Selective protein adsorption on ZnO thin films for biofunctional nano-platforms

The immobilization of albumin and lysozyme by spontaneous adsorption on ZnO films, deposited by metal-organic chemical vapour deposition (MOCVD), has been investigated. Quartz crystal microbalance with dissipation monitoring and X-ray photoelectron spectroscopy analyses show that, at physiological pH, the two proteins exhibit different adsorption behaviours, namely albumin irreversibly adsorbs up to coverage of a half of monolayer, while lysozyme does not. Indeed, the high isoelectric point (IEP) of ZnO favors immobilization of biomolecules with lower IEP, assisted by electrostatic attraction in the proper pH range. This selective protein adsorption behaviour results very promising for ZnO nanoplatforms, consisting of hexagonally patterned ZnO nanoring arrays and SiO2 areas, obtained by colloidal template-catalyst assisted MOCVD.