Stimuli-responsive poly(caprolactone) vesicles for dual drug delivery under the gastrointestinal tract

We report the first example of carboxylic functionalized poly(caprolactone) (PCL) block copolymer vesicles as a novel dual drug delivery pH responsive vehicle for oral administration under the gastrointestinal (GI) tract. A new carboxylic functionalized caprolactone monomer was custom designed through multistep organic reactions and polymerized under controlled ROP using polyethylene glycol (PEG-2000) to produce amphiphilic diblocks, PEG-b-CPCLx, with x = 25, 50, 75, and 100. These carboxylic PCL block copolymers were self-organized into 100-250 nm vesicular assemblies in water. The size and shape of the vesicular assemblies were confirmed by light scattering, zeta potential, and electron microscopes. These vesicles were capable of loading both hydrophilic molecules (Rhodamine B, Rh-B) and hydrophobic drugs such as ibuprofen (IBU) and camptothecin (CPT) in the core and layer, respectively. These pH-responsive PCL vesicles were stable in strong acidic conditions (pH < 2.0, stomach) and ruptured to release the loaded cargoes under neutral or basic pH (7.0 ≤ pH, similar to that of small intestine). The drug release kinetics under simulated GI tract revealed that the individual drug loaded vesicles followed the combination of diffusion and erosion pathway, whereas the dual drug loaded vesicles predominantly followed the diffusion controlled process. Thus, the custom designed PCL vesicles open up new area of pH stimuli responsive polymer vehicles for delivering multiple drugs in oral drug delivery which are yet to be explored for biomedical applications.