Taking advantage of the exceptional catalytic properties, Pd based ENMs have

been

used

in

a

number

of

important

chemical

reactions,

manufacturing

pharmaceuticals, degrading hazardous pollutants, and detection of different analytes.

Different studies have been performed to examine the antimicrobial capacity of Pd

NPs, which provides an indication of their usefulness as target antimicrobial

compounds. Like, Adams et al. (2014) reported the first investigation of size-

dependent antibacterial activity of Pd NPs against GN (E. coli) and GP (S. aureus)

bacterial growth culture. Results showed that Pd NPs are highly antimicrobial, and

fine-scale differences in size can alter their antimicrobial activity. Fang et al. (2018)

reported the facet-dependent antibacterial properties for Pd NCs where {100}-

faceted Pd cubes were observed to kill GN bacteria (S. aureus) more efficiently

than {111}-faceted Pd octahedrons counterparts which displayed better results

against GN bacteria (E. coli).

In recent years, tellurium (Te) and selenium (Se) (Guisbiers et al. 2016; Lara et al.

2018) based NPs have gained interest as potential antibacterial agents. Tellurite

(TeO3

2) ions have antibiotic properties and have been used to inhibit the growth of

a several microorganisms, including penicillin-insensitive bacteria. Lin et al. (2012)

investigated the morphology-dependent antibacterial activity of Te NMs. In a typical

experiment, Te NMs with four distinct morphologies (i.e. nanowires, nano-pencils,

nano-rice, and nano-cubes) were fabricated and further tested for their antibacterial

activity against E. coli. The antibacterial activity of Te NMs was obtained in the

following order: nano-cubes > nano-rice > nano-pencils > nanowires. Moreover,

antibacterial activity of Te NMs was reported to be higher than Ag NPs, while

toxicity towards mammalian cells was lower than that Ag NPs, which according to

authors clearly suggests that Te NMs have great potential for use as effective

antibacterial agents.

In another study, Cruz et al. (2019) biosynthesized the rod- and cubic-shaped Te

NPs by using the extracts of lemon, orange, and lime as reducing and capping agents

via microwave-assisted reaction. Te NPs showed an important antibacterial activity

against both GN (MDR E. coli) and GP bacteria (MRSA) in a range concentration

from 5 to 50 μg/mL over a 24 h time period with a main mechanism of inhibition

related to ROS production.

Se compounds have been extensively investigated because of their anticancer

properties and low toxicity, and Se NPs have been shown to exhibit lower cytotox-

icity relative to selenium compounds. Recently, Geoffrion et al. (2020) fabricated Se

NPs by a novel green process called pulsed laser ablation in liquids technique. Se

NPs

showed

a

dose-dependent

antibacterial

effect

towards

both

standard

(P. aeruginosa and S. epidermidis) and antibiotic resistant, i.e. MDR E. coli and

MRSA strains of bacteria at a range of concentrations between 0.05 and 25 ppm.

Besides, Se NPs were reported to show a low cytotoxic effect on human dermal

fibroblast cells up to a concentration level of 1 ppm as well as an anticancer effect on

human glioblastoma and melanoma cells at the same range of concentration. Huang

et al. (2019) fabricated the spherical shaped Se NPs with the size ranging from 40

to 200 nm and further investigated the influence of size on the cytotoxicity and

antibacterial activity. The antibacterial activity of the Se NPs was shown to be

514

M. Chauhan et al.