Phthalocyanine derivative as an antimicrobial agent against periodontitis-related multispecies biofilms

The activity of iron tetracarboxyphthalocyanine (FeTcPc) was investigated in the formation of subgingival biofilm by bacterial species associated with periodontal disease. A multispecies biofilm model was developed using the Calgary biofilm device and incubated at 37 °C under anaerobic conditions for 7 days. Starting from day 3, the biofilm was treated with FeTcPc twice daily for one minute over four days, at concentrations ranging from 1,000 to 10,000 μM. Chlorhexidine at 0.12% and the vehicle used to dissolve the test agent, phosphate-buffered saline (PBS), served as positive and negative controls, respectively. After 7 days, the biofilm metabolic activity was measured using 2,3,5-triphenyl tetrazolium chloride (TTC) to differentiate metabolically active cells from inactive ones. Finally, the microbial profile of the treated biofilm was assessed using the DNA-DNA hybridisation method. FeTcPc at 10,000 μM and chlorhexidine treatments reduced the total bacterial counts, without a significant difference from each other. Additionally, FeTcPc at 10,000 μM inhibited the growth of 7 microorganisms when compared with the negative control, highlighting effects on <i>Porphyromonas gingivalis</i>, <i>Tannerella forsythia</i> and <i>Fusobacterium nucleatum vincentii</i>. The study demonstrated that FeTcPc, at a concentration of 10,000 μM, was as effective as chlorhexidine (0.12%) in reducing the total bacterial counts and well-recognised periodontal pathogens levels in the subgingival biofilm, highlighting the potential of FeTcPc as an alternative to conventional periodontal treatments. These findings indicate that FeTcPc has a promising impact on the inhibition of key bacteria involved in periodontal disease, which may open new perspectives for targeted and less aggressive therapies.