Bioprinting Endothelial Cells With Alginate for 3D Tissue Constructs

Abstract

Advanced solid freeform fabrication (SFF) techniques have been an interest for constructing tissue engineered polymeric scaffolds because of its repeatability and capability of high accuracy in fabrication resolution at the scaffold macro- and microscales. Among many important scaffold applications, hydrogel scaffolds have been utilized in tissue engineering as a technique to confide the desired proliferation of seeded cells in vitro and in vivo into its architecturally porous three-dimensional structures. Such fabrication techniques not only enable the reconstruction of scaffolds with accurate anatomical architectures but also enable the ability to incorporate bioactive species such as growth factors, proteins, and living cells. This paper presents a bioprinting system designed for the freeform fabrication of porous alginate scaffolds with encapsulated endothelial cells. The bioprinting fabrication system includes a multinozzle deposition system that utilizes SFF techniques and a computer-aided modeling system capable of creating heterogeneous tissue scaffolds. The manufacturing process is biologically compatible and is capable of functioning at room temperature and relatively low pressures to reduce the fluidic shear forces that could deteriorate biologically active species. The deposition system resolution is 10 microm in the three orthogonal directions XYZ and has minimum velocity of 100 microm/s. The ideal concentrations of sodium alginate and calcium chloride were investigated to determine a viable bioprinting process. The results indicated that the suitable fabrication parameters were 1.5% (w/v) sodium alginate and 0.5% (w/v) calcium chloride. Degradation studies via mechanical testing showed a decrease in the elastic modulus by 35% after 3 weeks. Cell viability studies were conducted on the cell encapsulated scaffolds for validating the bioprinting process and determining cell viability of 83%. This work exhibits the potential use of accurate cell placement for engineering complex tissue regeneration using computer-aided design systems.

Guidelines for standardization of bioprinting: a systematic study of process parameters and their effect on bioprinted structures

“…Several articles have related the decrease in cell viability after printing to polymer content [3] or printing pressure [4,5]. However, increasing polymer content and viscosity have been reported to improve printing resolution [6,7] and mechanical properties [5]. The understanding of the rheological properties of bioinks including shear thinning, yield stress, viscosity and shear recovery are important in evaluating the printing parameters and material related mechanical properties.…”

Recent cell printing systems for tissue engineering

“…The bioink requires several characteristics: (1) 3D printability with uniform viscosity, (2) physical and chemical crosslink ability that enables 3D shape maintenance after printing, (3) cyto-compatibility that supports favorable cell viability and assists cell proliferation and differentiation, and (4) biodegradability after transplantation into a host for the emission of decomposed wastes [58,59] . Currently, the most widely used bioink materials in cell printing are alginate, collagen, hyaluronic acid, gelatin, pluronic F127, polyethylene glycol dimethacrylate [60][61][62] , etc.…”

3D bioprinting for cell culture and tissue fabrication

“…The gelation process of a bioink matrix has a crucial role in both the resolution and cell viability [24]. Furthermore, the mechanical properties and degradation behavior not only affect cell growth, proliferation and differentiation, but also long-term biocompatibility in the fabricated tissues [25][26][27][28].…”