Functionalised type-I collagen as a hydrogel building block for bio-orthogonal tissue engineering applications

Abstract

In this study, we derivatized type I collagen without altering its triple helical conformation to allow for facile hydrogel formation via Micheal addition of thiols to methacrylates without the addition of other crosslinking agents. This method provides the flexibility needed for fabrication of injectable hydrogels or pre-fabricated implantable scaffolds, using the same components by tuning the modulus from Pa to kPa. Enzymatic degradability of the hydrogels can be also easily fine tuned by variation of the ratio and type of cross-linking component. The structural morphology reveals lamellar structure mimicking native collagen fibrils. The versatility of this material is demonstrated by its use as a pre-fabricated substrate for culturing human corneal epithelial cells, and as an injectable hydrogel for 3-D encapsulation of cardiac progenitor cells.Keywords: bio-orthogonal chemistry, tissue engineering, pre-fabricated scaffolds, injectable scaffolds, cell compatible. IntroductionThe extracellular matrix (ECM) provides mechanical support as well as instructive signals for cell development, migration, proliferation, survival and function. Natural biopolymers derived from the ECM are therefore by nature, very biocompatible and bio-interactive. [1][2][3] The most abundant is collagen that has extensively been used to prepare scaffolds for tissue repair and engineering. This structural ECM component has, however limited number of functional groups that can be used for direct crosslinking. 4, 5 The main functional groups are amine and carboxylic acids, which allows collagen to crosslinked (e.g. via UV, thermal heating, carbodiimides, epoxy or aldehyde crosslinkers). Conversely, synthetic polymers such as poly (ethylene) glycols, poly (lactic acids), poly (methacryl/acryl amides) etc.), are easily chemically modified for facile processing than collagen.6 However, synthetic polymers have issues with biocompatibility, degradability and do not completely integrate within the host.7-9 Hence, synthetic routes to introduce biocompatible crosslinkable modifications on the protein structure, (reactive moieties), are highly desirable for the development of the next generation of regenerative materials for tissue engineering. Particularly, introducing reactive moieties in collagen would expand its functionality allowing for development of a wider range of scaffolds that can serve as regeneration templates. 10, 11 Several routes to render collagen more processable while retaining its in vitro/ in vivo or clinical bio interactive capacity for promoting tissue regeneration have been explored. [12][13][14] The simplest method is blending collagen with natural or synthetic polymers (such as hyaluronic acid, chitosan, poly(ethylene oxide), polylactic acid, and polyglycolic acid) to fabricate scaffolds. 5, 15 Crosslinked collagen-chitosan hydrogels, which were mechanically stronger than collagen alone, promoted angiogenesis and has been used for islet transplantations in murine models. 16 Li et al.co-polymerized collagen with lam...

Photochemically crosslinked cell‐laden methacrylated collagen hydrogels with high cell viability and functionality

“…41 Hydrogel stability is an important factor to determine whether photochemical crosslinking can aid in slowing down the enzymatic degradation of collagen hydrogels once implanted in vivo. 31,42 Results from the degradation study are in agreement with a previous study that showed that CMA hydrogels photochemically crosslinked with I2959 degraded significantly slower compared to uncrosslinked hydrogels. 27 Specifically, the residual mass of photochemically crosslinked hydrogels was reported to be around 60% at 3 h which is comparable to the results observed in the current study [ Fig.…”

“…Hydrogel stability is an important factor to determine whether photochemical crosslinking can aid in slowing down the enzymatic degradation of collagen hydrogels once implanted in vivo . Results from the degradation study are in agreement with a previous study that showed that CMA hydrogels photochemically crosslinked with I2959 degraded significantly slower compared to uncrosslinked hydrogels .…”

Bio-ink Materials for 3D Bio-printing

“…The bio-ink is emerged as the use of ink-jet printing, including polymer and hydrogel for scaffolds, growth factors, cells in tissue engineering. In this review, we focus the hydrogel for scaffold (10), capable to provide cellular microenvironment (11,12) and building blocks for 3D bio-printing (13). The hydrogels are the polymeric materials derived from naturally or synthetically, capable of embedding water in their three-dimensional network.…”

Organs-on-chips for the pharmaceutical development process: design perspectives and implementations

“…Hydrogels can e.g. be covalently crosslinked by click-reaction between thiols and methacrylated collagen [76] or methacrylated hyaluronic acid [77]. Physically crosslinked hydrogels rely on supramolecular connections such as electrostatic-or hydrophobic interactions, and hydrogen bonding.…”