y.; Zhou, M.; Zhu, B.; Wang, S.; Jia, A.; Dong, W.; Cai, C.; Zhang, J. Results of a 90-day safety assessment study in mice fed a glucan produced by Agrobacterium sp. ZX09. Food and chemical toxicology : an international journal

published for the British Industrial Biological Research Association 2011, 49, 2377-84. 30. Xiu, A. H.; Kong, Y.; Zhou, M. Y.; Zhu, B.; Wang, S. M.; Zhang, J. F. The chemical and digestive properties of a soluble glucan from Agrobacterium sp ZX09. 29



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 30 of 35

Carbohydrate Polymers 2010, 82, 623-628. 31. Collins, M. N.; Birkinshaw, C. Hyaluronic acid based scaffolds for tissue engineering--a review. Carbohydr Polym 2013, 92, 1262-79. 32. Zhao, S.; Zhou, F.; Li, L.; Cao, M.; Zuo, D.; Liu, H. Removal of anionic dyes from aqueous solutions by adsorption of chitosan-based semi-IPN hydrogel composites. Composites Part B: Engineering 2012, 43, 1570-1578. 33. Bhattacharya, S. S.; Mishra, A.; Pal, D.; Ghosh, A. K.; Ghosh, A.; Banerjee, S.; Sen, K. K. Synthesis and Characterization of Poly(acrylic acid)/Poly(vinyl alcohol)-xanthan Gum Interpenetrating Network (IPN) Superabsorbent Polymeric Composites. Polymer-Plastics Technology and Engineering 2012, 51, 878-884. 34. Dalafu, H.; Chua, M. T.; Chakraborty, S. Development of kappa-Carrageenan Poly(acrylic acid) Interpenetrating Network Hydrogel as Wound Dressing Patch.

Biomaterials 2010, 1054, 125-135. 35. Hou, R.; Nie, L.; Du, G.; Xiong, X.; Fu, J. Natural polysaccharides promote chondrocyte adhesion and proliferation on magnetic nanoparticle/PVA composite hydrogels. Colloids and surfaces. B, Biointerfaces 2015, 132, 146-54. 36. Hu, X. Y.; Wei, W.; Qi, X. L.; Yu, H.; Feng, L. D.; Li, J. J.; Wang, S. M.; Zhang, J. F.;

Dong,

W.

Preparation

and

characterization

of

a

novel

pH-sensitive

Salecan-g-poly(acrylic acid) hydrogel for controlled release of doxorubicin. Journal

of Materials Chemistry B 2015, 3, 2685-2697. 37. Wei, W.; Qi, X.; Liu, Y.; Li, J.; Hu, X.; Zuo, G.; Zhang, J.; Dong, W. Synthesis and characterization of a novel pH-thermo dual responsive hydrogel based on salecan 30


Page 31 of 35

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 poly(N,N-diethylacrylamide-co-methacrylic acid). Colloids and surfaces. B,

Biointerfaces 2015, 136, 1182-92. 38. Hu, X.; Feng, L.; Wei, W.; Xie, A.; Wang, S.; Zhang, J.; Dong, W. Synthesis and characterization

of

a

novel

semi-IPN

hydrogel

based

on

Salecan

and

poly(N,N-dimethylacrylamide-co-2-hydroxyethyl methacrylate). Carbohydr Polym 2014, 105, 135-44. 39. Tajima, H.; Yoshida, Y.; Yamagiwa, K. Experimental study of swelling and shrinking kinetics of spherical poly(N,N-diethylacrylamide) gel with continuous phase transition. Polymer 2011, 52, 732-738. 40. Hiratani, H.; Alvarez-Lorenzo, C. Timolol uptake and release by imprinted soft contact lenses made of N,N-diethylacrylamide and methacrylic acid. Journal of

Controlled Release 2002, 83, 223-230. 41. Liu, B.; Wang, J.; Ru, G.; Liu, C.; Feng, J. Phase Transition and Preferential Alcohol Adsorption of Poly(N,N-diethylacrylamide) Gel in Water/Alcohol Mixtures.

Macromolecules 2015, 48, 1126-1133. 42. Dragan, E. S.; Cocarta, A. I. Smart Macroporous IPN Hydrogels Responsive to pH, Temperature, and Ionic Strength: Synthesis, Characterization, and Evaluation of Controlled Release of Drugs. ACS Appl Mater Interfaces 2016, 8, 12018-30. 43. Wei, W.; Hu, X.; Qi, X.; Yu, H.; Liu, Y.; Li, J.; Zhang, J.; Dong, W. A novel thermo-responsive hydrogel based on salecan and poly(N-isopropylacrylamide): synthesis and characterization. Colloids and surfaces. B, Biointerfaces 2015, 125, 1-11. 31



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 32 of 35

44. Dragan, E. S.; Apopei, D. F. Multiresponsive macroporous semi-IPN composite hydrogels based on native or anionically modified potato starch. Carbohydr Polym 2013, 92, 23-32. 45. Guilherme, M. R.; da Silva, R.; Rubira, A. F.; Geuskens, G.; Muniz, E. C. Thermo-sensitive hydrogels membranes from PAAm networks and entangled PNIPAAm: effect of temperature, cross-linking and PNIPAAm contents on the water uptake and permeability. Reactive and Functional Polymers 2004, 61, 233-243. 46. Maeda,

Y.;

Nakamura,

T.;

Ikeda,

I.

Change

in

solvation

of

poly(N,N-diethylacrylamide) during phase transition in aqueous solutions as observed by IR spectroscopy. Macromolecules 2002, 35, 10172-10177. 47. Chen, J.; Liu, M.; Liu, H.; Ma, L.; Gao, C.; Zhu, S.; Zhang, S. Synthesis and properties

of

thermo-

and

pH-sensitive

poly(diallyldimethylammonium

chloride)/poly(N,N-diethylacrylamide) semi-IPN hydrogel. Chemical Engineering

Journal 2010, 159, 247-256. 48. Idziak, I.; Avoce, D.; Lessard, D.; Gravel, D.; Zhu, X. X. Thermosensitivity of Aqueous Solutions of Poly(N,N-diethylacrylamide). Macromolecules 1999, 32, 1260-1263. 49. Stile, R. A.; Burghardt, W. R.; Healy, K. E. Synthesis and Characterization of Injectable Poly(N-isopropylacrylamide)-Based Hydrogels That Support Tissue Formation in Vitro. Macromolecules 1999, 32, 7370-7379. 50. Coronado, R.; Pekerar, S.; Lorenzo, A. T.; Sabino, M. A. Characterization of thermo-sensitive hydrogels based on poly(N-isopropylacrylamide)/hyaluronic acid. 32


Page 33 of 35

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


Polymer Bulletin 2011, 67, 101-124. 51. Ngadaonye, J. I.; Geever, L. M.; Cloonan, M. O.; Higginbotham, C. L. Photopolymerised thermo-responsive poly(N,N-diethylacrylamide)-based copolymer hydrogels for potential drug delivery applications. Journal of Polymer Research 2012, 19. 52. Almeida, N.; Mueller, A.; Hirschi, S.; Rakesh, L. Rheological studies of polysaccharides for skin scaffolds. J. Biomed. Mater. Res., Part A 2014, 102A, 1510-1517. 53. Rossi, F.; Ferrari, R.; Castiglione, F.; Mele, A.; Perale, G.; Moscatelli, D. Polymer hydrogel functionalized with biodegradable nanoparticles as composite system for controlled drug delivery. Nanotechnology 2015, 26, 015602. 54. Lopes, C. M. A.; Felisberti, M. I. Mechanical behaviour and biocompatibility of poly(1-vinyl-2-pyrrolidinone)-gelatin IPN hydrogels. Biomaterials 2003, 24, 1279-84. 55. Zhang, N.; Liu, M.; Shen, Y.; Chen, J.; Dai, L.; Gao, C. Preparation, properties, and drug release of thermo- and pH-sensitive poly((2-dimethylamino)ethyl methacrylate)/poly(N,N-diethylacrylamide) semi-IPN hydrogels. J. Mater. Sci. 2011, 46, 1523-1534. 56. Li, Z.; Shen, J.; Ma, H.; Lu, X.; Shi, M.; Li, N.; Ye, M. Preparation and characterization

of

pH-

and

temperature-responsive

hydrogels

with

surface-functionalized graphene oxide as the crosslinker. Soft Matter 2012, 8, 3139-3145. 57. Zhang, J.-T.; Bhat, R.; Jandt, K. D. Temperature-sensitive PVA/PNIPAAm 33



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

semi-IPN hydrogels with enhanced responsive properties. Acta biomaterialia 2009, 5, 488-97. 58. Ngadaonye, J. I.; Geever, L. M.; Killion, J.; Higginbotham, C. L. Development of novel chitosan-poly(N,N-diethylacrylamide) IPN films for potential wound dressing and biomedical applications. Journal of Polymer Research 2013, 20. 59. Tian, G.; Zheng, X.; Zhang, X.; Yin, W.; Yu, J.; Wang, D.; Zhang, Z.; Yang, X.; Gu, Z.; Zhao, Y. TPGS-stabilized NaYbF4:Er upconversion nanoparticles for dual-modal fluorescent/CT imaging and anticancer drug delivery to overcome multi-drug resistance. Biomaterials 2015, 40, 107-116 60. Zhang, L.; Ma, Y.; Zhao, C.; Zhu, X.; Chen, R.; Yang, W. Synthesis of pH-responsive hydrogel thin films grafted on PCL substrates for protein delivery. J.

Mater. Chem. B 2015, 3, 7673-7681

Table of Contents Graphic Smart macro-porous salecan/poly(N,N-diethylacrylamide) semi-IPN hydrogel for anti-inflammatory drug delivery Wei Wei, Xiaoliang Qi, Junjian Li, Gancheng Zuo, Zuo, Wei Sheng, Jianfa Zhang, Wei Dong*

34


Page 34 of 35

Page 35 of 35

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


35


Poly(N,N-diethylacrylamide) Semi-IPN

Recommend Documents