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C.G. Thanos, K. Kauper, S. Sherman, W. Bell, R. Provencal, P. Chauvin, W. Tao; Alkaline Hydrolysis of Poly (ethylene terepthalate) Yarn for Improving Cell Attachment and Long-Term Viability in the NT-501 Intraocular Device . Invest. Ophthalmol. Vis. Sci. 2003;44(13):4459.
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Purpose: Our group has demonstrated reduced retinal degeneration in the rcd-1 dog model for retinitis pigmentosa following the intraocular implantation of a membrane-encapsulated device containing cells that secrete CNTF. The device consists of a poly(ether sulfone) membrane surrounding a scaffolding of poly(ethylene terepthalate) (PET) yarn, loaded with a cell suspension, and sealed with a urethane acrylate adhesive. It is established that these devices survive for at least 8 months in a closed container, but it is hypothesized that by creating a microtexture on the surface of the scaffold, viability can be enhanced and prolonged. Additionally, a controlled biomass may be achieved as well as further regulation of CNTF secretion. Methods: Both PET and poly(butylene terepthalate) (PBT) yarn were subjected to alkaline hydrolysis in 1, 5, or 8 N NaOH for varying amounts of time at 23°C, 65°C, or 100°C. Bath sonication was also employed in some cases to enhance the reaction. Samples were rinsed with distilled water, vacuum-dried overnight, and the degree of surface etching was characterized using scanning electron microscopy (SEM) and image-analysis software. For the in vitro component of the study, NT-501 devices were manufactured with an average length of 1.1 cm, sterilized, and loaded with either of two cell lines; NT-201-6A (high CNTF producer) or NT-201-10 (low CNTF producer). The device groups were fabricated to have varying degrees of etched yarn. Final devices were incubated for 2, 4, 8, or 12 weeks at 37°C in a closed container with 40 mL endothelial serum-free media (ENDO-SFM). Following the incubation period, CNTF production was analyzed by incubating devices in fresh ENDO-SFM for 24 hours followed by detection with an ELISA. Cell density was assessed using image analysis on plastic sections generated after the 24-hour pulse. Results: Both scaffold materials were successfully etched by alkaline hydrolysis. SEM analysis revealed that the degree of etching and size of the surface pitting was proportional to increases in concentration, time, and temperature. Primary pitting was induced with 1N NaOH after 3 hours at 65°C, and increasing the other variables controlled secondary and further degrees of surface pitting. Device performance and long-term viability of devices fabricated from this scaffolding will be discussed. Conclusions: Alkaline hydrolysis is an effective way to create a texture on the surface of PET and PBT yarn. Time, temperature, and concentration were all shown to be parameters affecting the reaction.
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