Evaluation of antibacterial effect of a cationic porphyrin derivative on Pseudomonas aeruginosa in photodynamic therapy

•Photodynamic antibacterial chemotherapy(PACT) is a promising therapeutic modality for the treatment of bacterial diseases. PACT is based on the use of nontoxic photosensitizer and visible light to induce the microbial pathogens photo inactivation.•Compared to the conventional antibacterial therapy, PACT has its special advantages, such as multi-target damage to pathogens; higher selective for killing the pathogens than normal cells; whether bacteria, fungal, viral or even parasitic in nature can be killed and it is difficult for pathogens to develop resistance.•Porphyrins are a class of heterocyclic aromatic compounds constituted by four subunits of pyrrole type linked by methynic bridges. The presence of these compounds is ubiquitous in nature which form the core section of hemoglobin, cytochrome and chlorophyll in nature, porphyrins and their derivatives can also be widely used in the research of PACT. Because of the character of microbial cell walls, cationic porphyrins have a higher affinity to the microbial cells than other porphyrins. In this paper, we evaluate the antibacterial activity of a cationic porphyrin derivative on Pseudomonas aeruginosa in vitro, and preliminarily explore its antibacterial mechanism. Pseudomonas aeruginosa is a gram-negative bacterium without spores, and it is one of the pathogens that easily cause secondary infectious diseases when human immune function is low. The purpose of this study is to explore the inhibitory effect of photodynamic antibacterial chemotherapy-induced by cationic porphyrin derivative on clinical P. aeruginosa and its mechanism. The uptake of photosensitizer by P. aeruginosa and L929 cells was measured by an ultraviolet spectrophotometer. Effect of laser energy density on the bacterial activity of P. aeruginosa and post antibiotic effect were measured by bacterial suspension and tenfold dilution method. Flow cytometry and scanning electron microscopy were used to observe the activity and morphological changes of P. aeruginosa after PACT treatment. The uptake of Tetra-ATPP-Lys-by P. aeruginosa and L929 was shown as concentration-dependent and time-dependent. However the uptake of L929 cell had a clear difference with P. aeruginosa at the same time and concentration intervals(P