Electrochemical Analysis of Ultrathin Polythiolsiloxane Films for Surface Biomodification

The ability of different crosslinkers to crosslink nanometer thick films of the polymer poly(mercaptopropyl)methylsiloxane (PMPMS), thus stabilizing these films on solid supports, was investigated. The four crosslinkers included 1,11-bismaleimidotriethyleneglycol (BM(PEG)3), tris-(2-maleimidoethyl)amine (TMEA), bismaleimidohexane (BMH), and 1,1′-(methylenedi-4,1-phenylene) bismaleimide (BMDPM). PMPMS films treated with the four crosslinkers were compared in the effectiveness of achieved crosslinking, continuity and stability of the films to rearrangement at elevated temperatures, and modification with single-stranded DNA. The results of electrochemical analyses show that more hydrophilic crosslinkers had difficulty reacting fully with PMPMS thiols, even in these nanometer thin layers. This observation highlights the critical importance of selecting crosslinkers that are chemically compatible. Optimal selection of crosslinker yielded films in which the polymer film was largely incapable of rearranging, even at elevated temperatures, yielding reproducible and stable layers. These results validate use of these supports for applications such as monitoring thermal denaturation of immobilized DNA duplexes.