Effect of pretreatment of Candida biofilm cells with silver nanoparticles on the adhesion capacity to human epithelial cells and polystyrene surface

Objectives: The pathogenicity of Candida spp. has been recognized by some factors, including adhesion to host cells or inert surfaces and biofilm formation. In addition, the dispersal of biofilm cells may act as a continuous source of infection. Thus, the aim of this study was to evaluate the adhesion capacity of Candida albicans and Candida glabrata cells recovered from Candida biofilms treated with silver nanoparticles (SN) to human epithelial cells and polystyrene surface. Methods: Candida biofilms (48 h) were formed in 6-well polystyrene microtiter plates and treated during 24 h with SN (diameter of 5 nm) at concentrations of 13.5 and 54 µg/mL. Controls devoid of SN were included in this study. After the treatment period, biofilms were scraped from the wells and resuspended in phosphate buffered saline. These Candida cell suspensions (107 viable cells/mL in RPMI medium) were added to HeLa cells monolayers or to empty wells of a 24-well microtiter plate (to study adhesion to polysterene). After 2 h of contact, the adhesion capacity of the yeasts to HeLa cells and polystyrene surfaces was determined using crystal violet staining. Results: Compared to the controls, the adhesion of Candida biofilm cells (pretreated with SN) to HeLa cells and polystyrene surfaces was significantly reduced. This reduction was higher when biofilm cells were pretreated with SN in a concentration of 54 µg/mL. Conclusion: These findings allow to conclude that SN may induce changes in viable yeasts, since they decrease their adhesion capacity, which can, consequently, cause lower dissemination of Candida infections

Antifungal activity of different silver nanoparticles suspensions against Candida biofilms

Objective: The tolerance of Candida biofilms to conventional antifungal drugs has stimulated the search for new therapies that could prevent or treat Candida-associated denture stomatitis. The objectives of this study were (i) to assess the antibiofilm activity of different silver nanoparticles (SN) suspensions against Candida albicans and Candida glabrata biofilms and (ii) to evaluate the effect of these nanoparticles on the matrix composition and the structure of Candida biofilms. Method: SN of three different average sizes (5, 10 and 60 nm) were used in this study. Biofilms of an oral clinical isolate of C. albicans and C. glabrata were formed for 48 h. These biofilms were exposed to different concentrations of SN for a period of 24 h. Antibiofilm activity of SN was determined by total biomass quantification (using crystal violet staining) and colony forming units enumeration. The extracellular matrices of Candida biofilms were extracted and analyzed chemically in terms of proteins, carbohydrates and DNA. Scanning electron microscopy (SEM) and epifluorescence microscopy were used to analyze the structure and morphology of the biofilms. Result: SN were effective in reducing total biomass (around 90%) of C. glabrata biofilms. All SN suspensions showed significant reduction of the number of cultivable cells at concentrations equal to or higher than 108 µg/mL. The particle size and the type of stabilizing agent did not interfere in the antibiofilm activity of SN. Interestingly, SN induce modifications in the contents of protein, carbohydrate and DNA of the extracellular matrices of Candida biofilms. SEM and epifluorescence investigations revealed structural differences in spatial arrangement and damage in the cell walls of biofilm cells, compared to the controls. Conclusion: SN present therapeutic potential and might be useful in the treatment of denture stomatitis

Silver colloidal nanoparticle stability: influence on Candida biofilms formed on denture acrylic

Our aim in this study was to evaluate how the chemical stability of silver nanoparticles (SNs) influences their efficacy against Candida albicans and C. glabrata biofilms. Several parameters of SN stability were tested, namely, temperature (50ºC, 70ºC, and 100ºC), pH (5.0 and 9.0), and time of contact (5 h and 24 h) with biofilms. The control was defined as SNs without temperature treatment, pH 7, and 24 h of contact. These colloidal suspensions at 54 mg/L were used to treat mature Candida biofilms (48 h) formed on acrylic. Their efficacy was determined by total biomass and colony-forming unit quantification. Data were analyzed using analysis of variance and the Bonferroni post hoc test (=0.05). The temperature and pH variations of SNs did not affect their efficacy against the viable cells of Candida biofilms (P > 0.05). Moreover, the treatment periods were not decisive in terms of the susceptibility of Candida biofilms to SNs. These findings provide an important advantage of SNs that may be useful in the treatment of Candida-associated denture stomatitis.We thank Dr David Williams, Cardiff University, Cardiff, UK, for providing the strain 324LA/94. The authors also thank Sao Paulo Research Foundation (FAPESP, process 2009/15146-5), Brazil, for supporting the work of D. R. M. The authors are indebted to Laboratorio Interdisciplinar de Eletroquimica e Ceramica, Federal University of Sao Carlos, Brazil, in the name of Andressa Kubo, for preparing and characterizing the colloidal suspensions of silver nanoparticles

Adhesion of Candida biofilm cells to human epithelial cells and polystyrene after treatment with silver nanoparticles

This study investigated the adhesion to human epithelial cells and polystyrene surface of viable yeasts recovered from Candida biofilms treated with silver nanoparticles (SN). Biofilm resuspended Candida cells were added to HeLa cells or to empty wells of microtiter plates and the adhesion was verified using crystal violet staining. The adhesion of Candida cells was significantly reduced, mainly when biofilms were pretreated with 54 μg/mL SN. These new findings allow to conclude that SN may induce changes in viable yeasts, which can decrease the dissemination of Candida infections, mainly in susceptible patients.We thank Dr. David Williams (Cardiff University, Cardiff, UK) for providing the strain 324LA/94, and George Duchow for the English review. Silver colloidal nanoparticles used herein were prepared by LIEC-CMDMC and INCTMN/FAPESP-CNPq, Sao Carlos, Brazil. This study was supported by CAPES (grant BEX 1221/10-8) and FAPESP (2009/15146-5), Brazil

Controlling the Electronic, Structural, and Optical Properties of Novel MgTiO 3 /LaNiO 3 Nanostructured Films for Enhanced Optoelectronic Devices

International audienceThis study systematically investigated the electronic, structural, and optical properties of MgTiO 3 (MTO), LaNiO 3 (LNO), and MgTiO 3 /LaNiO 3 (MTO/LNO) nanostructured films grown on Si (100) substrates by the pulsed laser deposition (PLD) method. The structural characterizations obtained by X-ray diffraction revealed a preferred (003) orientation for the MTO film, while the LNO film was polycrystalline. The diffraction peaks corresponded to a rhombohedral structure, which was confirmed by micro-Raman (MR) spectroscopy for both nanostructured films. The MTO/LNO heterostructure was polycrystalline and exhibited the diffraction peaks of both the MTO and the LNO phases. Additionally, the results revealed that the LNO films did not have a significant photoluminescence (PL) emission, while an intense broad infrared luminescence centered at 724 nm appeared for the MTO nanostructured film. Surprisingly, for the MTO/LNO heterostructure, the PL emission profile exhibited a dual-color emission with an intense broad luminescence in the blue region (maximum centered at 454 nm) and an intense near-infrared emission (maximum centered at 754 nm), respectively, mainly because of the effect of interface defects, which induced a significant change in the PL behavior. Therefore, our experimental results correlated with the theoretical simulations based on the periodic density functional theory formalism and contributed to a deeper understanding of the charge/energy transfer processes occurring in the MTO/LNO/Si interfaces, and toward the exploitation of the close relationship between the structure and properties of these new functional materials

Silver colloidal nanoparticles : antifungal effect against Candida albicans and Candida glabrata adhered cells and biofilms

The aim of this study was to evaluate the effect of silver nanoparticles (SN) against Candida albicans and Candida glabrata adhered cells and biofilms. SN (average diameter 5 nm) were synthesized by silver nitrate reduction with sodium citrate and stabilized with ammonia. Minimal inhibitory concentration (MIC) tests were performed for C. albicans (n = 2) and C. glabrata (n = 2) grown in suspension following the Clinical Laboratory Standards Institute microbroth dilution method. SN were applied to adhered cells (2 h) or biofilms (48 h) and after 24 h of contact their effect was assessed by enumeration of colony forming units (CFUs) and quantification of total biomass (by crystal violet staining). The MIC results showed that SN were fungicidal against all strains tested at very low concentrations (0.4-3.3 μg ml(-1)). Furthermore, SN were more effective in reducing biofilm biomass when applied to adhered cells (2 h) than to pre-formed biofilms (48 h), with the exception of C. glabrata ATCC, which in both cases showed a reduction ∼90%. Regarding cell viability, SN were highly effective on adhered C. glabrata and respective biofilms. On C. albicans the effect was not so evident but there was also a reduction in the number of viable biofilm cells. In summary, SN may have the potential to be an effective alternative to conventional antifungal agents for future therapies in Candida-associated denture stomatitis

Silver colloidal nanoparticles: antifungal effect against adhered cells and biofilms of Candida albicans and Candida glabrata

The aim of this study was to evaluate the effect of silver nanoparticles (SN) against Candida albicans and Candida glabrata adhered cells and biofilms. SN (average diameter 5 nm) were synthesized by silver nitrate reduction with sodium citrate and stabilized with ammonia. Minimal inhibitory concentration (MIC) tests were performed for C. albicans (n = 2) and C. glabrata (n = 2) grown in suspension following the Clinical Laboratory Standards Institute microbroth dilution method. SN were applied to adhered cells (2 h) or biofilms (48 h) and after 24 h of contact their effect was assessed by enumeration of colony forming units (CFUs) and quantification of total biomass (by crystal violet staining). The MIC results showed that SN were fungicidal against all strains tested at very low concentrations (0.4-3.3 mu g ml(-1)). Furthermore, SN were more effective in reducing biofilm biomass when applied to adhered cells (2 h) than to pre-formed biofilms (48 h), with the exception of C. glabrata ATCC, which in both cases showed a reduction similar to 90%. Regarding cell viability, SN were highly effective on adhered C. glabrata and respective biofilms. on C. albicans the effect was not so evident but there was also a reduction in the number of viable biofilm cells. In summary, SN may have the potential to be an effective alternative to conventional antifungal agents for future therapies in Candida-associated denture stomatitis.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES