Development and Characterization of a Multifunctional Alginate-Chitosan Hydrogel Incorporating Nano-Hydroxyapatite and Thymus vulgaris for Wound Dressing Applications

Despite significant advances in wound dressing materials, a critical challenge remains in developing a single multifunctional platform that simultaneously provides mechanical integrity, controlled bioactive delivery, and broad-spectrum antimicrobial protection for complex and infected wounds. To address this gap, the present study synthesized and evaluated an innovative alginate-chitosan-based composite hydrogel reinforced with hydroxyapatite nanoparticles (HA) and thyme extract ( Thymus vulgaris ) for advanced wound dressing applications. The primary goal was to create a multifunctional system with optimized mechanical, swelling, biological, and antimicrobial properties. FESEM analyses revealed a uniform distribution and porous morphology in the final sample (Alg/HA/Chi/Ext), while XRD results confirmed a gradual decrease in crystallite size and crystallinity degree from 89.5% for pure HA to 21.7% for the final composite, indicating enhanced amorphous character and intermolecular interactions. Tensile testing demonstrated a significant improvement in the UTS (50 MPa) and, notably, toughness (1087.5 kJ/m³) of the final sample compared to pure alginate hydrogel. This composite exhibited high swelling capacity (766%) similar to pure alginate, but with much better structural stability. The MTT assay confirmed superior biocompatibility and increased cell viability (88% after 72 hours). Release studies showed a biphasic profile for the final sample, which followed the Korsmeyer-Peppas kinetic model. Significantly, this hydrogel demonstrated potent antimicrobial activity against Bacillus cereus (98.99% inhibition) and the fungus Aspergillus flavus (99.12% inhibition), with very low MIC values (below 5 µg/mL). The developed Alg/HA/Chi/TE hydrogel exhibited significantly enhanced antimicrobial activity (p < 0.05) and superior extract-loading capacity compared with the other formulations, while maintaining controlled release behavior and acceptable biodegradation characteristics. These findings demonstrate the potential of the proposed multifunctional composite as a promising platform for sustained delivery of natural therapeutics in wound-healing applications. Nevertheless, further in vivo studies and sterilization validation are required before clinical translation.