Synthesis, characterization, and application of methylene blue functionalized reduced graphene oxide for photodynamic therapy in root canal treatment

BACKGROUND & OBJECTIVE: Root canal infections are challenging to eradicate with conventional methods due to their complexity. Traditional chemical irrigants often fail to reach all bacterial colonies. Methylene blue (MB), used in photoactivated disinfection (PAD), generates reactive oxygen species (ROS) upon light activation, effectively killing bacteria. This study aimed to synthesize, characterize, and explore MB-functionalized reduced graphene oxide (MB/rGO) for enhanced photoactivated disinfection in root canal treatment.

METHODS: This in-vitro study was conducted from April 2024 to September 2024 at Universiti Sains Malaysia and King Faisal University. Graphene oxide (GO) was reduced by dispersing GO in deionized water with sonication, followed by adding sodium hydroxide (NaOH) under vigorous stirring. The suspension obtained was centrifuged, washed, and dried to yield reduced graphene oxide (rGO). For functionalization, rGO was dispersed in ethanol and mixed with methylene blue (MB) solution, followed by stirring and drying to obtain MB-functionalized rGO. The antibacterial and antifungal activities of MB alone and in combination with rGO, with or without laser exposure, were tested using the agar well diffusion method. The paired sample t-test was used to compare the inhibition zones for different treatment groups of E. faecalis and C. albicans.

RESULTS: FTIR analysis confirmed successful functionalization by identifying specific functional groups of rGO and MB. Similarly, Raman spectroscopy indicated that GO-MB had an intermediate level of defects, and SEM analysis confirmed slight morphological changes with MB molecules attached to the rGO surface. Moreover, the antimicrobial test revealed that MB/rGO with laser performed significantly better (p=0.042) than MB/rGO without laser and MB with laser group (p=0.034) against E. faecalis.

CONCLUSIONS: The functionalization of MB with rGO and its application with laser treatment significantly enhanced antimicrobial and antifungal activity, suggesting potential benefits for endodontic treatments and other dental applications.