Continuous Sensing of Lactate Dehydrogenase with a Competitive Particle-Based Sensor for Monitoring Cell Death

The development of sensors for the continuous monitoring of cell death will give opportunities to gain insights into the dynamics of living biosystems and enable interventions to maintain cell viability. Existing analytical methods mostly require access to cell material or yield single-point readouts, limiting their utility for long-term measurements. To enable minimally invasive time-resolved monitoring, we describe the development of a sensing technology for continuous detection of lactate dehydrogenase (LDH), a universal protein biomarker of cell membrane disruption. The sensor is based on Biosensing by Particle Motion (BPM), which detects LDH through changes in motion of biofunctionalized particles interacting with a biofunctionalized sensing surface. We developed an affinity-based competitive sensor with the LDH analogue on the particles and anti-LDH antibodies on the surface, allowing LDH in solution to reduce particle-surface binding. Antibody candidates were screened for intrinsic reversibility, and one with fast dissociation kinetics was selected to enable a dynamic response to both increasing and decreasing LDH levels. The sensor showed detection in the nanomolar range with minute-scale response times, operating in buffer and in cell culture medium. These results establish the feasibility of continuous LDH sensing using BPM, providing a foundation for the development of time-resolved, reagent-free sensors for minimally invasive monitoring of cell death in living biosystems. Such sensors hold promise for applications in bioprocess control, drug screening, toxicity testing, and biomedical research.