This contribution demonstrates a simple and reproducible method for fabricating surface-tethered polymer brushes that vary in grafting density for peptide adsorption and cell-adhesion studies. Surface-initiated atom transfer radical polymerization, along with thiol self-assembly, was used to generate these nanothin polymer brush layers of poly((polyethylene glycol) methacrylate). A preliminary kinetic study was done to measure the layer thickness growth rate at room temperature from flat gold substrates presenting different polymerization initiator molecule surface densities. The results described in this paper show that layer properties such as wettability and dry layer thickness depend strongly on initiator surface density. Ultimately, the interactions of small peptides and cells were correlated with surface properties, which continue to be a major research theme in biomedical and biomaterials research.