Biodegradable PHB–Alginate Composite Matrix for Controlled Endolysin Release

Introduction

Infection control and efficient local delivery of antimicrobial proteins remain key challenges for advanced wound dressings. This work presents a fully biodegradable composite wound dressing that combines an electrospun poly(3-hydroxybutyrate) (PHB) fibrous mat with a Ca²⁺-crosslinked alginate hydrogel layer acting as a reservoir for therapeutic proteins (endolysins).

Methods

The composite was fabricated in three stages. First, a porous PHB fibrous mat was produced by electrospinning PHB from 6–8% (w/v) solutions in a hexafluoroisopropanol/chloroform system, with parameters adjusted to obtain fibers of 1–4 µm in diameter. Second, a 2% (w/v) aqueous sodium alginate solution was prepared and the protein was introduced at room temperature. Third, the electrospun PHB mat was placed into the alginate solution prior to gel formation, so that during subsequent crosslinking it became fully submerged/embedded within the gel layer; gelation was achieved by Ca²⁺ diffusion crosslinking through a dialysis membrane (5% CaCl₂, 20 min). Morphology was evaluated by scanning electron microscopy, mechanical properties by tensile testing, and protein content by the Bradford assay (595 nm; BSA calibration). Encapsulation efficiency was calculated as the ratio of experimentally loaded to theoretically introduced protein.

Results

The approach yields a porous, mechanically supportive PHB scaffold fully integrated within a biocompatible alginate hydrogel coating, enabling homogeneous protein distribution in a biodegradable composite structure.

Conclusions

The proposed fully biodegradable PHB/alginate composite dressing provides a mechanically robust, porous framework embedded within a protein-loaded hydrogel layer, offering a promising platform for local delivery of endolysins and other therapeutic proteins in wound care.