Microfabricated calorimeters for thermometric enzyme linked immunosorbent assay in one-Nanoliter droplets.

Advances in microfabrication allow for highly sensitive calorimeters with dramatically reduced volume, decreased response time and increased energy resolution. These calorimeters hold the potential for designs of ELISA platforms competitive with fluorescent and chemiluminescent technologies. We have developed a new assay platform using conventional ELISA reagents to produce a thermal signal quantifiable using calorimetry. Our optimized micromachined calorimeters have nL reaction volumes and a minimum detectable power of 375 pW/Hz1/2. We demonstrate rapid quantification in a model system of trastuzumab, a humanized monoclonal antibody used in the treatment of HER2 overexpressing breast cancers, in human serum using a HER2 peptide mimetic. Trastuzumab concentration and reaction time constant correlated well (R2 = 0.954) and can be used to determine trastuzumab concentrations. The limit of detection for the ThermometricELISA (TELISA) was 10 μg/ml trastuzumab in human serum. TELISA allows for a simple readout, reduction in assay time, sample and reagent volumes and has the potential to become a point of care multiplexed platform technology.