The inhibition of Candida albicans secreted aspartyl proteinase by triangular gold nanoparticles

Objective(s): The aim of this study was to synthesize triangular gold nanoparticles, and then to evaluate their capability for inhibition of Candida albicans secreted aspartyl proteinase 2 (Sap2). Materials and Methods: To synthesize the nanoparticles, hydrogen tetrachloroaurate and hexadecyl trimethyl ammonium bromide were incubated in presence of Sn(IV) meso-tetra(N-methyl-4-pyridyl) porphine tetratosylate chloride, and then characterized. Next, thirty clinical isolates of Candida albicans were obtained from patients suffering from vaginal candidiasis. Each Candida albicans isolate was first cultured in YCB-BSA medium, incubated for 24 h at 35 degrees C. Then, 100 mu L of triangular gold nanoparticles at three concentrations (16, 32, and 64 mu g/mL) were added to Candida suspension, and incubated for 24 and 48 h at 35 degrees C. To evaluate Sap activity, 0.1 mL of medium and 0.4 mL of 0.1 M sodium citrate buffer (pH 3.2) containing BSA 1% w/v were added, and incubated 15 minutes at 37 degrees C. Then, the optical density of each tube was read at 280 nm. Enzyme activity was expressed as the amount (mu M) of tyrosine equivalents released per min per ml of culture supernatant. Results: This study showed that the size of the nanoparticles was 70 +/- 50 nm. Sap activity evaluation demonstrated triangular gold nanoparticles could inhibit the enzyme, and the higher incubation time and concentration led to more decrease of Sap activity. Conclusion: For the first time, we demonstrated triangular gold nanoparticles as a novel inhibitor of Sap enzyme which may be useful for treatment of candidiasis.