Antibacterial activities of cationic porphyrins and porphyrin encapsulated gold nanorods on bacterial cell lines

Bacterial infections form part of the major causes of mortality and morbidity around the world more especially in developing and under-developed countries. Cationic porphyrins have been reported to display better efficacy in antimicrobial photodynamic therapy activity. The purpose of this study was to synthesise the cationic porphyrins; (TAP) and (TPyP) and evaluate their pharmacokinetics and metabolic interactions with the DNA gyrase subunit A. The antibacterial activity of the nano-conjugates was evaluated against Staphylococcus aureus (ATCC 25925), Enterococcus faecalis (ATCC 29212) and Klebsiella pneumoniae (ATCC 4352) using the micro-dilution assay without light. AutoDock Vina was used to assess the molecular interactions between ligands and the DNA gyrase subunit A. The SwissADME online tool was used to assess the pharmacokinetic properties of the nano-conjugates, while the ADMETlab online tool was used to assess the ability to inhibit the hERG gene, human hepatotoxicity and mutagenicity. The test nano-conjugates showed broad-spectrum antibacterial activity against all tested bacterial strains with the MIC values in a range of 0.42 ± 0.1 to2.6 ± 0.7 mg/ml. The nano-conjugates revealed good molecular interaction with DNA gyrase subunit A with their binding free energy in the range of -8.3 to -8.7 kcal/ mol. They are predicted to be P-glycoprotein (P-gp) substrates, able to penetrate the blood-brain barrier and non-inhibitors of cytochrome P450 (CYP) isomers (CYP 2C19, CYP 2C9 and CYP 2D6). Both nanoconjugates have the potential to cause cardiotoxic and mutagenic effects but not hepatotoxic effects. The results show that the synthesized compounds have the potential as anti-bacterial PDT agents.