Antimicrobial photodynamic therapy: Single-walled carbon nanotube (SWCNT)-Porphyrin conjugate for visible light mediated inactivation of Staphylococcus aureus

Due to the excessive use of antibiotics over the years, the microorganisms have developed resistance to numerous drugs. The growth of multi-resistant organisms (MROs) heads due to the insufficient treatment with the currently available medications which present a great threat to the biotic component of the environment as well as to the food technology sectors. The goal of this research was to develop a nano-composite made up of single-walled carbon nanotubes (SWCNTs) and amine-functionalized porphyrin, which could further be used for the anti-microbial studies in presence of visible light showing photodynamic effect to inactivate cells. Photodynamic antimicrobial chemotherapy is gaining significant interest due to its capabilities as an innovative form of antimicrobial treatment. The development of anti-microbial photodynamic therapy (a-PDT) is a non-antibiotic access to inactivate microorganisms. We examined the synthesis of amine-functionalized porphyrin and conjugated it to the oxidised single-walled carbon nanotubes (SWCNTs). By the use of appropriate amount of single-walled carbon nanotubes (SWCNTs), we have shown the interaction between the porphyrin conjugated nanotubes and the bacterial cells in presence of visible light led to the cell membrane damage, concluding that SWCNT-porphyrin conjugates can be used as an antibacterial agent. The characterization of the oxidised SWCNT and SWCNT-porphyrin conjugates was determined by field emission scanning electron microscopy (FE-SEM), which provides detailed information about the composition and the morphological analysis. The particle size measurements were carried out by transmission electron microscopy (TEM). On investigating under the florescence microscopy, red fluorescence was observed. Thus, these properties demand us to design this facile material comprised of SWCNT-aminoporphyrin conjugates that shows potent antibacterial activity.

Antimicrobial and antibiofilm photodynamic therapy against vancomycin resistant Staphylococcus aureus (VRSA) induced infection in vitro and in vivo

Biofilm mediated infection caused by multi-drug resistant bacteria are difficult to treat since it protects the microorganisms by host defense system, making them resistant to antibiotics and other antimicrobial agents. Combating such type of nosocomial infection, especially in immunocompromised patients, is an urgent need and foremost challenge faced by clinicians. Therefore, antimicrobial photodynamic therapy (aPDT) has been intensely pursued as an alternative therapy for bacterial infections. aPDT leads to the generation of reactive oxygen species (ROS) that destroy bacterial cells in the presence of a photosensitizer, visible light and oxygen. Here, we elucidated a possibility of its clinical application by reducing the treatment time and exposing curcumin to 20 J/cm² of blue laser light, which corresponds to only 52 s to counteract vancomycin resistant Staphylococcus aureus (VRSA) both in vitro and in vivo. To understand the mechanism of action, the generation of total reactive oxygen species (ROS) was quantified by 2'-7'-dichlorofluorescein diacetate (DCFH-DA) and the type of phototoxicity was confirmed by fluorescence spectroscopic analysis. The data showed more production of singlet oxygen, indicating type-II phototoxicity. Different anti-biofilm assays (crystal violet and congo red assays) and microscopic studies were performed at sub-MIC concentration of curcumin followed by treatment with laser light against preformed biofilm of VRSA. The result showed significant reduction in the preformed biofilm formation. Finally, its therapeutic potential was validated in skin abrasion wistar rat model. The result showed significant inhibition of bacterial growth. Furthermore, immunomodulatory analysis with rat serum was performed. A significant reduction in expression of proinflammatory cytokines TNF-α and IL-6 were observed. Hence, we conclude that curcumin mediated aPDT with 20 J/cm² of blue laser treatment (for 52 s) could be used against multi-drug resistant bacterial infections and preformed biofilm formation as a potential therapeutic approach.

Enhanced antimicrobial activity through the combination of antimicrobial photodynamic therapy and low-frequency ultrasonic irradiation

The rapid increase of antibiotic resistance in pathogenic microorganisms has become one of the most severe threats to human health. Antimicrobial photodynamic therapy (aPDT), a light-based regimen, has offered a compelling nonpharmacological alternative to conventional antibiotics. The activity of aPDT is based on cytotoxic effect of reactive oxygen species (ROS), which are generated through the photosensitized reaction between photon, oxygen and photosensitizer. However, limited by the penetration of light and photosensitizers in human tissues and/or the infiltration of oxygen and photosensitizers in biofilms, the eradication of deeply located or biofilm-associated infections by aPDT remains challenging. Ultrasound irradiation bears a deeper penetration in human tissues than light and, sequentially, can promote drug delivery through cavitation effect. As such, the combination of ultrasound and aPDT represents a potent antimicrobial strategy. In this review, we summarized the recent progresses in the area of the combination therapy using ultrasound and aPDT, and discussed the potential mechanisms underlying enhanced antimicrobial effect by this combination therapy. The future research directions are also highlighted.

Comparison of different laser-based photochemical systems for periodontal treatment

PURPOSE

The main aim in periodontitis treatment is to remove supragingival and subgingival biofilm. Mechanical treatment to eliminate pathogenic bacteria is limited by morphological conditions on the root surface. This study assessed the antibacterial effectiveness of different laser-based photochemical systems, particularly a novel curcumin-based option.

METHODS

Ninety-one titanium bars were inoculated with an artificial biofilm of common pathogenic periodontal bacteria and inserted into an artificial periodontal pocket model. The following groups (n = 13) were tested: 1, curcumin solution plus SLB laser irradiation (C + L; 445 nm, 0.6 W, 25% duty cycle, 100 Hz, 10 s); 2, curcumin solution (Cur); 3, dimethyl sulfoxide solution (DMSO); 4, SiroLaser Blue (SLB) - laser irradiation (445 nm, 0.6 W, 25% duty cycle, 100 Hz, 10 s); 5, antimicrobial photodynamic therapy (aPDT); 6, antimicrobial photothermal therapy (aPTT); 7, control. The samples were stored in Eppendorf tubes and analyzed microbiologically using quantitative real-time polymerase chain reaction (PCR). The main parameter for analyzing group differences was the total bacterial load. Statistical analysis was performed with nonparametric methods.

RESULTS

Statistically significant reductions in bacterial count were observed in all experimental groups (p < 0.05). The mean percentage reductions were as follows: SLB, 95.03%; aPDT, 83.91%; DMSO, 95.69%; C + L, 97.15%. No statistically significant differences in bacteria reduction were observed for laser alone (SLB), DMSO, or curcumin with or without additional laser irradiation.

CONCLUSIONS

The greatest antibacterial efficacy was observed in samples treated with aPTT. Using curcumin as a photosensitizing agent for 445 nm laser irradiation did not result in improved antibacterial effectiveness in comparison with laser alone.

Antimicrobial photodynamic therapy (aPDT) against vancomycin resistant Staphylococcus aureus (VRSA) biofilm disruption: A putative role of phagocytosis in infection control

Biofilm mediated infections have major clinical impact. Staphylococcus aureus is a pathogen that frequently causes biofilm forming infections, such as those associated with medical devices and persistent wounds. Microorganisms embedded in biofilm are impervious to antibiotics and other antimicrobial agents, thus they are difficult to eliminate. The upsurge of multi-drug resistant strains makes treating such illnesses even more difficult. Therefore, new strategies are required to combat such type of infections. In this work, we have proposed an alternative therapeutic option to eradicate preformed biofilm of vancomycin resistant Staphylococcus aureus (VRSA) and enhanced phagocytosis by neutrophils in fresh human blood using curcumin mediated antimicrobial photodynamic therapy (aPDT).At sub-MIC of curcumin, different anti-biofilm assays and microscopic examinations were performed, followed by 20 J/cm² of blue laser light irradiation which corresponds to 52 s only. The result showed significant disruption of VRSA biofilm. Moreover, when curcumin-aPDT treated VRSA biofilm was exposed to whole blood from healthy donors, it was nearly completely eradicated. The present study suggests that curcumin-aPDT enhanced phagocytosis may be a useful strategy for inactivating VRSA biofilms adhering to medical implant surfaces.

Enhanced anti-microbial effect through cationization of a mono-triazatricyclodecane substituted asymmetric phthalocyanine

Antimicrobial photodynamic therapy (aPDT) is an effective way to combat infectious diseases and antibiotic resistance. Photosensitizer is a key factor of aPDT and has triggered extensive research interest. In this study, a new asymmetric Zn(II) phthalocyanine mono-substituted with a triazatricyclodecane moiety (compound 3) and its cationic N-methylated derivative (compound 4) were synthesized. Their photodynamic antimicrobial activities were evaluated using bioluminescent bacterial strains. Compound 3 showed phototoxicity only toward the Gram-positive bacteria, whereas the cationic derivative compound 4 exhibited strong anti-bacterial activity against both Gram-positive and Gram-negative strains. These bacterial species were eradicated (>4.0 logs or 99.99% killing) at appropriate concentrations of compound 4 with 12.7 J/cm² of red light, demonstrating compound 4 as a potent aPDT agent.

Selective photodynamic inactivation of Helicobacter pylori by a cationic benzylidene cyclopentanone photosensitizer - an in vitro and ex vivo study

The rise in the antibiotic resistance rate of Helicobacter pylori has led to an increasing eradication failure of this carcinogenic bacterial pathogen worldwide. This underlines the need for alternative antibacterial strategies against H. pylori infection. Antimicrobial photodynamic therapy (aPDT) is a promising non-pharmacological antibacterial technology. In this study, the selective killing activities of three benzylidene cyclopentanone (BCP) photosensitizers (Y1, P1 and P3) towards H. pylori over normal human gastric epithelial GES-1 cells were evaluated and the ex vivo photodynamic inactivation effect was preliminarily assessed on twelve H. Pylor-infected mice. Results showed that under the irradiation of 24 J/cm² 532 nm laser, Y1, P1 and P3 at 2.5 μM induced a 3-log₁₀ reduction of H. pylori CFU (99.9% killing). Confocal images showed that P3, unlike Y1 and P1, could not be uptaken by GES-1 cells. P3 at 2.5 to 20 μM showed not significant (p > 0.05) phototoxicity to GES-1 cells, nevertheless, Y1 and P1 under the same concentrations exhibited remarkable phototoxicity to GES-1 cells. In the co-culture of H. pylori and GES-1 cells, P3 at 2.5 μM led to a complete eradication of H. pylori under the irradiation of 24 J/cm² 532 nm laser. While for the GES-1 cells, no significant (p > 0.05) phototoxicity was observed under the same aPDT dosage. The ex vivo experiments showed that P3 mediated aPDT resulted in 82.4% to 100% reduction of H. pylori CFU without damaging the gastric mucosa. To sum up, P3 is a promising anti-H. pylori photosensitizer with the ability to selectively photo-inactivate H. pylori while sparing normal gastric tissues.

Antimicrobial Photodynamic Therapy in the Nasal Decolonization of Maintenance Hemodialysis Patients: A Pilot Randomized Trial

RATIONALE & OBJECTIVE

Infections are an important cause of mortality among patients receiving maintenance hemodialysis. Staphylococcus aureus is a frequent etiological agent, and previous nasal colonization is a risk factor for infection. Repeated antimicrobial decolonization reduces infection in this population but can induce antibiotic resistance. We compared photodynamic therapy, a promising bactericidal treatment that does not induce resistance, to mupirocin treatment among nasal carriers of S aureus.

STUDY DESIGN

Randomized controlled pilot study.

SETTING & PARTICIPANTS

34 patients receiving maintenance hemodialysis who had nasal carriage of S aureus.

INTERVENTIONS

Patients were randomly assigned to decolonization with a single application of photodynamic therapy (wavelength of 660nm, 400mW/cm², 300 seconds, methylene blue 0.01%) or with a topical mupirocin regimen (twice a day for 5 days).

OUTCOME

Nasal swabs were collected at time 0 (when the carrier state was identified), directly after treatment completion, 1 month after treatment, and 3 months after treatment. Bacterial isolates were subjected to proteomic analysis to identify the species present, and antimicrobial susceptibility was characterized.

RESULTS

All 17 participants randomized to photodynamic therapy and 13 of 17 (77%) randomized to mupirocin were adherent to treatment. Directly after treatment was completed, 12 participants receiving photodynamic therapy (71%) and 13 participants treated with mupirocin (77%) had cultures that were negative for S aureus (risk ratio, 0.92 [95% CI, 0.61-1.38]; P=0.9). Of the patients who had negative cultures directly after completion of photodynamic therapy, 67% were recolonized within 3 months. There were no adverse events in the photodynamic therapy group.

LIMITATIONS

Testing was restricted to assessing nasal colonization; infectious complications were not assessed.

CONCLUSIONS

Photodynamic therapy is a feasible approach to treating nasal carriage of S aureus. Future larger studies should be conducted to determine whether photodynamic therapy is equivalent to the standard of care with mupirocin.

FUNDING

Government grant (National Council for Scientific and Technological Development process 3146682020-9).

TRIAL REGISTRATION

Registered at ClinicalTrials.gov with study number NCT04047914.

Effectiveness of laser pulsed irradiation for antimicrobial photodynamic therapy

The aim of this study was to compare two types of light irradiation devices for antimicrobial photodynamic therapy (aPDT). A 660-nm light-emitting diode (LED) and a 665-nm laser diode (LD) were used for light irradiation, and 0.1 mg/L TONS 504, a cationic chlorin derivative, was used as the photosensitizer. We evaluated the light attenuation along the vertical and horizontal directions, temperature rise following light irradiation, and aPDT efficacy against Staphylococcus aureus under different conditions: TONS 504 only, light irradiation only, and TONS 504 with either LED (30 J/cm2) or LD light irradiation (continuous: 30 J/cm2; pulsed: 20 J/cm2 at 2/3 duty cycle, 10 J/cm2 at 1/3 duty cycle). Both LED and LD light intensities were inversely proportional to the square of the vertical distance from the irradiated area. Along the horizontal distance from the nadir of the light source, the LED light intensity attenuated according to the cosine quadrature law, while the LD light intensity did not attenuate within the measurable range. Following light irradiation, the temperature rise increased as the TONS 504 concentration increased in the order of pulsed LD < continuous LD < LED irradiation. aPDT with light irradiation only or TONS 504 only had no antimicrobial effect, while aPDT with TONS 504 under continuous or pulsed LD light irradiation provided approximately 3 log reduction at 30 J/cm2 and 20 J/cm2 and approximately 2 log reduction at 10 J/cm2. TONS 504-aPDT under pulsed LD light irradiation provided anti-microbial effect without significant temperature rise.

Photoresponsive nitric oxide photocage/photodynamic integrated prodrug for advanced management of drug-resistant bacteria-infected wound therapy

Single treatment methods for wound infections caused by drug-resistant bacteria often fail to simultaneously achieve high antimicrobial efficacy and wound healing efficiency. Therefore, it is crucial to develop a small molecule prodrug that can achieve both goals, in this context, we have engineered a green-light-activated nitric oxide photocage/photodynamic therapeutic prodrug, designed to release NO, which not only potentiates antimicrobial efficacy but also facilitates collagen accumulation at the wound interface, thereby expediting the wound healing process. Additionally, it mitigates tissue inflammation by suppressing the NF-κB signaling pathway. In addition, the introduction of the photosensitiser rhodamine can be used for antimicrobial photodynamic therapy (aPDT) against Methicillin-resistant Staphylococcus aureus (MRSA). aPDT exhibits enhanced antimicrobial efficacy by specifically targeting and disrupting bacterial cell membranes. Notably, this treatment significantly reduced bacterial viability in vitro and accelerated healing of MRSA-induced wound infections even at low concentrations. The developed NO photocage/photodynamic prodrug RhB-NO-1 is biocompatible and has demonstrated the ability to significantly accelerate the healing process of diabetic foot ulcers (DFU), making it a promising next-generation pharmacological treatment for chronic wound management.

Bioluminescent Models to Evaluate the Efficiency of Light-Based Antibacterial Approaches

The emergence of microbial resistance to antimicrobials among several common pathogenic microbial strains is an increasing problem worldwide. Thus, it is urgent to develop not only new antimicrobial therapeutics to fight microbial infections, but also new effective, rapid, and inexpensive methods to monitor the efficacy of these new therapeutics. Antimicrobial photodynamic therapy (aPDT) and antimicrobial blue light (aBL) therapy are receiving considerable attention for their antimicrobial potential and represent realistic alternatives to antibiotics. To monitor the photoinactivation process provided by aPDT and aBL, faster and more effective methods are required instead of laborious conventional plating and overnight incubation procedures. Bioluminescent microbial models are very interesting in this context. Light emission from bioluminescent microorganisms is a highly sensitive indication of their metabolic activity and can be used to monitor, in real time, the effects of antimicrobial agents and therapeutics. This chapter reviews the efforts of the scientific community concerning the development of in vitro, ex vivo, and in vivo bioluminescent bacterial models and their potential to evaluate the efficiency of aPDT and aBL in the inactivation of bacteria.

Unveiling the potent antimicrobial photodynamic therapy in Gram-positive and Gram-negative bacteria - Water remediation with monocharged chlorins

Water pollution is a significant concern worldwide, and it includes contaminants such as antibiotic-resistant pathogens. Antimicrobial photodynamic therapy (aPDT) offers a non-invasive and non-toxic alternative for the inactivation of these microorganisms. So, this study reports the synthesis, structural characterisation, photophysical properties, and aPDT efficacy of cationic free-base and zinc(II) chlorin (Chl) derivatives bearing N,N-dimethylpyrrolydinium groups (H2Chl 1a and ZnChl 1b). The aPDT assays were performed against two bacterial models: Staphylococcus aureus (Gram-(+)) and Escherichia coli (Gram-(-)). The H2Chl 1a and ZnChl 1b distinct's solubility profile, coupled with their ability to generate singlet oxygen (1O2) under light exposure, (H2Chl 1a, ФΔ = 0.58 < TPP, ФΔ = 0.65 < ZnChl 1b, ФΔ = 0.83) opens up their potential application as photosensitizers (PS) in aPDT. The effectiveness of H2Chl 1a and ZnChl 1b at 1.0 and 5.0 μM in aPDT against S. aureus and E. coli at 500 W m-2 (total exposure time: 60-120 min) showed a viability reduction >6.0 log10 CFU mL-1. Additionally, KI was used as a coadjuvant to potentiate the photoinactivation of E. coli, reaching the method's detection limit (>4.0 log10 RLU). As most of the PS developed to inactivate Gram-negative bacteria are cationic with three or more charges, the fact that the H2Chl 1a and ZnChl 1b with only one cationic charge photoinactivate E. coli at low concentrations and with a reduced light dose, it is an importing discovery that deserves further exploration. These monocharged chlorin dyes have the potential for water remediation.

Evaluation of cytotoxicity impacts of combined methylene blue-mediated photodynamic therapy and intracanal antibiotic medicaments on dental stem cells

Root canal therapy is a predominant method for treatment of dental pulp and periapical diseases. Conventional methods such as mechanical instrumentations, chemical irrigation and intracanal medicaments pose a huge limitation to root canal disinfection as they kill bacteria and dental stem cells simultaneously. Therefore, much attention has been focused on finding more efficacious antibacterial methods that has no or negligible cytotoxicity for dental stem cells. Herein, we hypothesized that combining antibacterial medicaments with Antimicrobial photodynamic therapy (aPDT) and methylene blue (MB) as a photosensitizer would be effective in reducing death of dental pulp stem cells (DPSCs). To examine this, DPSCs were isolated from third molar teeth through enzymatic digestion. Isolated cells were cultured in αMEM and when reached adequate confluency, were used for further analysis. Cytotoxicity effect of different groups of MB, DAP, MB, LED and their combination on DPSCs was analyzed using MTT assay. DPSCs membrane integrity as a marker of live cells was assessed through measuring lipid peroxidation and lactate dehydrogenase (LDH) release into extracellular space. Results showed that the combination of LED, MB and TAP or aPDT, MB and DAP was more effective in reducing DPSCs death rate compared to TAP and DAP administration alone. Moreover, Malondialdehyde (MDA) and LDH levels were found to be decreased in cells exposed to combination treatment in comparison with single TAP or DAP therapy. Our study shows the promising perspectives of employing combined aPDT, MB and antibiotic medicaments for reduction of dental stem cell death.