Tuning the Toughness of an Alginate Micro-gel for Cell-instructed Delivery

The cell-instructed delivery system was designed to control the release behavior of cell by tuning the mechanical properties of the cell delivery carrier. First, alginate molecules were substituted with methacrylates and mixed with pure alginate molecules to prepare micro-gel crosslinked with Ca2+ ions. Then, the poly(ethylene glycol) diacrylate (PEGDA) was added to incorporate interpenetrating covalent cross-links in an ionically cross-linked alginate micro-gel. Controlling the degree of substitution of methacrylates and chemical cross-links tuned the alginate micro-gel with varying stiffness and toughness. This study discovered that the cells differentiated into neurons were hatching and released in the alginate micro-gel with W-T (work to fracture) of 213 J/m(2) and E (elastic modulus) of 7.5 kPa. Overall, the results of this study will be highly useful in designing cell-instructed delivery devices by systematically controlling the mechanical properties of the gel according to the cell traction force.