Abstract
The photodynamic effect has been widely recognized as a therapeutic approach for infectious diseases, particularly with the growing interest in natural photosensitizers. Unfortunately, many researchers have spent significant time and effort exploring and optimizing their experimental workflows. In this study, we provide a detailed account into the photodynamic action of the natural photosensitizer curcumin on the biofilm infection of Cutibacterium acnes (C. acnes) in an in vitro model of human keratinocyte inflammation. We sequentially performed the construction and suspension preparation of C. acnes biofilm in vitro, isolation and cultivation of human keratinocytes, co-cultivation of C. acnes biofilm-derived suspension with human keratinocytes, preparation of curcumin solution, and the photodynamic action of curcumin on the co-cultivation system. Subsequently, we conducted real-time quantitative polymerase chain reaction (qPCR), enzyme-linked immunosorbent assay ( ELISA), Western blot (WB), and NF-κB nuclear translocation detection. The results showed that curcumin alone had an anti-inflammatory effect at concentrations above 20 µM in the abovementioned inflammation model. However, when combined with blue light irradiation, curcumin exhibited anti-inflammatory effects even at a concentration as low as 5µM, and we found that curcumin's photodynamic action was achieved by blocking the TLR2/MAPK/NF-κB pathway. These experimental steps will save researchers time and effort in conducting experiments related to the photodynamic action of photosensitizers on cell infection models.
