Effects of Antimicrobial Photodynamic Therapy Mediated by Free Curcumin and Curcumin-Associated Superparamagnetic Iron Oxide Nanoparticles on Candida spp. and Microcosm Biofilms Associated with Denture Stomatitis

Abstract

Antimicrobial photodynamic therapy (aPDT) has emerged as a promising strategy for managing infections associated withCandidaspp. In this context, nanoformulations of photosensitizers have been investigated to enhance the antimicrobial effects of established compounds, such as curcumin (CUR). In the present study, we evaluated the efficacy of aPDT mediated by curcumin-associated superparamagnetic iron oxide nanoparticles (CUR-SPION) and CUR againstCandidaspp. and complex heterotypic biofilms. Clinical samples were collected from the prosthesis surfaces and oral mucosa of 5 patients clinically diagnosed with denture stomatitis.Candidaisolates were identified using Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS). CUR-SPION were synthesized via the coprecipitation method, allowing the incorporation and association of CUR with the nanoparticles during their formation. Subsequently, their size, morphology, stability, and surface charge were characterized. The isolates were then subjected to treatment with CUR and CUR-SPION, followed by aPDT using visible blue light (wavelength of 420 nm, power output of 1,250 mW, power density of 0.16 W/cm2, and energy density ranging from 0.79–12.78 J/cm2) in planktonic cultures, monotypic biofilms, and microcosm biofilms. Candidayeasts were detected in 3 patients and identified asC. albicansandC. dubliniensis. For both species, the minimum inhibitory concentration (MIC) of CUR was 64 μg/mL in the nonirradiated group and 4 μg/mL after aPDT. In contrast, CUR-SPION exhibited MIC values >64 μg/mL under all conditions tested. CUR-mediated aPDT decreasedCandidacell viability at 4 μg/mL and within 2 h of treatment by 3.6 log10 CFU/mL forC. dubliniensisP1, 3.2 log10 CFU/mL for C. albicans P2, and 2.0 log10 CFU/mL forC. dubliniensisP3, while CUR-SPION-aPDT showed no effect on biofilm viability. CUR-mediated aPDT also significantly reduced the viability of microcosm biofilms, causing inhibitions (log10 CFU/mL) of 1.3 to 2.2 for streptococci, 1.4 to 3.1 for mutans streptococci, 1.5 to 2.2 for staphylococci, and 1.2 to 3.1 for yeast. In conclusion, CUR-mediated aPDT was effective againstC. albicansandC. dubliniensisisolated from denture stomatitis, with an extended spectrum, targeting fungi and bacteria in microcosm biofilms. In contrast, CUR-SPION showed no antifungal activity againstCandidaunder the conditions tested.