Zinc, Tin and Silver Porphyrins (TPP, TCPP, TMPP, THPP, TPPS, TMPyP) as photosensitizers in antibacterial photodynamic therapy for chronic wounds: A screening study

Abstract

Continuous proliferation of bacteria in a wound delays its healing process, and could further extend to becoming a chronic wound infection. The effectiveness of different porphyrins as a photosensitizer in antibacterial photodynamic therapy for the inactivation of some wound-colonizing bacteria was studied as a screening experiment. Meso-tetra(4-methoxyphenyl) porphyrin, (TMPP), meso-tetra(4-hydroxyphenyl) porphyrin (THPP), meso-tetra(4-carboxyphenyl) porphyrin, (TCPP), meso-tetra(N-methyl-4-pyridyl) porphyrin, (TMPyP) were synthesized, each complexed with zinc, tin and silver. The in-vitro and photo-toxicity properties of the porphyrins and their complexes were assessed on some selected wound colonizing multi-drug resistant bacterial strains (Staphylococcus aureus, Klebsiella pneumoniae, Proteus mirabilis, and Escherichia coli) using agar well diffusion method. Photo-toxicity of the compounds were investigated using a 100-Watt tungsten lamp while the in-vitro toxicity was carried out in the dark.  The results were compared with previously reported work carried out by this group on meso-tetra(phenyl)porphyrin (TPP), meso-tetra(4-sulphonatophenyl) porphyrin, (TPPS) and their corresponding Zn, Sn and Ag complexes. Most of the porphyrins showed biocidal activities against three of the test isolates with an exception to Proteus sp. ZnTMPyP and ZnTHPP only showed photo-toxic activities against the four test isolates. While SnTHPP, ZnTPPS, ZnTCPP, and SnTCPP all exhibited both toxic and photo-toxic activities against all four bacterial isolates. The Ag-porphyrins had the poorest inactivation activity.