Demonstration of MEMS-based differential scanning calorimetry for determining thermodynamic properties of biomolecules

We demonstrate microelectromechanical system (MEMS)-based differential scanning calorimetry (DSC) for characterizing thermodynamic properties of biomolecules. The MEMS device consists of a pair of polydimethylsiloxane (PDMS) calorimetric microchambers and fluid handling microchannels, with each chamber 1.2 μl in volume and based on a freestanding SU-8 diaphragm. A nickel–chromium thermopile, and nickel heaters and temperature sensors, are integrated on the diaphragms to allow thermal measurement and control. During DSC measurements, the chambers are filled with a biomolecular solution and reference buffer, respectively. As the solution temperatures are varied continuously over a range of interest, the biomolecular thermal power is measured via the thermopile output, and then used to compute the thermodynamic parameters of the biomolecule. We present results from applying the device to DSC measurements of the unfolding of the proteins lysozyme and ribonuclease A. The enthalpy of unfolding and melting temperature of the proteins obtained are in agreement with published data.