Development of on-chip cell domes using Ca-alginate hydrogel shells for non-adherent cell studies

Cell domes are hemispherical microstructures comprising hydrogel shells that enclose cells within their cavities. They are approximately 500 and 300 μm in radius and height, respectively. Multiple domes can be fabricated in an array on a single glass plate to facilitate optical observations and provide a localised and stable environment for non-adherent cell studies. However, current limitations, such as cytotoxicity, reduced cell viability and complex fabrication strategies, hinder their advancements. Thus, we address these limitations by proposing a cell dome system based on calcium ion (Ca²⁺)-crosslinked alginate hydrogel shells anchored to glass plates. The fabrication process was significantly streamlined and improved compared to previously reported enzyme-mediated methods, rendering it more accessible for biomedical applications. The resulting cell domes exhibited excellent adhesion stability to glass plates, maintaining an adhesion rate of >90% following 168 h of incubation under cell culture conditions. Enclosed K562 cells, which represent a non-adherent erythroleukemia cell line, exhibited consistent viability (>95%) and a 14-fold increase in cell proliferation over 72 h. The hydrogel shell enabled reagents, such as calcein-AM and ethidium homodimer-1, to enter the dome from the external environment. In addition, reagents could be transferred to the enclosed cells from within the dome by pre-depositing them onto the glass prior to dome preparation. Our proposed Ca-alginate cell dome broadens the application of cell domes as a scalable and versatile platform for high-throughput drug screening and cellular analysis, offering precise control over non-adherent cell studies.