A Novel Method for Preparing Poly(vinyl alcohol ... - ACS Publications

Subscriber access provided by TUFTS UNIV

Article

A novel method for preparing poly (vinyl alcohol) hydrogels : preparation, characterization, and application Shuaijiang Ma, Shiwei Wang, Qian Li, Yuting Leng, Lianhui Wang, and Guo-Hua Hu Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/acs.iecr.7b01812 • Publication Date (Web): 21 Jun 2017 Downloaded from http://pubs.acs.org on June 23, 2017

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.

Industrial & Engineering Chemistry Research 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 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

Industrial & Engineering Chemistry Research

A novel method for preparing poly (vinyl alcohol) hydrogels : preparation, characterization, and application Shuaijiang Maa, Shiwei Wanga*, Qian Lia*, Yuting lengb*, Lianhui Wangc, Guo-Hua Hud a. National Center for International Joint Research of Micro-Nano Molding Technology, School of Mechanics & Engineering Science, Zhengzhou University, Zhengzhou, 450001, China b. Key Laboratory of Chemical Biology and Organic Chemistry of Henan Province, College of Chemistry and Molecular Engineering, Zhengzhou University, Zhengzhou, 450001, China c. School of Biomedical Sciences, Huaqiao University, Xiamen, 361021, China. d. Laboratory of Reactions and Process Engineering (LRGP), CNRS-University of Lorraine, 1 rue Grandville, BP 20451, 54001 Nancy, France. Abstract：：This work provides a new method to prepare poly(vinyl alcohol) (PVA) hydrogel. Comparing with the traditional repeated freeze-thaw method, the physical crosslinking method were adopted to prepare a high strength hydrogel by one step. The morphology, melting and crystallization behaviours, and mechanical properties of the hydrogel were investigated. The hydrogels have a high water content and re-swelling rate, as well as a high melting temperature and mechanical strength. It also have a stable cross-linked structure in the temperature range of 20-65°C. The hydrogel fracture surface shows ductile and brittle fracture morphology. The protrusions in the hydrogel three-dimensional topography are more numerous and homogeneous when the solvent preparation ratio is 4-6. Based on the good plasticity of the hydrogels, tubular hydrogels with inner diameters of 1 to 6 mm are also prepared to widen their applications. Keywords：：Polyvinyl alcohol; Hydrogel; Mechanical properties; Morphology

1. Introduction Today cardiovascular and cerebrovascular diseases are the most important diseases threatening human health and life. Artificial vascular interventional therapy and vascular bypass surgery are now commonly used in clinical treatment.1 Vascular bypass surgery is often limited by the shortage of autologous vessels due to severe vascular stenosis, and many of such cases are unsuitable for stent implantation. With the development of tissue engineering, artificial blood *

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

Page 2 of 17

vessels have become a research hotspot, and related materials and preparation methods have been widely studied. Currently, transplantation of synthetic vascular materials such as polyesters and expanded polytetrafluoroethylene (ePTFE) have shown good results in large diameter blood vessels (diameter greater than 6 mm),2 with higher long-term potency after transplantation. However, in small diameter blood vessels (diameter less than 6 mm), transplantation has easily led to intimal hyperplasia, thrombosis, vascular stenosis, obstruction, etc.3 Electrospinning technology is often used in the preparation of tissue engineering products. Nano-fibre membranes have large specific surface areas that are beneficial to nutrient transport, and exchange between cells and effective cellular responses.4 However, the cells can only grow into the fibrous sublayers due to the compactness and longitudinal collapse shortage of the fibre membranes.5 Polyvinyl alcohol (PVA) is a water-soluble polymer which results from the hydrolysis of polyvinyl acetate and contains many polar hydroxyl groups on the molecular chain. As the molecular chain can easily form hydrogen bonds and has a symmetrical and regular structure, it exhibits good filmability, water solubility, emulsification and adhesion.6 PVA hydrogels can be used as artificial vascular material replacements based on their low toxicity, good biocompatibility,7-9 good mechanical properties,10 and high water content. Millonet al. demonstrated that the mechanical properties of the polyvinyl alcohol tubular structure were similar to those of the porcine aorta.11 In addition, polyvinyl alcohol hydrogels could match the mechanical properties of the vascular system.12,13 At the same time, researchers found that the addition of different polymers could improve the toughness, stiffness,14 biocompatibility,15,16 porosity and degradation properties of PVA gels,17 thereby widening the application fields of PVA gels. Physical crosslinking of PVA hydrogels is often prepared by a repeated freeze-thaw method that was first proposed by Peppas et al. in 1975 among numerous PVA gel preparation methods. 18,19

Compare with other methods to prepare the PVA gel, mixed solvent physical cross-linking method shows many advantages, such as no chemical cross-linking agents and less time consume. Compared with the traditional freezing-thawing method, the physical cross-linking gel has the advantages of simple molding process and higher gel preparation efficiency and gel strength. In this study, PVA is dissolved in a mixed solvent at high temperature. PVA gel is obtained without 2


Page 3 of 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


freezing by natural cooling of the mixed solvent to room temperature. In this way, the solvent can be removed by immersion in deionized water. Solution casting moulds with adjustable diameters are also designed to prepare PVA microtubule hydrogels to study the plasticity of the PVA gel. This paper will provide a simple process for the preparation of PVA hydrogels, which have a great potential for tissue engineering applications.

2. Experiments 2.1. Materials Polyvinyl alcohol (PVA, Chemical Pure, Tianjin Kermel Chemical Reagent Co., Ltd.) with an average molecular weight of 5.0×105 g/mol. Dimethyl sulfoxide (DMSO, Analytical Reagent, Tianjin Kermel Chemical Reagent Co., Ltd.). N,N-dimethyl formamide (DMF, Analytical Reagent, Tianjin Kermel Chemical Reagent Co., Ltd.). Deionized water (Prepared in laboratory) were used. 2.2. Preparation of PVA hydrogel Solutions of PVA(12%w/w) were prepared by dissolving PVA in mixed DMSO-DMF with a volume ratios of 2-8, 3-7, 4-6, and 5-5, respectively. The PVA solutions were placed in an oven at 130 °C for 3 h. After PVA was dissolved completely, the mixtures were stirred for 30 min to dissolve PVA evenly in the mixed solvent. Bubbles in the solutions were removed by ultrasonication. The resulting solutions were cast in dumbbell-type standard stretch-spline moulds and were cooled naturally to room temperature over 12 h. The specimens were immersed in deionized water to extract the solvents for 48 h, with the deionized water renewed every 12 h. The gel splines were used for the tensile test. 2.3. Mould design and preparation of gel tubes To verify the gel plasticity and provide the basis for its application in tissue engineering, microtubule moulds were designed as shown in Figure 1 to prepare microtubules with inner diameters below 6 mm. The mould comprised a mould body, a mould core and two concentric fixing device. The mould body had a cylindrical cavity, and its two ends were fitted with concentric fixing devices. One core end was connected to the concentric fixing device, and the other was fixed in the cylindrical cavity through the concentric fixing device coaxial with the cylindrical cavity. The inner diameter of the mould body was adjustable from 2 to 6 mm, and the outer diameter of the mandrel was adjustable from 1 to 5 mm. There is a step-like concentric 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 17

fixing device to ensure uniform wall thickness of the microtubule.

Figure 1. Moulds assembly

2.4. Characterization 2.4.1. Water content testing The PVA hydrogels were cast into wafers having a diameter of 20 mm and a thickness of approximately 1.4 mm. Three samples were prepared for each PVA hydrogel, and the mass of each sample was determined and recorded as M0. Then, the samples were placed in an oven at 50 °C and dried to a constant mass, noted as Mf. The water content of PVA gel recorded as Ww was calculated by equation 1,20

Ww =

M0 - Mf × 100% M0

(1)

2.4.2. Re-swelling degree testing PVA hydrogels, in the form of wafers with a diameter of 20 mm and thickness of 1.4 mm, were immersed in deionized water until the mass no longer increased. The final hydrated mass was recorded as Mh. The PVA hydrogel swelling degree recorded as S was calculated by equation 2,20

S =

Mh × 100% M0

(2)

2.4.3. Differential Scanning Calorimetry Analysis The melting and cooling characterization of the PVA xerogels were investigated by differential scanning calorimetry (USA, TA, Q2000), and the heating/cooling rate was 20 °C/min, and the temperature range was from 10 °C to 240 °C. 2.4.4. Rheological properties The stability of the PVA hydrogels was determined by a dynamic rotary rheometer (USA, TA, DHR2). The temperature range was set from 25 °C to 80 °C, the strain was 1 %, the frequency was 10 rad/s, and the heating rate was 20 °C/min. 2.4.5. Mechanical properties The tensile strength test was carried out using an electronic universal testing machine (China, 4


Page 5 of 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


SUNS Technology, UTM2203) . The crosshead speed was 20 mm/min. 2.4.6. Fracture morphology The fracture morphology of the tensile test hydrogels were analysed using a polarized optical microscope (Japan, Olympus, BX51). 2.4.7. Inner morphology The morphological structures of the inner hydrogels were characterized by atomic force microscopy (USA, Agilent, 7500). 2.4.8. Cell culture experiment Before cell culture experiments, the tube should be soaked in medical alcohol for 24 hours and then washed three times with deionized water. Finally, ultraviolet ray was performed for half an hour to further sterilize. Using Phosphate Buffered Saline (PBS, CORNING) to clean the samples and soak for 24 hours, UV irradiation for half an hour. After soaking for 24 hours in culture medium, each sample was inoculated with 10000-20000 human umbilical vein endothelial cells(huvEc). 10% fetal bovine serum (BI) was added to the culture medium(1640, BI) to carry out cell culture at 5% CO2 and 37℃. Media was replaced every days and assays were performed at days 1 and 3 to characterize cell viability and proliferation. The cell viability of the tubes was characterized using a Live/Dead Viability/Cytotoxicity Assay Kit for Animal Cells(CORNING) to determine how many cells were living and dead on days 1 and 3. This kit contained green fluorescent Calcein-AM to image the cytoplasm of living cells, and Propidium Iodide (PI) to image cell death by penetrating broken cellular membranes. The staining solution was prepared following the manufacturer’s instructions. For the live/dead assay, the medium was first removed from the tubes and cells. Then phosphate Buffered saline was used to gently wash the tube and cells. Following this, an appropriate amount of the staining solution was added directly to the tubes with cells and incubated 30 minutes at room temperature. The cells were observed using Fluorescent Inverted microscope (Leica Microsystems CMS GmbH, DMI3000 M).

3. Results and Discussion 3.1. Structural stability analysis The physical cross-linked hydrogels show reversible structure, so the stability test of a hydrogel is very prerequisite for its applications. Figure 2 shows the stabilities of the hydrogels prepared in 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 17

different solvent ratios under the temperature range from 25 °C to 80 °C. The PVA hydrogels had good structural stability from 25 °C to 65 °C for all different solvent ratios, which is suitable for the requirement of tissue engineering materials. The hydrogel storage modulus was significantly lower when the DMSO-DMF solvent ratio is 4-6, which may be due to the higher water content in the hydrogel.

Figure 2. Temperature sweep of hydrogels prepared with different DMSO-DMF solvent ratios

3.2. Swelling properties Table 1 shows the water content and swelling recovery rate of hydrogels prepared with different solvent ratios. All PVA hydrogels had high water contents that were above 80 %. The water content and the swelling recovery rate after immersion for 72 h were the highest, being 86.47 % and 68.40 %, respectively. These results are consistent with the fact that the storage modulus of the 4-6 hydrogel was the smallest. The reason why water content of the PVA hydrogel re-swelling compared with initial is lower is that the average distance in the drying process is shortened, leading the cross-linking density in the gel network increasing, resulting in decreased hydrogel recovery.21 Table 1. Water content and swelling degree of hydrogels prepared with different DMSO-DMF solvent ratios

Samples

2-8

3-7

4-6

5-5

WW(%)

85.74±0.23

84.01±0.18

86.47±0.13

82.98±0.08

S(%)

49.95±0.10

59.99±0.93

68.40±0.94

66.51±0.12

3.3. Thermal properties 6


Page 7 of 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


Figure 3 and Figure 4 show the cooling and the second heating curves DSC curves of the mixed-solvent hydrogels. It can be seen from the figures that whatever the solvent ratio is, the PVA xerogel formed after the solvent treatment had a crystallization temperature of at least 25 °C above that of the raw PVA. On the other hand, the melting temperature of the PVA xerogels treated with different proportions of solvents was at least 7 °C above that of the raw PVA. Their degrees of crystallinity were also higher than that of the raw PVA. Table 2 gathers the data of the crystallization temperature (Tc) , melting temperature (Tm), melting enthalpy (∆H) and degree of crystallization ( Xc ). Table 2. DSC results of the hydrogels prepared with different DMSO-DMF solvent ratios Samples

2-8

3-7

4-6

5-5

PVA

TC (°C)

202.95

199.92

203.91

200.15

172.69

Tm (°C)

222.99

217.40

220.59

227.73

210.37

ΔH (J/g)

45.91

55.29

67.02

42.81

40.24

XC（%）

33.12

39.89

48.36

30.89

29.03

The degree of crystallinity XC was calculated using equation 3

XC =

∆H × 100% ∆H 0

(3)

∆H and ∆H0 are the melting enthalpy of the samples and the 100 % crystalline raw material, respectively, with ∆H0 = 138.6 J/g.22,23 The above results show that the mixed-solvent treatment provided the PVA with a more stable structure that was more difficult to destroy. Reasons for the improvement in the thermal performances are unknown. A hypothesis is that during the mixed solvent treatment the PVA gels formed a more dense molecular chain network.

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

Page 8 of 17

Figure 3. Cooling curve of hydrogels prepared with different DMSO-DMF solvent ratios

Figure 4. Second melting curves of hydrogels prepared with different DMSO-DMF solvent ratios 3.4. Mechanical properties and tensile fracture morphologies Figure 5 and Figure 6 show the tensile strengths and elongations at break of the PVA hydrogels prepared with different solvent ratios, respectively. The 4-6 PVA hydrogel exhibited the highest tensile strength and reached 1.14 MPa, which was even close to that of the GO (graphene oxide)-PVA composite hydrogel prepared by repeated freezing-thawing reported by Chen et al., namely 1.1 MPa.24 The reason that the 4-6 PVA hydrogel exhibited the highest tensile strength may be due to its highest degree of crystallinity, as per the DSC results. The PVA hydrogels prepared from the different solvent ratios all had elongations at break of above 500 %, good toughness and certain deformation recovery. Previous studies showed that the strength of PVA hydrogels increased significantly with increasing PVA concentration in a certain range.25 The concentration of the PVA gels in this work was 12 %. Therefore, there would be room for further 8


Page 9 of 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


improvement in strength of the PVA gels.

Figure 5. Tensile strength of PVA hydrogels prepared with different DMSO-DMF solvent ratios

Figure 6. Elongation at break of PVA hydrogels prepared with different DMSO-DMF solvent ratios

The PVA hydrogel was prepared by different solvent ratios to exhibit similar unique fracture morphology. Figure 7 shows the tensile fracture morphologies of the hydrogels from a polarized microscope. The tensile section consisted of two parts, as indicated by ○ 1 and ○ 2 in Figure 7a. The pre-fracture period was a fan-shaped extension region consisting of many fringes that radiated from the edges to the centre, and the hydrogel spline exhibited a ductile fracture property. However, the second part showed the brittle fracture feature. To the best of the authors’ knowledge, at present there have been no reports on similar findings. Reasons for this unique fracture features remain unknown and deserve further investigations.

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

Page 10 of 17

Figure 7. Tensile fracture morphologies of PVA hydrogels prepared with DMSO-DMF mixed solvents ratio of 4-6 . Magnification: a-50 times; b-100 times; c-200 times

3.5. Surface morphologies of PVA xerogels Figure 8 shows the three-dimensional surface morphologies of the PVA xerogels formed at different solvent ratios, and Figure 9 shows the three-dimensional phase diagrams of the sample surfaces.

Figure 8. Three-dimensional morphology of PVA xerogels prepared with different DMSO-DMF solvent ratios

10


Page 11 of 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


Figure 9. Three-dimensional phase diagrams of PVA xerogels prepared with different DMSO-DMF solvent ratios

Based on the swelling and re-swelling results combined with the three-dimensional surface morphology results, it is proposed that the phase angle difference of the phase diagrams was caused by holes on the sample surfaces for the pure PVA system and is speculated that the PVA hydrogels had a micro-pore structure, as shown in Figure 8 and Figure 9. The shrinkage of the hydrogels compressed holes that were sunken in the gel surface after the water molecules evaporated during the drying process. The xerogels exhibited irregularities in the size and distribution of the depression areas. Hydrogel shows a three-dimensional network structure. The areas of the three-dimensional holes of the network filled with solvent and the protrusions of the hydrogel areas to provide gel strength in Figure 8. Three-dimensional network structure of the PVA hydrogel prepared in this method is at nano level. Compared with the PVA xerogels obtained with different solvent ratios, the protrusions in the three-dimensional topography were more numerous and homogeneous when the solvent ratio was 4-6. This indicate that the high performances of the 4-6 hydrogel were related to its unique structural features. 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

Page 12 of 17

3.6. Plasticity and Application Figure 10 shows two small tubular hydrogels, with their inner diameter, outer diameter, and wall thickness noted as I.D., O.D., and W.T., respectively. In fact, the hydrogels obtained in this work had good plasticity, and could theoretically be formed in any shape, such as spherical and dropper-like, as long as a suitable mould is used. The spherical hydrogels exhibited good elasticity: they were not damaged after repeated bounce test. (see the supporting information)

Figure 10. Small calibre PVA hydrogel tubes.

PVA can be used as vascular material to replace the diseased vessels.26 In this paper, the cell culture experiments were carried on the PVA hydrogel micro-tube. The results of cell growth are shown in Figure 11.

Figure 11. Cells culture of the PVA hydrogel (a) one day (b) 3days

In Figure 11, the results show that hydrogel micro-tubes can provide matrix for cell growth and have certain biocompatibility, while experiments show that not all the cells can survive for a long time. A possible reason may be that the material surface without further surface treatment, causing 12


Page 13 of 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


cells do not better adhere to the wall, so that the cells can't survive for a long time27.

4. Conclusions In this work, PVA hydrogels were prepared by physical crosslinking upon dissolving a raw PVA into a mixture of DSMO and DMF. Optimum hydrogel structure and properties were obtained when the DSMO-DMF solvent ratio was 4-6. This preparation method is more efficient than the traditional cycle freeze-thawing method, providing PVA hydrogels with good mechanical strength and improved melting temperature and crystallinity. Excellent plasticity and microtubule mould designs offer the possibility of manufacturing small diameter blood vessels.

Associated Content Supporting Information The supplementary figures and video are summarized in the Supporting Information.

Author Information Corresponding Author *Tel.:(+86) 371-67767993. Fax:(+86) 371-67767993. E-mail: [email protected]; [email protected]; [email protected] Notes The authors declare no competing financial interest.

Acknowledgements The authors acknowledge the National Science Fund ( No. 51603192 and No. 11372286 ), the Basic and Advanced Technology Research Project of Henan Province ( No. 152300410033 and No. 162300410003 ), and the International Technological Cooperation Project ( No. 2015DFA30550 ) for their financial support of this project. The project is sponsored by the Scientific Research Foundation for Returned Overseas Chinese Scholars, State Education Ministry. The project is also supported by the Open Project of State Key Laboratory Cultivation Base for Non-mental Composites and Functional Materials ( No. 15zxfk06 ).

References：： (1) Liu, Y.; Vrana, N. E.; Cahill, P. A.; Mcguinness, G. B. Physically crosslinked composite hydrogels of PVA with natural macromolecules: Structure, mechanical properties, and endothelial 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

Page 14 of 17

cell compatibility. J. Biomed. Mater. Res. A. 2009, 90, 492. (2) J. Negishi, K. Nam, T. Kimura, Y. Hashimoto, S. Funamoto. Fabrication of a heparin–PVA complex hydrogel for application as avascular access. J. Biomed. Mater. Res. B. 2014, 102, 1426–1433. (3)Y. Hong, S.H. Ye, A. Nieponice, L. Soletti, D.A. Vorp. A small diameter, fibrous vascular conduit generated from a poly(ester urethane)urea and phospholipid polymer blend. Biomaterials. 2009, 30, 2457-2467 (4) W. Liu, S. Thomopoulos, Y. Xia. Electrospun nanofibers for regenerative medicine. Adv. Healthc. Mater. 2012, 1, 10-25. (5) E. Ercolani, G.C. Del, A. Bianco. Vascular tissue engineering of small-diameter blood vessels: reviewing the electrospinning approach. J. Tissue Eng Regen Med. 2013, 9, 861–888. (6) S. Williams. Mechanical testing of a new biomaterial for potential use as a vascular graft and articular cartilage substitute. Georgia Institute of Technology. 1998. (7) C.M. Hassan, N.A. Peppas. Structure and applications of poly(vinyl alcohol)hydrogels produced by conventional crosslinking or by freezing/thawing methods. Adv. Polym. Sci. 2000, 153, 37-65. (8) S.L. Bourke, M. AlKhalili, T. Briggs, B.B. Michniak, J. Kohn, L.A. Poole-Warren. A photo-crosslinked poly(vinyl alcohol) hydrogel growth factor release vehicle for wound healing applications. AAPS. J. 2003, 5, 101-111. (9) Y. Jiang, A. Schädlich, E. Amado, C. Weis, E. Odermatt. In-vivo studies on intraperitoneally administrated poly(vinyl alcohol). J. Biomed. Mater. Res. B. 2010, 93, 275-284. (10) J.A. Stammen, S. Williams, D.N. Ku, R.E. Guldberg. Mechanical properties of a novel PVA hydrogel in shear and unconfined compression. Biomaterials. 2001, 22, 799-806. (11) L.E. Millon, M.P. Nieh, J.L. Hutter, W.K. Wan. SANS Characterization of an Anisotropic Poly(vinyl alcohol) Hydrogel with Vascular Applications. Macromolecules. 2007, 40, 511-518. (12) D.T. Mathews, Y.A. Birney, P.A. Cahill, G.B. Mcguinness. Vascular cell viability on polyvinyl alcohol hydrogels modified with water-soluble and -insoluble chitosan. J. Biomed. Mater. Res. B. 2008, 84, 531–540 (13) N.E. Vrana, Y. Liu, G.B. Mcguinness, P.A. Cahill. Characterization of Poly(vinyl alcohol)/ 14


Page 15 of 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


Chitosan Hydrogels as Vascular Tissue Engineering Scaffolds. Macromol. Symp. 2008, 269, 106-110 (14) T.H. Kim, D.B. An, S.H. Oh, M.K. Kang, H.H. Song, J.H. Lee. Creating stiffness gradient polyvinyl alcohol hydrogel using a simple gradual freezing-thawing method to investigate stem cell differentiation behaviors. Biomaterials. 2014, 40, 51-60. (15) C.E. Macias, H. Bodugoz-Senturk, O.K. Muratoglu. Quantification of PVA hydrogel dissolution in water and bovine serum. Polymer. 2013, 4, 724-729. (16) M.F. Cutiongco, D.E. Anderson, M.T. Hinds, E.K. Yim. In vitro and ex vivo hemocompatibility of off-the-shelf modified poly(vinyl alcohol) vascular grafts. Acta. Biomater. 2015, 25, 97–108. (17) P.J. Martens, S.J. Bryant, K.S. Anseth. Tailoring the degradation of hydrogels formed from multivinylpoly(ethylene glycol) and poly(vinyl alcohol) macromers for cartilage tissue engineering. Biomacromolecules. 2003, 4, 283-292. (18) S.R. Stauffer, N.A. Peppast. Poly(vinyl alcohol) hydrogels prepared by freezingthawing cyclic processing. Polymer. 1992, 33, 3932-3936. (19) D.A. Shipp. Reversible-Deactivation Radical Polymerizations. POLYM REV. 2011, 51, 99-103. (20) M. Huang, D. Cai, Y. Liu, J. Sun, J. Wang. Investigation of a-PVA/s-PVA Hydrogels Prepared by Freezing-thawing Method. Fiber. Polym. 2012, 13, 955-962. (21)R. Rodríguez, C. Alvarez-Lorenzo, A. Concheiro. Cationic cellulose hydrogels: kinetics of the cross-linking process and characterization as pH-/ion-sensitive drug delivery systems. J. Controlled Release, 2003, 86, 253-265. (22) S.K. Mallapragada, N.A. Peppas. Dissolution mechanism of semi-crystalline poly (vinyl alcohol) in water. J. Polym. Sci. Pol. Phys. 1996, 34, 1339-1346 (23) N.A. Peppas, E.W. Merrill. Differential scanning calorimetry of crystallized pvahydrogels. J. Appl. Polym. Sci. 1976, 20, 1457-1465 (24) J. Chen, X. Shi, L. Ren, Y. Wang. Graphene oxide/PVA inorganic/organic interpenetrating hydrogels with excellent mechanical properties and biocompatibility. Carbon. 2016, 111, 18-27. (25) Y. Pan, J. Ding, Y. Chen, Q. Shen. Study on mechanical and optical properties of poly(vinyl 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

Page 16 of 17

alcohol) hydrogel used as soft contact lens. Mater. Technol. 2015, 31, 266-273. (26) M. Chaouat, C.L. Visage, W. E. Baille, B. Escoubet, F. Chaubet. A Novel Cross-linked Poly(vinyl alcohol) (PVA) for Vascular Grafts. Adv. Funct. Mater. 2008, 18, 2855-2861. (27) Y. Liu, N.E. Vrana, P.A. Cahill, G.B. Mcguinness. Physically crosslinked composite hydrogels of PVA with natural macromolecules: structure, mechanical properties, and endothelial cell compatibility. J. Biomed. Mater. Res. B. 2009 , 90B(2), 492–502.

16


Page 17 of 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


For Table of Contents Only

17


A Novel Method for Preparing Poly(vinyl alcohol ... - ACS Publications

Recommend Documents