Speaker
Description
Extrusion bio-printing is the most direct and inexpensive method for printing three-dimensional cell models. This technique provides interesting solutions to generate more complex architectures than the already existing 3D models but still presents significant drawbacks that once solved will improve its field of application in regenerative medicine and advanced 3D biological models. To print complex structures with a larger volume, it is necessary to have available an important quantity of cells. There is also significant cellular stress during the printing process when extruding the ink, due in part to shear stress, which can induce the apoptosis or inability of the deposited cells.1 One of the common answers to these problems is the use of soft hydrogels having little mechanical strength, implying a lack of structural integrity of the printed designs. For this purpose, we produced new hyper porous micro-scaffolds of PLGA reducing the shear stress experienced by printed cells.
We developed a novel method of producing porous PLGA with a simple double emulsion and enhanced the cell adhesion of the particles’ surface by adding two types of coating. With these micro-scaffolds, we put in place a 3D cell culture method using said micro-scaffolds to improve cell proliferation before printing by acting as micro-carriers. We combined these cellularized micro-scaffolds with a bottom-up method of bio-printing of complex 3D structures and integrated them into various types of bio-inks, engineered either for the maximum survival of cells or for the construction of highly complex 3D structures. Ultimately, these micro-scaffolds are capable of protecting the cells during the bio-printing process by absorbing most of the shear stress inherent to all extrusion bio-printing. We also printed more complex structures, composed of structured layers of stained mesenchymal and cancerous cells, thus creating an organoid. The observation in time of the movement of cells inside the organoid allowed us to quantify the interaction and migration of cells with and without our micro-scaffolds.
We produced Polylysine or Collagen coated PLGA micro-scaffolds with an average size of 100 µm in diameter with a porosity of 25-45 %. Our results show an augmentation up to 400% of cell proliferation when cultured with said particles. The viability after printing is augmented with the use of our micro-particles, with a survival rate between 85 and 91% with our particles and between 75 and 83% without the micro-scaffolds. When printing more complex structures with co-cultures of tumorous cells with mesenchymal cells, the presence of our micro-scaffolds increase the migration of stem cells towards the tumorous cells.
Finally, the overall results offer new insights regarding bio-printing and cellular proliferation and migration in response to the presence of micro-scaffolds. Our new process promotes high cell productivity and viability before and during bio-printing. The use of our micro-scaffolds would make it easier, faster and more efficient to produce three-dimensional cellular structures and to analyze the behaviour and interactions of different cell types in this 3D environment.
- Boularaoui, S., Al Hussein, G., Khan, K. A., Christoforou, N. & Stefanini, C. Bioprinting 20, e00093 (2020).
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