HEALTH NEWS

Study Title:

Silver has Antifungal Properties

Study Abstract

Aim:  The purpose of this work was to evaluate the size-dependent antifungal activity of different silver nanoparticles (SN) colloidal suspensions against Candida albicans and Candida glabrata mature biofilms.

Methods and Results:  The research presented herein used SN of three different average sizes (5, 10 and 60 nm), which were synthesized by the reduction of silver nitrate through sodium citrate and which were stabilized with ammonia or polyvinylpyrrolidone. Minimal inhibitory concentration (MIC) assays were performed using the microdilution methodology. The antibiofilm activity of SN was determined by total biomass quantification (by crystal violet staining) and colony forming units enumeration. MIC results showed that all SN colloidal suspensions were fungicidal against the tested strains at very low concentrations (0·4–3·3 μg ml−1). With regard to biomass quantification, SN colloidal suspensions were very effective only against C. glabrata biofilms, achieving biomass reductions around 90% at a silver concentration of 108 μg ml−1. In general, all SN suspensions promoted significant log10 reduction of the mean number of cultivable biofilm cells after exposure to silver concentrations at or higher than 108 μg ml−1. Moreover, the results showed that the particle size and the type of stabilizing agent used did not interfere in the antifungal activity of SN against Candida biofilms.

Conclusions:  This study suggests that SN have antifungal therapeutic potential, but further studies are still required namely regarding formulation and delivery means.

Significance and Impact of the Study:  SN may contribute to the development of new strategies for the improvement of oral health and quality of life particularly of the complete denture wearers.

From press release:

Yeasts which cause hard-to-treat mouth infections are killed using silver nanoparticles in the laboratory, scientists have found. These yeast infections, caused by Candida albicans and Candida glabrata target the young, old and immuno-compromised. Professor Mariana Henriques, University of Minho, and her colleagues hope to test silver nanoparticles in mouthwash and dentures as a potential preventative measure against these infections.


Professor Henriques and her team, who recently published their research in the Society for Applied Microbiology's journal Letters in Applied Microbiology, looked at the use of different sizes of silver nanoparticles to determine their anti-fungal properties against Candida albicans and Candida glabrata. These two yeasts cause infections including oral thrush and dental stomatitis, a painful infection affecting around seven out of ten denture wearers. Infections like these are particularly difficult to treat because the microorganisms involved form biofilms.

The scientists used artificial biofilms in conditions which mimic those of saliva as closely as possible. They then added different sizes and concentrations of silver nanoparticles and found that different sizes of nanoparticles were equally effective at killing the yeasts. Due to the diversity of the sizes of nanoparticles demonstrating anti-fungal properties the researchers hope this will enable the nanoparticles to be used in many different applications.

Some researchers have expressed concerns around the safety of nanoparticle use but the authors stress this research is at an early stage and extensive safety trials will be carried out before any product reaches the market.

Professor Henriques comments: With the emergence of Candida infections which are frequently resistant to the traditional antifungal therapies, there is an increasing need for alternative approaches. So, silver nanoparticles appear to be a new potential strategy to combat these infections. As the nanoparticles are relatively stable in liquid medium they could be developed into a mouthwash solution in the near future.

Moving forward Professor Henriques hopes to integrate silver nanoparticles into dentures which could prevent infections from taking hold.

Study Information

D.R. Monteiro, S. Silva, M. Negri, L.F. Gorup, E.R. de Camargo, R. Oliveira, D.B. Barbosa and M. Henriques.
Silver nanoparticles: influence of stabilizing agent and diameter on antifungal activity against Candida albicans and Candida glabrata biofilms
Letters in Applied Microbiology
2012 March
University of Minho, Portugal.