Generation of Oxygenating Fluorinated Methacrylamide Chitosan Microparticles to Increase Cell Survival and Function in Large Liver Spheroids.

Despite advances in the development of complex culture technologies, the utility, survival, and function of large 3D cell aggregates, or spheroids, are impeded by mass transport limitations. The incorporation of engineered microparticles into these cell aggregates offers a promising approach to increase spheroid integrity through the creation of extracellular spaces to improve mass transport. In this study, we describe the formation of uniform oxygenating fluorinated methacrylamide chitosan (MACF) microparticles via a T-shaped microfluidic device, which when incorporated into spheroids increased extracellular spacing and enhanced oxygen transport via perfluorocarbon substitutions. The addition of MACF microparticles into large liver cell spheroids supported the formation of stable and large spheroids (>500 µm in diameter) made of a heterogeneous population of immortalized human hepatoma (HepG2) and hepatic stellate cells (HSCs) (4 HepG2/1 HSC), especially at a 150:1 ratio of cells to microparticles. Further, as confirmed by the albumin, urea, and CYP3A4 secretion amounts into the culture media, biological functionality was maintained over 10 days due to the incorporation of MACF microparticles as compared to controls without microparticles. Importantly, we demonstrated the utility of fluorinated microparticles in reducing the number of hypoxic cells within the core regions of spheroids, while also promoting the diffusion of other small molecules in and out of these 3D in vitro models.

Mixing Optimization in Grooved Serpentine Microchannels.

Computational fluid dynamics modeling at Reynolds numbers ranging from 10 to 100 was used to characterize the performance of a new type of micromixer employing a serpentine channel with a grooved surface. The new topology exploits the overlap between the typical Dean flows present in curved channels due to the centrifugal forces experienced by the fluids, and the helical flows induced by slanted groove-ridge patterns with respect to the direction of the flow. The resulting flows are complex, with multiple vortices and saddle points, leading to enhanced mixing across the section of the channel. The optimization of the mixers with respect to the inner radius of curvature (Rin) of the serpentine channel identifies the designs in which the mixing index quality is both high (M > 0.95) and independent of the Reynolds number across all the values investigated.