Laser speckle imaging for biofilm viability assessment: a noninvasive alternative to the MTT assay

Accurate measurement of cell viability in biofilms is critical in biology and medicine. We propose two laser speckle-based methods to assess the viability of Candida tropicalis biofilms. Time-varying speckle images were processed using temporal correlation analysis and frequent-motion imaging, and the resulting metrics were compared against the standard MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. A high Pearson correlation coefficient (>0.99) was observed between both speckle-based metrics and MTT. For C. tropicalis biofilms in microplates, the proposed approach provides a rapid, low-cost, and non-destructive proxy for cell viability and is expected to be transferable to other fungal and bacterial biofilms and other cell-based systems.