TABLE 6.

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

Polymeric NPs	Size/shape	Conjugated antibiotic	Conjugate’s chemistry	Targeted bacteria	Target site	Mechanism of action	Reference
PLGA	260 nm, spherical	Azithromycin, Rifampin	Each PLGA NP system can load 25% rifampicin or azithromycin, by weight, through surface conjugation.	Chlamydia trachomatis	C. trachomatis infected live cells.	Dual mechanisms of action: firstly, enhanced efficacy of combined azithromycin and rifampin therapy reduces chlamydia burden. Secondly, sustained drug release at the acute and persistent inclusion sites. Due to different drug release kinetics, only 25% of azithromycin and 12% rifampin can be delivered in the first three days. This lessened drug load at the infection site may subvert antibiotic resistance.	Toti et al. (2011)
PLGA	50–400 nm, spherical	Rifampicin	Each PLGA NP conjugate can encapsulate 10–30% Rifampicin, by weight, through surface functionalization.	Mycobacterium bovis BCG	Macrophage and phagolysosome	PLGA-rifampicin conjugates have a unique mechanism of internalization and intracellular trafficking. Once internalized in the macrophages, the conjugates reside in the phagolysosomes for 6–7 days. This sustained slow release of rifampicin kills BCG mycobacterium in the infected cells. Such a lower drug dose is less susceptible to antibiotic resistance development.	Kalluru et al. (2013)
Surface charge-switching PLGA-PLH-PEG (D, L-lactic-co-glycolic acid)-b-poly (L-histidine)-b-poly (ethylene glycol)	196 ± 7.8 nm, spherical	Vancomycin (Van)	Van is encapsulated onto the NP surface by solvent evaporation/double emulsion method.	Escherichia coli (ATCC11229), Staphylococcus aureus (ATCC25923)	Cell wall	Under basic conditions, negatively charged NPs do not interact with non-targeted sites. Only under acidic conditions (pH 5.5–6.0), the PLGA-PLH-PEG NP’s PLH (imidazole group) part exponentially gains positive surface charges. These anions actively attach the targeted sites (negatively charged bacterial cell wall elements) in a strong multivalent electrostatic binding. Eventually, strong antibacterial effects occur by the controlled release of vancomycin.	Radovic-Moreno et al. (2012)