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

The Effect of Photodynamic Therapy on Enterococcus spp. and Its Application in Dentistry: A Scoping Review

Enterococci spp. are Gram-positive bacteria that cause mild to severe infections, many associated with the oral cavity, such as periapical infections and healthcare-associated infections (HAIs). Many of these infections become serious diseases that are difficult to resolve, specifically when multidrug-resistant (MDR) strains cause them. In recent years, the number of MDR strains of Enterococcus spp. has increased significantly. This increased prevalence of MDR strains produces significant pressure to generate more antimicrobial therapies, but there is a decline in the production of new antibiotics, driving the development of complementary therapies, such as photodynamic therapy (PDT). PDT combines a photosensitizer agent (PS), light, and oxygen to cause photooxidative stress in bacterial cells. PDT can eradicate Enterococcus spp. contaminations, improve the classic cleaning processes, and eradicate the bacteria in dental pieces. PDT's effectiveness can be improved with nanoparticles that function as carriers. Our work aims to describe the advances in PDT against Enterococcus spp. as a complement to antibiotic therapy, focusing on infections by Enterococcus faecium and Enterococcus faecalis, dental hygiene, and using nanoparticles to improve the antimicrobial effect. A systematic bibliographic search without a meta-analysis was conducted on various databases, using inclusion and exclusion criteria to identify the most relevant research. Of the 193 non-redundant articles found, 65 were selected for a systematic review, from which a summary table was created and a manual description was made. Photodynamic therapy for treating E. faecium and E. faecalis is a widely studied area, with promising results concerning bactericidal effectiveness and reductions in biofilm formation, particularly in regard to dental hygiene. Because most of the studies were conducted in vitro or ex vivo, the results indicated that there were not sufficient data to initiate clinical trials for safety and efficacy studies on humans.

Globus Lucidus: A porcine study of an intracranial implant designed to deliver closed, repetitive photodynamic and photochemical therapy in glioblastoma

OBJECTIVE

Herein we describe initial results in a porcine model of a fully implantable device designed to allow closed, repetitive photodynamic treatment of glioblastoma (GBM).

METHODS

This implant, Globus Lucidus, is a transparent quartz glass sphere with light-emitting diodes releasing wavelengths of 630 nm (19.5 mW/cm2), 405 nm (5.0 mW/cm2) or 275 nm (0.9 mW/cm2). 5-aminolevulinic acid was the photosensitizing prodrug chosen for use with Globus Lucidus, hence the implants illuminated at 630 nm or 405 nm. An additional 275 nm wavelength-emittance was included to explore the effects of photochemical therapy (PCT) by ultraviolet (UV) light. Twenty healthy domestic pigs underwent right-frontal craniotomies. The Globus Lucidus device was inserted into a surgically created right-frontal lobe cavity. After postoperative recovery, irradiation for up to 30 min daily for up to 14 d, or continuous irradiation for up to 14.6 h was conducted.

RESULTS

Surgery, implants, and repeated irradiations using the different wavelengths were generally well tolerated. Social behavior, wound healing, body weight, and temperature remained unaffected. Histopathological analyses revealed consistent leukocyte infiltration around the intracerebral implant sites with no significant differences between experimental and control groups.

CONCLUSION

This Globus Lucidus porcine study prepares the groundwork for adjuvant, long-term, repeated PDT of the GBM infiltration zone. This is the first report of a fully implantable PDT/PCT device for the potential treatment of GBM. A preclinical effectivity study of Globus Lucidus PDT/PCT is warranted and in advanced stages of planning.

Toluidine blue O directly and photodynamically impairs the bioenergetics of liver mitochondria: a potential mechanism of hepatotoxicity

Toluidine blue O (TBO) is a phenothiazine dye that, due to its photochemical characteristics and high affinity for biomembranes, has been revealed as a new photosensitizer (PS) option for antimicrobial photodynamic therapy (PDT). This points to a possible association with membranous organelles like mitochondrion. Therefore, here we investigated its effects on mitochondrial bioenergetic functions both in the dark and under photostimulation. Two experimental systems were utilized: (a) isolated rat liver mitochondria and (b) isolated perfused rat liver. Our data revealed that, independently of photostimulation, TBO presented affinity for mitochondria. Under photostimulation, TBO increased the protein carbonylation and lipid peroxidation levels (up to 109.40 and 119.87%, respectively) and decreased the reduced glutathione levels (59.72%) in mitochondria. TBO also uncoupled oxidative phosphorylation and photoinactivated the respiratory chain complexes I, II, and IV, as well as the F_oF₁-ATP synthase complex. Without photostimulation, TBO caused uncoupling of oxidative phosphorylation and loss of inner mitochondrial membrane integrity and inhibited very strongly succinate oxidase activity. TBO's uncoupling effect was clearly seen in intact livers where it stimulated oxygen consumption at concentrations of 20 and 40 μM. Additionally, TBO (40 μM) reduced cellular ATP levels (52.46%) and ATP/ADP (45.98%) and ATP/AMP (74.17%) ratios. Consequently, TBO inhibited gluconeogenesis and ureagenesis whereas it stimulated glycogenolysis and glycolysis. In conclusion, we have revealed for the first time that the efficiency of TBO as a PS may be linked to its ability to photodynamically inhibit oxidative phosphorylation. In contrast, TBO is harmful to mitochondrial energy metabolism even without photostimulation, which may lead to adverse effects when used in PDT.

Impact of antimicrobial photodynamic therapy on the bond-strength and penetration of endodontic sealers: A systematic review

BACKGROUND

Antimicrobial photodynamic therapy (aPDT) has been used for the disinfection of root canals. Studies have been carried out on its effect on the bond-strength and penetration of endodontic sealers. The aim of this systematic review is to critically analyze the literature and summarize the outcomes of these studies.

MATERIALS AND METHODS

An electronic search was conducted on research databases PubMED/Medline, ISI Web of Knowledge, Embase, Scopus and Europe PMC using the following the medical subject headings (MeSH) terms and keywords: [((endodontic sealer) OR (endodontic sealant) OR (root canal sealer)) AND ((anti-microbial photodynamic therapy) OR (laser-assisted) OR (light-assisted) OR (photosensitive dye) OR (photosensitizer)) AND ((bond-strength) OR (penetration))] for all literature published from inception to September 2022. Clinical studies, animal studies, laboratory investigations and case reports were included. Data was extracted and the quality of the included studies was assessed.

RESULTS

Of the 204 studies screen initially, 12 laboratory studies were included in this review. Majority of the outcomes revealed that aPDT does not have an adverse impact on the bond-strength or sealer penetration. Furthermore, AH Plus (an epoxy-based sealer) resulted in higher bond-strengths than other types of sealers (MTA Fillapex, Sealapex and Bioceramics). 11 studies were graded as having 'medium' quality and one study was graded as 'low'.

CONCLUSION

Within the limitations of this review, aPDT does not have a significant impact on the bonding and penetration of endodontic sealers. Future studies should focus on standardization and optimization of aPDT procedures when assessing their impact on the interaction between sealers and dentine.

Comparison of bacterial disinfection efficacy using blue and red lights on dental implants contaminated with Aggregatibacter actinomycetemcomitans

OBJECTIVES

The purpose of this study was to determine the bacterial disinfection efficacy of four photosensitizers (PSs; curcumin, riboflavin, toluidine blue O, and phycocyanin) with blue diode laser (Blue DL) and blue light-emitting diode (Blue LED) or Red DL and Red LED in dental implants contaminated with Aggregatibacter actinomycetemcomitans.

MATERIALS AND METHODS

A total of 60 dental implants were contaminated with A. actinomycetemcomitans. All implants were then randomized into ten different disinfection modalities (n = 6 implants per group). The irradiation wavelength in Blue DL and Blue LED or Red DL and Red LED was 450, 430-460, 635, and 630 nm, respectively and its applied energy density was 60 J/cm² in all groups. Group IX was served as the control group and in group X disinfection was performed with 0.2% chlorhexidine. After the treatments, the colony forming units (CFUs)/ml were calculated to determine antimicrobial effects of each treatment.

RESULTS

All disinfection methods significantly reduced bacteria amounts of dental implants inoculated with A. actinomycetemcomitans compared to control group. The CFU/ml in LED group was significantly lower than the DL in all studied groups.

CONCLUSION

aPDT could be an effective supplement in dental implants disinfection. The LED, proved to be better in reducing CFU/ml of A. actinomycetemcomitans on dental implants surface than DL.

The effect of high-risk HPV E6/E7 mRNA on the efficacy of topical photodynamic therapy with 5-aminolevulinic acid for cervical high-grade squamous intraepithelial lesions

BACKGROUND

E6 and E7 high-risk human papillomavirus (HR-HPV) oncoproteins are closely associated with the initiation and progression of cervical cancer (CC) and pre-cancerous lesions. Cervical high-grade squamous intraepithelial lesions (HSIL), as pre-cancerous lesions, have a 5% chance of progressing to invasive cancer. Topical 5-aminolevulinic acid photodynamic therapy (ALA-PDT) is a novel non-invasive targeted therapy for intraepithelial lesions. Herein, we analyzed the effect of HR-HPV E6/E7 mRNA on ALA-PDT for cervical HSIL.

METHODS

A retrospective analysis of 148 HR-HPV-positive patients diagnosed with cervical HSIL and receiving ALA-PDT was carried out. ALA-PDT was performed with 20% ALA thermosensitive gel, and irradiation at wavelength of 635 nm and density of 80-100 J/cm² for 20-30 min. The therapeutic instruments of LED and semiconductor laser were applied for cervical lesions and lesions in endocervical canal, respectively. All patients were tested for HPV E6/E7 mRNA before and after PDT, and then followed up at 3, 6, and 12 months after treatment, and every six months thereafter.

RESULTS

At the 6-month follow up, the complete remission (CR) rate of patients' lesions was 86.5% (128/148), whereas the total HPV clearance rate was 72.3% (107/148). It was evident that positive E6/E7 mRNA before treatment had a significant effect on HPV clearance rate (66.3% VS 81.4%, P=0.045) and CR rate (80.9% VS 94.9%, P=0.015). The E6/E7 mRNA associated with HPV16/18 and HPV16/18 combined with other HR-HPV (HPV16/18 and other HR-HPV) affected HPV clearance (P=0.035) and lesions CR (P=0.039), respectively. Moreover, persistently positive E6/E7 mRNA after treatment was closely associated with poor efficacy (HPV clearance rate: P=0.000, CR rate: P=0.000). Throughout the follow up period, two cases recurred but none of the patients progressed.

CONCLUSIONS

This study has shown that ALA-PDT is an effective, safe, and alternative treatment for cervical HSIL, especially for the patients of childbearing age. However, its efficacy is relatively poor in patients with persistently positive E6/E7 mRNA before and after treatment, who are insensitive to ALA-PDT.

An Electroluminodynamic Flexible Device for Highly Efficient Eradication of Drug-Resistant Bacteria

Photodynamic therapy (PDT) has attracted wide attention in antibacterial applications due to its advantages of spatial-temporal selectivity, noninvasiveness, and low incidence to develop drug resistance. To make it more convenient, universal, and manipulatable for clinical application, a conceptually antibacterial strategy, namely "electroluminodynamic therapy" (ELDT), is presented by nanoassembly of an electroluminescent (EL) material and a photosensitizer, which is capable of generating reactive oxygen species (ROS) in situ under an electric field, i.e., the fluorescence emitted by the EL molecules excites the photosensitizer to generate singlet oxygen (¹ O₂ ), for the oxidative damage of pathogens. Based on the scheme of ELDT, a flexible therapeutic device is fabricated through a hydrogel loading with ELDT nanoagents, followed by integration with a flexible battery, satisfying the requirements of being light and wearable for wound dressings. The ELDT-based flexible device presents potent ROS-induced killing efficacies against drug-resistant bacteria (>99.9%), so as to effectively inhibit the superficial infection and promote the wound healing. This research reveals a proof-of-concept ELDT strategy as a prospective alternative to PDT, which avoids the utilization of a physical light source, and achieves convenient and effective killing of drug-resistant bacteria through a hydrogel-based flexible therapeutic device.

Residual antibacterial effects of a mixture of silver nanoparticles/calcium hydroxide and other root canal medicaments against Enterococcus faecalis

Background/purpose

Intracanal medicaments with high residual inhibition effects are used to achieve successful endodontic treatment and prevent reinfection. This in vitro study aimed to assess antimicrobial residual effects of different intracanal medicaments against Enterococcus faecalis (E. faecalis) in root dentin one week after drug therapy.

Materials and methods

Seventy human teeth were standardized to have 15 mm of length and were prepared by ProTaper rotary system. The teeth were randomly divided into six experimental (n = 10) and two control (n = 5) groups and subjected to drug therapy as follows; group CHX: 2% chlorhexidine gel, group CH: calcium hydroxide paste, group CH/CHX: mixture of calcium hydroxide and 2% CHX, group TAP: triple antibiotic paste, group DAP: double antibiotic paste, group CH/AgNPs: mixture of CH paste and silver nanoparticle suspension. After one week, the medicaments were removed from the root canals and E. faecalis was inoculated into the canals. The teeth were incubated at 37 °C for 24 h. Using a size 40 hedstrom file, dentin chips were collected and number of colony forming units were counted.

Results

The difference between all experimental groups was statistically significant in this regard (P < 0.05) except for DAP and TAP groups, in which, no bacterial colony was noted after culture. After DAP and TAP, the lowest colony count was noted in CH/AgNPs, CH/CHX and CHX groups. The highest colony count was noted in CH group.

Conclusion

Our results showed favorable residual antibacterial effects of TAP, DAP and CH/AgNP medicaments after one week of application.

Efficacy of antimicrobial photodynamic therapy and Er,Cr:YSGG laser-activated irrigation on dentinal tubule penetration of MTA-based root canal sealer: a confocal microscopy study

BACKGROUND

Antimicrobial photodynamic therapy (aPDT) and laser-activated irrigation (LAI) are adjunctive therapies developed to enhance the effectiveness of root canal disinfection. Sealer penetration into dentinal tubules is significant for preventing re-infection, and the sealer's penetration ability is affected by the chemo-mechanical preparation of the root canal. This study aimed to evaluate the efficacy of aPDT and LAI on dentinal tubule penetration of MTA-based root canal sealer.

METHODS

Forty single-rooted mandibular premolars were divided into four groups (n = 10): control, methylene blue 50 mg/L (MB50), curcumin 500 mg/L (C500), and Er,Cr:YSGG and sodium hypochlorite (LAI). The smear removal efficiency of the groups on intraradicular dentin was evaluated with a scanning electron microscope (SEM). Confocal laser scanning microscopy (CLSM) was performed to determine the depth of penetration of MTA Fillapex into dentinal tubules. Data were analyzed statistically.

RESULTS

The maximum penetration depth of the C500 group was significantly higher than that of the other groups in all three levels of root sections (p<0.05). Regarding mean penetration depth, the highest values were obtained from the C500 group. However, there was no statistically significant difference between the C500 and MB50 groups in the middle and coronal thirds of the root (p>0.05). The LAI group showed the lowest penetrated area percentage in the middle and coronal third of the root (p<0.05). The C500 and LAI groups were more effective in removing the smear layer than the control and MB50 groups.

CONCLUSION

aPDT could enhance the penetration of MTA-based root canal sealer into dentin tubules.