Bio-Synthesis of Aspergillus terreus Mediated Gold Nanoparticle: Antimicrobial, Antioxidant, Antifungal and In Vitro Cytotoxicity Studies

Abstract

Gold nanoparticles (GNP) were bio-fabricated utilizing the methanolic extract of the endophytic isolate Aspergillus terreus. The biosynthesised gold nanoparticles (GNP023) were characterised using UV-visible spectroscopy (UV-Vis); transmission electron microscopy (TEM), Fourier-transform nfrared spectroscopy (FTIR) and X-ray diffraction (XRD) studies. The bio-fabricated GNP023 displayed a sharp SPR peak at 536 nm, were spherically shaped, and had an average size between 10-16 nm. The EDX profile confirmed the presence of gold (Au), and XRD analysis confirmed the crystalline nature of GNP023. The antimicrobial activity of GNP023 was investigated against several food-borne and phytopathogens, using in vitro antibacterial and antifungal assays. The maximum zone of inhibition was observed for S. aureus and V. cholera at 400 μg /mL, whereas inhibition in radial mycelial growth was observed against Fusarium oxysporum and Rhizoctonia solani at 52.5% and 65.46%, respectively, when challenged with GNP023 (200 μg/mL). Moreover, the gold nanoparticles displayed significant antioxidant activity against the ABTS radical, with an IC₅₀ of 38.61 µg/mL, and were non-toxic when tested against human kidney embryonic 293 (HEK293) cells. Thus, the current work supports the application of myco-synthesised gold nanoparticles as a versatile antimicrobial candidate against food-borne pathogens.

Keywords: Aspergillus sp.; antibacterial; antifungal; endophytic fungi; gold nanoparticles.

Figure 1

(A) UV-absorption spectra of gold nanoparticles GNP023 for reaction of the fungal extract with HAuCl₄ solution and (B) comparison between nanoparticles synthesis by HAuCl₄ solution and the biomass of A. terreus AREF023.

Figure 2

(A) Effect of pH on GNPs production, (B) effect of fungal biomass concentration on GNPs production and (C) effect of temperature on GNPs production.

Figure 3

(A) Transmission electron micrograph of gold nanoparticle GNP023 and (B) EDX spectrum, confirming a sharp peak in the range of 1–5 keV, confirming the presence of gold. In both (A) and (B) EDX spectrum the largest peak is C (at about 0.5 KeV), second largest is Cu (at about 8 KeV), and third largest is Au (at about 2 KeV).

Figure 4

Dynamic light scattering study representing (A) size distribution (Average size −45.53 nm) and (B) zeta potential (−28.2).

Figure 5

FTIR analysis spectra of A. terreus AREF023 extract and gold nanoparticles GNP023.

Figure 6

XRD patterns of bio-synthesized gold nanoparticles GNP023.

Figure 7

UHPLC Chromatograms of extract of A. terreus AREF023.

Figure 8

Zones of inhibition produced by GNP023 against bacterial pathogens (A)—S. aureus, (B)—S. typhimurium, (C)—Methicillin resistant S. aureus (MRSA) and (D)—V. cholerae. [V–Vancomycin; Ch—Chloramphenicol; 100—GNP023 100 µg/mL; 200—GNP023 200 µg/mL; 400—GNP023 400 µg/mL; C—Control].

Figure 9

Antifungal activity of GNP023 s against plant pathogenic fungi, (A) Rhizoctonia solani and (B) Fusarium oxysporum. PDA plates were amended with different concentrations of GNP023 s: (i) control, (ii) 25 μg/mL, (iii) 50 μg/mL, (iv) 100 μg/mL and (v) 200 μg/mL of gold nanoparticles GNP023.

Figure 10

(A) ABTS antioxidant activity of the gold nanoparticle GNP023, in comparison to controls and standards Trolox, Ascorbic acid and TBHQ. (B) Development of a pBSK DNA nicking assay with gold nanoparticle GNP023. Lane 1—Native pBSK DNA; Lane 2—pBSK DNA with Fenton’s reagent; Lane 3—pBSK DNA with 25 μg/mL Curcumin and Fenton reagent; and Lanes 4 to 7—pBSK DNA with Fenton’s reagent and GNP023 (25–200 μg/mL, respectively) (Type I—closed circular DNA forms; Type II/III—open circular DNA forms).

Figure 11

Effect of gold nanoparticle GNP023 on HEK 293 T normal cell line.