Targeted polymer-based antibiotic delivery system: A promising option for treating bacterial infections via macromolecular approaches

Antibiotic therapy is the routine method for treating bacterial infections and has saved hundreds of millions of lives over the last century. However, low bioavailability, side effects, and emergence of antibiotic-resistant bacteria are usually associated with the systemic administration of antibiotics. Polymer-based antibiotic delivery system (PADS), as a solution to the limitations of conventional antibiotic therapy, has received significant attention, for it is able to protect antibiotics from premature metabolism and optimize the pharmacokinetics. Moreover, PADS can be elaborately modified to target the infection sites through the specific ligand-receptor interactions in an active manner, or through the responses to endogenous and exogenous stimuli in a passive manner. Multiple polymeric nano-constructions have been used thus far to fabricate PADS, such as polymeric liposomes, polymeric micelles, highly branched polymers and dendrimers, and polymeric nanogels, exhibiting enhanced therapeutic effects compared with the corresponding free antibiotics. In addition, hybrid nanoplatforms integrating the inorganic or biological components have also been developed for PADS, which have the potential to achieve complementary and synergistic effects with antibiotic therapy. In this paper, we reviewed the advances that have been made in PADS for the treatment of bacterial infections in the past five years, highlighting the design principles and targeting capability, in an attempt to provide new insights for further researches.