Star -PCL shape memory polymer (SMP) scaffolds with tunable transition temperatures for enhanced utility.

Thermoresponsive shape memory polymers (SMPs) prepared from UV-curable poly(ε-caprolactone) (PCL) macromers have the potential to create self-fitting bone scaffolds, self-expanding vaginal stents, and other shape-shifting devices. To ensure tissue safety during deployment, the shape actuation temperature ( i.e. , the melt transition temperature or T m of PCL) must be reduced from ∼55 °C that is observed for scaffolds prepared from linear -PCL-DA ( M n ∼ 10 kg mol -1 ). Moreover, increasing the rate of biodegradation would be advantageous, facilitating bone tissue healing and potentially eliminating the need for stent retrieval. Herein, a series of six UV-curable PCL macromers were prepared with linear or 4-arm star architectures and with M n s of 10, 7.5, and 5 kg mol -1 , and subsequently fabricated into six porous scaffold compositions (10k, 7.5k, 5k, 10k★, 7.5k★, and 5k★) via solvent casting particulate leaching (SCPL). Scaffolds produced from star -PCL-tetraacrylate ( star -PCL-TA) macromers produced pronounced reductions in T m with decreased M n versus those formed with the corresponding linear -PCL-diacrylate ( linear -PCL-DA) macromers. Scaffolds were produced with the desired reduced T m profiles: 37 °C < T m < 55 °C (self-fitting bone scaffold), and T m ≤ 37 °C (self-expanding stent). As macromer M n decreased, crosslink density increased while % crystallinity decreased, particularly for scaffolds prepared from star -PCL-TA macromers. While shape memory behavior was retained and radial expansion pressure increased, this imparted a reduction in modulus but with an increase in the rate of degradation.