Investigation of isomeric tetra-cationic porphyrin activity with peripheral [Pd(bpy)Cl]+ units by antimicrobial photodynamic therapy

• Application of tetra-cationic Pd(II)-porphyrins against bacteria. • Use of porphyrins in the treatment of bacteriosis. • 3-PdTPyP tetra-cationic porphyrin meta isomer is very effectiveness in photo-inactivation of bacteria. In this work, we report the antimicrobial photoinactivation using tetra-cationic porphyrins with peripheral palladium(II) complexes against bacterial strains. Two different isomeric Pd(II)-porphyrins were used and applied in PDI experiments in the strains Gram negative bacilli Escherichia coli , Klebsiella pneumoniae and Pseudomonas aeruginosa and a Gram positive cocci Staphylococcus aureus . All experiments are conducted with adequate concentration (without aggregation) of photosensitizer under white-light irradiation over 2 h . We showed that the most effective PS caused a significative reduction in the concentration of viable bacteria. The present results show that porphyrin with positively charge at meta position ( 3-PtTPyP ) are more efficient photosensitizer against bacteria strains. In this way, tetra-cationic porphyrins might be promising antibacterial PDI agents with potential applications in clinical cases.