In this work, we synthesized electroactive and degradable
microgels based on biomacromolecular building blocks, which enable the controlled release of therapeutic drugs. Functional
chitosan-poly(
hydroquinone) (Ch:PHQ)
microgels exhibiting redox-active and pH-sensitive properties were synthesized by an oxidative polymerization in an inverse miniemulsion system. Physically crosslinked
microgels were formed by polymerization of
hydroquinone in the presence of
chitosan through the formation of hydrogen bonds between PHQ and Ch. A series of
microgel samples with variable Ch : PHQ ratios were synthesized. These obtained
microgels exhibit pH-responsive properties due to the protonation/deprotonation of amino-groups of
chitosan in the
microgel system. Poly(
hydroquinone) is a redox-active
polymer exhibiting a two-electron/
proton-transfer behavior and conveys this property to the
microgels as confirmed by cyclic voltammetry. In addition, the
microgels can be switched by electrochemical means: they swell in the oxidized state or shrink in the reduced state. In the presence of
urea or
lysozyme, the
microgels undergo a fast degradation due to the disruption of hydrogen bonds acting as physical crosslinks in the
microgel networks or due to the cleavage of glucosidic linkages of the incorporated
chitosan scaffold, respectively.
Doxorubicin (DOX), an anticancer drug, could be effectively encapsulated into the
microgels and released in the presence of an
enzyme, indicating that these biodegradable
microgels could be used as drug delivery vehicles for
tumor cells.