42. Self-fitting Vaginal Stents from Biodegradable, Shape Memory Polymers.

Vaginal stents are used to prevent fibrosis after vaginal reconstruction. Currently, physicians must create their own makeshift stents in the operating room. There is a critical need for a new pediatric vaginal stent. We have developed a biodegradable shape-memory polymer (SMP) foam stent that can assume a secondary compressed shape for deployment and expand at physiological temperatures. Herein, we describe the development of the SMP chemistry with target transition temperature and emulsion-templating approach to generate SMP foams with shape memory behavior. Polycaprolactone diacrylate (linear-PCL-DA) and tetracrylate (star-PCL-TA) macromers were synthesized. Differential scanning calorimetry was used to characterize the transition temperature (Tm) and percent crystallinity. Foams were fabricated via emulsion templating. Briefly, PCL-DA and -TA solutions in toluene were emulsified with water (25:75) using a polyglycerol polyricinoleate 4125 (10%w/w) surfactant and 2.5% BAPO photoinitiator. The emulsion was photocrosslinked, vacuum dried, and subsequently annealed at 85°C for 1 hour. SEM image analysis was used to characterize the pore structure and compressive testing performed. Shape fixity/recovery of the foams were evaluated by crimping to 50% with the percent change determined against pre-crimped dimensions. Linear-PCL-DA displayed a transition temperature at Tm=55 °C compared to new star-PCL-TA at Tm=43°C. Emulsion templating provided uniform pore architectures. Functional evaluations of the foams determined self-expansion of the linear-PCL-DA at ∼55°C compared to the new 10 kDa star-PCL-TA at 37°C in less than 5 minutes. Despite a concomitant reduction in crystallinity, all scaffolds retained strong fixity behavior. The compressive modulus of star-PCL-TA (modulus = 0.45 MPa) scaffolds were lower than that of linear-PCL-DA (modulus = 0.8 MPa). The reduced stiffness of the star-PCL-TA provided a softer foam towards balancing the maintaining of caliber and comfort while preventing substantial deformation (10.2%) under Valsalva forces. This new SMP foam shows promise in generating a self-fitting vaginal stent. By altering the architecture of the PCL macromer from a linear to a star architecture, we have successfully lowered the transition temperature to allow for effective deployment at physiological temperatures. Supporting Figures or Tables https://www.abstractscorecard.com/uploads/Tasks/upload/19245/RGXGDRUQ-1377960-2-ANY(1).pdf [ABSTRACT FROM AUTHOR]