strongly dependent on size where Se NPs with size of 81 nm showed the maximal

growth inhibition and killing effect of methicillin-sensitive (MSSA) and methicillin-

resistant S. aureus bacteria (MRSA). The Se NPs were reported to have multimodal

mechanisms of action that includes the depletion of internal ATP, disruption of

membrane potential and ROS production.

27.5

Summary

With ever-growing resistance against common disinfectants and antibiotics,

microorganisms have challenged the modern science and medicine for the effective

and sustainable treatment of infectious diseases. It is evident from the literature that

application of metal-based ENMs can be considered as a suitable alternative to

antimicrobial agents and appear to have high potential to solve the problem of the

emergence of AMR. Several valuable studies have been documented in the field of

antibacterial ENMs in the recent years.

However, the exact mode of action of these ENMs still remains elusive. There-

fore, to address the main mechanism for antibacterial activity of metal-based ENMs

will be worth to address in future research. There are still some unanswered

questions on the penetration of metal-based ENMs into the bacterial cell wall. The

ENMs have enormous therapeutic potential, but there are some toxicity issues that

restrict their current usage and required to be addressed. Environmental disposal of

NMs is also a matter of concern since they are reported to contribute to some

environmental problems. A greener approach needs to replace the ongoing methods

of synthesis of ENMs.

Therefore, in order to exploit ENMs for their antimicrobial potential, a perfect

balance should be achieved highlighting the potentials of ENMs along with masking

the limitations at the same time with utmost care. Finally, it can be concluded that in

the near future, metal-based ENMs with minimal toxicity can plausibly be used as

alternatives to conventional antimicrobial agents for eradicating the several patho-

genic microorganisms.

References

Abd-El-Aziz AS, Agatemor C, Etkin N (2017) Antimicrobial resistance challenged with metal-

based antimicrobial macromolecules. Biomaterials 118:27–50

Abebe B, Zereffa EA, Tadesse A, Murthy HA (2020) A review on enhancing the antibacterial

activity of ZnO: mechanisms and microscopic investigation. Nanoscale Res Lett 15(1):1–19

Abraham EP, Chain E, Fletcher CM, Gardner AD, Heatley NG, Jennings MA, Florey HW (1941)

Further observations on penicillin. Lancet 238(6155):177–189

Adams CP, Walker KA, Obare SO, Docherty KM (2014) Size-dependent antimicrobial effects of

novel palladium nanoparticles. PLoS One 9(1):e85981

Allaker RP (2010) The use of nanoparticles to control oral biofilm formation. J Dent Res 89:1175–

1185

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