Chitosan Ameliorates Candida auris Virulence in a Galleria mellonella Infection Model.

Candida auris has emerged as a multidrug-resistant nosocomial pathogen over the last decade. Outbreaks of the organism in health care facilities have resulted in life-threatening invasive candidiasis in over 40 countries worldwide. Resistance by C. auris to conventional antifungal drugs such as fluconazole and amphotericin B means that alternative therapeutics must be explored. As such, this study served to investigate the efficacy of a naturally derived polysaccharide called chitosan against aggregative (Agg) and nonaggregative (non-Agg) isolates of C. aurisin vitro and in vivo. In vitro results indicated that chitosan was effective against planktonic and sessile forms of Agg and non-Agg C. auris In a Galleria mellonella model to assess C. auris virulence, chitosan treatment was shown to ameliorate killing effects of both C. auris phenotypes (NCPF 8973 and NCPF 8978, respectively) in vivo Specifically, chitosan reduced the fungal load and increased survival rates of infected Galleria, while treatment alone was nontoxic to the larvae. Finally, chitosan treatment appeared to induce a stress-like gene expression response in NCPF 8973 in the larvae likely arising from a protective response by the organism to resist antifungal activity of the compound. Taken together, results from this study demonstrate that naturally derived compounds such as chitosan may be useful alternatives to conventional antifungals against C. auris.

Virulence Factors in Candida albicans and Streptococcus mutans Biofilms Mediated by Farnesol.

The aim of this study was to evaluate the effect of farnesol on the production of acids and hydrolytic enzymes by biofilms of Streptococcus mutans and Candida albicans. The present study also evaluated the time-kill curve and the effect of farnesol on matrix composition and structure of single-species and dual-species biofilms. Farnesol, at subinhibitory concentrations, showed a significant reduction in S. mutans biofilm acid production, but did not alter C. albicans hydrolytic enzyme production. The number of cultivable cells of both microorganisms was significantly reduced after 8 h of contact with farnesol. Extracellular matrix protein content was reduced for biofilms formed in the presence of farnesol. In addition, confocal laser scanning and scanning electron microscopy displayed structural alterations in all biofilms treated with farnesol, which included reduction in viable cells and extracellular matrix. In conclusion, farnesol showed favorable properties controlling some virulence factors of S. mutans and C. albicans biofilms. These findings should stimulate further studies using this quorum-sensing molecule, combined with other drugs, to prevent or treat biofilm-associated oral diseases.

Role of tyrosol on Candida albicans, Candida glabrata and Streptococcus mutans biofilms developed on different surfaces.

PURPOSE: To assess the effect of tyrosol on the production of hydrolytic enzymes (by Candida biofilm cells) and acid (by Streptococcus mutans biofilms), as well as to quantify single and mixed biofilms of these species formed on acrylic resin (AR) and hydroxyapatite (HA). METHODS: Candida and S. mutans biofilms were formed on AR and HA in the presence of tyrosol during 48 hours. Next, acid proteinase, phospholipase and hemolytic activities of Candida biofilm cells were determined, while acid production by S. mutans biofilms was assessed by pH determination. The effect of tyrosol on mature biofilms (96 hours) was evaluated through quantification of total biomass, metabolic activity, number of colony-forming units and composition of biofilms' extracellular matrix. Data were analyzed by one- and two-way ANOVA, followed by Tukey's and Holm-Sidak's tests (α = 0.05). RESULTS: Treatments with tyrosol were not able to significantly reduce hydrolytic enzymes and acid production by Candida and S. mutans. Tyrosol only significantly reduced the metabolic activity of single biofilms of Candida species. CLINICAL SIGNIFICANCE: Tyrosol on its own had a limited efficacy against single and mixed-species oral biofilms. Its use as an alternative antimicrobial for topical therapies still demands more investigation.

Biofilm formation by Candida albicans and Streptococcus mutans in the presence of farnesol: a quantitative evaluation.

The aim of this study was to evaluate the effect of the QS molecule farnesol on single and mixed species biofilms formed by Candida albicans and Streptococcus mutans. The anti-biofilm effect of farnesol was assessed through total biomass quantification, counting of colony forming units (CFUs) and evaluation of metabolic activity. Biofilms were also analyzed by scanning electron microscopy (SEM). It was observed that farnesol reduced the formation of single and mixed biofilms, with significant reductions of 37% to 90% and 64% to 96%, respectively, for total biomass and metabolic activity. Regarding cell viability, farnesol treatment promoted significant log reductions in the number of CFUs, ie 1.3-4.2 log10 and 0.67-5.32 log10, respectively, for single and mixed species biofilms. SEM images confirmed these results, showing decreases in the number of cells in all biofilms. In conclusion, these findings highlight the role of farnesol as an alternative agent with the potential to reduce the formation of pathogenic biofilms.

Effect of tyrosol on adhesion of Candida albicans and Candida glabrata to acrylic surfaces.

The prevention of adhesion of Candida cells to acrylic surfaces can be regarded as an alternative to prevent denture stomatitis. The use of quorum sensing molecules, such as tyrosol, could potentially interfere with the adhesion process. Therefore, the aim of this study was to assess the effect of tyrosol on adhesion of single and mixed cultures of Candida albicans and Candida glabrata to acrylic resin surfaces. Tyrosol was diluted in each yeast inoculum (10(7) cells/ml in artificial saliva) at 25, 50, 100, and 200 mM. Then, each dilution was added to wells of 24-well plates containing the acrylic specimens, and the plates were incubated at 37°C for 2 h. After, the effect of tyrosol was determined by total biomass quantification, metabolic activity of the cells and colony-forming unit counting. Chlorhexidine gluconate (CHG) was used as a positive control. Data were analyzed using analysis of variance (ANOVA) and the Holm-Sidak post hoc test (α = 0.05). The results of total biomass quantification and metabolic activity revealed that the tyrosol promoted significant reductions (ranging from 22.32 to 86.16%) on single C. albicans and mixed cultures. Moreover, tyrosol at 200 mM and CHG significantly reduced (p < 0.05) the number of adhered cells to the acrylic surface for single and mixed cultures of both species, with reductions ranging from 1.74 to 3.64-log10. In conclusion, tyrosol has an inhibitory effect on Candida adhesion to acrylic resin, and further investigations are warranted to clarify its potential against Candida infections.

Nanocarriers of Miconazole or Fluconazole: Effects on Three-Species Candida Biofilms and Cytotoxic Effects In Vitro.

The contribution of different Candida species in oral fungal infections has stimulated the search for more effective therapies. This study assessed the antibiofilm effects of nanocarriers of miconazole (MCZ) or fluconazole (FLZ) on Candida biofilms, and their cytotoxic effects on murine fibroblasts. Three-species biofilms (Candida albicans/Candida glabrata/Candida tropicalis) were formed on 96-well plates, and they were treated with nanocarriers (iron oxide nanoparticles coated with chitosan-"IONPs-CS") of MCZ or FLZ at 39/78/156 µg/mL; antifungals alone at 156 µg/mL and artificial saliva were tested as positive and negative controls, respectively. Biofilms were analyzed by colony forming units (CFU), biomass, metabolic activity, and structure/viability. The cytotoxicity (L929 cells) of all treatments was determined via 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide (MTT) reduction assay. Data were submitted to one- or two-way ANOVA, followed by Tukey's or Fisher LSD's tests (p < 0.05). IONPs-CS-MCZ at 78 µg/mL promoted similar antibiofilm and cytotoxic effects compared with MCZ at 156 µg/mL. In turn, IONPs-CS-FLZ at 156 µg/mL was overall the most effective FLZ antibiofilm treatment, surpassing the effects of FLZ alone; this nanocarrier was also less cytotoxic compared with FLZ alone. It can be concluded that both nanocarriers are more effective alternatives to fight Candida biofilms compared with their respective positive controls in vitro, being a promising alternative for the treatment of oral fungal infections.

A nanocarrier system that potentiates the effect of miconazole within different interkingdom biofilms.

BACKGROUND: Novel and new therapeutic strategies capable of enhancing the efficacy of existing antimicrobials is an attractive proposition to meet the needs of society. OBJECTIVE: This study aimed to evaluate the potentiating effect of a miconazole (MCZ) nanocarrier system, incorporated with iron oxide nanoparticles (IONPs) and chitosan (CS) (IONPs-CS-MCZ). This was tested on three representative complex interkingdom oral biofilm models (caries, denture and gingivitis). MATERIALS AND METHODS: The planktonic and sessile minimum inhibitory concentrations (MICs) of IONPs-CS-MCZ against different Candida albicans strains were determined, as well as against all represented bacterial species that formed within the three biofilm models. Biofilms were treated for 24 hours with the IONPs-CS nanocarrier system containing MCZ at 64 mg/L, and characterized using a range of bioassays for quantitative and qualitative assessment. RESULTS: MIC results generally showed that IONPs-CS-MCZ was more effective than MCZ alone. IONPs-CS-MCZ also promoted reductions in the number of CFUs, biomass and metabolic activity of the representative biofilms, as well as altering biofilm ultrastructure when compared to untreated biofilms. IONPs-CS-MCZ affected the composition and reduced the CFEs for most of the microorganisms present in the three evaluated biofilms. In particular, the proportion of streptococci in the biofilm composition were reduced in all three models, whilst Fusobacterium spp. percentage reduced in the gingivitis and caries models, respectively. CONCLUSION: In conclusion, the IONPs-CS-MCZ nanocarrier was efficient against three in vitro models of pathogenic oral biofilms, showing potential to possibly interfere in the synergistic interactions among fungal and bacterial cells within polymicrobial consortia.

Novel nanocarrier of miconazole based on chitosan-coated iron oxide nanoparticles as a nanotherapy to fight Candida biofilms.

Overexposure of microorganisms to conventional drugs has led to resistant species that require new treatment strategies. This study prepared and characterized a nanocarrier of miconazole (MCZ) based on iron oxide nanoparticles (IONPs) functionalized with chitosan (CS), and tested its antifungal activity against biofilms of Candida albicans and Candida glabrata. IONPs-CS-MCZ nanocarrier was prepared by loading MCZ on CS-covered IONPs and characterized by physicochemical methods. Minimum inhibitory concentration (MIC) of the nanocarrier was determined by the microdilution method. Biofilms were developed (48 h) in microtiter plates and treated with MCZ-carrying nanocarrier at 31.2 and 78 µg/mL, in both the presence and absence of an external magnetic field (EMF). Biofilms were evaluated by total biomass, metabolic activity, cultivable cells (CFU), extracellular matrix components, scanning electron microscopy and confocal microscopy. Data were analyzed by two-way ANOVA and Holm-Sidak test (p < 0.05). A nanocarrier with diameter lower than 50 nm was obtained, presenting MIC values lower than those found for MCZ, and showing synergism for C. albicans and indifference for C. glabrata (fractional inhibitory concentration indexes of <0.12 and <0.53, respectively). IONPs-CS-MCZ did not affect total biomass and extracellular matrix. IONPs-CS-MCZ containing 78 µg/mL MCZ showed a superior antibiofilm effect to MCZ in reducing CFU and metabolism for single biofilms of C. albicans and dual-species biofilms. The EMF did not improve the nanocarrier effects. Microscopy confirmed the antibiofilm effect of the nanocarrier. In conclusion, IONPs-CS-MCZ was more effective than MCZ mainly against C. albicans planktonic cells and number of CFU and metabolism of the biofilms.

Novel Colloidal Nanocarrier of Cetylpyridinium Chloride: Antifungal Activities on Candida Species and Cytotoxic Potential on Murine Fibroblasts.

Nanocarriers have been used as alternative tools to overcome the resistance of Candida species to conventional treatments. This study prepared a nanocarrier of cetylpyridinium chloride (CPC) using iron oxide nanoparticles (IONPs) conjugated with chitosan (CS), and assessed its antifungal and cytotoxic effects. CPC was immobilized on CS-coated IONPs, and the nanocarrier was physico-chemically characterized. Antifungal effects were determined on planktonic cells of Candida albicans and Candida glabrata (by minimum inhibitory concentration (MIC) assays) and on single- and dual-species biofilms of these strains (by quantification of cultivable cells, total biomass and metabolic activity). Murine fibroblasts were exposed to different concentrations of the nanocarrier, and the cytotoxic effect was evaluated by MTT reduction assay. Characterization methods confirmed the presence of a nanocarrier smaller than 313 nm. IONPs-CS-CPC and free CPC showed the same MIC values (0.78 µg mL-1). CPC-containing nanocarrier at 78 µg mL-1 significantly reduced the number of cultivable cells for all biofilms, surpassing the effect promoted by free CPC. For total biomass, metabolic activity, and cytotoxic effects, the nanocarrier and free CPC produced statistically similar outcomes. In conclusion, the IONPs-CS-CPC nanocarrier was more effective than CPC in reducing the cultivable cells of Candida biofilms without increasing the cytotoxic effects of CPC, and may be a useful tool for the treatment of oral fungal infections.

Antibiofilm effect of chlorhexidine-carrier nanosystem based on iron oxide magnetic nanoparticles and chitosan.

This study synthesized and characterized a chlorhexidine (CHX)-carrier nanosystem based on iron oxide magnetic nanoparticles (IONPs) and chitosan (CS), and evaluated its antimicrobial effect on mono- and dual-species biofilms of Candida albicans and Streptococcus mutans. CHX was directly solubilized in CS-coated IONPs and maintained under magnetic stirring for obtaining the IONPs-CS-CHX nanosystem. Antimicrobial susceptibility testing for planktonic cells was performed by determining the minimum inhibitory concentration (MIC) of the nanosystem and controls. The effects of the IONPs-CS-CHX nanosystem on the formation of mono- and dual-species biofilms, as well as on pre-formed biofilms were assessed by quantification of total biomass, metabolic activity and colony-forming units. Data were analyzed by the Kruskal-Wallis' test or one-way analysis of variance, followed by the Student-Newman-Keuls' or Holm-Sidak's tests (α = 0.05), respectively. Physico-chemical results confirmed the formation of a nanosystem with a size smaller than 40 nm. The IONPs-CS-CHX nanosystem and free CHX showed similar MIC values for both species analyzed. In general, biofilm quantification assays revealed that the CHX nanosystem at 78 µg/mL promoted similar or superior antibiofilm effects compared to its counterpart at 39 µg/mL and free CHX at 78 µg/mL. These findings highlight the potential of CS-coated IONPs as preventive or therapeutic agents carrying CHX to fight biofilm-associated oral diseases.

Iron Oxide Nanoparticles for Biomedical Applications: A Perspective on Synthesis, Drugs, Antimicrobial Activity, and Toxicity.

Medical applications and biotechnological advances, including magnetic resonance imaging, cell separation and detection, tissue repair, magnetic hyperthermia and drug delivery, have strongly benefited from employing iron oxide nanoparticles (IONPs) due to their remarkable properties, such as superparamagnetism, size and possibility of receiving a biocompatible coating. Ongoing research efforts focus on reducing drug concentration, toxicity, and other side effects, while increasing efficacy of IONPs-based treatments. This review highlights the methods of synthesis and presents the most recent reports in the literature regarding advances in drug delivery using IONPs-based systems, as well as their antimicrobial activity against different microorganisms. Furthermore, the toxicity of IONPs alone and constituting nanosystems is also addressed.

Síntese e avaliação dos efeitos de um nanocarreador de miconazol sobre microrganismos orais / Synthesis and evaluation of the effects of a miconazole nanocarrier on oral microorganisms

A presente tese teve como objetivo geral preparar, caracterizar e avaliar os efeitos antimicrobianos de um nanocarreador de miconazol (MCZ) à base de nanopartículas magnéticas de óxido de ferro (NPsMOF) funcionalizadas com quitosana (QS). Assim, dois subprojetos (SP1 e SP2) foram desenvolvidos e apresentaram os seguintes objetivos específicos: SP1) Preparar, caracterizar e avaliar os efeitos do nanocarreador NPsMOF-QS-MCZ sobre células planctônicas e biofilmes simples e misto de Candida albicans e Candida glabrata; SP2) Avaliar o efeito do nanocarreador na composição de três diferentes modelos de biofilmes polimicrobianos patogênicos orais (gengivite, prótese total e cárie dentária). A primeira etapa do SP1 consistiu em revestir as NPsMOF com QS e carregar este core-shell com MCZ, a fim de caracterizar este nanocarreador por métodos físico-químicos. As concentrações inibitórias mínimas (CIMs) do nanocarreador foram determinadas pelo método da microdiluição em caldo, usando o índice da concentração inibitória fracionária a fim de avaliar se houve interação sinergística entre os compostos. Ainda, biofilmes simples e mistos de Candida foram formados no fundo de placas de 24 ou 96 poços por 48 h e, em seguida, tratados por 24 h com NPsMOF-QS-MCZ carreando MCZ a 31,2 e 78 µg/ml, na presença e ausência de um campo magnético externo. Os biofilmes foram avaliados quantitativamente por biomassa total, atividade metabólica, contagem de unidades formadoras de colônias (UFCs) e composição da matriz extracelular. Os dados foram analisados por ANOVA a dois fatores, seguida pelo teste de Holm-Sidak (p<0,05). Ainda, a estrutura dos biofilmes foi avaliada qualitativamente por microscopia eletrônica de varredura e microscopia confocal. Os resultados do SP1 mostraram que o nanocarreador apresentou diâmetro menor que 50 nm e valores de CIM menores do que aqueles encontrados para MCZ sozinho, com efeito sinérgico sobre C. albicans. NPsMOF-QS-MCZ a 78 µg/ml foi mais eficaz que MCZ sozinho na redução de UFCs e atividade metabólica de biofilmes misto e simples de C. albicans. A biomassa total dos biofilmes e a matriz extracelular não foram afetadas pelo nanocarreador, e a aplicação de um campo magnético externo não melhorou seu efeito antibiofilme. As imagens de microscopia confirmam que tratamentos com o nanocarreador, principalmente na maior concentração, apresentaram maior atividade antibiofilme. Com relação ao SP2, as CIMs de NPsMOF-QS-MCZ foram determinadas para diferentes espécies microbianas, e todos os biofilmes polimicrobianos foram desenvolvidos por 5 dias e tratados por 24 h com NPsMOF-QS-MCZ a 64 µg/ml. Após o tratamento, os biofilmes foram avaliados quanto à biomassa total, atividade metabólica, contagem de UFCs e análise composicional por PCR quantitativo. Microscopia eletrônica de varredura foi usada para analisar a estrutura do biofilme. As diferenças entre os grupos foram determinadas por teste t não pareado (p<0,05). Os resultados do SP2 mostraram que NPsMOF-QS-MCZ foi mais eficaz que MCZ sozinho contra a maioria das células fúngicas e bacterianas testadas. Ainda, este nanocarreador foi capaz de reduzir a atividade metabólica, biomassa total e UFCs (p<0,05) dos biofilmes, além de alterar a sua ultraestrutura. Por fim, NPsMOF-QS-MCZ afetou a composição dos três biofilmes polimicrobianos avaliados, reduzindo principalmente os números de Streptococcus spp. e alterando a prevalência das espécies nos biofilmes. Em suma, os resultados dos SP1 e SP2 permitiram concluir que o nanocarreador melhorou o efeito antimicrobiano do MCZ, dependendo da espécie e parâmetro de biofilme avaliados. O nanocarreador também mostrou potencial para interferir nas interações sinergísticas entre células fúngicas e bacterianas dentro de biofilmes polimicrobianos(AU)

The present thesis aimed to prepare, characterize and evaluate the antimicrobial effects of a miconazole (MCZ) nanocarrier based on iron oxide magnetic nanoparticles (IONPs) functionalized with chitosan (CS). Thus, two subprojects (SP1 and SP2) were developed and had the following specific objectives: SP1) To prepare, characterize and evaluate the effects of the IONPs-CS-MCZ nanocarrier on planktonic cells and singleand dual-species biofilms of Candida albicans and Candida glabrata; SP2) To evaluate the effect of IONPs-CS-MCZ on the composition of three different models of oral pathogenic biofilms (gingivitis, denture and dental caries). The first step of SP1 was to coat IONPs with CS and to load this core-shell association with MCZ, in order to characterize this nanocarrier by physicochemical methods. The minimum inhibitory concentrations (MICs) of the nanocarrier were determined by the microdilution method, using the fractional inhibitory concentration index in order to assess whether there was synergistic interaction between the compounds.. In addition, single- and dual-species biofilms of Candida species were formed at the bottom of 24- or 96-well plates for 48 h and, in sequence, treated for 24 h with IONPs-CS-MCZ carrying MCZ at 31.2 and 78 µg/ml, in both the presence and absence of an external magnetic field. Biofilms were quantitatively evaluated by total biomass, metabolic activity, counting of colony forming units (CFUs) and extracellular matrix components. Data were analyzed by twoway ANOVA, followed by Holm-Sidak test (p <0.05). In addition, the structure of biofilms was qualitatively evaluated by scanning electron microscopy and confocal microscopy. The results from SP1 showed that IONPs-CS-MCZ presented diameter smaller than 50 nm, and MIC values lower than those found for MCZ alone, with synergistic effect on C. albicans. Moreover, 78 µg/ml IONPs-CS-MCZ was more effective than MCZ alone in reducing CFUs and metabolic activity of single biofilms of C. albicans and dual-species biofilms. Total biofilm biomass and extracellular matrix were not affected by the nanocarrier, and the application of an external magnetic field did not improve the nanocarrier effects. Microscopy images confirm that treatments with the nanocarrier, mainly in the highest concentration, exhibited greater antibiofilm activity. Regarding SP2, the MICs of IONPs-CS-MCZ were determined for different microbial species, and all polymicrobial biofilms were developed for 5 days and treated for 24 h with IONPs-CS-MCZ at 64 µg/ml. After treatment, the biofilms were evaluated for total biomass, metabolic activity, counting of CFUs and quantitative PCR analysis. Scanning electron microscopy was used to analyze the biofilm ultrastructure. Differences between groups were determined by unpaired t-test (p<0.05). Results from SP2 showed that IONPs-CS-MCZ was more effective than MCZ alone against most fungal and bacterial cells tested. Moreover, this nanocarrier was able to reduce the metabolic activity, total biomass and CFUs (P<0.05) of the biofilms, besides altering their ultrastructure. Finally, IONPs-CS-MCZ affected the composition of the three evaluated biofilms, mainly reducing the numbers of Streptococcus spp. and changing the prevalence of species in the biofilms. From the results obtained by SP1 and SP2, it was possible to conclude that the nanocarrier improved the antimicrobial effect of MCZ, depending on the species and biofilm parameter evaluated. Nanocarrier also showed potential to interfere in the synergistic interactions among fungal and bacterial cells within polymicrobial biofilms(AU)