Quartz Crystal Microbalance Biosensor Development: Chain Length Effects On Aqueous Signal Response

R.D. Craven, N.C. Fawcett, and J.A. Evans

Department of Chemistry and Biochemistry, The University of Southern Mississippi

P.O. Box 5043, Hattiesburg, Mississippi, USA, 39406-5043

Principle Author email: richard.craven@usm.edu

Abstract

The quartz crystal microbalance (QCM) has long been used as an inertia sensor in varied applications. Our group has applied this device to nucleic acid hybridization measurements since 1984. Until recently, quantitative measurements were only obtainable on genomic length nucleic acids in a dry state. The use of short oligomer probes has proved difficult since the required rinse steps prior to drying denature short, double-stranded hybrids. It is necessary to acquire measurements in an aqueous state for short oligomer probes. Measurement of tethered macromolecules in solution is more complex due to differing physical properties of the components. One major property is hybrid chain length. The QCM is only sensitive to added layers within a given region, known as the overlayer, above its surface. Chains longer than the overlayer thickness may not fully be detected when suspended in solution. In this study increasing lengths of end-attached, double-stranded DNA in buffer have been used to study the empirical relationship between length and sensitivity so that qualitative and probable quantitative results can be obtained. With a known relationship the QCM could be used for fast, quantitative detection of pathogenic organisms and for other genetically specific tests.