Use of photodynamic therapy and chitosan for inactivacion of Candida albicans in a murine model

Different wavelengths of laser: are they significant for treatment of denture stomatitis?: an in-vitro study

BACKGROUND

Denture stomatitis (DS) is an inflammatory disorder that affects the mucosal surface underneath the dentures and frequently causes oral mucosal irritation, discomfort, and altered taste perception, which prevents people from consuming enough nutrients. One of the main causes of DS is an overgrowth of the fungus Candida albicans (C. albicans). A possible alternative treatment for Candida infections is thought to be laser therapy. The aim of this study was to evaluate how different wavelengths of laser would affect growth and pathogenic properties of Candida albicans.

METHODS

A concentration of 106 viable cells/ml of Candida albicans were used in the preparation process. Four groups were created from the specimens. Culturing of the control group was completed with no intervention. The other 3 groups received laser radiation for 60 seconds at a power of 1W. The 2nd and 3rd groups were irradiated with diode laser at a wavelength of 940 nm and 980 nm respectively. The 4th group was irradiated with Nd-YAG laser at a wavelength of 1064 nm. Turbidimetric growth was defined as variations in the optical density of fungal growth. These measures were made at three different times: baseline, 48 hours, and 72 hours.

RESULTS

In both groups of diode laser, the growth of Candida albicans showed no remarkable differences at baseline, after 48 and 72 hours using a power of 1 W and duration of 60 seconds. The Nd-YAG group showed significant increase in optical density after 48 hrs then significant decrease after 72 hrs. The optical density values in the control group showed no notable difference between the control and diode study groups at different time periods. However, the Nd:YAG group showed a statistically significant difference compared to the control and the 2 diode laser groups.

CONCLUSIONS

Different laser parameters have a different effect on growth and pathogenic properties of Candida albicans. Diode laser therapy with wavelengths 940 and 980 nm used in continuous mode with power of 1 W for duration of 60 seconds can result in proliferation of Candida albicans instead of destroying them. Nd:YAG laser, used in pulsed mode, with power of 1 W for a duration of 60 seconds can be used to destroy Candida albicans and therefore, can be used as an effective treatment for denture stomatitis.

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.

Enhancing effect of chitosan on methylene blue-mediated photodynamic therapy against C. albicans: a study in planktonic growth, biofilms, and persister cells

Chitosan (CS) is a natural polymer extracted from the exoskeleton of crustaceans. Due to its cationic structure, CS has been studied as a possible enhancer of antimicrobial photodynamic therapy (aPDT). The objective was to evaluate the association of CS with methylene blue (MB)-mediated aPDT on Candida albicans, investigating its effects on planktonic growth, biofilms, and cells persistent to fluconazole. The ability of CS to interfere with MB absorption by Candida cells was also evaluated. For the assays, planktonic cells of C. albicans were cultivated for 24 h, and the biofilms were formed for 48 h. For the induction of persister cells, C. albicans was cultivated with high concentration of fluconazole for 48 h. Treatments were performed with MB, CS or MB+CS, followed by irradiation with LED (660 nm). As results, aPDT with MB (300 µm) reduced the planktonic cells by 1.6 log10 CFU, while the MB+CS association led to a reduction of 4.8 log10 CFU. For aPDT in biofilms, there was a microbial reduction of 2.9 log10 CFU for the treatment with MB (600 µm) and 5.3 log10 CFU for MB+CS. In relation to persister cells, the fungal reductions were 0.4 log10 CFU for MB and 1.5 log10 CFU for MB+CS. In the absorption assays, the penetration of MB into Candida cells was increased in the presence of CS. It was concluded that CS enhanced the antimicrobial activity of aPDT in planktonic growth, biofilms, and persister cells of C. albicans, probably by facilitating the penetration of MB into fungal cells.

Photosensitizers Mediated Photodynamic Inactivation against Fungi

Superficial and systemic fungal infections are essential problems for the modern health care system. One of the challenges is the growing resistance of fungi to classic antifungals and the constantly increasing cost of therapy. These factors force the scientific world to intensify the search for alternative and more effective methods of treatment. This paper presents an overview of new fungal inactivation methods using Photodynamic Antimicrobial Chemotherapy (PACT). The results of research on compounds from the groups of phenothiazines, xanthanes, porphyrins, chlorins, porphyrazines, and phthalocyanines are presented. An intensive search for a photosensitizer with excellent properties is currently underway. The formulation based on the existing ones is also developed by combining them with nanoparticles and common antifungal therapy. Numerous studies indicate that fungi do not form any specific defense mechanism against PACT, which deems it a promising therapeutic alternative.

Synergistic antimicrobial effect of photodynamic therapy and chitosan on the titanium-adherent biofilms of Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa: An in vitro study

BACKGROUND

To date, no studies on the combined use of photodynamic therapy (PDT) and chitosan against peri-implantitis have been published. The aim of this study was to evaluate the possible synergistic antimicrobial effect of PDT and chitosan on the titanium-adherent biofilms of Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa.

METHODS

A total of 60 titanium discs were included in this study. The discs were randomized into three bacterial contaminations (n = 20 discs per bacterium). After being cultured (incubated for 48 hours) they were randomized again into four different disinfection modalities (n = 5 discs per treatment): control (without treatment), PDT, chitosan 3 mg/mL, and PDT + chitosan 3 mg/mL. After the treatments, the colony forming units (CFU) were measured to determine antimicrobial effects, and field emission scanning electron microscopy (FESEM) was used to study cell morphology and titanium adherence.

RESULTS

For all the evaluated bacteria and all the variables studied the order from highest to lowest antimicrobial effectiveness was: PDT + chitosan 3 mg/mL > chitosan 3 mg/mL > PDT > control. Although, all disinfection methods were significantly effective when compared to control, the combined treatment of PDT + chitosan 3 mg/mL had the greatest antimicrobial effect against the three studied bacteria.

CONCLUSIONS

The combination of PDT and chitosan has a synergistic antimicrobial effect against the bacteria S. aureus, E. coli, and P. aeruginosa, all closely related to peri-implantitis. However, further in vivo studies are needed because this study provides data based on an in vitro scenario that might not be extrapolated to patients with peri-implantitis.

In vivo antifungal activities of farnesol combined with antifungal drugs against murine oral mucosal candidiasis

The antifungal resistence of oral candidiasis is a serious clinical issue. The in vivo efficacy of farnesol combined with antifungals for oral candidiasis remains unknown. The possible therapeutic effects of a combination of farnesol and antifungal drugs and the regulation of inflammatory cytokines in murine oral candidiasis were investigated in this study. An experimental oral candidiasis model was constructed using ICR mice. Farnesol at 25 and 50 μM did not change IL-17, IFN-γ and TNF-α production during oral candidiasis compared with that of the control infected mice. The co-applications of farnesol (50 μM) and nystatin, farnesol (4 μM, 8 μM) and itraconazole, farnesol (25, 50 μM), and fluconazole enhanced the therapeutic activity of the antifungal agents alone against oral candidiasis. The effective combinations reduced the number of colony forming units (CFU) of Candida albicans isolated from the oral cavity and oral lesions on the tongue.

Nanoparticles in Dentistry: A Comprehensive Review

In recent years, nanoparticles (NPs) have been receiving more attention in dentistry. Their advantageous physicochemical and biological properties can improve the diagnosis, prevention, and treatment of numerous oral diseases, including dental caries, periodontal diseases, pulp and periapical lesions, oral candidiasis, denture stomatitis, hyposalivation, and head, neck, and oral cancer. NPs can also enhance the mechanical and microbiological properties of dental prostheses and implants and can be used to improve drug delivery through the oral mucosa. This paper reviewed studies from 2015 to 2020 and summarized the potential applications of different types of NPs in the many fields of dentistry.

Curcumin-loaded Pluronic® F-127 Micelles as a Drug Delivery System for Curcumin-mediated Photodynamic Therapy for Oral Application

Antimicrobial photodynamic therapy (aPDT) is promising for oral decontamination. Curcumin has been used as photosensitizer; however, the hydrophobic properties can negatively affect aPDT. This study evaluated the aPDT efficacy using Cur-loaded Pluronic^® F-127 micelles against Streptococcus mutans and Candida albicans biofilms. Micelles characterization was performed by zeta potential, dynamic light scattering, transmission electron microscopy, absorption and fluorescence spectroscopy. Cur concentrations, cell viability by CFU mL^-1 and confocal microscopy were determined. Data were analyzed by parametric and nonparametric tests under 5%. Cur-loaded Pluronic^® F-127 exhibited spherical shape, suitable particle size (≤100 nm), adequate polydispersity index, best stability, lower photodegradation and autoaggregation compared to unloaded-Cur. Both microorganisms were sensitive to Cur-loaded Pluronic^® F-127 micelles aPDT, with minimum inhibitory concentration (MIC) of 270 μm and 2.1093 μm for S. mutans and C. albicans suspended culture, respectively. Cur-loaded Pluronic^® F-127 aPDT exhibited antibacterial/antifungal effect against the biofilms (~3 log₁₀ reduction; P ≤ 0.05); however, similar to unloaded (P ≥ 0.05). Confocal images confirmed these results. Cur-loaded Pluronic^® F-127 micelles exhibited good photo-chemical properties and may be a viable alternative to deliver Cur and to improve aPDT effect during the treatment of dental caries. Moreover, Pluronic^® micelles can enhance the solubility, stability, permeability and control the release of Cur.

Effect of a Combination of Photodynamic Therapy and Chitosan on Streptococcus mutans (An In Vitro Study)

Introduction: This study aimed to assess the effect of photodynamic therapy (PDT) and chitosan separately and in combination on Streptococcus mutans. Methods: This in vitro experimental study evaluated 216 microbial samples in 6 groups. First, 5 µL of 0.5 McFarland standard suspension of S. mutans was added to each well of an ELISA microplate; 100 µL of Mueller Hinton broth was also added to each well; 180 wells contained S. mutans suspension while 36 wells were devoid of bacteria. Group 1 served as the negative control and had no bacteria. Group 2 served as the positive control and S. mutans in the positive control wells did not undergo any intervention. In groups 3 and 4, PDT with a 50 mW low-level laser was performed for 30 and 40 seconds respectively. In group 5, 3 mg/mL of chitosan (100 µL) was used. In group 6, 3 mg/mL (100 µL) of chitosan was used in combination with PDT (50 mW laser for 30 seconds). The laser was irradiated under aseptic conditions at a 660 nm wavelength with 50 mW power. Data were analyzed using one-way ANOVA and Tukey's test. Results: PDT combined with chitosan showed maximum bactericidal effect followed by PDT for 40 seconds and chitosan groups (P < 0.05). PDT for 30 seconds showed a minimum bactericidal effect (P < 0.05). All pairwise comparisons revealed significant differences (P < 0.001). Conclusion: Chitosan and PDT alone can be used to decrease the S. mutans count. However, their combined use has a greater bactericidal effect on S. mutans .

Candida-Associated Denture Stomatitis and Murine Models: What Is the Importance and Scientific Evidence?

Considering the high prevalence and recurrence of Candida-associated denture stomatitis (CADS), in vivo studies in animal models are necessary before those in humans to evaluate new therapeutic strategies. This study aimed to review the literature on murine models of CADS induction using acrylic intraoral devices simulating dentures. Rats are recommended as experimental animals in these models as well as the adoption of a pasty diet. For maintenance in the proper position during the experiments, intraoral appliances must be obtained by individual impressions, using and retained exclusively by cementation on the molars. The region of interest for histopathological analysis was standardized as that corresponding to the area between the first molars. However, there is no consensus among the studies on the CADS induction rat models in relation to the Candida albicans inoculation and need for immunosuppression and/or administration of antibacterial drugs of animals. The greatest difficulty of the available models refers to maintaining the course of the lesion for a sufficient period to evaluate the effectiveness of the proposed treatment, considering the rapid and efficient murine immune response to candidal colonization. Therefore, future studies are necessary for the development of a robust and reproducible CADS model.

Chitosan-Based Drug Delivery Systems for Optimization of Photodynamic Therapy: a Review

Drug delivery systems (DDS) can be designed to enrich the pharmacological and therapeutic properties of several drugs. Many of the initial obstacles that impeded the clinical applications of conventional DDS have been overcome with nanotechnology-based DDS, especially those formed by chitosan (CS). CS is a linear polysaccharide obtained by the deacetylation of chitin, which has potential properties such as biocompatibility, hydrophilicity, biodegradability, non-toxicity, high bioavailability, simplicity of modification, aqueous solubility, and excellent chemical resistance. Furthermore, CS can prepare several DDS as films, gels, nanoparticles, and microparticles to improve delivery of drugs, such as photosensitizers (PS). Thus, CS-based DDS are broadly investigated for photodynamic therapy (PDT) of cancer and fungal and bacterial diseases. In PDT, a PS is activated by light of a specific wavelength, which provokes selective damage to the target tissue and its surrounding vasculature, but most PS have low water solubility and cutaneous photosensitivity impairing the clinical use of PDT. Based on this, the application of nanotechnology using chitosan-based DDS in PDT may offer great possibilities in the treatment of diseases. Therefore, this review presents numerous applications of chitosan-based DDS in order to improve the PDT for cancer and fungal and bacterial diseases.

The effect of low level laser on number of Candida albicans colonies in-vitro: a new finding

Background

Candida albicans is a commensal organism that causes a wide variety of diseases in humans. One of these diseases is oral candidiasis, which occurs at a high recurrence rate in spite of available treatments. The purpose of this study was to compare the effect of low-level laser therapy (LLLT) with the use of nystatin on in-vitro growth of Candida albicans.

Method

We prepared two samples of Candida albicans at different concentrations: 10⁴ viable cells/ml and 10⁶ viable cells/ml. Specimens from each sample were divided into a control group, a nystatin-treated group, and a group treated with LLLT. The control group was cultured without any intervention. The second group was treated with nystatin and the solution was vibrated for 30 s or 60 s. The third group was irradiated with a gallium-aluminum-argon (Ga-Al-Ar) diode laser (Epic 10; Biolase Inc.)in continuous mode using a wavelength of 940 nm and a power of 1 W for 30 s or 60 s (38 J/cm² and 76 J/cm²). The specimens from the nystatin group and the LLLT group were cultured and the number of colony-forming units (CFU/ml) for each group was counted and compared.

Results

Nystatin completely eliminated the colonies (0 colonies) in all specimens. There was an increase in the number of colonies in the LLLT group for both cell concentrations at 30 s and at 60 s. However, this increase was statistically significant only for a concentration of 10⁴ viable cells/ml at an exposure time of 30s. The increase in the concentration of 10⁶ viable cells/ml at both 30 s and 60 s was statistically significant compared with the control group, although the highest number of colonies remained after an exposure time of 60s.

Conclusion

LLLT led to an increase in the growth of Candida colonies. However, there was no significant difference related to the exposure time between the different cell concentrations.

In vivo biocompatibility of an interim denture resilient liner containing antifungal drugs

STATEMENT OF PROBLEM

Antifungal agents incorporated into interim denture resilient liners have been suggested as an adjunct treatment for denture stomatitis (DS). However, before applying this protocol to humans, biocompatibility analysis of such drugs in animal models is required.

PURPOSE

The purpose of this animal study was to evaluate the in vivo biocompatibility of an interim resilient liner modified with minimum inhibitory concentrations (MICs) of antifungal drugs for Candida albicans biofilm.

MATERIAL AND METHODS

Sixty Wistar rats were divided into 6 groups (n=5): PC=positive control/no protocol; IOD (intraoral device)=rats using an acrylic resin palatal device (PD); Tru=rats using a PD relined with Trusoft; and Ny (nystatin), Chx (chlorhexidine diacetate), and Ke (ketoconazole) groups=rats using a PD relined with Trusoft + drug MICs. The rats were sacrificed at 7 or 14 days of trial. Histopathological qualitative analysis was performed by comparing photomicrographs of histological sections of the intermolar region. Morphological changes in the epithelium and keratin were quantitatively analyzed by computerized planimetry, and data were analyzed by using 2-way ANOVA and the Tukey HSD test (α=.05).

RESULTS

Quantitative analysis showed that only PD containing Ke significantly decreased the thickness and area of the keratin compared with the other groups (P<.001), which showed no differences between each other (P>.05). These results agreed with those of qualitative analysis.

CONCLUSIONS

Incorporation of MICs of Ny and Chx in Trusoft did not induce histopathological changes in the rat palatal mucosa, suggesting the in vivo biocompatibility of this DS treatment.

Pulsed electric field-assisted sensitization of multidrug-resistant Candida albicans to antifungal drugs

AIM

Determine the influence of pH on the inactivation efficiency of Candida albicans in pulsed electric fields (PEF) and evaluate the possibilities for sensitization of a drug-resistant strain to antifungal drugs.

MATERIALS & METHODS

The effects of PEF (2.5-25 kVcm^-1) with fluconazole, terbinafine and naftifine were analyzed at a pH range of 3.0-9.0. Membrane permeabilization was determined by flow cytometry and propidium iodide.

RESULTS

PEF induced higher inactivation of C. albicans at low pH and increased sensitivity to terbinafine and naftifine to which the strain was initially resistant. Up to 5 log reduction in cell survival was achieved.

CONCLUSION

A proof of concept that electroporation can be used to sensitize drug-resistant microorganisms was presented, which is promising for treating biofilm-associated infections.