Received on April 26, 2005
Accepted on July 18, 2005

Oak Ridge Conference

Direct Quantification of Analyte Concentration by Resonant Acoustic Profiling

¹ Akubio Ltd., Cambridge, United Kingdom

^* To whom correspondence should be addressed. E-mail: mcooper{at}akubio.com.

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 (IL-1), 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-1 and recombinant human myoglobin) and quantified binding of cofactors (NADP⁺ and NAD⁺) to the enzyme glucose dehydrogenase. Lower limits of detection were 1 nmol/L (17 ng/mL) for both IL-1 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 application 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.