Three in-one fenestrated approaches of yolk-shell, silver-silica nanoparticles: A comparative study of antibacterial, antifungal and anti-cancerous applications

Abstract

Yolk-shell-based silica-coated silver nanoparticles are prominently used in the biomedical field aas well as bare silver nanoparticles for various biological applications. The present work narrates the synthesis and silica coating of metallic silver nanoparticles and investigates their antibacterial, antifungal, and anticancerous activity. Both synthesized nanoparticles were characterized by TEM, and SEM-EDX. The average size of silver nanoparticles was 50 nm, while after coating with silica, the average size of silica-coated silver nanoparticles was 80 nm. The nanoparticles' antibacterial, antifungal, and anticancer properties were comparatively examined in vitro. Agar well diffusion method was employed to explore the antibacterial activity against gram-positive bacteria (Bacillus cereus) and gram-negative bacteria (Escherichia coli) at different concentrations and antifungal activity against Candida Albicans. To understand the minimum concentration of both nanoparticles, we employed the minimum inhibitory concentration (MIC) test, against bacterial and fungal strains, which was dose dependent. We learned that bare silver nanoparticles showed high antibacterial activity, whereas silica-coated silver nanoparticles surpassed their antifungal capability over bare silver nanoparticles against Candida albicans. The anticancer activity of the as-prepared nanoparticles was executed in opposition to the prostate cancer cell (PC-3) line by MTT assay, which showed meaningful activity. Following this, flow cytometry was also effectuated to learn about the number of apoptotic and necrotic cells. The results of this study demonstrate the dynamic anti-cancerous, antibacterial, and antifungal activities of bare silver nanoparticles and silica-coated silver nanoparticles for a long-lasting period.

Keywords: Energy-dispersive X-ray spectroscopy; MTT-assay; Minimum inhibitory concentration; Nanoparticles; Prostrate cancer.

Graphical abstract

Fig. 1

Selected Area Electron Diffraction (SAED) pattern of (a) Ag nanoparticles and (b) Ag@SiO₂ nanoparticles were acquired by administering the electron beam at right angles, perpendicular to the selected domain. Both tailored nanoparticles display concentric rings indicating the nanoparticles' exceedingly crystalline nature. SEM images of the Ag nanoparticles SEM images of the Ag nanoparticles (c), (d), and Ag@SiO₂ nanoparticles at different magnifications (e) and (f). It is visible that the Ag nanoparticles have a spherical shape and images of Ag@SiO₂ nanoparticles exhibit a distinct coating of silica layer on the surface of the silver. EDX analysis reveals that prepared Ag nanoparticles contain sodium, chlorine, and some amount of nitrogen and oxygen (g) whereas Ag@SiO₂ nanoparticles display a burgeoning peak of silica. Some minor peaks of silver, aluminum, sodium, and oxygen are also visible in the represented graph of the elemental analysis (h).

Fig. 2

Antibacterial activity of nanoparticles against Gram-positive bacteria Bacillus cereus by employing concentrations 1 and 2, (a), (b) respectively. In both studies, Ag nanoparticles manifested vigorous antibacterial activity showing a zone of inhibition of 20 mm, 23 mm, respectively in contrast to silica-coated Ag nanoparticles, with the zone of inhibition of 10 mM and 20 mM (c) antibacterial activities of both the nanoparticles at concentration 1 against Gram-negative bacteria Escherichia coli; exhibiting zone of inhibition 17 mM by Ag nanoparticles and 10 mM by silica-coated Ag nanoparticles (d) at concentration 2; Ag nanoparticles revealed zone of inhibition of 10 mM, whereas, silica-coated Ag nanoparticles exhibited 17 mm of inhibiting zone.

Fig. 3

Minimum inhibitory concentration (MIC) of Ag nanoparticles (denoted in red-colored bars) and Silica coated Ag nanoparticles (shown in black colored bars) against Gram +ve bacteria Bacillus cereus (a). Ag nanoparticles exhibit lofty anti-microbial activity with increasing concentrations whereas coated silver nanoparticles show a lower MIC score. MIC against Gram -ve bacteria - Escherichia coli for measuring the activity of Ag nanoparticles and Silica coated Ag nanoparticles (displayed in black -colored bars); both the two nanoparticles revealed higher MIC scores with increasing concentration. The performed experiment showed significant results with a p-value 0.05 in treated concentrations. MIC of Ag nanoparticles and Silica Ag nanoparticles against fungus, Candida albicans (c); Ag nanoparticles (denoted in red-colored bars) and Silica coated Ag nanoparticles (shown in black-colored bars). Here coated Ag nanoparticles exhibit towering anti-microbial activity with increasing concentrations, whereas bare silver nanoparticles show a lower MIC score. (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article.)

Fig. 4

Antifungal activity of nanoparticles against Candida albicans by using positive and negative control (a). (b) On concentration 1, both the nanoparticle flaunts approx similar antifungal activities by showing a zone of inhibition of 11 mm (c) On concentration 2, Ag nanoparticles unveil a zone of inhibition of 10 mm whereas silica-coated Ag nanoparticles surpassed antifungal activity over bare silver nanoparticles by exhibiting 12 mm of the inhibiting zone.

Fig. 5

Viability of PC-3 cells after 24 hours of incubation (at 37 C, 5%CO2) with various concentrations of Ag nanoparticles (a) and silica coated Ag nanoparticles in comparison with untreated cells (negative control) and cells treated with cisplatin, evaluated in MTT reduction assay. The IC₅₀ value was figured based on the MTT assay of Ag nanoparticles (b) and silica-coated Ag nanoparticles (d).

Fig. 6

Optical images of PC-3 cells in control group (a), treated for 24 hours with Ag nanoparticles and silica coated Ag nanoparticles (b) and (c) respectively, revealed significant variations in the morphology.

Fig. 7

Microscopic images of the (a) Untreated PC-3 cells and (b) Cisplatin treated PC-3 cells. Changes in the surface structure of the cell-monolayer are observable after treatment with Cisplatin is evident. Morphological variation on the confluency of PC-3 cell monolayer, when exposed to the Ag nanoparticles 10 μg/mL (c) 20 μg/mL (d) 40 μg/mL (e) 60 μg/mL (f) 80 μg/mL (g); for 24 h. The cytotoxic effects of silica coated Ag nanoparticles on PC-3 cell monolayer when exposed to the concentrations: 10 ug/mL (h), 20 ug/mL (i), 40 ug/mL (j), 60 ug/mL (k), 80 ug/mL (l).

Fig. 8

Annexin V - PI expression study of the test compounds, control (a), Ag nanoparticles (b), and silica coated Ag nanoparticles (c) against PC-3 cell line by employing BD FACS Calibur, Cell Quest Pro Software (Version: 6.0).