Poly (L-lysine)-graft-dextran (PLL-g-dex), graft copolymers with dextran side chains grafted onto a poly(L-lysine) backbone, previously shown to be effective as stabilizers of DNA triple helices and as carriers of functional genes to target cells or tissues, were employed in this work to prevent nonspecific adsorption of proteins, as determined by means of optical waveguide lightmode spectroscopy. PLL-g-dex copolymers readily adsorb from aqueous solution onto negatively charged oxide surfaces and significantly reduce nonspecific protein adsorption onto bare silica-titania surfaces. While effective and equivalent surface adsorption and antifouling properties were observed for PLL-g-dex copolymers in a variety of architectures, nanotribological analysis by atomic force microscopy was able to distinguish between the different brush densities produced.