Online resistance monitoring during autometallographic enhancement of colloidal Au labels for DNA analysis

DNA diagnostics at the point-of-care requires biosensors that rely on highly sensitive transducers and are producible at low cost. A promising candidate technology is based on direct electrical detection of autometallographically enhanced Au labeled analytes. We present a substantial improvement to the previously used method by introducing online DC resistance monitoring during the autometallographic enhancement process. Since multi-step enhancement, washing, drying, and measurement cycles are eliminated, our method takes the direct electrical detection method a step further to applicability in a point-of-care environment. The feasibility of the novel method is demonstrated by its application in a simple DNA hybridization assay and the analysis of a single nucleotide polymorphism (SNP) using allele-specific hybridization. Unequivocal discrimination of all possible base pairing combinations in the SNP assay has been achieved. The SNP assay in particular indicates the potential of the method for analyte quantification. (C) 2003 Elsevier B.V. All rights reserved.