Laboratory study demonstrates rapid detection of Escherichia coli using chip calorimetry and magnetic beads, indicating potential for monitoring low-level bacterial contamination.
We present a new chip calorimeter for fast and quantitative measurement of metabolic heat rates of microorganisms attached to magnetic beads. In biomagnetic separation (BMS) experiments, Escherichia coli K12 immobilized on nonspecifically functionalized beads has a specific heat rate of around 1 pW per cell at 37°C. Therefore, at least 2 × 104 bacteria are required to exceed the calorimetric signal resolution of 20 nW. If the samples to be analyzed have the original volume of 4 mL, bacteria at less than 104 cells mL−1 should be detectable. In practice, we achieved the detection of approximately 2 × 104 cells mL−1. The method presented here might also find some applications in the investigation of biofilms and study of biomolecular interactions.
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Lerchner et al. (2012) studied this question.