Centrifugal microfluidic chip with an air gap for oil-free production of enhanced adipogenic multicellular microspheres†

Hydrogel microspheres, derived from natural or synthetic materials, serve as crucial platforms for three-dimensional (3D) cell culture and tissue engineering. While traditional production methods like emulsification and microfluidics are widely used, they often involve complex processes and oil phases that can compromise biocompatibility. Here, we present a novel centrifugal microfluidic device with an air gap for producing hydrogel microspheres. Centrifugal force provides a driving force for uniform parallel channels, enabling high-throughput microsphere generation while ensuring size uniformity. The system enables precise size control through centrifugal speed modulation, producing microspheres with diameters ranging from 140.6 ± 17.3 μm to 417.1 ± 34.4 μm with a coefficient of variation below 4.8%. The air gap within the microchannel establishes a step-structure that enables oil-free microsphere generation while ensuring biocompatibility. Moreover, by blending a collagen solution into sodium alginate as the matrix, oil-free microspheres with an interpenetrating polymer network (IPN) can be fabricated, which exhibit excellent biocompatibility to support the culture and adipogenic differentiation of mesenchymal stem cells (MSCs). When cells are cultured with a microsphere-formed scaffold, they exhibit aggregation behavior for enhanced cell–cell communication, which further elevated their adipogenic differentiation potential. Overall, this simplified, high-throughput approach offers a unique platform for applications in cell delivery, drug screening, and tissue engineering.