Microfluidic Generation Of Porous Microcarriers For Cell Research

Three-dimensional(3D)cell culture is a kind of cell culture technique which aims to maintaining the 3D structures,phenotypes and differentiation functions of cells in vitro.Compared with conventional two-dimensional(2D)cultures,the 3D approaches have shown great ability to mimic the complex cellular interactions and in vivo micro-environmental conditions that make the recovery of 3D structures and partial functions of the original tissue physiology possible.Thus,3D cell culture plays a great role in various fields such as cell biology,drug discovery,and tissue engineering.Microcarriers,defined as a kind of support matrix for biomaterials,have emerged as novel biomimetic 3D cell culture platforms because of their suitable chemical composition,surface topography,and degree of porosity.They combine the advantages of both adherent culture and suspension culture and achieve the large-scale cultivation of cells with sufficient oxygen and nutrient supply.Several approaches have been proposed for fabricating microcarriers,such as photolithography,micromolding,electrojetting,microfluidics,and 3D printing.In comparison with other approaches,microfluidic generation of microcarriers is a promising technique for 3D cell culture due to the advantages of excellent monodispersity,precise size control,high throughput,and good micro-environmental control.However,the traditional microcarriers are suffered from the flow-induced shear stress,the lack of effective nutrient exchange pathways for inner cells,and simple material composites.Thus,in this articles,we fabricated porous microcarriers based on microfluidic techniques to improve the structures and functions of traditional microcarriers for cell research.In addition,we also developed a precise sample loading method on microplates based on the microfluidic droplet manipulation technique,which simplified the complicated operation steps of microplate sample loading in cell biology assays.The detailed research works are as follows:(1)Based on double-emulsion templates,we present novel microfluidic porous microcarriers for cell spheroid culture that consist of external-internal connected scaffold structures and biopolymer matrix fillers.The biomimetic scaffold structure of the porous microcarriers not only avoided the imposition of shear forces on the encapsulated cells but also provided a confined microenvironment for cell self-assembly,whereas the biopolymers in the porous cores of the microcarriers could act as an ECM microenvironment to promote the formation of multicellular spheroid aggregates.This research has important application values in evaluating the biocompatibility of different materials as well.(2)We present novel cell microcarriers with controllable macropores and heterogeneous microstructures with the capillary array microfluidic technology.The sizes of the microcarriers and their inner macropores could be well tailored by adjusting the flow rates of the microfluidic phases;this was of great importance in guaranteeing a sufficient supply of nutrients during cell culture.In addition,by infusing multiple cell-dispersed pregel solutions into the capillaries,the microcarriers with spatially heterogeneous cell encapsulations for cell co-culture and mimicking physiological structures and functions could also be achieved.(3)We developed a new near-infrared(NIR)light-responsive graphene oxide(GO)hydrogel microcarrier system for controllable cell capture and release.With optimal GO/hydrogel concentrations and irradiation conditions,cells with high viability could be released effectively from the microcarriers.The NIR-responsive GO hydrogel microcarriers were able to prevent the cultured cells from being attacked by the immune system and facilitate tumor proliferation and angiogenesis in immunocompetent mice models.This work plays a great role in tumor and drug researches.(4)We present a smart surface with tunable wettability to manipulate the sliding pathways of droplets for loading sample droplets precisely in microplates,which simplified the complicated operation steps of microplate sample loading in cell biology assays.The design has good reversibility,fast response,simple but persistent regulation,and application importance in the field of biochemical detection.