Nanostructured ZnO as multifunctional carrier for a green antibacterial drug delivery system—A feasibility study [*V.Tullio and R.Cavalli contributed equally to this work]

The physico–chemical and biological properties of nanostructured ZnO are combined with the non-toxic and eco-friendly features of the scCO2-mediated drug loading technique to develop a multifunctional antimicrobial drug delivery system for potential applications in wound healing. Two nanostructured ZnO (NsZnO) with different morphologies were prepared through wet organic-solvent-free processes and characterized by means of powder X-ray diffraction, field emission scanning electron microscopy (FESEM), and nitrogen adsorption analysis. The antimicrobial activity of the two samples against different microbial strains was investigated together with the in vitro Zn2+ release. The results indicated that the two ZnO nanostructures exhibited the following activity: S. aureus > C. albicans > K. pneumoniae. A correlation between the antimicrobial activity, the physico–chemical properties (specific surface area and crystal size) and the Zn2+ ion release was found. Ibuprofen was, for the first time, loaded on the NsZnO carriers with a supercritical CO2-mediated drug impregnation process and in vitro dissolution studies of the loaded drug were performed. A successful loading up to 14% w/w of ibuprofen in its amorphous form was obtained. A preliminary drug release test showed that up to 68% of the loaded ibuprofen could be delivered to a biological medium, confirming the feasibility of using NsZnO as a multifunctional antimicrobial drug carrier.