TABLE 2.

Different types of metallic nAbts and their associated functions.

Metallic NPs	Size/shape	Conjugated antibiotic	Conjugate’s chemistry	Targeted bacteria	Target site	Mechanism of action	Reference
Silver (Ag)	4 nm, spherical	Ampicillin (Amp)	Citrate coated AgNPs can load 1.06 × 10-6 mol of Amp by functionalization on to AgNPs surface	Pseudomonas aeruginosa, Vibrio cholerae, Escherichia coli	Cell wall and cell membrane	Approx. Five hundred twenty-three molecules of Amp/AgNP bring a combined antibacterial effect of Amp and AgNP, resulted in a ten-fold decreased amount of Amp-AgNP conjugate to kill β-lactam resistant bacteria at a faster rate compared to free Amp.	Brown et al. (2012)
Gold (Au)	10–12 nm, spherical	Gentamicin	The three NH2 groups of gentamicin non-covalently strongly bind with AuNP by hydrogen bonding.	Staphylococcus aureus (ATCC29213)	Cell wall	AuNP conjugates selectively bind with the cell wall, penetrate and deliver a large gentamicin amount.	Ahangari et al. (2013)
Gold (Au)	4–5 nm, spherical	Vancomycin (Van)	Phenyl group of Van attaches with AuNP by Au-S bonds. Each Au NP links with approx. 31 Van molecules on its surface.	Vancomycin-resistant enterococci, Escherichia coli	Cell membrane	Van-capped AuNP serves as a multi/polyvalent inhibitor to the bacterial cell membrane.	Gu et al. (2003)