Antibiotic-Loaded Fibers of Polyhydroxyalkanoate Blends: Morphological Evolutions and Strain-Induced Micromechanics

Electrospun fibers of polyhydroxyalkanoate (PHA), blended with PCL or PBS, were loaded with linezolid (LIN) to investigate induced morphological evolution, crystallization, and strain-induced deformation micromechanics. Up to the optimal nucleating concentration of 2 wt %, LIN was fully encapsulated, increasing PCL crystallinity from 33% to 72% and PHA crystallization enthalpy by 56%. At 3 wt %, PHA/PBS fibers developed discrete hollow, anisotropic LIN crystalline clusters through confinement-directed growth, whereas PHA/PCL fibers displayed a homogeneous nano-granular surface coating of LIN. Solid-state NMR revealed closer segmental interactions in PHA/PBS and moderate phase separation in PHA/PCL. In situ tensile SAXS and SEM disclosed brittle craze-to-crack fracture in PHA/PBS-LIN fibers but semi-ductile deformation in PHA/PCL-LIN fibers, involving multiple crazes, necking, and the in situ generation of an internal nanofibrillar bridging network within the craze cavities. This morphology, formed by flow-induced and LIN-nucleated crystallization, modulates the deformation mechanism and supports the design of PHA antibiotic-loaded scaffolds with controlled release.