One‐Step Photoactivation of a Dual‐Functionalized Bioink as Cell Carrier and Cartilage‐Binding Glue for Chondral Regeneration

Abstract

Cartilage defects can result in pain, disability, and osteoarthritis. Hydrogels providing a chondroregeneration-permissive environment are often mechanically weak and display poor lateral integration into the surrounding cartilage. This study develops a visible-light responsive gelatin ink with enhanced interactions with the native tissue, and potential for intraoperative bioprinting. A dual-functionalized tyramine and methacryloyl gelatin (GelMA-Tyr) is synthesized. Photo-crosslinking of both groups is triggered in a single photoexposure by cell-compatible visible light in presence of tris(2,2'-bipyridyl)dichlororuthenium(II) and sodium persulfate as initiators. Neo-cartilage formation from embedded chondroprogenitor cells is demonstrated in vitro, and the hydrogel is successfully applied as bioink for extrusion-printing. Visible light in situ crosslinking in cartilage defects results in no damage to the surrounding tissue, in contrast to the native chondrocyte death caused by UV light (365–400 nm range), commonly used in biofabrication. Tyramine-binding to proteins in native cartilage leads to a 15-fold increment in the adhesive strength of the bioglue compared to pristine GelMA. Enhanced adhesion is observed also when the ink is extruded as printable filaments into the defect. Visible-light reactive GelMA-Tyr bioinks can act as orthobiologic carriers for in situ cartilage repair, providing a permissive environment for chondrogenesis, and establishing safe lateral integration into chondral defects.

Protein-Based 3D Biofabrication of Biomaterials

“…Photo-cross-linking inks are often used because the process is fast and provides good control. However, photo-initiators and UV-light can be cytotoxic, thus preventing this technique from being used in situ [ 128 , 129 ]. Chemical cross-linking, however, will most of the time result in some sort of cytotoxicity.…”

Stem Cells and Extrusion 3D Printing for Hyaline Cartilage Engineering

“…ACPCs maintain good chondrogenic potential after extending the monolayer culture, unlike mature chondrocytes [ 160 ]. ACPCs were already used in the EBB process developed with a gelatin-based bioink playing two key roles—the ink provides a scaffold to encapsulate the cells and acts as glue so that the extruded material directly adheres to the defect surface in situ [ 161 ]. ACPCs must be more deeply investigated to evaluate the chondrogenic potential of those cells.…”

“…In most cases, researchers work with a standard density optimized within that range [ 108 , 117 , 118 , 119 , 120 , 155 , 157 ]. In one study working with chondroprogenitors, a high density of 20 × 10 6 was also selected [ 161 ]. Very few studies used low cell densities, but they achieved good chondrogenic results [ 154 , 158 ].…”

“…In extrusion-based constructs, culture media supplementation with growth factors is essential for the redifferentiation of embedded chondrocytes or MSC differentiation induction. TGF-β1 is used in many different studies involving embedded ACPCs [ 161 ] or MSCs [ 163 , 175 ]. Extruded gels can also be cultured in medium supplemented with TGF-β3 to induce chondrocyte redifferentiation [ 157 ] or MSC chondrogenesis [ 143 , 165 ], or in coculture substitutes containing both cell types [ 173 ].…”

Applications of Gelatin Methacryloyl (GelMA) Hydrogels in Microfluidic Technique-Assisted Tissue Engineering

“…However, UV light, which was contained in the fabrication procedure of GelMA, is harmful to the organism, for instance, excessive UV light exposure during cross-linking can reduce the survival rate of cells [ 34 , 35 , 36 ]. Hence, novel cross-linking methods for GelMA hydrogels have been proposed [ 37 , 38 , 39 , 40 , 41 , 42 , 43 ]. Different physical properties and cell response parameters of GelMA hydrogels are of great significance to illuminate the applicability of GelMA hydrogels in different biomedical applications.…”