Relationship Between Structure And Antimicrobial Activity Of Zinc Oxide Nanoparticles: An Overview

Figures & data

Figure 1 Formation of reactive oxygen species by ZnO NPs.

Figure 2 Suggested mechanisms of action of ZnO NPs against bacteria. (1) ZnO NPs release Zn²⁺ ions, which can be internalised into the bacterial cell and disrupt the enzymatic system. (2) ROS production (causing the destruction of cellular components such as DNA, proteins and lipids): O₂⁻ and HO₂⁻ (do not penetrate the membrane, but direct contact causes damage) and H₂O₂ (internalised). (3) Internalisation within the bacteria cell and direct contact cause damage such as the loss of cellular integrity.

Table 1 Summary Of The More Relevant Results Found In The Review

MOs Tested	Methods Used	Size	Shape	Conclusions	Reference
S. aureus and E. coli	Colony count method	i) Length 1 um and diameter 100 nm; ii) Length 500–600 nm and diameter 100 nm; iii) 30 nm	i) Prism; ii) ellipse. iii) spherical	Better activity was observed for NPs with a smaller size and spherical morphology	^Citation58
S. aureus and E. coli	Colony count method	i) 45 nm; ii) 76 nm; iii) 65 nm	i) Flower-like, ii) hexagonal-rod, iii) spherical	Better activity was observed for NPs with a smaller size and flower-like morphology	^Citation57
C. albicans, A. braseliensis, E. coli, P.aeruginosa and S. aureus	Disk diffusion and MIC	i) 14.7 nm; ii) 17.5 nm; iii) 76.2 nm	i) Platelet; ii) platelet, iii) rod-like	Greater antimicrobial activity was found for NPs with a small crystal size, high porosity and larger pores	^Citation26
S. aureus; S. epidermidis; S. pyogenes; E. faecalis; B. subtilis; B. cereus; E. coli, P. vulgaris, S. typhimurium, S. flexneri, P. alcaligenes, and E. aerogenes	Culture turbidity, and colony count method	12 to 212 nm	Not defined	Better results were found with smaller NPs	^Citation12
E. coli	Disk diffusion, MIC and MBC	12 nm, 45 nm and 2 µm	Spherical	The antibacterial activity was higher for ZnO suspension of 12 nm	^Citation2
E. coli	Disk diffusion and MIC	25 to 300 nm	Spherical	Size, oxygen defects and surface modification of ZnO NPs play critical roles in toxicological activity of ZnO NPs	^Citation59
S. aureus and E. coli	Disk diffusion and MIC	20.2 nm, 27.1 nm and 36.8 nm	Spherical	Smaller size exhibits better antibacterial activity	^Citation50
S. aureus and E. coli	MIC and MBC	5 nm to 38 nm	Spherical	Smaller size exhibits better antibacterial activity and the size influences the type of activity	^Citation43

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