Grafting of polypeptides on solid substrates by initiation of N-carboxyanhydride polymerization by amino-terminated self-assembled monolayers

A series of mixed self-assembled monolayers of functionalized (Br(CH2)(11)SiCl3) and unfunctionalized (CH3(CH2)(10)SiCl3) alkyltrichlorosilanes of different compositions have been prepared on bulk silicon substrates. By in situ modification of these monolayers the bromo end groups were transformed to amino end groups as shown by X-ray photoelectron spectroscopy measurements. The change of hydrophilicity was monitored by water contact angle measurements, showing the expected decrease of contact angles with increase amino group content on the surface. These substrates were used to initiate N-carboxyanhydrides in dioxane to yield alpha-helical polypeptides grafted from the surface. The thicknesses of the obtained polymer layers were measured with ellipsometry and X-ray reflectometry. Fourier transform infrared measurements confirm that the grafted polymers are in the alpha-helical conformation.