All‐Optical Thermometry Monitoring Biochemical Kinetics with NV Centers in Diamond

Abstract

Nanothermometers enable label‐free measurement of biochemical processes with extremely small sample consumption, which is essential to high‐throughput assays for enzyme searching and drug screening. However, high sensitivity and long‐term chemical stability are still crucial challenges for current nanothermometers. Here, the nitrogen‐vacancy centers in diamond are chosen as atomic thermometers and apply the diamond thermometry to kinetic monitoring of biochemical reactions. The performance of all‐optical diamond thermometry are tested under severe chemical conditions with strong acids and bases. Diamond thermometry demonstrates a sensitivity of 80 mK Hz−0.5 and chemical stability of 62 mK even in the presence of a drastic pH change during neutralization reactions. The thermodynamics of two enzyme‐catalyzed processes: adenosine triphosphate hydrolysis and urea hydrolysis, are further analyzed. The enthalpy changes obtained at the submicron scale by diamond thermometry are in good agreement with commercial macroscopic isothermal titration calorimetry. This method could offer a universal characterization technique for biochemical studies at the femtoliter scale.