Electrospun Polyphosphate Coacervate Glass Fibers in the System P₂O₅–CaO–MgO–Na₂O–Fe₂O₃ for Wound Healing

This study investigates a series of phosphate-glass fibers (PGFs) in the system P₂O₅-CaO-MgO-Na₂O-Fe₂O₃ with various Fe contents (0, 0.1, 0.5, 1, and 2 wt %) prepared via electrospinning of polyphosphate coacervate gels. This method is preferable over the traditional high-temperature melt-spinning technique used for PGF production as it represents a more cost-effective and sustainable route. Structural analysis performed via Fourier transform Infrared spectroscopy shows that PGFs are mainly formed by polyphosphate chains containing Q¹ and Q² units. Thermal analysis demonstrates that the amorphous nature of the PGFs can be preserved up to calcination temperatures in the range 450-520 °C, with crystallization temperatures increasing with the iron content. Dissolution studies were performed by immersing the PGFs in deionized water and analyzing the species released (P, Ca, Mg, Fe, and Na) via microwave plasma atomic emission spectroscopy at regular intervals up to 72 hours (h). Results show that both iron and phosphate anion release increases with iron loading, suggesting that the phosphate network is weakened by an increasing amount of iron. Given that PGFs are particularly advantageous in wound healing due to their fibrous morphology, their cytocompatibility was assessed by seeding human keratinocytes (HaCaTs) in contact with the dissolution products of PGFs after 24 h of immersion at three different ratios of dissolution products to cell medium (1:100, 3:100, and 5:100). No cytotoxicity was observed for any of the ratios studied. Moreover, the dissolution products of some PGFs resulted in an enhanced growth of HaCaTs, with the best result being observed when using dissolution products from PGFs containing 0.1 wt % of Fe and a dissolution product-cell medium ratio of 5:100. Dissolution products from PGFs with an Fe content up to 0.5 wt % have also demonstrated antibacterial activity against the bacterium <i>Escherichia coli</i> (<i>E. coli</i>). A preliminary test on the efficacy of PGFs in wound healing via <i>ex vivo</i> studies on human skin has demonstrated that the PGFs in direct contact with the wound promote 84% wound closure.