Manufacturing synthetic viscoelastic antigen-presenting cells for immunotherapy

This protocol details the preparation and functionalization of viscoelastic synthetic antigen-presenting cells (APCs) for T cell activation, designed to enhance immunotherapeutic efficacy. Using a high-throughput microfluidic system and post-processing, we create cell-sized sodium alginate microbeads with tunable stiffness, viscoelasticity and surface chemistry, enabling them to better mimic the physical and activation properties of natural APCs. The protocol includes fabrication of synthetic cells with defined sizes, crosslinking strategies to achieve desirable mechanical properties, surface functionalization via click chemistry for attaching activation molecules, and characterization methods for mechanical and biochemical properties. Compared with traditional matrices or rigid microbeads, this approach allows precise control over the mechanical and biochemical features of synthetic APCs, ensuring optimal T cell activation. The resulting synthetic cells support robust T cell activation and expansion, enhance the CD8/CD4 T cell ratio, promote T memory stem cell (TMSC) formation and improve chimeric antigen receptor transduction efficiency, leading to superior tumor-killing efficacy in vitro and in vivo. Additionally, these synthetic cells can be efficiently removed from T cells after activation using simple centrifugation or calcium chelation, preserving the activated T cells. The complete protocol, including fabrication, functionalization and quality assessment, requires ~1 week to complete. Users should have experience in microfluidics, biomaterial handling, bioconjugation techniques and basic cell culture. This platform can be adapted for broader applications in immune cell engineering.