3d scaffold fabrication with ppfdef using micro stereolithography

3D scaffold fabrication with PPF/DEF using micro-stereolithography Jin Woo Lee, Phung Xuan Lan, Byung Kim, Geunbae Lim, Dong-Woo Cho * Department of Mechanical Engineering, POSTECH, Pohang, Gyeongbuk 790-784, Republic of Korea Available online 15 Februa ry 2007 Abstract Current studies on scaffold fabrication have focused on overcoming the limitations imposed by the mechanical properties of existing biodegradable materials and the irregular structures they produce. Recently, several promising biodegradable materials were introduced, including poly(propylene fumarate) (PPF). In addition, the development of micro-stereolithography allows the fabrication of free-form 3D microstructures by dividing a desired shape into several slices of a given thickness. This technology, however, requires a low-viscosity resin to fabricate fine structures, which excludes the use of PPF. To fabricate precise 3D scaffolds using micro-stereolithography, we cre- ated a syste m in which the visco sity of PPF was reduc ed by adding diethyl fumarate. The fabri cated scaffo ld was steri lize d, and fibroblasts in cell culture medium were seeded onto the structure. Cells were fixed and freeze-dried after 4, 7, and 28 days of culture. Under scann ing electro n micro scopy , we observed that the cells were able to attac h to the scaffo ld surface and grow. 2007 Elsevier B.V. All rights reserved. Keywords: Micro-stereolithography; Poly(propylene fumarate) (PPF); Diethyl fumarate (DEF); 3D scaffold fabrication; Cell culture 1. Introduction Although the concept of tiss ue eng ine erin g has great potential, it remains largely undeveloped due to the lack of biocompatibl e, biode grada ble materi als with suitab le mec han ical pro per ties . Fort una tely , new biodeg radable materials were recently developed, including poly(propylene fumarate) (PPF), which may resolve these limitations. In 1988, Sanderson first produced PPF by the transesterifi- cat ion of die thy l fumara te (DEF) and propylene gly col using a par a-to lue ne sul fon ic acid catalys t [1]. Gerhart et al. (1989), Domb et al. (1989), Yaszemski et al. (1994), and Gresser et al. (1995) also prepared PPF using their own methods [1]. Interestingly, the mechanical properties of synthetic PPF are similar to those of trabecular bone [2] . In spite of the limitless potential of bioscaffold technology, the exi stin g met hod s for fab ricating scaffolds are unsatisfactory in terms of 3D free-form fabrication, preci- sion, and pore standardization. Micro-stereo lithogr aphy is a new technology that can be used to fabricate free-form 3D microstructures using a UV laser and a low-viscosity UV-curable liquid photopolymer. This paper describes a modi fied synthetic method for produc ing a biodeg radable PPF pho topoly mer tha t can be used in micro-stereolithography. We fabricated scaffolds using this system and observed the adhesion and growth of fibroblasts seeded onto the structures. 2. Experi ments 2.1. Synthesis of the materials PPF was synthesized vi a a condensatio n reactio n, according to Gerhart et al. [3] with the following modifica- tions: 1.5 mol of fumaric acid (174 g powder) and 1.65 mol of propylene glycol (155.5 g liquid) were placed in a triple- necked 1-L flask with an overhead electrical stirrer, a ther- mometer, and a Barrett trap beneath a condenser. During synthe sis, the mix tur e was stirred continuou sly betwee n 130 and 150 rpm. After 1.5 h, the temperature of the solu- tion was increased from room temperature to 145 C, and boiled vigorously. Within several minutes, water began to collect in the Barrett trap. During the 2–3 h, the mixture 0167-9317/$ - see front matter 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.mee.2007.01.267 * Corresponding author. Tel.: +82 54 279 2171. E-mail address: [email protected] (D.-W. Cho). www.elsevier.com/locate/mee Microelectronic Engineering 84 (2007) 1702–1705

3d scaffold fabrication with ppfdef using micro stereolithography

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