聚丙三醇癸二酸酯（PGS）在軟組織工程上是一種很有前途的彈性體。因為PGS成纖維型態過程複雜、較困難耗時，但還是有人使PGS成纖維型態，正因為製程困難，所以在這研究中推出一個做法，是用一種比較容易電紡的材料，選用PVA做電紡材料來當作犧牲支架，再加入PGS溶液，讓PGS溶液包覆在PVA纖維的外面，犧牲掉PVA後，做成具有圓柱形孔洞(channel)微結構的PGS薄膜且具有纖維大小的孔洞。因為PGS是熱固性彈性體，在真空烘箱中固化溫度和時間為120℃/130℃、24/48小時，以增加最終材料的交聯程度。PGS包覆在PVA纖維的外側，加水以洗去PVA纖維，使薄膜微結構變為圓柱形孔洞(channel)結構，它類似於電紡纖維排列。PGS薄膜的機械性質隨著圓柱形孔洞(channel)微結構在特定方向的排列而可以被調整。該薄膜必須能夠製成特定方向排列的結構，其機械性質可以透過固化條件和特定方向微結構來進行調整。為了評估薄膜的機械性質，我們在製造各種固化條件下的PGS薄膜並具有凹槽(groove)微結構。微結構和測試條件，其中包括固化條件是有影響其機械性質。PGS薄膜隨著固化時間增長和固化溫度增加，導致楊氏係數增加和斷裂應變下降。藉由調控PVA纖維方向性，讓PGS薄膜也具有方向性，依據管狀支架製備方法，我們藉著包捆具有方向性的PGS薄膜，做出有夾角(30度、60度)的管狀支架，拿去做管狀機械測試，其軸與纖維夾角越大，則環向彈性模數越大。支架為組織工程中一大要素，提供適合細胞生長之微結構，其中用電紡絲製作出來的支架，其纖維排列方向也會影響細胞生長的型態。所以預期PGS薄膜表面的凹槽(groove)微結構方向排列也要能導引細胞的分布，使細胞做生長排列，以滿足組織工程的要求。在本研究中，我們的目標是做一個PGS薄膜，其薄膜具有圓柱形孔洞(channel)的微結構，類似於纖維排列的薄膜，隨著圓柱形孔洞(channel)的特定方向排列，其可調整 PGS薄膜的機械性質，使其PGS薄膜具有非等向性的特性。

Poly(glycerol sebacate) (PGS) is an attractive biodegradable elastomer for engineering soft tissues. PGS, however, is mechanically isotropic, which limits its applications as many soft tissues have anisotropic behaviors in the body. Electrospinning has been used to make mechanically anisotropic membranes. Because electrospinning thermosetting polymer such as PGS is challenging, anisotropic membranes made of PGS electrospun fibers are not easy to achieve. In this study, we aimed at fabricate a mechanically anisotropic PGS membrane with the use of sacrificial fibers. First, electrospun poly(vinyl alcohol) (PVA) membranes were prepared. The PVA fibrous membrane was then embeded in PGS prepolymer. The resulting composite membrane was then cured in a vaccum oven at 120oC or 130oC for 1 or 2 days. Finally, PVA fibers were removed by water, leaving numerous fiber-like voids in the PGS matrix. We found that the mechanical properties of the membrane depended on curing temperature and reaction time. Increasing curing temperature and reaction time led to a increased Young's modulus and a decreased elongation at break of the PGS membrane. In particular, by employing electrospun PVA membranes containing aligned fibers, mechanically anisotropic PGS membrane was achieved. Tubular structure was formed by wrapping the PGS membranes with axisymmetric fiber-like voids. The compliance of the tubular construct was found to be dependent on the pitch angle of the helical structure.

[1] F. Y., et al. (2012). "Gradient nanofibrous chitosan/poly epsilon-caprolactone scaffolds as extracellular microenvironments for vascular tissue engineering." Biomaterials 33(3): 762-770.

[2] Hu, J. J., et al. (2012). "Construction and characterization of an electrospun tubular scaffold for small-diameter tissue-engineered vascular grafts: A scaffold membrane approach." Journal of the Mechanical Behavior of Biomedical Materials 13: 140-155.

[3]Isayama, N., et al. (2014). "Histological maturation of vascular smooth muscle cells in in situ tissue-engineered vasculature." Biomaterials 35(11): 3589-3595.

[4]Bourget, J. M., et al. (2012). "Human fibroblast-derived ECM as a scaffold for vascular tissue engineering." Biomaterials 33(36): 9205-9213.

[5] Koski, A., et al. (2004). "Effect of molecular weight on fibrous PVA produced by electrospinning." Materials Letters 58(3-4): 493-497.

[6]Zeytuncu, B., et al. (2014). "Preparation and Characterization of UV-Cured Hybrid Polyvinyl Alcohol Nanofiber Membranes by
Electrospinning." Materials Research-Ibero-American Journal of Materials 17(3): 565-569.

[7]Gao, Q., et al. (2013). "Hydrophilic non-wovens made of cross-linked fully-hydrolyzed poly(vinyl alcohol) electrospun nanofibers." Polymer 54(1): 120-126.

[8]Mitsak, A. G., et al. (2012). "Mechanical characterization and non-linear elastic modeling of poly(glycerol sebacate) for soft tissue engineering." Journal of the Mechanical Behavior of Biomedical Materials 11: 3-15.

[9] Wang, Y. D., et al. (2002). "A tough biodegradable elastomer." Nature Biotechnology 20(6): 602-606.

[10]Gao, J., et al. (2006). "Macroporous elastomeric scaffolds with extensive micropores for soft tissue engineering." Tissue Engineering 12(4): 917-925.

[11]Wang, Y. D., et al. (2003). "In vivo degradation characteristics of poly(glycerol sebacate)." Journal of Biomedical Materials Research Part A 66A(1): 192-197.

[12]Sundback, C. A., et al. (2005). "Biocompatibility analysis of poly(glycerol sebacate) as a nerve guide material." Biomaterials 26(27): 5454-5464.

[13]Motlagh, D., et al. (2006). "Hernocompatibility evaluation of poly(glycerol-sebacate) in vitro for vascular tissue engineering." Biomaterials 27(24): 4315-4324.

[14]Bettinger, C. J., et al. (2006). "Micro fabrication of poly (glycerol-sebacate) for contact guidance applications." Biomaterials 27(12): 2558-2565.

[15]Bettinger, C. J., et al. (2006). "Three-dimensional microfluidic tissue-engineering scaffolds using a flexible biodegradable polymer." Advanced Materials 18(2): 165-+.

[16]Vunjak-Novakovic, G., et al. (2006). "Cardiac tissue engineering: effects of bioreactor flow environment on tissue constructs." Journal of Chemical Technology and Biotechnology 81(4): 485-490.

[17]Xu, B., et al. (2015). "Fabrication, mechanical properties and cytocompatibility of elastomeric nanofibrous mats of poly(glycerol sebacate)." European Polymer Journal 64: 79-92.

[18]Xu, B., et al. (2013). "Non-linear elasticity of core/shell spun PGS/PLLA fibres and their effect on cell proliferation." Biomaterials 34(27): 6306-6317.

[19]Jeffries, E. M., et al. (2015). "Highly elastic and suturable electrospun poly(glycerol sebacate) fibrous scaffolds." Acta Biomaterialia 18: 30-39.

[20]Sant, S., et al. (2013). "Effect of biodegradation and de novo matrix synthesis on the mechanical properties of valvular interstitial cell-seeded polyglycerol sebacate-polycaprolactone scaffolds." Acta Biomaterialia 9(4): 5963-5973.

[21]Kharaziha, M., et al. (2013). "PGS:Gelatin nanofibrous scaffolds with tunable mechanical and structural properties for engineering cardiac tissues." Biomaterials 34(27): 6355-6366.

[22] Choolani, M., et al. (2007). "FastFISH: technique for ultrarapid fluorescence in situ hybridization on uncultured amniocytes yielding results within 2 h of amniocentesis." Molecular Human Reproduction 13(5-6): 355-359.

[23] Wang, Y. D., et al. (2002). "A tough biodegradable elastomer." Nature Biotechnology 20(6): 602-606.

[24]LeBlon, C. E., et al. (2013). "In vitro comparative biodegradation analysis of salt-leached porous polymer scaffolds." Journal of Applied Polymer Science 128(5): 2701-2712.

[25]Frydrych, M. and B. Q. Chen (2013). "Large three-dimensional poly(glycerol sebacate)-based scaffolds - a freeze-drying preparation approach." Journal of Materials Chemistry B 1(48): 6650-6661.

[26]Zeytuncu, B., et al. (2014). "Preparation and Characterization of UV-Cured Hybrid Polyvinyl Alcohol Nanofiber Membranes by Electrospinning." Materials Research-Ibero-American Journal of Materials 17(3): 565-569.

[27]Zeytuncu, B., et al. (2014). "Preparation and Characterization of UV-Cured Hybrid Polyvinyl Alcohol Nanofiber Membranes by Electrospinning." Materials Research-Ibero-American Journal of Materials 17(3): 565-569.

[28]Chen, Q. Z., et al. (2011). "Manipulation of mechanical compliance of elastomeric PGS by incorporation of halloysite nanotubes for soft tissue engineering applications." Journal of the Mechanical Behavior of Biomedical Materials 4(8): 1805-1818.

[29]Kemppainen, J. M. and S. J. Hollister (2010). "Tailoring the mechanical properties of 3D-designed poly(glycerol sebacate) scaffolds for cartilage applications." Journal of Biomedical Materials Research Part A 94A(1): 9-18.

[30] Chen, Q. Z., et al. (2008). "Characterisation of a soft elastomer poly(glycerol sebacate) designed to match the mechanical properties of myocardial tissue." Biomaterials 29(1): 47-57.

[31]Liu, Q. Y., et al. (2007). "Structure and properties of thermoplastic poly(glycerol sebacate) elastomers originating from prepolymers with different molecular weights." Journal of Applied Polymer Science 104(2): 1131-1137.

[32] Jaafar, I. H., et al. (2010). "Spectroscopic evaluation, thermal, and thermomechanical characterization of poly(glycerol-sebacate) with variations in curing temperatures and durations." Journal of Materials Science 45(9): 2525-2529.

[33]Sundback, C. A., et al. (2005). "Biocompatibility analysis of poly(glycerol sebacate) as a nerve guide material." Biomaterials 26(27): 5454-5464.

[34]Yamaguchi, S. (1992). "Analysis of Stress-Strain Curves at Fast and Slow Velocities of Loading Invitro in the Transverse Section of the Rat Incisor Periodontal-Ligament Following the Administration of Beta-Aminopropionitrile." Archives of Oral Biology 37(6): 439-444.

[35]Komatsu, K. and M. Chiba (1993). "The Effect of Velocity of Loading on the Biomechanical Responses of the Periodontal-Ligament in Transverse Sections of the Rat Molar Invitro." Archives of Oral Biology 38(5): 369-375.

[36]Lee, M. C. and R. C. Haut (1992). "Strain Rate Effects on Tensile Failure Properties of the Common Carotid-Artery and Jugular Veins of Ferrets." Journal of Biomechanics 25(8): 925-927.

[37]Zong, X. H., et al. (2002). "Structure and process relationship of electrospun bioabsorbable nanofiber membranes." Polymer 43(16): 4403-4412.

[38]Crapo, P. M., et al. (2008). "Seamless tubular poly(glycerol sebacate) scaffolds: High-yield fabrication and potential applications." Journal of Biomedical Materials Research Part A 86A(2): 354-363.

[39]Gao, J., et al. (2007). "Poly(glycerol sebacate) supports the proliferation and phenotypic protein expression of primary baboon vascular cells." Journal of Biomedical Materials Research Part A 83A(4): 1070-1075.

[40]Lee, K. W., et al. (2011). "Substantial expression of mature elastin in arterial constructs." Proceedings of the National Academy of Sciences of the United States of America 108(7): 2705-2710.

[41]Crapo, P. M. and Y. D. Wang (2010). "Physiologic compliance in engineered small-diameter arterial constructs based on an elastomeric substrate." Biomaterials 31(7): 1626-1635.

[42] Sant, S., et al. (2011). "Hybrid PGS-PCL microfibrous scaffolds with improved mechanical and biological properties." Journal of Tissue Engineering and Regenerative Medicine 5(4): 283-291.

[43] Sarkar, S., et al. (2005). "Vascular tissue engineering: microtextured scaffold templates to control organization of vascular smooth muscle cells and extracellular matrix." Acta Biomaterialia 1(1): 93-100.