Physico-mechanical Evaluation of Electrospun Nanofibrous Mats of Poly(3-hydroxybutyrate)/Poly(butylene succinate) Blends with Enhanced Swelling-Dynamics and Hydrolytic Degradation-Kinetics Stability for Pliable Scaffold Substrates

Biodegradable blends of PHB/Bio-PBS were successfully electrospun with solvent system 2,2,2-trifluoroethanol as the solvent to obtain electrospun mats (EMs) of fiber diameters ranging from 534 +/- 135 to 181 +/- 84 nm. The addition of CaCl2 led to defect/bead free morphology of PHB and PHB/Bio-PBS blends with the exception for Bio-PBS at similar to 20 wt% concentration. Bio-PBS based electrospun mats with CaCl2 led to the lowest fiber diameter (due to high conductivity and low viscosity of solution). Further, our study indicates that PHB/Bio-PBS blends displayed shear-thinning behavior with reduction in solution viscosity which in turn remained in tune with increasing Bio-PBS concentration. DSC studies indicated a more significant drop in crystallinity for PHB/Bio-PBS blends and as well corroborated by WAXD. Mechanical properties were affected by immiscibility, resulting in lower tensile strength from similar to 4.0 to similar to 2.0 MPa and tensile modulus from similar to 186 to similar to 64 MPa, while strain-at-break increased from similar to 1.5 to similar to 46.5% with Bio-PBS content in PHB matrix. Electrospun mats with up to 50% Bio-PBS loading demonstrated optimal ductility and strength and also exhibited a tensile modulus comparable to that of cancellous bone. Additionally, the blend with similar to 50 wt% of Bio-PBS showed increased hydrophobicity (116 degrees) and decreased swelling characteristics (84%) compared to neat PHB (95 degrees and 124%). Hydrolytic degradation studies showed improved structural robustness and consistent morphology in Bio-PBS based electrospun mats even after 30 days in phosphate buffer solution compared to PHB based mats. Thus, up to 50 wt% Bio-PBS incorporation into Polyhydroxyalkanoates matrices, i.e. in the blends with 50:50 composition ratio the mats obtained showed enhanced pliability in combination with the desired extent of physico-mechanical properties and stiffness for soft bone tissue engineering.