A Novel Step-T-Junction Microchannel for the Cell Encapsulation in Monodisperse Alginate-Gelatin Microspheres of Varying Mechanical Properties at High Throughput

Abstract

Cell encapsulation has been widely employed in cell therapy, characterization, and analysis, as well as many other biomedical applications. While droplet-based microfluidic technology is advantageous in cell microencapsulation because of its modularity, controllability, mild conditions, and easy operation when compared to other state-of-art methods, it faces the dilemma between high throughput and monodispersity of generated cell-laden microdroplets. In addition, the lack of a biocompatible method of de-emulsification transferring cell-laden hydrogel from cytotoxic oil phase into cell culture medium also hurtles the practical application of microfluidic technology. Here, a novel step-T-junction microchannel was employed to encapsulate cells into monodisperse microspheres at the high-throughput jetting regime. An alginate–gelatin co-polymer system was employed to enable the microfluidic-based fabrication of cell-laden microgels with mild cross-linking conditions and great biocompatibility, notably for the process of de-emulsification. The mechanical properties of alginate-gelatin hydrogel, e.g., stiffness, stress–relaxation, and viscoelasticity, are fully adjustable in offering a 3D biomechanical microenvironment that is optimal for the specific encapsulated cell type. Finally, the encapsulation of HepG2 cells into monodisperse alginate–gelatin microgels with the novel microfluidic system and the subsequent cultivation proved the maintenance of the long-term viability, proliferation, and functionalities of encapsulated cells, indicating the promising potential of the as-designed system in tissue engineering and regenerative medicine.

Review on Bioinspired Design of ECM-Mimicking Scaffolds by Computer-Aided Assembly of Cell-Free and Cell Laden Micro-Modules

“…These building blocks can be manufactured in the form of microspheres, either solid or porous, hydrogels, and fibres, depending on cell source and tissue architecture requirements [ 81 , 82 , 83 , 84 ]. Microfluidic emulsion is one of the most investigated techniques for the high-throughput production of monodisperse nano and microparticles featuring pre-defined composition, shape, and drug loading capability [ 85 ]. Microspheres with a narrow and controllable diameter distribution and interconnected porosity can be obtained by fluidic emulsion and gelation processes [ 81 , 82 , 86 , 87 , 88 ].…”

“…Porous PCL microspheres with a bioinspired trabecular structure that supported in vitro the adhesion, growth, and biosynthesis of human dermal fibroblasts were fabricated by using polyethylene oxide as porogen [ 81 ]. Alginate-gelatin microspheres with varying stiffness, stress-relaxation, and viscoelasticity were obtained by controlling the composition of the starting co-polymer [ 85 ]. Microfluidic can be conveniently combined with the UV-lithography technique for continuously synthesizing microparticles featuring a variety of different shapes and sizes [ 89 , 90 ].…”

Betulin Stimulates Osteogenic Differentiation of Human Osteoblasts-Loaded Alginate–Gelatin Microbeads

“…Another study showed that gelatin in the alginate mixture leads to improved cell adhesion properties because of the RGD (Arg–Gly–Asp) residue inside the microbeads [ 19 ]. An alginate–gelatin mixture was tested with various cell types, e.g., rat cardio myoblasts [ 21 , 22 , 23 , 24 ], H9C2 [ 22 ], U937 [ 25 , 26 ], HepG2 [ 27 ], Hatac [ 20 ], and human endothelial cells (HUVEC) [ 24 ].…”