Biogenic Vaterite Calcium Carbonate-Silver/Poly(Vinyl Alcohol) Film for Wound Dressing

Vaterite, a spherical polymorph of CaCO₃, shows potential as a carrier for the stable and controlled release of silver nanoparticles (AgNPs), preventing their aggregation or loss of efficacy during application. Furthermore, the embedding of CaCO₃-Ag in a poly(vinyl alcohol) (PVA) matrix helps effectively encapsulate and protect the CaCO₃-Ag microspheres and provides mechanical stability for better contact with the wound surface. This article focuses on the fabrication of an antimicrobial and biocompatible absorbent film embedded with precipitated biogenic vaterite CaCO₃-Ag microspheres. The impact of vaterite CaCO₃-Ag on the physical, chemical, nanomechanical, biocompatibility, and antimicrobial properties of the PVA films was investigated. The morphology study revealed a bilayer film structure with an inactive and active surface containing homogeneously distributed vaterite CaCO₃-Ag. The X-ray photoelectron spectroscopy (XPS) analysis of the spin-orbit splitting in the Ag 3d_5/2 and Ag 3d_3/2 peaks indicated the presence of both metallic and ionic states of silver in vaterite CaCO₃-Ag prior to its incorporation into the PVA polymer matrix. However, upon embedding in the PVA matrix, a subsequent transformation to solely ionic states was observed. The nanomechanical properties of PVA improved, and the reduced modulus and hardness increased to 14.62 ± 5.23 and 0.64 ± 0.29 GPa, respectively. The films demonstrate a significant activity toward Gram-negative Escherichia coli bacteria. The release of AgNPs was studied in both open and closed systems at pH 6, mimicking the pH environment of the wound, and it demonstrated a dependency on the type of capping agent used for synthesis and loading of AgNPs. The results further revealed the biocompatibility of the prepared films with human dermal fibroblast cells at a concentration of ≤5 mg/mL, making them applicable and functional for wound dressing applications.