Additive-Mediated Stability Enhancement of Bakuchiol-Loaded Alginate Core–Shell Microcapsules Fabricated by Coaxial Electrospray

Abstract

Bakuchiol is a bioactive compound with promising cosmetic and pharmaceutical applications. However, its poor stability toward light, oxygen, and environmental conditions limits its practical use. In this study, bakuchiol-loaded alginate microcapsules were fabricated via coaxial electrospray, and the effects of polymer additives on the stability and structural properties of the microcapsules were systematically investigated. Optimized electrospray conditions produced spherical microcapsules with uniform particle size and morphological characteristics consistent with the proposed core–shell configuration. The optimized formulation achieved an encapsulation efficiency of 91.0 ± 1.5%. Polyvinylpyrrolidone (PVP) and carboxymethyl chitosan (CMCS) were incorporated as functional additives to modulate the alginate polymer network. Rheological, FTIR, and mechanical analyses indicated that additive-mediated intermolecular interactions significantly influenced shell rigidity, swelling behavior, and storage stability. PVP-containing formulations exhibited improved dimensional stability and retained more than 90% of the encapsulated bakuchiol after 12 weeks of storage, whereas excessive CMCS incorporation promoted swelling and accelerated bakuchiol leakage, particularly under alkaline conditions. The enhanced stability of the PVP-containing formulations was attributed to hydrogen-bonding interactions that reinforced the polymer network, demonstrating an effective strategy for improving the long-term stability of oxidation-sensitive bioactive compounds in cosmetic and pharmaceutical encapsulation systems.