Crosslinked pH-responsive polymersome via Diels-Alder click chemistry: A reversible pH-dependent vesicular nanosystem

Herein, we have developed pH-responsive shape-persistent polymersomes made of well-defined amphiphilic poly(ethylene oxide)-block-poly(diisopropylaminoethyl methacrylate-co-furfuryl methacrylate)s PEO-b-P(DPA-co-FMA) by exploiting Diels-Alder chemistry as a robust and simple crosslinking method. Using Photo-induced Copper Mediated Reversible Deactivation Radical Polymerization, we synthesized PEO-b-P(DPA-co-FMA) with optimal block ratios that favor the formation of polymersomes in aqueous media having pH-responsive P(DPA-co-FMA) membranes. Owing to the existence of furfuryl pendant groups within the polymersome membranes, the crosslinking of pH-responsive P(DPA-co-FMA) chains can be achieved via Diels-Alder chemistry. Interestingly, the resulting crosslinked polymersomes swell when the pH in the solution is decreased so that it lies in a biologically relevant range, as was demonstrated by cryogenic transmission electron microscopy. Here, the polymersome's ability to swell can be controlled by adjusting the amount of crosslinker. A minimum threshold of crosslinking density is needed for the polymersomes to swell while an excess amount of crosslinker quenched their ability to swell. Furthermore, crosslinked polymersomes are capable of encapsulating hydrophilic model drug, such as Rhodamine B. At pH 7.20, due to the compact and hydrophobic membrane, the diffusion of the dye from the interior of the polymersomes to the media is minimized, while the pronation of PDPA at an acidic pH of 4.00, enables a permeable membrane, allowing the loaded cargo to leak much more quickly. The shape-persistent polymersomes that we developed herein, are a promising nano-platform for use in drug delivery applications.