Biosynthesis of silver nanoparticles with antimicrobial and anticancer properties using two novel yeasts

Abstract

AgNPs are nanomaterials with many potential biomedical applications. In this study, the two novel yeast strains HX-YS and LPP-12Y capable of producing biological silver nanoparticles were isolated. Sequencing of ribosomal DNA-ITS fragments, as well as partial D1/D2 regions of 26S rDNA indicated that the strains are related to species from the genus Metschnikowia. The BioAgNPs produced by HX-YS and LPP-12Y at pH 5.0-6.0 and 26 °C ranged in size from 50 to 500 nm. The antibacterial activities of yeast BioAgNPs against five pathogenic bacteria were determined. The highest antibacterial effect was observed on P. aeruginosa, with additional obvious effects on E. coli ATCC8099 and S. aureus ATCC10231. Additionally, the BioAgNPs showed antiproliferative effects on lung cancer cell lines H1975 and A579, with low toxicity in Beas 2B normal lung cells. Therefore, the AgNPs biosynthesized by HX-YS and LPP-12Y may have potential applications in the treatment of bacterial infections and cancer.

Figure 1

Schematic illustration of experimental process in this study.

Figure 2

Colony morphology [(a) HX-YS; (c) LPP-12 Y] and SEM micrographs [(b) HX- YS; (d) LPP-12Y] (SEM at 2.0 kV and *8000).

Figure 3

Phylogenetic tree based on the ribosomal DNA-ITS fragments [(a) HX-YS; (b) LPP-12Y] and 26S rDNA D1/D2 regions [(c) HX-YS; (d) LPP-12Y] of two novel yeasts strains constructed using the neighbor-joining method.

Figure 4

Absorption spectra of solutions with different concentrations of Ag⁺ (1 mM, 10 mM, 20 mM and 40 mM) ; water and broth of yeasts as control group, this reaction happens in a conical flask wrapped with tinfoil at 28 °C for 4 d [(a) solutions are treated with HX-YS; (b) solutions are treated with LPP-12].

Figure 5

Absorption spectra of solutions with different pH (from 1.0 to 8.0) ; this reaction happens in a conical flask wrapped with tinfoil at 28 °C for 4 d [(a) solutions are treated with HX-YS; (b) solutions are treated with LPP-12].

Figure 6

Optimal time for AgNPs synthesis: AgNPs solutions were synthesized under the optimal conditions at 28 °C in the dark, Ag⁺ concentration is 10 mM, and adjust the pH of HX-YS treated AgNPs solutions to 6.0, LPP-12Y is 5.0; OD value was determined everyday at the maximum absorption wavelength of AgNPs: the maximum absorption wavelength of AgNPs solutions treated with HX-YS fermentation broth is 450 nm, while LPP-12Y is 430 nm [(a) solutions are treated with HX-YS; (b) solutions are treated with LPP-12].

Figure 7

SEM images of AgNPs (AgNPs was synthesized under the optimal conditions at 28 °C in the dark for 6d, Ag⁺ concentration is 10 mM, and adjust the pH of HX-YS treated AgNPs solutions to 6.0, LPP-12Y is 5.0) [(a) AgNPs synthesized by HX-YS; (b) AgNPs synthesized by LPP-12].

Figure 8

Antimicrobial activity of silver nanoparticles against various pathogenic bacterial strains shown by filtering paper diffusion method [(A) E. coli ATCC8099; (B) S. aureus ATCC6538; (C) B. subtilis ATCC6051; (D) M. albican ATCC10231; (E) P. aeruginosa)] (a: AgNPs from LPP-12Y; b: 100 μg/mL Kanamycin; c: 100 μg/mL Ampicillin; d: AgNPs from HX- YS; ck: PDA).

Figure 9

Histogram showing cellular viability of A549 and H1975 and Beas 2B cells after exposure to different concentrations of AgNPs. The untreated cells by AgNPs as control is included.