Parametric optimization of silk protein–chitosan core–sheath nanofibers via coaxial electrospinning

Abstract Coaxial electrospinning represents a versatile platform for the fabrication of nanofibrous materials with spatially controlled composition and tunable structure–property relationships, broadening their potential across advanced materials applications. In this study, composite nanofibrous films were fabricated from natural biopolymers using a systematically optimised coaxial electrospinning approach. Core–sheath fibres consisting of a silk fibroin (SF) core and a silk sericin (SS)–chitosan (CS) shell were produced through progressive optimisation of solvent systems, blend ratios, and processing parameters. Morphological characterisation by scanning electron microscopy (SEM) demonstrated that fibre diameter, uniformity, and structural integrity were strongly governed by electrospinning configuration and shell composition, with sericin-rich SS: CS blends yielding the most stable and uniform fibres. Transmission electron microscopy (TEM) provided supportive evidence of a core-sheath architecture, revealing distinguishable inner and outer regions within individual fibres. Fourier-transform infrared spectroscopy (FTIR) confirmed the coexistence of all three biopolymers and highlighted composition-dependent differences in molecular organisation. Functional assessment via moisture vapour transmission rate (MVTR) measurements revealed a strong dependence of moisture permeability on electrospun film thickness, with thinner mats exhibiting higher and more stable vapour transmission. Overall, this work establishes the feasibility of producing SF/SS–CS core-sheath nanofibrous scaffolds with controlled morphology, composition, and moisture transport properties through careful process optimisation. Through systematic comparison of spinning configuration, solvent system, and shell composition, this study identifies the critical parameters required for stable and reproducible fabrication of silk-based core–shell nanofibers via coaxial electrospinning.