pH-responsive pitted polymer particles with surface morphologies from cup shaped to multicavities

Polymeric particles that combine pH responsiveness and anisotropic morphology are reported, based on cross-linked 2-(diethylamino)ethyl methacrylate (DEA) coated polystyrene (PS) particles, obtained via a seeded polymerization procedure. DEA coating results in a single cavity within the seed particles, providing a cup-shaped final morphology. Two hydrophilic monomers, 2-(dimethylamino)ethyl methacrylate (DMA) and allylamine (AAm), are also used to further functionalize the particle surfaces. Through controlled monomer ratios, four pitted particles with different chemical compositions are prepared: DEA, DEA/DMA (two different ratios), and DEA/AAm. Monomer composition precisely tunes the resulting particle morphology, with the ability to change from cup shaped to multicavity. The pH-dependent release properties of the pitted particles are investigated using Rhodamine 6G at pH 6.5 and 7.4. Analysis of drug release kinetics with the Korsmeyer-Peppas model shows the drug release mechanism varies depending on the pH as well as the polymer composition. The biocompatibility of particles is assessed via the MTT cell viability assay.