Emulsion-Templated Gel Embedding: A Microfluidics-Free Method for Scalable Cell Encapsulation in Hydrogel Microcapsules

Encapsulation of single cells within uniform hydrogel microcapsules enables controlled three-dimensional culture and quantitative analysis of cell behavior; however, most existing approaches rely on microfluidic devices or complex encapsulation processes that limit accessibility. Here, we introduce emulsion-templated gel embedding (ETE), a microfluidics-free method that embeds cells within uniform gelatin beads using prefabricated bead templates to predefine capsule size prior to encapsulation. In ETE, cells and monodisperse gelatin beads are co-encapsulated within water-in-oil droplets generated by particle-templated emulsification (PTE), followed by thermal dissolution and re-gelation of the gelatin to form cell-laden beads of defined size. The resulting cell-laden gelatin beads can subsequently serve as templates for agarose shell formation, yielding hollow-core agarose microcapsules after gelatin dissolution. Cells encapsulated within microcapsules via ETE exhibit proliferation comparable to microfluidic-derived capsules, indicating that simplified processing does not compromise biological performance. By defining capsule size through prefabricated gelatin templates rather than relying on microfluidic flow control during encapsulation, ETE provides a practical and reproducible strategy for generating uniform hydrogel microcapsules for cell culture and biomedical applications.