This document summarizes a study that investigated using an extract of Equisetum arvense (EQ), a type of horsetail plant, to synthesize silver nanoparticles (AgNPs) via an environmentally-friendly method. The EQ-AgNPs showed strong antibacterial effects against both gram-positive and gram-negative bacteria. Specifically, the EQ-AgNPs inhibited the growth of E. coli, S. aureus, P. aeruginosa, and L. monocytogenes bacterial strains associated with various infections. The findings suggest EQ-AgNPs have potential as an effective and eco-friendly nano-based antibacterial formulation for healthcare use.

1. Equisetum arvense mediated synthesis of silver nanoparticles and its application as antibacterial suspension
Miona Miljković1†, Slađana Davidović1, Suzana Dimitrijević1 , Antonije Onjia 1 and Aleksandra Nešić2
1University of Belgrade, Faculty of Technology and Metallurgy, Serbia
2 University of Belgrade, Vinča Institute of Nuclear Sciences, Serbia
High consumption of antibiotics has led to resistance of pathogenic microorganisms, which prompted the testing of antimicrobial activity of various plant extracts
or other substances in order to find new antimicrobial agents. Alternatively, silver and silver-based topical dressings have been used to treat bacterial infections. To
overcome the problems associated with the excessive usage of antibiotics and chemicals, there is a need of eco-friendly synthesis and inexpensive antimicrobial
agent(s) to treat infectious. Metallic nanoparticles (MNPs) have been receiving considerable attention in recent years because of their unique properties and a
wide range of applications in various fields, including medicine. Among the various MNPs, silver nanoparticles have been widely studied because of their
exceptional characteristic features. Recent research indicates a great potential for the application of biological molecules in an eco-friendly process for obtaining
AgNPs, thus avoiding the use of hazardous chemicals. Extracts of various plants and groups of microorganisms are most exploited in such processes.
On the other hand, this paper examines the possibility of using pulverized waste biomass obtained from the processing of medicinal herbs which, only in Serbia,
reaches about 100 tons annually. From economical point of view, utilization of such waste material with low cost price (if any) is profitable because it can be
transformed in other valuable products. In this study, we developed eco-friendly method to synthesize silver nanoparticles (AgNPs) using aqueous extract of
Equisetum arvense (EQ), (dust remained after production of tea) and evaluated their effect on both Gram+ and Gram– bacteria, associated with different
infections.
Figure 4: The effect of EQ, AgNO 3 and EQ-AgNPs (0.5 or 24h) on wound associated bacterial cultures.
1—EQ ; 2—AgNO 3 ; 3—EQ-AgNPs (0.5h) and 4—EQ-AgNPs (24h). EQ—Equisetum arvense ; AgNO 3 —
Silver nitrate; EQ-AgNPs—Equisetum arvense reduced silver nanoparticles.
EQ-AgNPs displayed a prominent antibacterial activity against all tested bacterial strains. The findings of the present study suggest that the EQ-AgNPs could
be a pharmaceutically useful nano-based formulation to eradicate the bacterial infection in healthcare institution.
Acknowledgements
The authors thank to Ministry of Education, Science and Technological Development of the Republic of Serbia for support of this investigation trough
the project TR 31035.
†mmiljkovic@tmf.ac.bg.rs
Figure 1. The UV–visible absorption spectrum of EQ-AgNPs. A) The absorption of EQ-AgNPs synthesized
with two different EQ extracts (extraction time 0.5h ( ) and 24 h ( )) show the surface plasma
resonance at 430 nm. B) The absorption of EQ-AgNPs synthesized with EQ extract after 24 h of
extraction, after 1 day ( ) and 5 days ( ).
In quantitative test EQ-AgNPs showed antibacterial activity against all of
the studied bacteria strains, but most effective were against Gram –
strains. Interestingly, a better antibacterial action of EQ-AgNPs was noted
on its overnight incubation with all the tested bacteria.
nm.
330,00 400,00 500,00 600,00 700,00
Abs.
1,200
1,000
0,500
0,000
nm.
330,00 400,00 500,00 600,00 700,00
Abs.
1,200
1,000
0,500
0,000
Figure 2: The FT-IR spectrum of (a) EQ extract and (b) EQ-AgNPs.
EQ — Equisetum arvense ; EQ-AgNPs —
Equisetum arvense reduced silver nanoparticles.
The appearance of brown color and absorption at 430 nm have
inferred the formation of EQ-AgNPs.
In well diffusion test both EQ-
AgNPs formulations showed
inhibition of growth on all five
tested bacterial strains, but
highest antimicrobial activity was
measured against two Gram– (E.
coli and P. aeruginosa) and one
Gram+ (S. aureus) bacterial
strains (Fig.4).
Figure 3. The percentage of viable cell reduction obtained
after 2 and 12 h incubation with EQ-AgNPs against five different strains. EQ-AgNPs
formulations after A) 0.5 h extraction time and B) 24h extraction time.
The observed peak shifts (higher to lower; vice versa) in the FT-IR
spectrum of EQ-AgNPs, demonstrating the involvement of various
functional groups [C –O like phenol group, (C = O) carboxylic acid, C
–N, and O –H hydroxyl groups] of EQ phytochemicals in the bio-
reduction of Ag + and the stabilization of Ag0 .
0
20
40
60
80
100
E.coli
S.aureus
L. monocytogenes
P. aeruginosa
E. faecalis
2 hours
12 hours
R(%)
0
20
40
60
80
100
E.coli
S.aureus
L. monocytogenes
P. aeruginosa
E. faecalis
2 hours
12 hours
R(%)
Equisetum
arvense (EQ)
Extraction
After 0.5
and 24h
at 45°C
Left in the
dark
UV Visible Spectrophotometer
Well test
E. coli ATCC 25922,
S. aureus ATCC 25923,
E. faecalis ATCC 29812,
P. aeruginosa ATCC 2739 &
L. monocytogenes IM2002*
Quantitative test:
R (%)=[(𝐶0−𝐶)/C0]×100
C0- the initial number of
microorganisms (inoculum)
C-the number of microorganism
colonies of the samples
*isolate from the 'Institute of Meat Hygiene and Technology' from 2002