Bioprinting Complex Cartilaginous Structures with Clinically Compliant Biomaterials

Abstract

wileyonlinelibrary.comwith rapid production of patient-specifi c grafts, allowing precise control over internal and external architecture and customized mechanical properties. These techniques can be used for printing biological materials together with living cells, hence the term "bioprinting." 3D bioprinting offers researchers a unique way of depositing cell-laden biocompatible materials, the so-called bioinks, in high-resolution structures with a line thickness on the order of hundreds of microns. Due to the promise of such a technology, several commercial bioprinters have entered the market and bioinks are the subject of intense investigation. [1][2][3] Bioink formulation is often considered one of the most critical aspects of high-resolution cellular bioprinting.Cellular printing requires a bioink with two key properties, namely printability and cytocompatible crosslinking. The identifi cation of printable polymeric systems is mainly done through rheological evaluation of a material's shear thinning behavior and shear recovery. Shear thinning correlates directly with a bioink's ability to be extruded at low pressure (<3 bar), something which ensures high postprinting cell viability. [ 4 ] Shear recovery, on the other hand, relates to the ink's resistance to fl ow after printing, which ensures high fi delity of the printed structure. The presence of cells, however, greatly restricts the crosslinking options as physiologic temperature and pH need to be maintained and harsh chemicals avoided. Hydrogel bioinks can be crosslinked via covalent or physical interactions or a combination thereof. Ultraviolet light initiated crosslinking of (meth)acrylated polymers has been used most often in bioinks, but the presence of potentially toxic monomers and photoinitiators may complicate clinical translation. [5][6][7][8] Physically crosslinked gelation based on temperature, hydrophobic/hydrophilic or ionic interactions has been utilized for precrosslinking of several bioink materials including poly( N -isopropylacrylamide) conjugated hyaluronan (HA-pNIPAAm), [ 9 ] gelatin, [ 10,11 ] alginate, [ 12 ] and gellan. [ 13 ] Precrosslinking before printing or directly during deposition to stabilize the printed lines is generally followed by a fi nal crosslinking which further increases the mechanical properties and stabilizes the whole structure.For cartilage engineering applications, natural polymers from animal or plant sources including alginate, collagen, gelatin, Bioprinting is an emerging technology for the fabrication of patient-specifi c, anatomically complex tissues and organs. A novel bioink for printing cartilage grafts is developed based on two unmodifi ed FDA-compliant polysaccharides, gellan and alginate, combined with the clinical product BioCartilage (cartilage extracellular matrix particles). Cell-friendly physical gelation of the bioink occurs in the presence of cations, which are delivered by co-extrusion of a cation-loaded transient support polymer to stabilize overhanging structures. Rheological properties of...

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

“…Direct comparison of bioink properties is important in order to be able to select specific inks for specific applications. A standardized testing protocol consisting of rheological and mechanical assessments was used to compare three commercially available bioinks to Vivoflow, which was physically crosslinked with cations for one and 24 h [14]. The commercial bioinks are referred to based on their main composition as Gel-MA (10% gelatin methacrylate [5,18,19] photo-crosslinked with 0.05% Ircacure I2959, BioGel from BioBots), PEG-DA (polyethyleneglycol-diacrylate photo-crosslinked with photoinitiator, BioInk from regenHu AG, [20] and NC-Alg (1.36% nanocellulose and 0.5% alginate crosslinked with cationic solution, Cellink from Cellink) [21].…”

“…Similar results for pure gellan gum gels [22] and pure alginate gels [23] have been previously reported. Vivoflow bioink was designed for cartilage bioprinting [14] and primary bovine chondrocytes were mixed into the ink prior to printing. The cell laden bioprinted structures were monitored over 21 days for the changes in cell viability and amount of DNA.…”

“…These properties are a function of the material itself, as well as bioprinting process parameters ( Figure 1B). Printed tensile specimens have been used to investigate the interaction of lines and layers [9][10][11][12][13][14][15][16][17], however, a systematic investigation of how process parameters influence these properties has not been conducted. Terminology to describe the tensile measurements include two crucial aspects.…”

Three-Dimensional Bioprinting and Its Potential in the Field of Articular Cartilage Regeneration

“…[33][34][35] An alternative strategy to generate bioactive constructs based on 3D printing technologies involves the embedding of biological cues that stimulate encapsulated cells or attracts and/or stimulates cells from the host. Hydrogel-based bioinks allow for the incorporation of growth factors, bioactive proteins, peptides, chemicals, and matrix components, 36 and printing procedures have so far not shown any negative effects on the activity of these biological cues 17,[37][38][39] (Table 1- 3). Large molecules that are constituents of the native cartilage matrix, such as hyaluronic acid, 40,41 can be used as promising biological cues for cartilage regeneration.…”

Creating biomaterials with spatially organized functionality

“…Scaffolds can be printed into anatomical-like structures, such as ears, noses, meniscuses, and vertebral disks, using computer tomography data or 3D models. 43 …”