Efficacy of 5% Aminolaevulinic Acid and Red Light on Enterococcus faecalis in Infected Root Canals

Assessment of photodynamic therapy efficacy against Escherichia coli-Enterococcus faecalis biofilms using optical coherence tomography

Significance

In orthopedic trauma surgery, spatially structured biofilm ecosystems of bacteria that colonize orthopedic devices account for up to 65% of all healthcare infections, including tens of millions of people affected in the United States. These biofilm infections typically show increased resistance to antibiotics due to their structure and composition, which contributes significantly to treatment failure. Anti-biofilm approaches are needed together with clinically usable microscopic-resolution imaging techniques for treatment efficacy assessment.

Aim

Antimicrobial photodynamic therapy (aPDT) has been recently proposed to combat clinically relevant biofilms (chronic wound infections, dental biofilms, etc.) using photosensitizers excited with visible light to generate reactive oxygen species that can kill bacteria residing within pathogenic biofilms. We aim to assess the efficacy of this treatment for eradication of biofilms typically present on surfaces of orthopedic devices (e.g., intramedullary nails and osseointegrated prosthetic implants).

Approach

In the first phase reported here, we test aPDT in vitro by growing biofilms of Escherichia coli and Enterococcus faecalis bacteria (two of the seven most common pathogens found in orthopedic trauma patients) inside soft lithography-fabricated microfluidic devices. We treat these biofilms with 5-aminolevulinic acid (5-ALA)-based aPDT, evaluate treatment efficacy with optical coherence tomography, and compare with regular clinical antibiotic treatment outcomes.

Results

The antibacterial efficiency of 5-ALA-based aPDT showed nonlinear dependence on the photosensitizer concentration and the light power density, with low parameters ( 30    J / cm 2 light dose, 100    mg / mL 5-ALA concentration) being significantly more effective than antibiotic-treated groups ( p < 0.01 ), reaching 99.98% of bacteria killed at 150    J / cm 2 light dose and 200    mg / mL 5-ALA concentration setting.

Conclusions

Performed experiments enable the translation of this portable treatment/imaging platform to the second phase of the study: aPDT treatment response assessment of biofilms grown on orthopedic hardware.

Molecular docking and antimicrobial activities of photoexcited inhibitors in antimicrobial photodynamic therapy against Enterococcus faecalis biofilms in endodontic infections

Antimicrobial photodynamic therapy (aPDT) is a promising approach to combat antibiotic resistance in endodontic infections. It eliminates residual bacteria from the root canal space and reduces the need for antibiotics. To enhance its effectiveness, an in silico and in vitro study was performed to investigate the potential of targeted aPDT using natural photosensitizers, Kojic acid and Parietin. This approach aims to inhibit the biofilm formation of Enterococcus faecalis, a frequent cause of endodontic infections, by targeting the Ace and Esp proteins. After determining the physicochemical characteristics of Ace and Esp proteins and model quality assessment, the molecular dynamic simulation was performed to recognize the structural variations. The stability and physical movement of the protein-ligand complexes were evaluated. In silico molecular docking was conducted, followed by ADME/Tox profiling, pharmacokinetics characteristics, and assessment of drug-likeness properties of the natural photosensitizers. The study also investigated the changes in the expression of genes (esp and ace) involved in E. faecalis biofilm formation. The results showed that both Kojic acid and Parietin complied with Lipinski's rule of five and exhibited drug-like properties. In silico analysis indicated stable complexes between Ace and Esp proteins and the natural photosensitizers. The molecular docking studies demonstrated good binding affinity. Additionally, the expression of the ace and esp genes was significantly downregulated in aPDT using Kojic acid and Parietin with blue light compared to the control group. This investigation concluded that Kojic acid and Parietin with drug-likeness could efficiently interact with Ace and Esp proteins with a strong binding affinity. Hence, natural photosensitizers-mediated aPDT can be considered a promising adjunctive treatment against endodontic infections.

What Is the Impact of Antimicrobial Photodynamic Therapy on Oral Candidiasis? An In Vitro Study

This study aimed to evaluate the ability of photodynamic therapy, based on the use of a gel containing 5% delta aminolaevulinic acid (ALAD) for 45' followed by irradiation with 630 nm LED (PDT) for 7', to eradicate Candida albicans strains without damaging the gingiva. C. albicans oral strains and gingival fibroblasts (hGFs) were used to achieve these goals. The potential antifungal effects on a clinical resistant C. albicans S5 strain were evaluated in terms of biofilm biomass, colony forming units (CFU/mL) count, cell viability by live/dead analysis, and fluidity membrane changes. Concerning the hGFs, viability assays, morphological analysis (optical, scanning electronic (SEM), and confocal laser scanning (CLSM) microscopes), and assays for reactive oxygen species (ROS) and collagen production were performed. ALAD-mediated aPDT (ALAD-aPDT) treatment showed significant anti-biofilm activity against C. albicans S5, as confirmed by a reduction in both the biofilm biomass and CFUs/mL. The cell viability was strongly affected by the treatment, while on the contrary, the fluidity of the membrane remained unchanged. The results for the hGFs showed an absence of cytotoxicity and no morphological differences in cells subjected to ALAD-aPDT expected for CLSM results that exhibited an increase in the thickening of actin filaments. ROS production was augmented only at 0 h and 3 h, while the collagen appeared enhanced 7 days after the treatment.

Photodynamic Suppression of Enterococcus Faecalis in Infected Root Canals with Indocyanine Green, TroloxTM and Near-Infrared Light

Recently, our group showed that additional supplementation of Trolox™ (vitamin E analogue) can significantly enhance the antimicrobial photodynamic effect of the photosensitizer Indocyanine green (ICG). Up to now, the combined effect has not yet been investigated on Enterococcus faecalis in dental root canals. In the present in vitro study, eighty human root canals were inoculated with E. faecalis and subsequently subjected to antimicrobial Photodynamic Therapy (aPDT) using ICG (250, 500, 1000 µg/mL) and near-infrared laser light (NIR, 808 nm, 100 Jcm-2). Trolox™ at concentrations of 6 mM was additionally applied. As a positive control, irrigation with 3% NaOCl was used. After aPDT, root canals were manually enlarged and the collected dentin debris was subjected to microbial culture analysis. Bacterial invasion into the dentinal tubules was verified for a distance of 300 µm. aPDT caused significant suppression of E. faecalis up to a maximum of 2.9 log counts (ICG 250 µg/mL). Additional application of TroloxTM resulted in increased antibacterial activity for aPDT with ICG 500 µg/mL. The efficiency of aPDT was comparable to NaOCl-irrigation inside the dentinal tubules. In conclusion, ICG significantly suppressed E. faecalis. Additional application of TroloxTM showed only minor enhancement. Future studies should also address the effects of TroloxTM on other photodynamic systems.

Red Light and 5% Aminolaevulinic Acid (5%) Inhibit Proliferation and Migration of Dysplastic Oral Keratinocytes via ROS Production: An In Vitro Study

Undiagnosed and untreated oral precancerous lesions often progress into malignancies. Photodynamic therapy (PDT) might be a minimally invasive alternative to conventional treatments. 5-aminolevulinic acid (5-ALA) is one of the most commonly used photosensitizers in PDT, and it is effective on many cancer types. However, its hydrophilic characteristic limits cell membrane crossing. In the present study, the effect of a newly formulated gel containing 5% 5-ALA in combination with red light (ALAD-PDT) on a premalignant oral mucosa cell line was investigated. The dysplastic oral keratinocyte (DOK) cells were incubated with ALAD at different concentrations (0.1, 0.5, 1, and 2 mM) at two different times, 45 min or 4 h, and then irradiated for 7 min with a 630 nm LED (25 J/cm2). MTT assay, flow cytometry, wound healing assay, and quantitative PCR (qPCR) were performed. ALAD-PDT exerted inhibitory effects on the proliferation and migration of DOK cells by inducing ROS and necrosis. mRNA analysis showed modulation of apoptosis-related genes' expression (TP53, Bcl-2, survivin, caspase-3, and caspase-9). Furthermore, there was no difference between the shorter and longer incubation times. In conclusion, the inhibitory effect of the ALAD-PDT protocol observed in this study suggests that ALAD-PDT could be a promising novel treatment for oral precancerous lesions.