Direct quantification of analyte concentration by resonant acoustic profiling

Background: Acoustic sensors that exploit resonating quartz crystals directly detect the binding of an analyte to a receptor. Applications include detection of bacteria, viruses, and oligonucleotides and measurement of myoglobin, interleukin 1 beta (1L-1 beta), and enzyme cofactors. Methods: Resonant Acoustic Profiling (TM) was combined with a microfluidic lateral flow device incorporating an internal reference control, stable linker chemistry, and immobilized receptors on a disposable sensor chip. Analyte concentrations were determined by analyzing the rate of binding of the analyte to an appropriate receptor. Results: The specificity and affinity of antibody-antigen and enzyme-cofactor interactions were determined without labeling of the receptor or the analyte. We measured protein concentrations (recombinant human IL-10 and recombinant human myoglobin) and quantified binding of cofactors (NADP(+) and NAD(+)) to the enzyme glucose dehydrogenase. Lower limits of detection were similar to 1 nmol/L (17 ng/mL) for both IL-1 beta and human myoglobin. The equilibrium binding constant for NADP' binding to glucose dehydrogenase was 2.8 mmol/L. Conclusions: Resonant Acoustic Profiling detects analytes in a relatively simple receptor-binding assay in < 10 min. Potential applications include real-time immunoassays and biomarker detection. Combination of this technology platform with existing technologies for concentration and presentation of analytes may lead, to simple, label-free, high-sensitivity methodologies for reagent and assay validation in clinical chemistry and, ultimately, for real-time in vitro diagnostics. (c) 2005 American Association for Clinical Chemistry.