Polymer-anchored DNA monolayers for electrochemical biosensing.

摘要

Recent technological advances have seen the development of various platforms for detecting biomolecular interactions. 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 suffers from a lack of methods for producing robust biomolecular films that can withstand prolonged use, especially at elevated temperatures.; This thesis reports on the development of a novel attachment scheme for immobilizing biomolecules to metal supports. Poly(mercaptopropyl)methylsiloxane (PMPMS) films chemisorbed on gold provide thermally stable, nanometer-thin, thiol-rich anchor layers suitable for subsequent attachment of biomolecules. The exceptional stability of PMPMS-anchored single stranded and double stranded DNA monolayers is anticipated to benefit applications in biomolecular diagnostics, as well as assist in fundamental investigations of biomacromolecules at interfaces.; XPS measurements show that self-assembled films of the PMPMS on gold are characterized by a thiolate-Au bond density 30% less than that for alkanethiol SAMs, reflecting conformational constraints imposed on the thiol groups by polymer connectivity. Films thinner than about 0.8 nm cannot maintain this surface coverage, and are expected to be discontinuous. Electrochemical impedance spectroscopy measurements show that continuous PMPMS films behave as impermeable barriers with thickness equivalent to their physical dimension. Modification of PMPMS films with the crosslinker bis-maleimido tetraethyleneglycol decreases the interfacial capacitance only slightly. Therefore, this modification presents a potential approach to crosslink and thus to stabilize PMPMS layers as well as to passivate them against nonspecific adsorption of solution species, with minimal penalty in terms of increased interfacial impedance. In an attempt to exploit PMPMS films in impedance-based biodiagnostics, initial studies have shown that immobilization of DNA to the PMPMS modified Au surfaces lowers the interfacial capacitance. Preliminary results on hybridization of target DNA to the probe modified surfaces show that impedance changes can be measured.