Confocal fluorescence imaging to evaluate the effect of antimicrobial photodynamic therapy depth on P. gingivalis and T. denticola biofilms

Non-surgical management of peri-implantitis with photodynamic therapy: A systematic review and meta-analysis of clinical parameters and biomarkers

OBJECTIVE

To evaluate the clinical and biomarker outcomes of photodynamic therapy (PDT) as an adjunct to non-surgical mechanical debridement (MD) in the management of peri‑implantitis, and to compare its efficacy to MD alone or other non-surgical treatment modalities.

DATA AND SOURCES

Electronic searches in PubMed, Web of Science, and CENTRAL were conducted. 4675 studies published until November 2023 were screened. Clinical studies reporting on non-surgical treatments involving PDT were selected. Meta-analyses assessed clinical parameters (bleeding on probing [BOP], probing depth [PD], plaque index [PI], crestal bone loss [CBL], clinical attachment level [CAL]) and biomarkers.

STUDY SELECTION

A total of 25 studies were included. The meta-analysis of randomized controlled trials revealed that both MD alone and MD+PDT significantly improved clinical and biomarker outcomes compared to baseline. The addition of PDT provided greater improvements at 3 months for BOP (SMD:0.90; 95 % CI:1.53 to -0.28; p = 0.005), PD (SMD:1.15; 95 % CI:1.72 to -0.58; p < 0.0001), PI (SMD:0.74; 95 % CI:1.15 to -0.33; p = 0.0004) and CBL (SMD:0.38; 95 % CI:0.73 to -0.03; p = 0.04). The additional benefits of PDT were less pronounced on CAL, mucosal recession, and inflammatory biomarkers. No significant changes were observed over extended follow-up periods.

CONCLUSIONS

Adjunct PDT significantly enhanced clinical outcomes, particularly for the short-term, with the most notable benefits observed in BOP, PD, PI, and CBL reductions. However, additional benefits in CAL, mucosal recession, and inflammatory biomarkers outcomes remain limited. Standardized protocols and long-term studies are warranted.

CLINICAL SIGNIFICANCE

PDT as an adjunct in non-surgical peri-implantitis management improves short-term clinical outcomes, particularly for BOP, PD, PI, and CBL. The benefits of adjunctive use with mechanical debridement offer a promising and minimally invasive approach. Further long-term research is needed to establish its role in routine clinical practice.

Photodynamic disruption of a polymicrobial biofilm of two periodontal species using indocyanine green-loaded nanospheres

OBJECTIVE

Antimicrobial photodynamic therapy (aPDT) is considered a potential treatment for biofilm infections, which have become an increasing health issue because of the rise in antimicrobial resistance. This study aimed to evaluate the bactericidal effect of aPDT using indocyanine green-loaded nanospheres with chitosan coating (ICG-Nano/c) against polymicrobial periodontal biofilms.

METHODS

Composite biofilms of Porphyromonas gingivalis and Streptococcus gordonii were constructed in 96-well plates, and aPDT with ICG-Nano/c and an 810 nm diode laser was performed either by direct irradiation or transmitting irradiation through a 3-mm-thick gingival model. The efficacy of ICG-Nano/c-based aPDT was compared with antibiotics (minocycline and amoxicillin). Additionally, attenuated aPDT under sublethal conditions was used to investigate gene expression related to the antioxidant response (oxyR and sod of P. gingivalis) and biofilm formation via quorum sensing (luxS of both species) with real-time polymerase chain reaction.

RESULTS

ICG-Nano/c-based aPDT significantly reduced the bacterial load in the biofilm, achieving at least a 2 log10 reduction in colony-forming units within 5 min for both irradiation methods. After 6 h of treatment, the bactericidal effects of aPDT and antibiotics were similar, but after 32 h, antibiotics were more effective, particularly against P. gingivalis. Attenuated aPDT showed a slight increase in sod expression in P. gingivalis, while luxS expression decreased in both bacteria.

CONCLUSION

The ICG-Nano/c-based aPDT system exerted a certain degree of bactericidal activity against a composite biofilm of periodontal bacteria. Therefore, it has potential as an alternative option or adjunctive therapy to conventional antibiotics in periodontal treatment.

High-Resolution Large-Area Image Analysis Deciphers the Distribution of Salmonella Cells and ECM Components in Biofilms Formed on Charged PEDOT:PSS Surfaces

Biofilms, comprised of cells embedded in extracellular matrix (ECM), enable bacterial surface colonization and contribute to pathogenesis and biofouling. Yet, antibacterial surfaces are mainly evaluated for their effect on bacterial cells rather than the ECM. Here, a method is presented to separately quantify amounts and distribution of cells and ECM in Salmonella biofilms grown on electroactive poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS). Within a custom-designed biofilm reactor, biofilm forms on PEDOT:PSS surfaces electrically addressed with a bias potential and simultaneous recording of the resulting current. The amount and distribution of cells and ECM in biofilms are analyzed using a fluorescence-based spectroscopic mapping technique and fluorescence confocal microscopy combined with advanced image processing. The study shows that surface charge leads to upregulated ECM production, leaving the cell counts largely unaffected. An altered texture is also observed, with biofilms forming small foci or more continuous structures. Supported by mutants lacking ECM production, ECM is identified as an important target when developing antibacterial strategies. Also, a central role for biofilm distribution is highlighted that likely influences antimicrobial susceptibility in biofilms. This work provides yet a link between conductive polymer materials and bacterial metabolism and reveals for the first time a specific effect of electrochemical addressing on bacterial ECM formation.

In vitro evaluation of anti-microbial efficacy of Trigonella foenum-graecum and its constituents on oral biofilms

Background and Objective

The extracts obtained from the leaves and seeds of Trigonella foenum-graecum (Fenugreek) are effective against various microbial infections. The phytoconstituents of Trigonella foenum-graecum have shown promising effects as anti-diabetics, anti-helmentic, anti-microbial, antifungal, and antipyretic, but its impact on oral pathogens is yet to be established. Therefore, the present study aimed to explore the antimicrobial efficacy of phytoconstituents of Trigonella foenum-graecum as compared to 0.2% chlorhexidine (CHX).

Materials and Methods

The methanolic extracts of Trigonella foenum-graecum i.e., fenugreek absolute (FA), diosgenin (DIO), and furanone (FU) were used in this study. The antimicrobial efficacy of these extracts was evaluated by testing the minimal inhibitory concentration, minimal bactericidal concentration (MBC), agar well-diffusion assay, colony-forming unit (CFU) count, and also by using confocal laser scanning microscopy (CLSM) against Staphylococcus aureus ATCC 25923, Enterococcus faecalis ATCC 29212, Escherichia coli ATCC 35218, and Pseudomonas aeruginosa ATCC 27853.

Results

The results of the study demonstrated that Trigonella foenum-graecum has anti-microbial activity comparable to 0.2% CHX. Well-diffusion assay and CFU count assay of the extracts showed statistically significant (P < 0.001) results. MIC and MBC values were observed for FA, DIO, and FU compared to CHX against these selected test organisms. These results were confirmed by visual validation with CLSM.

Conclusion

The use of herbal alternatives in periodontics might prove to be advantageous. Trigonella foenum-graecum can be used as a promising alternative to CHX against S. aureus, E. faecalis, E. coli, and P. aeruginosa for the management of oral and periodontal infections.

Photoinactivation and Photoablation of Porphyromonas gingivalis

Several types of phototherapy target human pathogens and Porphyromonas gingivitis (Pg) in particular. The various approaches can be organized into five different treatment modes sorted by different power densities, interaction times, effective wavelengths and mechanisms of action. Mode 1: antimicrobial ultraviolet (aUV); mode 2: antimicrobial blue light (aBL); mode 3: antimicrobial selective photothermolysis (aSP); mode 4: antimicrobial vaporization; mode 5: antimicrobial photodynamic therapy (aPDT). This report reviews the literature to identify for each mode (a) the putative molecular mechanism of action; (b) the effective wavelength range and penetration depth; (c) selectivity; (d) in vitro outcomes; and (e) clinical trial/study outcomes as these elements apply to Porphyromonas gingivalis (Pg). The characteristics of each mode influence how each is translated into the clinic.

Proposal and Verification of the Theory of Layer-by-Layer Elimination of Biofilm in Listeria monocytogenes

Biofilms are microbial communities that represent a high abundance of microbial life forms on Earth. Within biofilms, structural changes during clearance processes occur in three spatial and temporal dimensions; therefore, microscopy and quantitative image analysis are essential in elucidating their function. Here, we present confocal laser scanning microscopy (CLSM) in conjunction with ISA-2 software analysis for the automated and high-throughput quantification, analysis, and visualisation of biofilm interiors and overall biofilm properties in three spatial and temporal dimensions. This paper discusses the removal process of Listeria monocytogenes (LM) biofilms using slightly acidic electrolytic water, non-electrolytic hypochlorite water, and alternating the use of strongly acidic and strongly alkaline electrolytic water. The results show that the biofilm gradually thins and gutters from the initial viscous dense and thick morphology under the action of either biocide. This process is consistent with first-level kinetics. After CLSM filming to observe the biofilm structure, analysis software was used to process and quantify the biovolume, average biofilm thickness, biofilm roughness and other indicators; fluorescence enzyme markers were used to verify the remaining amount of extracellular nucleic acid. In this study, we proposed and validated the theory of layer-by-layer elimination of LM biofilm.

Fiber-optic sample illuminator design for the observation of light induced phenomena with transmission electron microscopy in situ: Antimicrobial photodynamic therapy

Antibacterial photodynamic therapy is a promising treatment for problematic infections caused by bacteria and fungi. Despite its undoubted effectiveness, the ultrastructural mechanism of microbial death remains not fully described and distinct organisms respond to the treatment with different efficacy. For this reason, it was decided to try imaging the process using the in situ transmission electron microscopy method. To conduct an observational experiment, the microscope was significantly modified. Liquid cell methods were used, electron doses and their influence on the sample were estimated, and a fiber-optic sample illuminator was designed and built. The modifications allowed for the light-induced characterization of photosensitizer-bacteria interaction. Microscope modification is a promising platform for further studies of light-induced phenomena in both life and material science.

Light-induced in situ transmission electron microscopy: Novel approach for antimicrobial photodynamic therapy imaging

The novel approach for imaging of antimicrobial photodynamic therapy processes presented in this work is based on transmission electron microscopy methods. With the use of liquid cell, illumination system, and lowered electron dose the successful light-induced in-situ observations on Staphylococcus aureus encapsulated with methylene blue were performed. Results showed that with specified imaging parameters it is possible to conduct reliable research on bacteria in electron microscope despite the unfavorable damaging effect of the highly energetic electron beam used for imaging. This approach differs from the common methods, as it provides direct observations of the processes occurring upon light illumination. The effects obtained with the proposed method are very promising and may serve to answer why different microorganisms respond to the therapy differently.

Effects of toothbrush abrasion on surface and antibacterial properties of hydroxyapatite-tryptophan complex with gray titania

Photocatalysts have attracted attention in the medical field for their antibacterial effects. However, typical photocatalysts are activated by ultraviolet rays, which may have adverse effects. Therefore, we focused on a new photocatalyst that is activated by visible light, hydroxyapatite (HAp), and amino acid complex with gray titania, and evaluated its antibacterial effects against Porphyromonas gingivalis and effect by toothbrushing. The test sample was a titanium alloy substrate, and four surface treatments were applied: (1) substrate only, (2) substrate with HAp complex, (3) substrate with HAp complex with gray titania, and (4) HAp-tryptophan complex with gray titania (TR). These surface treatments were evaluated with or without toothbrushing (8 total groups). Surface roughness (Sa), fluorescent X-ray analysis (XRF), and scanning electron microscopy (SEM) were used to evaluate surface properties. To investigate antibacterial effects, each sample was seeded with P. gingivalis, irradiated with red light, and total viable bacterial count was determined. For Sa measurement, TR showed no significant difference after toothbrushing. However, in XRF and SEM observation, TR exhibited peeling of the applied coating after toothbrushing. In the antibacterial test, TR showed a decrease in P. gingivalis under no toothbrushing condition. Conversely, with toothbrushing, the TR coating appeared to peel. However, no significant difference in P. gingivalis count was observed among all groups. HAp-tryptophan complex with gray titania coating showed an antibacterial effect against P. gingivalis when irradiated with visible light. However, toothbrushing can result in coat peeling and consequently reduce the antibacterial effect.

Methylene blue-mediated antimicrobial photodynamic therapy can be a novel non-antibiotic platform for bovine digital dermatitis

BACKGROUND

Bovine digital dermatitis (BDD) is one of the most important diseases that effect dairy cows. Methylene blue-mediated antimicrobial photodynamic therapy (MB-APDT) emerges as a promising technique to treat superficial infections in bovines.

METHODS

Twenty BDD lesions located at the skin horn transition of the claw of pelvic limbs of 16 cows were treated by MB-APDT, using a red LED cluster (λ = 660 nm, irradiance =60 mW/cm², exposure time = 40 s) combined with topical application of MB at 0.01 %; or by topical application of OXY (500 mg in 20 % solution). Each lesion was treated twice with an interval of 14 days. Lesions were weekly evaluated until day 28 by clinical analysis and by histological examination on days 0 and 28.

RESULTS

Both treatments led to a similar reduction of lesions area. At day 28, three lesions treated by OXY did not present completely recovery, whereas no lesions were observed in MB-APDT group. OXY resulted in a slight increase in type I and III collagen levels, while MB-APDT led to a significant increase in the total area of both collagen types. An abundant number of spirochetes were histologically observed in all lesions before treatments. On the 28th day, five lesions treated by OXY still presented a slight number of spirochetes, whereas in MB-APDT group no spirochetes were evidenced.

CONCLUSION

Our findings suggest that MB-APDT is more effective than OXY and could be used in Veterinary practice to fight BDD.

In vitro corrosion studies of stainless-steel dental substrates during Porphyromonas gingivalis biofilm growth in artificial saliva solutions: providing insights into the role of resident oral bacterium

Stainless-steel AISI 321 is an effective material for fabricating dental crowns and other implants utilized dental restorative protocols for elderly and pediatric populations. This unique clinical application is possible through the mechanical stability and corrosion-resistance properties of this metallic material. However, stainless-steel dental implants eventually fail, leading to the creation of surface cavities and cracks within their microstructures during persistent mechanical stresses and biocorrosion. In this study, the in vitro corrosion behaviour of a medical-grade stainless-steel dental substrate was investigated during Porphyromonas gingivalis biofilm growth process in artificial saliva culture suspension (ASCS). Among the causative bioagents of corrosion, P. gingivalis was chosen for this study since it is also responsible for oral periodontitis and a major contributing factor to corrosion in most dental implants. Increased P. gingivalis growth was observed within the incubation period under study as compact cellular clusters fouled the metal surfaces in ASCS media. This led to the corrosion of steel substrates after bacterial growth maturity within 90 days. Corrosion rate increased with higher CFU and bacterial incubation period for all test substrates due to biocorrosion incited by the volatile sulphide products of P. gingivalis metabolism. The presence of some of these volatile compounds has been observed from experimental evidences. Significant anodic degradation in the forms of localized pitting were also recorded by surface analytical techniques. Residual fluorinated ions within the ASCS media also increased the rate of anodic dissolution due to media acidity. This study has provided extensive insights into the fate of stainless-steel dental crown in oral environments infected by a resident oral bacterium. Influences of oral conditions similar to fluoride-enriched mouthwashes were reflected in a view to understanding the corrosion patterns of stainless-steel dental substrates.

A stainless-steel 321 dental substrate significantly corroded within Porphyromonas gingivalis growth culture in artificial saliva culture suspension, with and without NaF additive.

In vitro Assessment of Peri-implantitis Treatment Procedures: A Review

Background:

The prevalence of peri-implantitis is increasing continuously and such a biological complication significantly decreases implant survival and success. Although various treatment modalities have been identified for peri-implantitis, no completely efficient method has yet been established.

Objective:

The aim of this review was to evaluate the scientific literature regarding the in vitro effects of peri-implantitis treatment.

Methods:

A review of the literature was performed by using Google Scholar, PubMed/ MEDLINE and Science Direct databases. In vitro studies on peri-implantitis treatment modalities were selected. The search strategy identified 57 eligible studies. After selection, 21 articles met all the inclusion criteria and were included in the present review.

Results:

Included in vitro studies evaluated different types of peri-implantitis treatment modalities such as mechanical, chemical, combination and laser therapies. Combination therapies with the aid of adjuvants were found to be more effective compared to the studies that used only one type of treatment modality. Laser systems were also tested and displayed interesting results in terms of surface decontamination with a variability associated with selected parameters.

Conclusion:

This review was performed to evaluate the efficacy of the treatment modalities used for peri-implantitis in vitro. Although there are various effective treatment methods, none has been completely successful in removing the biofilms related to peri-implantitis. The findings imply the need for further studies to develop more effective antimicrobial treatment procedures.