Synthesis of Glycopolymer Micelles for Antibiotic Delivery

Abstract

In this work, we designed biodegradable glycopolymers consisting of a carbohydrate conjugated to a biodegradable polymer, poly(lactic acid) (PLA), through a poly(ethylene glycol) (PEG) linker. The glycopolymers were synthesized by coupling alkyne end-functionalized PEG-PLA with azide-derivatized mannose, trehalose, or maltoheptaose via the click reaction. The coupling yield was in the range of 40–50% and was independent of the size of the carbohydrate. The resulting glycopolymers were able to form micelles with the hydrophobic PLA in the core and the carbohydrates on the surface, as confirmed by binding with the lectin Concanavalin A. The glycomicelles were ~30 nm in diameter with low size dispersity. The glycomicelles were able to encapsulate both non-polar (rifampicin) and polar (ciprofloxacin) antibiotics. Rifampicin-encapsulated micelles were much smaller (27–32 nm) compared to the ciprofloxacin-encapsulated micelles (~417 nm). Moreover, more rifampicin was loaded into the glycomicelles (66–80 μg/mg, 7–8%) than ciprofloxacin (1.2–2.5 μg/mg, 0.1–0.2%). Despite the low loading, the antibiotic-encapsulated glycomicelles were at least as active or 2–4 times more active than the free antibiotics. For glycopolymers without the PEG linker, the antibiotics encapsulated in micelles were 2–6 times worse than the free antibiotics.