Extrusion-based 3D bioprinting of alginate-based tissue constructs

Abstract

Tissues engineering technology led to the development of biomedical scaffolds which are mainly used to biofabricate different artificial human organs. Bioprinting is a direct method to fabricate tissue constructs that can support cell growth. The development and formation of bioinks for 3D bioprinting is always considered as a challenge in the field of biofabrication and tissue engineering. Numerous hydrogels have been discovered to solve the problem of bioinks. An appropriate hydrogel used as bioink should have numerous properties for building scaffolds and tissue constructs. A blend of appropriate rheological and mechanical properties is desired. This paper presents comparisons of different hydrogels, their crosslinking mechanisms, an experimental procedure to investigate best proportions of alginate-based hydrogel and crosslinking solution and mathematical model to predict the process parameters of the extrusion-based 3D bioprinting process. The mathematical model gives the reader values of process parameters like average velocity, pressure ranges to obtain a definite geometry of the construct, and shear stress developed for cell viability prediction. The trials were taken using sodium alginate and cross-linking agent as calcium lactate. The process variables considered to design the experiments were nozzle diameter, pressure range, concentration of sodium alginate and concentration of crosslinking solution. The tissue constructs were evaluated based on their geometry (non-continuous, stable, aggregating and over-flowing) and increase in print area. The mathematical model used the rheological data to find out the shear thinning behavior of different concentrations of bioinks. The experimental data and theoretical data obtained from mathematical model were merged to speculate the printability of sodium alginate when used as a bioink. Taken together, these assessment techniques revealed significant insights into the requirements for printable inks and shear conditions present during the extrusion process and allow the rapid and reproducible characterization of a wide variety of inks for 3D bioprinting.