Nanocalorimeter Platform for Point-of-Care Medical Applications

Abstract

Point-of-care (POC) diagnostics is an important field of biomedical research, delivering rapid results in nonlaboratory settings. Advances in microfabrication have given rise to calorimeters with smaller reaction volumes, which maximizes the sensitivity and reduces the time constant by reducing the thermal mass of the sample and measurement system. Nanocalorimeters were developed capable of detecting heat in the nanojoule range with sub second resolution. Energy generated in enzyme-catalyzed reactions was used to develop assays for the quantification of target analytes termed thermometric enzyme-linked immunosorbent assays (TELISA). The potential for our device as a POC blood test for metabolic diseases was shown through the quantification of phenylalanine (Phe) in serum, an unmet necessary service in the management of phenylketonuria (PKU). Finite element numerical modeling was used to simulate an enzyme-catalyzed reaction within the microfluidic channel of the capillary calorimeter platform, then calculate a calorimeter signal based on the resulting temperature changes. The comprehensive model calibrated for changing enzyme kinetics and determined label enzyme amounts on the calorimeter platform. By combining the capillary fluidics with magnetic bead capture to deliver the analyte to the reaction volume, the platform was adapted for point-of-care use. For the first time, a POC highly sensitive TELISA is possible through delivery of the target analyte by functionalized magnetic beads, fluid handling powered entirely by capillary forces, and intuitive operation by hand pipetting of reagents.