Antimicrobial Behavior and Cytotoxicity of Indocyanine Green in Combination with Visible Light and Water-Filtered Infrared A Radiation against Periodontal Bacteria and Subgingival Biofilm

The widespread increase of antibiotic resistance highlights the need for alternative treatments such as antimicrobial photodynamic therapy (aPDT). This study aimed to evaluate the antimicrobial behavior and cytotoxicity of aPDT with indocyanine green (ICG) in combination with visible light (Vis) and water-filtered infrared A (wIRA). Representative periodontal bacteria (Parvimonas micra, Atopobium riame, Slackia exigua, Actinomyces naeslundii, Porphyromonas gingivalis, Fusobacterium nucleatum, Aggregatibacter actinomycetemcomitans, and Prevotella nigrescens) and subgingival in situ biofilms from periodontal patients were treated with aPDT for 5 min. ICG was used at different concentrations (50-500 mu g/mL) and the number of viable cells was determined in colony forming units (CFU). Untreated negative controls and 0.2% chlorhexidine as a positive control were also prepared. The cytotoxicity test on human keratinocytes in vitro was analyzed with the AlamarBlue assay after 5, 10, and 20 min, with four ICG concentrations, and at two temperatures (room temperature and 37 degrees C). The tested periodontal pathogens treated with aPDT were eliminated in a range between 1.2 and 6.7 log(10) CFU, except for A. naeslundii, which was killed at a lower range. The subgingival biofilm treated with aPDT expressed significant differences to the untreated controls except for at 300 mu g/mL ICG concentration. The cytotoxicity was directly related to the concentration of ICG and irradiation time. These observations raise questions concerning the use of this specific aPDT as an adjuvant to periodontal treatments due to its possible toxicity towards human gingival cells.

Automated summary

This study aimed to evaluate the antimicrobial properties and cytotoxicity of antimicrobial photodynamic therapy (aPDT) using indocyanine green (ICG) in combination with visible light (Vis) and water-filtered infrared A (wIRA). The results showed that aPDT effectively eliminated most periodontal bacteria and subgingival biofilms, but also exhibited cytotoxicity towards human gingival cells. These findings raise concerns about the potential toxicity of this specific aPDT as an adjuvant to periodontal treatments.