Sensitive detection of PDT-induced cell damages with luminescent oxygen nanosensors

In this work luminescent nanosensors specifically created for intracellular oxygen (ic-O₂) were utilized to assess photodynamic therapy (PDT) -induced cell damages. Firstly, ic-O₂ was demonstrated to be consumed much faster than extracellular O₂ with respective O₂ nanosensors. Using the ic-O₂ nanosensors, PDT-treated cells with different degree of impairment were then resolved according to the oxygen consumption rate (OCR). The evolving trend of cytotoxicity derived from OCRs was in agreement with cell viability obtained from 3-(4,5-cimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. Moreover, the direct damage of PDT on cell mitochondria was successfully detected by monitoring respiration instantly after PDT treatment, which is actually beyond the scope of MTT assay. These results suggest that fluorescence sensing of ic-O₂-associated cell respiration is promising and even may become a standardized method, complementary to MTT assay, to evaluate PDT-induced cytotoxicity.