Green Synthesis of Silver Nanoparticles: Structural Features and In Vivo and In Vitro Therapeutic Effects against Helicobacter pylori Induced Gastritis

Abstract

This study evaluates in vivo and in vitro anti-Helicobacter pylori (H. pylori) efficacy of silver nanoparticles (Ag-NPs) prepared via a cost-effective green chemistry route wherein Peganum harmala L. seeds extract was used as a reducing and capping agent. The structural features, as elucidated by surface plasmon resonance spectrophotometry, transmission electron microscopy, and powder X-ray diffraction spectroscopy, revealed the Ag-NPs synthesized to be polydispersed in nature and spherical in shape with 5-40 nm size. A typical Ag-NPs suspension (S5), with size being 15 nm, when tested in vitro against forty-two local isolates and two reference strains, showed a considerable anti-H. pylori activity. In case of in vivo trial against H. pylori induced gastritis, after oral administration of 16 mg/kg body weight of S5 for seven days, a complete clearance was recorded in male albino rates. In comparative time-killing kinetics, S5 exhibited dose- and time-dependent anti-H. pylori activity that was almost similar to tetracycline and clarithromycin, less than amoxicillin, but higher than metronidazole. Furthermore, S5 was found to be an equally effective anti-H. pylori agent at low (≤4) and high pH with no drug resistance observed even up to 10 repeated exposures while a significant drug resistance was recorded for most of the standard drugs employed. The present results revealed the potential of the synthesized Ag-NPs as safer bactericidal agents for the treatment of H. pylori induced gastritis.

Figure 1

(a) Effect of PH-sus on the SPR of typical sample S₅, (b) variation of the size of the silver-NPs with PH-sus using different techniques, SPR (♦), P-XRD (■), and TEM analysis (▲), (c) variation of SPR with temperature (S₅), (d) effect of time on the synthesis of sample S₅, and (e) stability of Ag-NPs versus time.

Figure 2

(a, e) TEM image and size distribution of S₅, (b, f) TEM image and size distribution of S₄, (c) TEM image of S₃, (d) TEM image of S₂, and (g) P-XRD pattern of S₅ and SAED pattern of S₅.

Figure 3

(a) FT-IR spectra of PH-sus and (b) FT-IR spectra of Ag-NPs (S₅).

Figure 4

In vivo therapeutic efficacy of silver nanoparticles.

Figure 5

Time- and dose-dependent killing curves for (a) silver nanoparticles, (b) tetracycline, (c) metronidazole, and (d) amoxicillin, against H. pylori strain NCTC 11637.

Figure 6

Effect of medium pH on the anti-H. pylori activities of silver nanoparticles against NCTC 11637.

Figure 7

Resistance developments in H. pylori strain NCTC 11637 after repeated exposure to silver nanoparticles and standard antibiotics.