Fluorescent nanodiamonds: preparation and quantum sensing for biological analysis

Fluorescent nanodiamonds (FNDs) have emerged as robust bioprobes owing to their exceptional photostability, biocompatibility, and embedded nitrogen-vacancy (NV) centers that enable quantum sensing. This Minireview summarizes recent progress in the preparation of FNDs for biological applications and in their use as quantum nanosensors for temperature, radical, and rotational/orientational readout in complex biological environments. We highlight how key materials parameters, including particle size, surface chemistry, and NV charge-state stability, govern both quantum performance and bioanalytical utility. We also discuss practical considerations for biological implementation, including microwave delivery, readout robustness, surface-related decoherence, and calibration for quantitative measurements in physiological environments. Finally, we outline emerging directions including site-specific and multiparameter quantum sensing, as well as integration with advanced imaging modalities. By linking materials design with experimentally demonstrated sensing modalities, this Minireview provides an updated perspective on the potential of FNDs for biological analysis.