TABLE 5.

Different types of chitosan-based nAbts and their associated functions.

Chitosan NPs	Size/shape	Conjugated antibiotic	Conjugate’s chemistry	Targeted bacteria	Target site	Mechanism of action	Reference
Poly (D-glucosamine) chitosan	124 ± 17 nm, spherical	Penicillin/streptomycin	Covalent bonding between chitosan and penicillin/streptomycin	Staphylococcus epidermidis (ATCC35984)	Cell wall and cell membrane	The electrostatic attraction of the polycationic nature (high surface charge density) of chitosan tightly adsorbs onto the bacterial cell wall’s anionic components. When synergized with CS nanocarrier, the slow-release kinetics of antibiotics ensures sustained drug delivery, disrupting the cell membrane, ultimately rapid cell death occurs.	Piras et al. (2015)
2, 6—diamino chitosan	80 nm, spherical	Novobiocin	The 6-position hydroxyl group of chitosan binds with novobiocin.	Listeria monocytogenes, MRSA USA300, Staphylococcus aureus (ATCC29213), Klebsiella pneumoniae (BAA2784), Acinetobacter Baumannii (ATCC17978, and BAA-2803), Pseudomonas aeruginosa (BAA2797), Pseudomonas aeruginosa PA01	Cell wall	The synergy of chitosan with novobiocin brings additional amino groups in the conjugate. This synergy increases the hydrophilicity of chitosan and enhances the proton sponge effect (higher cationic charge), resulting in enhanced antibacterial efficacy.	Si et al. (2021)
Chitosan/Fe3O4/Poly (ethylene glycol) PEG	30 nm, spherical	Gentamicin (Gent)	CS-loaded Fe3O4 NPs are combined with Gent by strong electrostatic interactions. The dicarboxylic acid groups of PEG bind CS- Fe3O4 NPs loaded Gent with PEG.	Staphylococcus aureus, Escherichia coli	Cell membrane	Gent release from Fe3O4-PEG NP is pH-dependent and greatly enhanced at low pH (5.5–6.5). This dependency suggests a high diffusion of Gent into the surrounding environment when pH is acidic and subsequent destruction of the cell membrane occurs. The CS and PEG groups of NPs induce positive surface charges to the bacterial membrane's negative surface charges, promoting a contact killing mechanism by the nanocomposites themselves.	Wang et al., (2018b)