Palladium as a Substrate for Self-Assembled Monolayers Used in Biotechnology

This paper describes self-assembled monolayers (SAMs) on palladium that resist the nonspecific adsorption of proteins and the adhesion of mammalian cells. These SAMs form when thin films of palladium are exposed to solutions of alkanethiol with the general structure HS(CH2)m(OCH2CH2)nOH (m = 2, 11; n = 3, 6, 7). Ellipsometry and surface plasmon resonance spectroscopy (using a palladium-on-gold substrate) showed that these SAMs resist adsorption of all proteins present in bovine serum. Microislands of SAMs of octadecanethiol on palladium allowed patterned adhesion and growth of mammalian cells (in a "sea" of oligo(ethyleneglycol)-terminated SAM). The oligo(ethyleneglycol)-terminated SAM resisted the invasion of cells for over four weeks under standard conditions of cell culture; similar SAMs on gold remained patterned for only two weeks.