Microgel-based modular 3D <i>in vitro</i> microfluidic cell culture platforms

The combination of 3D <i>in vitro</i> cell culture and microfluidic technology has emerged as a powerful approach in biomedical engineering. It offers a more physiologically relevant model compared to traditional 2D cell cultures by allowing the assembly of micro-sized cellular structures, known as microgels. These microgels can be prepared and fabricated to mimic the <i>in vivo</i> characteristics of an ECM. We report here an economical and feasible microfluidic 3D <i>in vitro</i> culture platform that offers real-time monitoring of cellular proliferation by encapsulating pH-sensing carbon dots (CDs) with cells in the microgels. These CDs were shown to effectively evaluate proliferation within cell-encapsulated microgels in comparison with the traditional Alamar blue assay. The biggest advantage of this platform is its ability to co-culture different cell types, achieved by encapsulating the cells within individual microgels, spatially separating them while maintaining close proximity. In this modular system, each microgel acts as a unit of a specific cell type, allowing easy retrieval of cells and control over cell densities. We established the efficacy of this concept by co-culturing Huh-7 and NIH-3T3 cells within different microgel combinations, under both static and dynamic flow conditions. The heterotypic interactions were explored by assessing the functionality using albumin assay and CYP3A4 gene expression studies, along with performing drug toxicity assays. The functionality studies confirmed results from existing literature studies by showing an improved hepatic function in the presence of NIH-3T3, even in the dynamic state. This platform can be expanded to include multiple cell types, creating a complex tissue-like effect without requiring spatial patterning techniques.