Antibacterial Evaluation of Zirconia Coated with Plasma-Based Graphene Oxide with Photothermal Properties

The alternative antibacterial treatment photothermal therapy (PTT) significantly affects oral microbiota inactivation. In this work, graphene with photothermal properties was coated on a zirconia surface using atmospheric pressure plasma, and then the antibacterial properties against oral bacteria were evaluated. For the graphene oxide coating on the zirconia specimens, an atmospheric pressure plasma generator (PGS-300, Expantech, Suwon, Republic of Korea) was used, and an Ar/CH₄ gas mixture was coated on a zirconia specimen at a power of 240 W and a rate of 10 L/min. In the physiological property test, the surface properties were evaluated by measuring the surface shape of the zirconia specimen coated with graphene oxide, as well as the chemical composition and contact angle of the surface. In the biological experiment, the degree of adhesion of Streptococcus mutans (S. mutans) and Porphyromonas gingivalis (P. gingivalis) was determined by crystal violet assay and live/dead staining. All statistical analyzes were performed using SPSS 21.0 (SPSS Inc., Chicago, IL, USA). The group in which the zirconia specimen coated with graphene oxide was irradiated with near-infrared rays demonstrated a significant reduction in the adhesion of S. mutans and P. gingivalis compared with the group not irradiated. The oral microbiota inactivation was reduced by the photothermal effect on the zirconia coated with graphene oxide, exhibiting photothermal properties.

The role of the light source in antimicrobial photodynamic therapy

Antimicrobial photodynamic therapy (APDT) is a promising approach to fight the growing problem of antimicrobial resistance that threatens health care, food security and agriculture. APDT uses light to excite a light-activated chemical (photosensitiser), leading to the generation of reactive oxygen species (ROS). Many APDT studies confirm its efficacy in vitro and in vivo against bacteria, fungi, viruses and parasites. However, the development of the field is focused on exploring potential targets and developing new photosensitisers. The role of light, a crucial element for ROS production, has been neglected. What are the main parameters essential for effective photosensitiser activation? Does an optimal light radiant exposure exist? And finally, which light source is best? Many reports have described the promising antibacterial effects of APDT in vitro, however, its application in vivo, especially in clinical settings remains very limited. The restricted availability may partially be due to a lack of standard conditions or protocols, arising from the diversity of selected photosensitising agents (PS), variable testing conditions including light sources used for PS activation and methods of measuring anti-bacterial activity and their effectiveness in treating bacterial infections. We thus sought to systematically review and examine the evidence from existing studies on APDT associated with the light source used. We show how the reduction of pathogens depends on the light source applied, radiant exposure and irradiance of light used, and type of pathogen, and so critically appraise the current state of development of APDT and areas to be addressed in future studies. We anticipate that further standardisation of the experimental conditions will help the field advance, and suggest key optical and biological parameters that should be reported in all APDT studies. More in vivo and clinical studies are needed and are expected to be facilitated by advances in light sources, leading to APDT becoming a sustainable, alternative therapeutic option for bacterial and other microbial infections in the future.

Clinical applications of antimicrobial photodynamic therapy in dentistry

Given the emergence of resistant bacterial strains and novel microorganisms that globally threaten human life, moving toward new treatment modalities for microbial infections has become a priority more than ever. Antimicrobial photodynamic therapy (aPDT) has been introduced as a promising and non-invasive local and adjuvant treatment in several oral infectious diseases. Its efficacy for elimination of bacterial, fungal, and viral infections and key pathogens such as Streptococcus mutans, Porphyromonas gingivalis, Candida albicans, and Enterococcus faecalis have been investigated by many invitro and clinical studies. Researchers have also investigated methods of increasing the efficacy of such treatment modalities by amazing developments in the production of natural, nano based, and targeted photosensitizers. As clinical studies have an important role in paving the way towards evidence-based applications in oral infection treatment by this method, the current review aimed to provide an overall view of potential clinical applications in this field and summarize the data of available randomized controlled clinical studies conducted on the applications of aPDT in dentistry and investigate its future horizons in the dental practice. Four databases including PubMed (Medline), Web of Science, Scopus and Embase were searched up to September 2022 to retrieve related clinical studies. There are several clinical studies reporting aPDT as an effective adjunctive treatment modality capable of reducing pathogenic bacterial loads in periodontal and peri-implant, and persistent endodontic infections. Clinical evidence also reveals a therapeutic potential for aPDT in prevention and reduction of cariogenic organisms and treatment of infections with fungal or viral origins, however, the number of randomized clinical studies in these groups are much less. Altogether, various photosensitizers have been used and it is still not possible to recommend specific irradiation parameters due to heterogenicity among studies. Reaching effective clinical protocols and parameters of this treatment is difficult and requires further high quality randomized controlled trials focusing on specific PS and irradiation parameters that have shown to have clinical efficacy and are able to reduce pathogenic bacterial loads with sufficient follow-up periods.

Cold plasma enamel surface treatment to increase fluoride varnish uptake

Among the available methods of enamel strengthening, fluoride varnish (FV) treatment has relatively better results. On the other hand, cold plasma technology has shown promising capacities in sterilizing the environment, surface modification, and improving adhesion. Accordingly, this study aimed to increase the adhesion of FV to the enamel surface to prolong the enamel interaction with FV with subsequently increased fluoride uptake by enamel. Emphasizing that the change in adhesion is evidence-based and has not been explicitly measured. For this purpose, we randomly divided twenty bovine teeth into two groups A (consisting of four teeth) and B (composed of four subgroups, each containing four teeth). Samples of group A and one specimen of each subset B investigated the effect of using Helium-DBD (He-DBDJ), Argon (ArJ), and Air-DBD jet on the enamel surface. Other B specimens are devoted to studying the release of FV fluoride ions from processed enamel. Two diagnostic techniques, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS), have been utilized to examine the samples' surface morphology and chemical analysis, respectively. Finally, the release of fluoride ions into distilled water was measured by an ion-selective electrode (ISE). SEM images showed that ArJ and Air-DBD significantly damaged enamel hexagonal structures, whereas, in the case of He-DBDJ, the hexagonal structures have only altered from convex to concave. EDX indicated an increase in calcium to phosphorus ratio and the amount of fluoride and sodium uptake on the enamel surface layer in the group processed with He-DBDJ plasma. The latter helps restore the damaged parts of the enamel. Analysis of fluoride released from the FV did not show a significant change owing to plasma processing (P ≤ 0.112). The combination of cold plasma and fluoride varnish treatment on the enamel surface might be considered as a more promising approach to increasing enamel resistance to tooth decay.

Analysis of enamel/restoration interface submitted cariogenic challenge and fluoride release

The treatment of high-risk patients still is a challenge. The understanding and development non-invasive, non-destructive, and non-ionizing techniques, can help to guide the treatment and the diagnosis of primary and recurrent caries. The present study evaluated the behavior of enamel/restoration interface after a cariogenic challenge by Fourier domain optical coherence tomography (FD-OCT), scanning electron microscopy (SEM) examination, and the fluoride release of the different restorative materials. Cavities (1.5 × 0.5 mm) were performed in enamel surface and divided into groups (n = 8): glass ionomer cement (GIC), resin-modified glass ionomer cement (RMGIC), and resin composite (RC). The samples were submitted to pH-cycling, and the solutions analyzed for cumulative fluoride by ion-analyzer. The morphology was analyzed by SEM through replicas. The optical attenuation coefficient (OAC) was calculated through exponential decay from the images generated by FD-OCT. Data were analyzed considering α = 0.05. OAC values increased for all groups after pH-cycling indicating demineralization (p < .05). Considering the remineralizing solution, RMGIC presented higher fluoride release rate, followed by GIC, while RC did not release any fluoride. Yet for the demineralizing solution, RMGIC and GIC released similar fluoride rates, overcoming RC (p < .05). Micrographs revealed no changes on the restorations margins, although enamel detachment was observed for RC and GIC after pH-cycling.

Effects of a derivative of reutericin 6 and gassericin A on the biofilm of Streptococcus mutans in vitro and caries prevention in vivo

It is known that Streptococcus mutans (S. mutans) is the leading cariogenic pathogen. Recently, an increasing number of antimicrobial peptides (AMPs) have been brought into consideration as anti-caries agents. Here, we designed and synthesized an AMP derived from reutericin 6 and/or gassericin A, named LN-7, and explored its effect on biofilm of S. mutans UA159 in vitro and development of dental caries in vivo. Antibacterial assays showed that LN-7 was more active against S. mutans (3.2 μM) than many peptide-based agents, capable of killing other types of Streptococci in oral cavity. In addition, LN-7 presented fast killing kinetics, with more than 97% S. mutans killed within 5 min. The mechanism of the antimicrobial activity mainly lies on the disruption of bacterial membrane. Effects of LN-7 on the biofilm formation and the viability of preformed biofilm were quantified by crystal violet staining, which showed that LN-7 could effectively inhibit the biofilm accumulation of S. mutans. Moreover, the biofilm of S. mutans treated with LN-7 displayed notable changes in bacterial viability and morphology, observed by confocal laser scanning microscopy and scanning electron microscopy. In addition, topical oral treatment with LN-7 could suppress the development of dental caries in vivo, reducing the occurrence of severe dental lesion in a rodent model. These results reveal a new peptide-based agent as a topical treatment for dental caries, opening the door to clinical studies to explore its potential for caries prevention.

Effect of photodynamic therapy on surface decontamination in clinical orthodontic instruments

The objective was to develop, characterize and test a box containing light emission diode (LED), Patent Deposit MU-BR20.2017.002297-3, which was named "Photodynamic Inactivation Device" (PID) and verify if it's suitable in microbial reduction or disinfection action of solid surfaces using PID. The equipment was made in a container of polypropylene with a lid of the same material and, for a better use of irradiation the internal part was covered with a layer of reflective aluminum. In addition, sixty boards of red LED 660 nm wavelength, containing three radiators each, for which the distribution of irradiation and spectral irradiance in all of the six internal faces were calculated in this device. That way, a low cost alternative was tested over three types of microorganisms present on the human microbiota: two strains Gram-positive (Gram +), Staphylococcus aureus and Streptococcus mutans and one strain Gram-negative (Gram -), Escherichia coli, inoculated in orthodontic instruments previously autoclaved. To assess the Photodynamic Inactivation (PDI) over these bacteria, instruments were contaminated by bacterial suspensions (3 × 10⁸ CFU/mL) and ulterior treatment with a solution of 100 μmol/L of MB for 20 min, and irradiated for another 20 min (energy density of 026 J/cm²). Microbial reduction was assessed by number counting of Colony Forming Units (CFU). At the end, microbial reduction of the surface of orthodontic metal instruments was compared with the positive group of each group. Results showed that PID caused a significant reduction (p < 0.05) of the microbial charge stuck in the orthodontic instruments. Thus, the photo prototype of the drawing is appropriate for phototherapy studies, granting it´s advantageous to the low level light therapy as well as for the antimicrobial photodynamic therapy. The perspective is that PID may potentialize the dissemination of phototherapy studies for determining its proper use in health science. And, thus, propose a low cost and atoxic alternative for disinfection of biomedical appliances as non-critical instruments, allowing also for use in the food industry.

Antimicrobial photodynamic therapy of Lactobacillus acidophilus by indocyanine green and 810-nm diode laser

This study investigated the efficacy of photodynamic therapy (PDT) using EmunDo as a photosensitizer against Lactobacillus acidophilus. A gallium aluminum arsenide diode laser was used in this experiment (810 nm, CW). Standard suspensions of Lactobacillus acidophilus were divided into six groups by treatment: 1) EmunDo, 2) diode laser (100 mW, 90 s), 3) diode laser (300 mW, 30 s); 4) EmunDo + diode laser (100 mW, 90 s), 5) EmunDo + diode laser (300 mW, 30 s), 6) control (no treatment). Bacterial suspensions from each group were subcultured onto the surface of MRS agar plates immediately and 24 h after treatment, and the viable microorganisms of Lactobacillus acidophilus were counted. The data were analyzed by ANOVA and student's t-test at p < 0.05. There was a significant between-group difference in the number of Lactobacillus acidophilus colonies in cell cultures obtained at 24 h after treatment (p < 0.001). The viable counts were significantly lower in EmunDo and both PDT groups, as compared to the other groups (p < 0.05). In the control and laser-irradiated groups, the number of colonies increased significantly at 24 h compared to the immediately after treatment (p < 0.05), whereas in both PDT groups, the number of colonies showed a significant reduction after 24 h of therapy (p < 0.05). Under the conditions used in this study, L. acidophilus colonies were susceptible to PDT after sensitization with EmunDo and exposure to diode laser. These findings imply that PDT is capable to reduce cariogenic bacteria, potentially leading to more conservative cavity preparation.

Evaluation of temperature change during antimicrobial photodynamic therapy with two different photosensitizers in dental caries

INTRODUCTION

Many attempts have been made in elimination of bacteria in infected and demineralized dentin to not only provide efficient bactericidal potential, but to have minimal damage for tooth structure. The aim of this study was to assess the temperature change during aPDT with ICG and TBO compared with conventional Diode laser irradiation.

MATERIALS AND METHODS

48 premolar teeth which were selected for this study. A class I cavity was drilled in each teeth, with dimensions of 2mm width, 4mm length and depth of 2.5-3.5mm, providing a dentinal wall of approximately 0.5mm for pulp chamber. Then teeth were randomly allocated in 4 experimental groups (n=12); Group 1: TBO+LED, Group 2: ICG+Diode Laser, Group 3: Diode laser with output power of 0.5W, Group 4: Diode laser with output power of 1W. Thermocouple device was held by experimenter hand and the sensor was in pulp chamber of the teeth. Heat generated during irradiation was reported on LCD screen by NUX Plus software. Repeated measure ANOVA was used in order to compare the temperature before and after laser application. Tukey HSD was used to compare the results between groups.

RESULTS

Temperature was risen for about 0.54±0.05°C for group 1, 1.67±0.14°C for group 2, 4.21±0.83°C for group 3, and 4. 50±0.32°C for group 4. The difference between group 1 & 2, 1 & 3 and 1 & 4 was significant (p<0.0001).

CONCLUSION

According to results of this study, Diode (with or without photosensitizer- 0.5 and 1W) can be safely used as alternative approach for disinfection after caries removal in thermal point of view.

Bactericidal effect of visible light in the presence of erythrosine on Porphyromonas gingivalis and Fusobacterium nucleatum compared with diode laser, an in vitro study

OBJECTIVES

Recently, photodynamic therapy (PDT) has been introduced as a new modality in oral bacterial decontamination. Besides, the ability of laser irradiation in the presence of photosensitizing agent to lethal effect on oral bacteria is well documented. Current research aims to evaluate the effect of photodynamic killing of visible blue light in the presence of plaque disclosing agent erythrosine as photosensitizer on Porphyromonas gingivalis associated with periodontal bone loss and Fusobacterium nucleatum associated with soft tissue inflammation, comparing with the near-infrared diode laser.

MATERIALS AND METHODS

Standard suspension of P. gingivalis and F. nucleatum were exposed to Light Emitting Diode (LED) (440-480 nm) used to photopolymerize composite resine dental restoration in combination with erythrosine (22 µm) up to 5 minutes. Bacterial sample were also exposed to a near-infrared diode laser (wavelength, 830 nm), using identical irradiation parameters for comparison. Bacterial samples from each treatment groups (radiation-only group, erythrosine-only group and light or laser with erythrosine group) were subcultured onto the surface of agar plates. Survival of these bacteria was determined by counting the number of colony forming units (CFU) after incubation.

RESULTS

Exposure to visible blue light and diode laser in conjugation with erythrosine significantly reduced both species examined viability, whereas erythrosine-treated samples exposed to visible light suggested a statically meaningful differences comparing to diode laser. In addition, bactericidal effect of visible light or diode laser alone on P. gingivalis as black-pigmented bacteria possess endogenous porphyrins was noticeably.

CONCLUSION

Our result suggested that visible blue light source in the presence of plaque disclosing agent erythrosine could can be consider as potential approach of PDT to kill the main gram-negative periodontal pathogens. From a clinical standpoint, this regimen could be established as an additional minimally invasive antibacterial treatment of plaque induced periodontal pathologies.

Comparative evaluation of photodynamic therapy using LASER or light emitting diode on cariogenic bacteria: An in vitro study

OBJECTIVE

The aim of this study was to evaluate in vitro the effect of photodynamic therapy (PDT) using LASER or light emitting diode (LED) on cariogenic bacteria (Streptococcus mutans [SM] and Lactobacillus casei [LC]) in bovine dentin.

MATERIALS AND METHODS

Twenty five fragments of dentin were contaminated with SM and LC strands and divided into five experimental groups according to the therapy they received (n = 5): C - control (no treatment), SCLED - no dye/LED application (94 J/cm(2)), SCLASER - no dye/LASER application (94 J/cm(2)), CCLED - dye/LED application (94 J/cm(2)) and CCLASER - dye/LASER application (94 J/cm(2)). The dye used was methylene blue at 10 mM. Dentin scrapes were harvested from each fragment and prepared for counts of colony forming units (CFU)/mL. The data were analyzed using Kruskal-Wallis, followed by Student-Newman-Keuls (α =0.05).

RESULTS

Regarding SM, groups CCLASER and CCLED showed a significant reduction in CFU/mL, which was statistically superior to the SCLASER, SCLED and C groups. Regarding LC, the groups CCLASER and CCLED caused a significant reduction in CFU/mL when compared with SCLASER, which showed intermediate values. SCLED and C had a lesser effect on reducing CFU/mL, where the former showed values similar to those of SCLASER.

CONCLUSIONS

In conclusion, PDT combined with LASER or LED and methylene blue had a significant antimicrobial effect on cariogenic bacteria in the dentin.

The susceptibility of Streptococcus mutans to antibacterial photodynamic therapy: a comparison of two different photosensitizers and light sources

Streptococcus mutans is the main etiological agent for dental caries. Recently, photodynamic therapy (PDT) has been introduced as a new modality in bacterial decontamination.

Photodynamic therapy has antifungal effect and reduces inflammatory signals in Candida albicans-induced murine vaginitis

BACKGROUND

Vaginal candidiasis (VC) is a disease that affects thousands of women of childbearing age, mainly caused by Candida albicans fungus. Photodynamic therapy (PDT) uses photosensitizing substances that are nontoxic in the dark, but able to produce reactive oxygen species when they are subjected to a light source. In this work our purpose was to investigate PDT effects on fungal burden and inflammatory cells in a murine model of C. albicans-induced vaginal candidiasis.

METHODS

Female BALB/c mice 6-10 weeks were estrogenized and maintained in this state during all experiment. After 72h, mices were inoculated intravaginally (IV) with 20μL of 2×10(5)C. albicans cells suspension. Mice were separated into 5 groups after five days: H (healthy), PBS (control), laser, MB (methylene blue) and PDT. PDT and MB groups received IV 20μL solution with 1mM of MB, others received PBS. PDT and laser groups were irradiated with a red laser (100mW, 660nm) in one (36J, 6min) or two sessions (18J, 3min). After the end of treatment, mice were submitted to microbiological and histomorphometric analysis with ImageJ software. Data were plotted by mean values and standard deviations of CFU/mL and percentage of inflammatory cells area. ANOVA and Bonferroni post-test were used and data were considered significant when p<0.05.

RESULTS

PDT significantly reduced C. albicans after the two tested protocols, however, percentage area of inflammatory cells was significantly reduced just with two sessions of PDT.

CONCLUSIONS

PDT with MB and red laser is a promising therapy for VC. It is able to reduce fungal infection in biofilm and inflammatory signals associated with VC in a murine model of vaginitis.

Photoelimination of Streptococcus mutans with two methods of photodynamic and photothermal therapy

BACKGROUND

Increasing resistance of oral pathogens to conventional antibacterial agents has resulted to find alternative therapies to overcome resistance development problems; hence this in vitro study was carried out to investigate the efficacy of photoelimination of Streptococcus mutans with two methods of photodynamic and photothermal therapy.

METHODS

Standard Suspensions of S. mutans were treated in two groups of photodynamic therapy with Toluidine blue O and Rhadachlorin(®) and photothermal therapy by EmunDo(®) and their individual light sources, then Bacterial suspension from each treatment was subcultured on the surface of Mueller-Hinton agar plates and bacterial growth was assessed. The results were analyzed by analysis of variance and Tukey test (p<0.05).

RESULTS

After treatments significant reduction of S. mutans viability in planktonic culture was observed in both groups of photodynamic and photothermal therapy with no priority.

CONCLUSION

Photoelimination can be a novel modality in the eradication of S. mutans colonies in near future.

Effects of photodynamic therapy on Gram-positive and Gram-negative bacterial biofilms by bioluminescence imaging and scanning electron microscopic analysis

OBJECTIVE

The aim of this study was to test photodynamic therapy (PDT) as an alternative approach to biofilm disruption on dental hard tissue, We evaluated the effect of methylene blue and a 660 nm diode laser on the viability and architecture of Gram-positive and Gram-negative bacterial biofilms.

MATERIALS AND METHODS

Ten human teeth were inoculated with bioluminescent Pseudomonas aeruginosa or Enterococcus faecalis to form 3 day biofilms in prepared root canals. Bioluminescence imaging was used to serially quantify and evaluate the bacterial viability, and scanning electron microscopic (SEM) imaging was used to assess architecture and morphology of bacterial biofilm before and after PDT employing methylene blue and 40 mW, 660 nm diode laser light delivered into the root canal via a 300 μm fiber for 240 sec, resulting in a total energy of 9.6 J. The data were statistically analyzed with analysis of variance (ANOVA) followed by Tukey test.

RESULTS

The bacterial reduction showed a dose dependence; as the light energy increased, the bioluminescence decreased in both planktonic suspension and in biofilms. The SEM analysis showed a significant reduction of biofilm on the surface. PDT promoted disruption of the biofilm and the number of adherent bacteria was reduced.

CONCLUSIONS

The photodynamic effect seems to disrupt the biofilm by acting both on bacterial cells and on the extracellular matrix.

Antimicrobial photodynamic therapy and photodynamic inactivation, or killing bugs with dyes and light--a symposium-in-print

In antimicrobial photodynamic therapy, the photosensitizer (PS) in its ground singlet state absorbs light to give the excited singlet state that can transition to the long-lived triplet state. This PS triplet may undergo energy transfer (Type 2) or electron transfer (Type 1) to oxygen to form reactive oxygen species (singlet oxygen and/or hydroxyl radicals) that can kill both Gram-positive and Gram-negative bacteria and fungi. Infections in animal models can also be treated.