Metal Cation Responsive Anionic Microgels: Behaviour Towards Biologically Relevant Divalent and Trivalent Ions
Anionic poly(vinylcaprolactam-co-itaconicacid-co-dimethylitaconate) microgels were synthesized via dispersion polymerization and their responsiveness towards cations, namely Mg2+, Sr2+, Cu2+ and Fe3+ was investigated. The itaconic moeities chelate the metal ions which act as a crosslinker and decrease the electrostatic repulsion within the network, leading to a decrease in the gel size. The responsiveness towards the metal ions concentration has been studied via dynamic light scattering (DLS) and the amount of ion bonded within the network has been quantified with ion chromatography. Through protonation of the carboxylate groups in the gel network, their interaction with the cations is significantly lowered, and the metals are consequently released back in solution. The amount of ion released was assessed also via ion chromatography for all four ions, whilst Mg2+ was also used as model ion to display the reversibility of the system. The microgels can bond and release over multiple cycles divalent cations without undergoing any loss of functionality. Moreover, these gels also selectively entrap Fe3+ in respect to the remaining divalent cations, opening the possibility to use the proposed gels in the digestive tract as biocompatible chelating agents to fight iron overaccumulation.