pH‐Responsive Cationic Microgels for Naproxen Delivery

In this work, cationic core‐shell microgels made from PNNPAM and two different amine monomers in core and shell are explored with respect to their interactions with the anionic drug naproxen. While the tertiary amine DAPMA is located inside the core to enable reversible capture of naproxen based on electrostatic interactions, the primary amine APMH in the shell opens the possibility for further conjugation of the microgels with other functionalities or biomolecules. The complementary use of different scattering, spectroscopic, and imaging techniques resolves the interaction of the microgels with the anionic drug naproxen. Despite having a cationic core, the interaction of naproxen and microgels is found to be mainly limited to the outer periphery of the microgels. With increasing pH, these interactions of electrostatic nature can be completely switched off. This enables the microgels to be used for the controlled uptake and release of naproxen, using pH as a trigger for the release.