Self Assembly Systems for Surface Modification and Drug Delivery

Self-assembled monolayers (SAMs) are ordered molecular assemblies that form spontaneously by the adsorption of a surfactant with a specific affinity of its headgroup to a substrate. The present work aims at developing a new monomolecular PEG-based adlayer system and its protein resistance properties, by exploiting the spontaneous formation of alkane phosphate SAMs on titanium oxide and their capability of tailoring the surface physico-chemical properties in a relatively simple and controlled way. The PEG alkane phosphates SAMs deposition was proved by X-ray photoelectron spectroscopy (XPS) and ellipsometry (VASE). Ellipsometry data were combined with optical waveguide lightmode spectroscopy (OWLS) data in order to correlate the protein resistance properties to PEG surface density. PEG density was controlled by varying the mole fraction of PEGterminated phosphates in the solutions used during the deposition process, leading to surfaces with different degrees of protein resistance. The surfaces were tested in vitro through the interaction with a cariogenic bacteria strain (S.mutans) and human osteoblasts. Bacteria adhesion was reduced by two orders of magnitudo on modified surfaces with respect to uncoated titanium. Furthermore, human osteoblasts adhesion and proliferation were reduced by the PEG density increase, however showing an enhanced metabolic activity.