Preparation and Characterization of Biohybrid Shape Memory Polymer Scaffolds

“Self-fitting” shape memory polymer (SMP) scaffolds have the potential to improve healing of irregular bone defects due to their ability to fill complex geometries. After exposure to temperatures greater than their melt transition temperature (T_m), scaffolds undergo shape recovery, expanding to the tissue perimeter for improved osseointegration and healing. SMP scaffolds were originally prepared from semi-crystalline, biodegradable linear-poly(ε-caprolactone)-diacrylate (linear-PCL-DA; M_n = 10k g mol-1; T_m = ~55 °C). However, PCL’s slow degradation rate (~2 years) and lack of bioactivity is a disadvantage to neotissue formation and integration. Thus, efforts to accelerate the rate of PCL degradation and enhance its bioactivity, while maintaining both shape memory and mechanical properties is necessary. Ideally, SMP bone scaffolds should also possess intrinsic antimicrobial activities, particularly with the growing rate antimicrobial resistance and the surge in hospital-associated infections (HAIs). Chitosan (CS), a cationic polysaccharide, has been extensively used to fabricate bone scaffolds due to its biocompatibility, bioactivity, biodegradability, and broad osteoconductive and antimicrobial properties. While CS is endowed with several advantageous properties relevant to bone tissue regeneration, its use is hindered due to poor mechanical properties and limited solubility. Herein, biohybrid SMP scaffolds were prepared from linear-PCL-DA and CS-<i>graft</i>-PCL (for increased processibility) [90:10 and 75:25 wt% ratio], exploiting both the shape memory behavior of PCL and the biological/antimicrobial properties of CS. CS containing scaffolds displayed mechanical properties (i.e., strength, modulus, and toughness) similar to PCL-only scaffolds, in addition to their pore properties (i.e., pore size and porosity) remaining consistent. The incorporation of CS into the SMP scaffolds slightly lowered their T_m from ~55 to ~52 °C in addition to improving their degradation kinetics. Overall, these biohybrid SMP scaffolds displayed adequate mechanical properties, high porosity (&gt; 60%), and improved degradation. The inclusion of CS is also promising as a functional component to not only improve bioactivity but also combat HAIs.