Avaliação da razão dímero/monômero nas formulações comerciais de Azul de Metileno empregados na terapia fotodinâmica antimicrobiana.

Abstract

Antimicrobial photodynamic therapy (aPDT) has been extensively studied in dentistry as an effective approach for treating localized infections, including periodontal and endodontic infections. Among the available photosensitizers (PS), methylene blue (MB) stands out as a widely recognized option in scientific literature due to its photodynamic efficiency. This efficiency, however, is directly influenced by the proportion of dimeric and monomeric forms of MB, which are significantly affected by the ionic interactions present in the solution, thereby impacting the PS's performance in photodynamic applications. This study employed spectroscopic methods to evaluate different commercial formulations of MB intended for aPDT in dentistry, comparing them with analytical-grade MB. The analyzed formulations included various commercial presentations, such as liquid solution, gel, lollipop, and laboratory prepared aqueous solution. The investigated concentrations ranged from 0.005% (w/v) to 0.01% (w/v), corresponding to 156.3 µM and 312.5 µM, respectively. The results revealed significant spectroscopic variations compared to the analytical-grade MB standard, with a marked trend toward the predominance of the dimeric form in almost all evaluated commercial formulations. This predominance of the dimeric form suggests a favoring of Type I photochemical reactions, which may be particularly relevant for antimicrobial efficacy. The study highlights the importance of optimizing commercial MB formulations to maximize their clinical efficiency in aPDT, especially in scenarios where antibiotic resistance poses significant challenges. Furthermore, the findings contribute to the advancement of identifying more effective formulations, offering a promising alternative for managing dental infections and expanding the therapeutic arsenal available for antimicrobial treatments.