Polymercaptosiloxane Anchor Films for Robust Immobilization of Biomolecules to Gold Supports

A central requirement in modification of solid surfaces with biological polymers is to tether the molecule of interest permanently and in a well-defined attachment geometry. Gold is perhaps the most popular metal support for research applications, yet it suffers from a lack of methods for producing robust biomolecular films that can withstand prolonged use, especially at elevated temperatures. In this report, the stability issue is addressed by first self-assembling a nanometer thick layer of a thiol-derivatized polysiloxane, poly(mercaptopropyl)methylsiloxane (PMPMS), on the gold support. Multivalent binding of the polymer thiols to the gold, combined with the polymer's hydrophobic nature, causes it to irreversibly adhere to the metal support. Thiol-terminated, 20mer DNA oligonucleotides are subsequently covalently linked to the PMPMS film using bismaleimide cross-linkers. Immobilization coverages of up to ∼1 × 101 ¹³ strands/cm² have been demonstrated. Significantly, the DNA monolayers can withstand prolonged exposure to near 100 °C conditions with minimal loss of strands from the solid support. The immobilized oligonucleotides retain ability to undergo sequence-specific hybridization, opening up applications in diagnostic and related areas.