(120d) Cooperativity Between Ionic Strength And Strand Coverage In Surface Hybridization

Solid-phase hybridization underpins modern microarray and biosensor technologies. While the underlying molecular process, namely sequence-specific recognition between complementary probe and target molecules, is fairly well-understood in bulk solution, this knowledge proves insufficient to adequately understand solid-phase hybridization. Using self-assembled DNA "probe" monolayers as a model system, the influence of ionic strength and probe coverage, and the cross-correlation between these parameters, on the hybridization of the probes to target strands in solution is systematically investigated and interpreted. Electroactive ferrocene and ruthenium compounds were employed to independently quantify the surface DNA probe and hybridized target coverages. The use of electrochemical labels enables in situ monitoring of the hybridization process as well as quantification of nonspecific versus sequence-specific attachments of targets. Results of these experiments can be summarized in a hybridization "map", with ionic strength and probe coverage as the independent parameters. Optimum conditions that lead to maximum targets per area or, alternately, maximum percentage of hybridized probes have been identified. These results advance physical understanding of solid-phase hybridization at a fundamental level in support of surface hybridization applications in life science research and medical diagnostics.