Programmable Cargo Release from Jet-Printed Microgel Particles via an In Situ Ionic Exchange Method

Hydrogel-based drug delivery systems hold significant clinical potential by enabling precise spatial and temporal control over therapeutic release, ranging from metabolites, macromolecules to other cellular and subcellular constructs. However, achieving programmable release of payloads with diverse molecular weights at distinct rates typically requires complex polymer designs that can compromise the accessibility and biocompatibility of the delivery system. We present a scalable method for producing injectable, micrometer-scale alginate hydrogel particles (microgels) with precisely tuned microstructures for multiplexed, programmable cargo release. Our approach integrates an established jetting technique with a simple postsynthesis ion-exchange process to fine-tune the cross-linked microstructure of alginate microgels. By varying cation type (Ca²⁺, Mg²⁺, Na⁺) and concentration, we systematically modulate the microgels' chemical and physical properties to control release rates of model compounds, including rhodamine B, methylene blue, and dextrans of various molecular weights. Additionally, a PEG-alginate composite microgel system is used to demonstrate the pre-programmed stepwise release of rhodamine B. These findings offer a straightforward strategy for postsynthetic manipulation of ionic microgels with controllable release performances, paving the way for advanced biomedical applications.