Effect of fiber insertion depth on antibacterial efficacy of photodynamic therapy against Enterococcus faecalis in rootcanals

Smart dental materials for antimicrobial applications

Smart biomaterials can sense and react to physiological or external environmental stimuli (e.g., mechanical, chemical, electrical, or magnetic signals). The last decades have seen exponential growth in the use and development of smart dental biomaterials for antimicrobial applications in dentistry. These biomaterial systems offer improved efficacy and controllable bio-functionalities to prevent infections and extend the longevity of dental devices. This review article presents the current state-of-the-art of design, evaluation, advantages, and limitations of bioactive and stimuli-responsive and autonomous dental materials for antimicrobial applications. First, the importance and classification of smart biomaterials are discussed. Second, the categories of bioresponsive antibacterial dental materials are systematically itemized based on different stimuli, including pH, enzymes, light, magnetic field, and vibrations. For each category, their antimicrobial mechanism, applications, and examples are discussed. Finally, we examined the limitations and obstacles required to develop clinically relevant applications of these appealing technologies.

Antibacterial Effect of Red Laser Therapy on Enterococcus faecalis Using Different Photosensitizers: An In Vitro Study

Objective

To assess the antibacterial effect of red laser using different photosensitizers such as methylene blue and malachite green on monoradicular premolars contaminated with E. faecalis ATCC 29212.

Methods

This was an in vitro experimental study. Monoradicular premolars (44, 45, 34, and 35) were used, which were treated with ProTaper Next. After instrument change, irrigation, disinfection, and aspiration were performed with 2 ml of 4% NaOCl with a NaviTip 30°G needle (Ultradent, South Jordan, UT, USA). Group 1: RL + MB (red laser associated with methylene blue photosensitizer), group 2: RL + MG (red laser associated with malachite green photosensitizer), and group 3: control (no treatment). The E. faecalis strain was cultured on trypticase soy agar (TSB) (Difco, Detroit, MI, USA) and incubated at 37°C for 24 h. After the incubation period, colony-forming units (CFU/ml) of each group were counted using the plate count method. The ANOVA test was used with a significance level of p < 0.05.

Results

Group 1 had the lowest antibacterial contamination as it averaged only 530 ± 581.3 CFU/ml, while group 2 had the highest contamination with an average of 1990 ± 542.5 CFU/ml. Comparison revealed that there were statistically significant differences between the RL + MB and RL + MG groups (p < 0.001).

Conclusions

Group 1 had the best antimicrobial potential because it presented the lowest contamination in CFU/ml of E. faecalis compared to group 2 and group 3.

Enhanced Antibacterial Activity of Indocyanine Green-Loaded Graphene Oxide via Synergistic Contact Killing, Photothermal and Photodynamic Therapy

Methicillin-resistant Staphylococcus aureus (MRSA) has become a serious threat to human's health. Recently, photodynamic/photothermal therapy (PDT/PTT) has emerged as promising strategies against antibiotics-resistant pathogens due to their broad antibacterial spectrum and negligible resistance. In this work, the photosensitizer indocyanine green (ICG) was loaded on graphene oxide (GO) nanosheets with good encapsulation efficiency high to 92.31%. Under near-infrared (NIR) irradiation, the anti-MRSA efficiency of GO (20 μg/ml), ICG (5 μg/ml) and ICG-GO (5 μg/ml-20 μg/ml) was 33.76%, 40.15% and 99.86%, respectively. We further showed that NIR irradiation mildly increased the temperature to 43.1 °C for ICG-GO, and lead to the highest reactive oxygen species (ROS) generation (316.51% and 157.11% compared to ICG alone and GO alone). In conclusion, ICG-GO has a great potential for antibacterial treatment due to its synergistic contact killing, photothermal and photodynamic activity.

Evaluation of antimicrobial photodynamic therapy with toluidine blue against Enterococcus faecalis: Laser vs LED

AIM

This study aimed to compare the antibacterial effect of antimicrobial photodynamic therapy (aPDT) by use of light emitting diode (LED) and diode laser light sources with toluidine blue (TBO) photosensitizer on Enterococcus faecalis (E. faecalis) biofilm in root canals of extracted single-canal human teeth.

METHODS

Eighty-five sound human single-canal teeth were chosen for this study and standardized to have 15 mm of root length. The root canals were prepared with ProTaper rotary files and inoculated and incubated with E. faecalis for one week. Samples were divided into five experimental (n = 15) groups of PDT with TBO/LED, TBO/diode laser, LED, TBO and diode laser and one negative (NaOCl) and one positive (no treatment) control group. Dentin chip samples were collected from inside the canals using size 40 hedstrom file. The number of colony forming units (CFUs) in each group was calculated.

RESULTS

Irrespective of the light source used for activation of photosensitizer (diode or LED), PDT was significantly more effective than other experimental groups (P < 0.001). No significant difference was noted between aPDT with diode laser or LED (P > 0.05). No significant difference was noted in colony count among other groups (LED, TBO, diode; P > 0.05).

CONCLUSION

The results showed that aPDT significantly decreased residual bacteria in the canal. Thus, it may be used as an adjunct for root canal disinfection. Both diode and LED are suitable light sources for this purpose and can be used alternatively.

Near-infrared NIR irradiation and sodium hypochlorite: An efficacious association to counteract the Enterococcus faecalis biofilm in endodontic infections

New strategies are necessary for the prevention of endodontic infections caused by Enterococcus faecalis, a common resistant pathogen and biofilm producer. Aim of the present study was to compare the effects of Near-Infrared (NIR) Light-Emitting Diode (LED) irradiation and different concentrations of sodium hypochlorite (NaOCl) alone or combined to each other on the E. faecalis biofilm, on artificial and human dentin surfaces. E. faecalis ATCC 29212 preformed biofilms, on polystyrene wells and on dentin discs, were treated with 880 nm NIR irradiation and NaOCl at 4%, 2.5%, 1% and 0.5% alone and combined to each other (NIR irradiation plus NaOCl 1% or 0.5%) at 5 and 10 min. Treated biofilms were compared to the controls for (i) biofilm biomass evaluation, (ii) CFU count for the quantification of cultivable cells and (iii) cells viability. All the detected experimental conditions displayed a significant reduction of biofilm biomass (p < 0.001) and CFUs/mL (p < 0.01) in respect to the controls on both tested surfaces. The effects on the E. faecalis biomass, colony count and cell viability were not time-dependent except for NaOCl 2.5% and 1% in the biofilm biomass reductions on human dentin discs. NIR-LED irradiation alone showed a reduction of E. faecalis aggregates without interfering with cell viability whereas NaOCl alone expressed a killing effect in a concentration dependent way. The combination of NIR-LED irradiation with NaOCl 1% and 0.5% displayed a double effect of cluster disaggregation and cell killing. In particular, NIR-LED irradiation combined with NaOCl 0.5% displayed an anti-biofilm activity major than those expressed by NaOCl 0.5% alone (p = 0.001) with a reduction of biomass 93% vs 71% and 97% vs 25% after 10 min, on polystyrene wells and human dentin discs, respectively. The innovative use of NIR-LED irradiation combined at short times with low concentration of NaOCl (1% and 0.5%) is capable to reach a significant effect on E. faecalis biofilm, especially on human dentin discs.

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.

An Insight into Advanced Approaches for Photosensitizer Optimization in Endodontics-A Critical Review

Apical periodontitis is a biofilm-mediated disease; therefore, an antimicrobial approach is essential to cure or prevent its development. In the quest for efficient strategies to achieve this objective, antimicrobial photodynamic therapy (aPDT) has emerged as an alternative to classical endodontic irrigation solutions and antibiotics. The aim of the present critical review is to summarize the available evidence on photosensitizers (PSs) which has been confirmed in numerous studies from diverse areas combined with several antimicrobial strategies, as well as emerging options in order to optimize their properties and effects that might be translational and useful in the near future in basic endodontic research. Published data notably support the need for continuing the search for an ideal endodontic photosensitizer, that is, one which acts as an excellent antimicrobial agent without causing toxicity to the human host cells or presenting the risk of tooth discoloration. The current literature on experimental studies mainly relies on assessment of mixed disinfection protocols, combining approaches which are already available with aPDT as an adjunct therapy. In this review, several approaches concerning aPDT efficiency are appraised, such as the use of bacteriophages, biopolymers, drug and light delivery systems, efflux pump inhibitors, negative pressure systems, and peptides. The authors also analyzed their combination with other approaches for aPDT improvement, such as sonodynamic therapy. All of the aforementioned techniques have already been tested, and we highlight the biological challenges of each formulation, predicting that the collected information may encourage the development of other effective photoactive materials, in addition to being useful in endodontic basic research. Moreover, special attention is dedicated to studies on detailed conditions, aPDT features with a focus on PS enhancer strategies, and the respective final antimicrobial outcomes. From all the mentioned approaches, the two which are most widely discussed and which show the most promising outcomes for endodontic purposes are drug delivery systems (with strong development in nanoparticles) and PS solubilizers.

Photoinactivation of ESKAPE pathogens: overview of novel therapeutic strategy

The emergence of antimicrobial drug resistance requires development of alternative therapeutic options. Multidrug-resistant strains of Enterococcus spp., Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumanii, Pseudomonas aeruginosa and Enterobacter spp. are still the most commonly identified antimicrobial-resistant pathogens. These microorganisms are part of the so-called 'ESKAPE' pathogens to emphasize that they currently cause the majority of hospital acquired infections and effectively 'escape' the effects of antibacterial drugs. Thus, alternative, safer and more efficient antimicrobial strategies are urgently needed, especially against 'ESKAPE' superbugs. Antimicrobial photodynamic inactivation is a therapeutic option used in the treatment of infectious diseases. It is based on a combination of a photosensitizer, light and oxygen to remove highly metabolically active cells.

Loss of the adhesion G-protein coupled receptor ADGRF5 in mice induces airway inflammation and the expression of CCL2 in lung endothelial cells

Background

Adhesion G-protein coupled receptor F5 (ADGRF5) was recently identified as an essential regulator of pulmonary surfactant homeostasis in alveolar type II cells. We previously showed that in addition to abnormal surfactant accumulation, Adgrf5-deficient (Adgrf5^−/−) mice exhibit emphysema-like signs, suggesting a possible role for ADGRF5 in immune regulation. Here, we extended the phenotypic analysis of Adgrf5^−/− mice to help understand its biological role in the lung, and especially in immune regulation.

Methods

Histological features of lungs were evaluated by Alcian blue and Masson’s trichrome staining. Quantitative real-time PCR (qPCR) and western blot analyses were performed to analyze the differential expression of genes/proteins related to airway inflammation in lungs between wildtype and Adgrf5^−/− mice. Acid–base status was assessed by performing blood gas tests and urine pH measurements. Inflammatory cell counting was performed using Giemsa-stained bronchoalveolar lavage cells. Serum IgE concentrations were determined by enzyme-linked immunosorbent assay. The expression of Ccl2, S100a8, S100a9, and Saa3 in primary lung endothelial cells (ECs) was determined by qPCR and/or western blotting. Finally, the effect of administrating RS504393 to 2-week-old Adgrf5^−/− mice on gene expression in the lungs was analyzed by qPCR.

Results

Adgrf5^−/− mice exhibited several features of chronic airway inflammation (mucous cell metaplasia, mucus hyperproduction, subepithelial fibrosis, respiratory acidosis, high serum IgE, mast cell accumulation, and neutrophilia) in parallel with elevated expression of genes involved in mucous cell metaplasia (Muc5ac, Muc5b, Slc26a4, and Clca1), fibrosis (Tgfb1, Col1a1, Fn1, and Tnc), and type 2 immune response (Il4, Il5, Il13, IL-25, and IL-33) at 12 and/or 30 weeks of age. In contrast, mRNA expression of Ccl2, S100a8, and S100a9 was upregulated in embryonic or neonatal Adgrf5^−/− lungs as well as in lung ECs of Adgrf5^−/− mice at 1 week of age. RS504393 treatment suppressed the upregulation of S100a8, S100a9, Slc26a4, and Il5 in Adgrf5^−/− lungs.

Conclusions

Targeted disruption of ADGRF5 results in the development of airway inflammation, which is likely mediated by the type 2 immune response and possibly CCL2-mediated inflammation. ADGRF5 also has a potential role in the regulation of genes encoding CCL2 in lung ECs, thereby maintaining immune homeostasis.

Electronic supplementary material

The online version of this article (10.1186/s12931-019-0973-6) contains supplementary material, which is available to authorized users.

The effect of indocyanine green loaded on a novel nano-graphene oxide for high performance of photodynamic therapy against Enterococcus faecalis

BACKGROUND

Recently developed photodynamic therapy (PDT) has gained attention for achieving effective root canal disinfection. Using an optimized nontoxic photosensitizer (PS), such as indocyanine green (ICG), is an imperative part of this technique. Therefore, the objective of the current study was to improve ICG photodynamic properties through incorporation of ICG into nano-graphene oxide (NGO) in order to produce NGO-ICG as a new PS and also to assess the antimicrobial effects of NGO-ICG against Enterococcus faecalis after photodynamic therapy.

MATERIALS AND METHODS

NGO-ICG was synthesized based on oxidation of graphite flakes and direct loading of ICG onto NGO. NGO-ICG formation was confirmed using the Fourier Transform Infrared Spectroscopy (FT-IR), Scanning Electron Microscopy (SEM), and UV-vis spectrometry. The antimicrobial and anti-biofilm potential of NGO-ICG-PDT against E. faecalis was assessed via colony forming unit and crystal violet assays, respectively.

RESULTS

FT-IR, SEM and UV-vis spectrometry confirmed successful synthesis of NGO-ICG containing 200μg/mL of ICG. NGO-ICG-PDT at an energy density of 31.2J/cm² showed a significant reduction (2.81 log) in the count of E. faecalis (P<0.05). NGO-ICG-PDT significantly reduced the biofilm formation ability of E. faecalis up to 99.4% (P<0.05). The overall antimicrobial and anti-biofilm potential of NGO-ICG-PDT was higher than PDT based on ICG (1000μg/mL) (47% and 21%, respectively).

CONCLUSION

Because NGO-ICG-PDT showed a significant reduction in the number and biofilm formation ability of E. faecalis at low ICG concentrations (200μg/mL), it could be a new approach to adjuvant treatment of endodontic infections.