Avaliação da atividade antimicrobiana e da toxicidade do Phtalox® em modelos in vitro e in vivo de Galleria mellonella

Abstract

Periodontal disease is a condition characterized by progressive deterioration of the soft and hard tissues that comprise the periodontal complex. This deterioration is the result of a complex interaction between imbalanced microbial communities and exacerbated immune responses in the gingival and periodontal tissues. In the context of this disease, the periodontopathogenic biofilm is a community of microorganisms composed of various bacterial species, such as Porphyromonas gingivalis and Tannerella forsythia. Supportive treatment for periodontal disease often involves the use of antibiotics, thus necessitating research focused on the development of new antibiotics capable of inhibiting or eliminating the biofilm. In this context, Phtalox ® (PHT) emerges as a potential antimicrobial agent. It is a modified iron phthalocyanine with carboxyl groups at its ends and iron at the center, exhibiting oxidizing properties that promote continuous generation of reactive oxygen in the presence of molecular oxygen. In this study, the minimum inhibitory concentration (MIC) determination test was performed using sessile bacteria. Additionally, a seven- day subgingival biofilm composed of 33 bacterial species was cultivated and treated. The metabolic activity and microbial composition of the biofilm were evaluated using the DNA-DNA hybridization technique, known as the Checkerboard technique. The Galleria mellonella model was used for in vivo toxicity and antimicrobial activity testing, as it is a method recognized by the National Network of Alternative Methods to Animal Use (RENAMA), where the larvae possess a cellular immune response mediated by phagocytic cells that can be compared to mammalian neutrophils. The results of the MIC test indicated that PHT did not perform well against the tested microorganisms under the conditions of the method. However, PHT at a concentration of 10,000 μM demonstrated statistically similar efficacy to Chlorhexidine 2.374 μM (CLX) in reducing the in vitro subgingival multispecies biofilm, inhibiting the growth of key disease pathogens. In vivo toxicity tests using the G. mellonella model demonstrated that the product is not toxic, even at high dosages. Furthermore, PHT proved to be as effective as CLX in promoting the survival of larvae infected with Staphylococcus aureus. These results highlight the potential of Phtalox ® as a promising alternative in the fight against periodontal disease.