Anticancer and antimicrobial activity of biosynthesized Red Sea marine algal silver nanoparticles

Abstract

Biosynthesis of silver nanoparticles (AgNPs) is emerging as a simple and eco-friendly alternative to conventional chemical synthesis methods. The role of AgNPs is expanding as antimicrobial and anticancer agents, sensors, nanoelectronic devices, and imaging contrast agents. In this study, biogenic AgNPs were synthesized using extracts of different marine algae species, including Ulva rigida (green alga), Cystoseira myrica (brown alga), and Gracilaria foliifera (red alga), as reducing and capping agents. The Physiochemical properties, cytotoxicity, anticancer and antimicrobial activities of the biosynthesized AgNPs were assessed. Surface plasmonic bands of the biosynthesized AgNPs capped with U. rigida, C. myrica, and G. foliifera extracts were visually observed to determine a colour change, and their peaks were observed at 424 nm, 409 nm, and 415 nm, respectively, by UV-Vis spectroscopy; transmission electron microscopy (TEM) indicated an almost spherical shape of AgNPs with nanoscale sizes of 12 nm, 17 nm, and 24 nm, respectively. Fourier transform-infrared (FTIR) spectroscopy analysis suggested that different molecules attached to AgNPs through OH, C=O, and amide groups. The major constituents of the aqueous algal extracts included, terpenoids, polyphenols, sulfonates, polysaccharides, fatty acids, chlorophylls, amide proteins, flavonoids, carotenoids, aliphatic fluoro compounds, volatile compounds, alkalines, pyruvic acid and agar groups. The cytotoxicity and anticancer activities of the biosynthesized AgNPs were assessed using Artemia salina nauplii, normal skin cell lines (HFb-4), and breast cancer cell lines (MCF-7 cell line). The lethality was found to be directly proportional to the AgNP concentration. The IC₅₀ values of C. myrica and G. foliifera AgNPs against A. saline nauplii were 5 and 10 μg ml^-1 after 4 h and 16 h, respectively, whereas U. rigida AgNPs did not exhibit cytotoxic effects. Anticancer activity of the biosynthesized AgNPs was dose dependent. The IC₅₀ values of the biosynthesized AgNPs were 13, 13, and 43 µg ml^-1 for U. rigida, C. myrica, and G. foliifera, respectively. U. rigida AgNPs particularly exhibited potent anticancer activity (92.62%) against a human breast adenocarcinoma cell line (MCF-7) with high selectivity compared the normal cells (IC₅₀ = 13 µg/ml, SI = 3.2), followed by C. myrica AgNPs (IC₅₀ = 13 µg/ml, SI = 3.07). Furthermore, the biosynthesized AgNPs exhibited strong antifungal activity against dermatophyte pathogenic moulds and mild antibacterial activity against the food borne pathogen bacteria. The highest antimicrobial activity was recorded for the U. rigida AgNPs, followed by those capped with C. myrica and G. foliifera extracts, respectively. AgNPs capped with the U. rigida extract exhibited the highest antimicrobial activity against Trichophyton mantigrophytes (40 mm), followed by Trichosporon cataneum (30 mm) and E. coli (19 mm), with minimal lethal concentration of 32 and 64 μg ml^-1 respectively. The study finally revealed that extracts of marine algal species, particularly U. rigida extracts, could be effectively used as reducing agents for the green synthesis of AgNPs. These AgNPs are considered efficient alternative antidermatophytes for skin infections and anticancer agents against the MCF-7 cell line.

Figure 1

Biosynthesis of AgNPs using different marine algal extracts, (a) U. rigida, C. myrica, and G. foliifera, as reducing and capping agents. The reduction of AgNO₃ by the algal extracts was visually evident from the colour change (brownish-yellow) of the reaction mixture after 48 h.

Figure 2

UV–vis spectra of the biosynthesized AgNPs capped by different marine algal extracts: (a) U. rigida, (b) C. myrica and (c) G. foliifera.

Figure 3

TEM images of the biosynthesized AgNPs capped by different marine algal extracts: (a) U. rigida, (b) C. myrica and (c) G. foliifera.

Figure 4

FTIR spectra of the extracts from different marine algal species: (a) U. rigida, (b) C. myrica and (c) G. foliifera.

Figure 5

FTIR spectra of the biosynthesized AgNPs capped by different marine algal extracts: (a) U. rigida, (b) C. myrica and (c) G. foliifera.

Figure 6

Survival (%) of Artemia salina treated with different concentrations (µg/ml) of biosynthesized AgNPs capped by different marine algal extracts, (a) U. rigida, (b) C. myrica and (c) G. foliifera, and the control (saline solution 3.2% NaCl) containing ten nauplii over 24 h. *= LC50 of C. myrica (b), **= LC50 of G. foliifera (c). Each value represents the mean of the sample ± SD (n = 3).

Figure 7

Viability of the human skin cell line (HFb-4) treated with different concentrations (µg/ml) of biosynthesized AgNPs capped by different marine algal extracts, (a) U. rigida, (b) C. myrica and (c) G. foliifera, and (d) non-biogenic AgNPs for 24 h. Each value represents the mean of the sample ± SD (n = 3).

Figure 8

IC50 of the human skin cell line (HFb-4) treated with different concentrations (µg/ml) of biosynthesized AgNPs capped by different marine algal extracts, (a) U. rigida, (b) C. myrica, (c) G. foliifera, and (d) non-biogenic AgNPs. Each value represents the mean of the sample ± SD (n = 3).

Figure 9

The microscopical visualization (20x) of the human skin cell line (HFb-4) distinguished the variation in the cell viability according to their treatment with biosynthesized AgNPs capped by different marine algal extracts, (a) U. rigida, (b) C. myrica, (c) G. foliifera, (d) non-biogenic AgNPs and (e) untreated control cells.

Figure 10

Reduction (%) and anticancer activity of Human Brest cancer cell lines (MCF-7) treated with different concentrations (µg/ml) of the biosynthesized AuNPs capped by different marine algal extracts: (a) U. rigida, (b) C. myrica and (c) G. foliifera and (d) nonbiogenic AuNPs during 24 h. Each value represents the mean of the sample ± SD for n = 3.

Figure 11

IC50 of the Human Brest cancer cell lines (MCF-7) treated with different concentrations (µg/ml) of biosynthesized AgNPs capped by different marine algal extracts, (a) U. rigida, (b) C. myrica, (c) G. foliifera, and (d) non-biogenic AgNPs. Each value represents the mean of the sample ± SD (n = 3).

Figure 12

The microscopical visualization (20 ×) of the human breast cancer cell line (MCF-7) distinguished the variation in the cell reduction according to their treatment with biosynthesized AgNPs capped by different marine algal extracts, (a) U. rigida, (b) C. myrica, (c) G. foliifera, (d) non-biogenic AgNPs and (e) untreated control cells.