Adhesion of Candida biofilm cells to human epithelial cells and polystyrene after treatment with silver nanoparticles
Graphical abstract
Introduction
Candida albicans followed by Candida glabrata are the major commensal pathogens that cause fungal infections in compromised patients, such as oral or gastrointestinal candidiasis, urinary tract infections (mainly vulvovaginal candidiasis) [1] and systemic or bloodstream infections [2]. The pathogenicity of these microorganisms is related to several virulence factors, including their ability to adhere to host epithelial cells and/or inanimate substrates, which is an important precondition for colonization, infection and biofilm formation [3], [4]. Additionally, Candida biofilms are resistant to a diversity of antimicrobial agents [4], and the fungal cells released from biofilms and which return to the planktonic state may act as a continuous source of disseminated infections.
In the light of these considerations, there is a significant interest in the use of alternative antifungal agents which might decrease or inhibit fungal adhesion capacity, preventing the colonization and infection by Candida species. Our research group verified that silver nanoparticles (SN) were more effective in inhibiting biofilm formation when applied in prophylaxis than on pre-formed Candida biofilms [5], and that the particle size and the type of stabilizing agent did not interfere in the antifungal activity of SN against those biofilms [6]. Thus, with the purpose of complementing these previous data, in this study we tested the hypothesis that C. albicans and C. glabrata viable cells recovered from Candida biofilms treated with SN exhibit significantly reduced adhesion capacity to human epithelial cells and polystyrene surfaces.
Section snippets
Synthesis of silver colloidal nanoparticles
In this research, the average size of SN used was approximately 5 nm. These nanoparticles were synthesized, stabilized and characterized as described previously [5].
Human epithelial cells
A monolayer of epithelial cells from a HeLa cell line with origin in human cervical carcinoma (obtained from Gulbenkian Institute of Science, Lisbon, Portugal) was grown (at 37 °C in 5% CO2) in Dulbecco's modified Eagle's medium (D-MEM; Gibco, Carlsbad, USA) supplemented with 10% fetal bovine serum (Gibco, USA) and 1%
Results and discussion
As it is possible to observe in Fig. 1a and b, compared to the control groups (biofilm cells without SN treatment), C. albicans 324LA/94 and C. glabrata D1 biofilm cells showed reductions in the capacity to adhere to HeLa cells by around 53% (p = .001) and 34% (p < .001) when pretreated with silver at 13.5 μg/mL and around 40% (p = .003) and 86% (p < .001) at a silver concentration of 54 μg/mL, respectively.
The number of yeast cells adhered to polystyrene surfaces is presented in Fig. 1c and d. C.
Conclusion
In conclusion, our results sustain the hypothesis that the pretreatment of Candida biofilm cells with SN significantly reduces the subsequent adhesion capacity of C. albicans 324LA/94 and C. glabrata D1 viable cells to human epithelial cells and polystyrene surfaces. These new findings highlight the potential use of SN in controlling the dissemination of Candida infections, especially in susceptible patients. However, additional studies with a wide number of strains, and directed to investigate
Acknowledgements
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, São Carlos, Brazil. This study was supported by CAPES (grant BEX 1221/10-8) and FAPESP (2009/15146-5), Brazil.
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