Capturing the dynamic variations of nanoscale viscosity within biological fluids is pivotal for deciphering the mechanisms of critical physiological and pathological processes, notably blood coagulation. However, this endeavor remains challenging due to the limitations of conventional techniques. Standard assays relying on bulk optical or rheological measurements lack the spatial resolution required for nanoscale viscosity analysis, failing to distinguish cascade processes in complex coagulation reactions. We present an optomagnetic nanorelaxometry platform that probes nanoscale viscosity in real time through analysis of magnetic nanoparticles' Brownian relaxation dynamics. Requiring a sample volume of 50 μL, the platform demonstrated quantitative accuracy in glycerol solutions and successfully tracked dynamic viscosity changes during collagen gelation. Most notably, during platelet-rich plasma coagulation, our platform revealed a nonmonotonic viscosity profile inaccessible to conventional assays, suggesting a novel methodological perspective on coagulation mechanisms. Evaluation with clinical anticoagulants and a thrombolytic agent further confirmed its practical utility, underscoring the platform's potential for pharmacological screening and point-of-care coagulation monitoring with nanoscale resolution.
Bi et al. (2026) studied this question.