Dual wavelength irradiation antimicrobial photodynamic therapy using indocyanine green and metformin doped with nano-curcumin as an efficient adjunctive endodontic treatment modality

Background: Indocyanine green (ICG) doped with nano-curcumin (N-CUR) can increase photosensitivity in antimicrobial photodynamic therapy (aPDT). Since metformin (Met) provides a synergistic advantage with photosensitivity, it was conjugated with N-CUR@ICG. Aim of the study was to evaluate the photosensitizing effect of N-CUR@ICG-Met used as a new photosensitizer in dual wavelengths irradiation (diode laser and light-emitting diode, LED) aPDT in root canals infected with Enterococcus faecalis biofilm. Materials and methods: Following synthesis and confirmation of N-CUR@ICG-Met by Scanning electrone microscope (SEM), Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD) and Zetasizer analysis, the mature microbial biofilm was formed. The quantitative and qualitative evaluations of E. faecalis biofilm were made using microbial viability and SEM analysis of the following groups of treatment modalities (n = 5): 1- N-CUR, 2- ICG, 3- Met, 4- N-CUR@ICG, 5- N-CUR@ICG-Met, 6- Diode laser, 7- LED, 8- aPDT/diode, 9- aPDT/LED, 10- aPDT/diode laser+ LED, 11- aPDT/LED+ diode laser, 12- 2.5 % sodium hypochlorite (NaOCl). In addition, E. faecalis not treated served as negative control. Data were statistically analyzed using One-way Analysis of Variance (ANOVA) and the post-Hoc Bonferroni tests with a level of significance set at P < 0.05. Results: SEM, FT-IR, XRD, Zetasizer analysis confirmed successful doping of ICG-Met onto/into N-CUR. The treatment modality of N-CUR@ICG-Met mediated aPDT/diode laser, aPDT/LED, aPDT/diode laser+ LED, and aPDT/LED+ diode laser statistically decreased the cell viability of E. faecalis for 69.40 %, 75.52 %, 82.74 %, and 83.84 %, respectively compared with the negative control group (P < 0.05). The double wavelengths irradiation technique, which exposed the N-CUR@ICG-Met with diode laser irradiation and immediately after with LED (i.e. group No. 10), as well as, N-CUR@ICG-Met with LED irradiation and immediately after with diode laser (i.e. group No. 11) reduced the viable E. faecalis count in biofilm structures statistically more than the other treatment modalities (P < 0.05). Conclusions: N-CUR@ICG-Met as a new photosensitizer in dual wavelengths irradiation method may improve anti-biofilm activity of aPDT against E. faecalis.