The release of zinc ions from and cytocompatibility of two zinc oxide dressings

Abstract

These in vitro studies examined the release of zinc ions from and the response of human dermal fibroblasts to two zinc oxide-medicated dressings: one with zinc oxide in an ointment base and one using polyvinylpyrrolidone (PVP), a hydrophilic polymer for the binding of zinc oxide particles. Zinc release from the dressings in buffered-saline (pH 7.4) was studied through a high-pore-density membrane (pore size, 0.40 microm) in a two-compartment model at 37 degrees C for three hours. Cytocompatibility of the dressings and 500 micromol/l of zinc ions was assessed using the MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) assay after exposure to monolayers of confluent normal human dermal fibroblasts to the dressing extracts for four hours. The zinc release rate from PVP-bound zinc oxide was more than two-fold higher than from zinc oxide in the ointment. Extract of the zinc oxide ointment, containing 150 micromol/l solubilised zinc, elicited a cytotoxic reaction, while the zinc oxide-PVP extract, containing 410 micromol/l solubilised zinc, and 500 micromol/l zinc chloride were non-cytotoxic to the fibroblasts. Zinc release in a simulated wound milieu appears to be inhibited when zinc oxide is incorporated in a lipophilic vehicle. It is hypothesised that the ointment vehicle induced cytotoxicity rather then the solubilised zinc oxide. None.