Hydrogel bioprinted microchannel networks for vascularization of tissue engineering constructs

Abstract

Vascularization remains a critical challenge in tissue engineering. The development of vascular networks within densely populated and metabolically functional tissues facilitate transport of nutrients and removal of waste products, thus preserving cellular viability over a long period of time. Despite tremendous progress in fabricating complex tissue constructs in the past few years, approaches for controlled vascularization within hydrogel based engineered tissue constructs have remained limited. Here, we report a three dimensional (3D) micromolding technique utilizing bioprinted agarose template fibers to fabricate microchannel networks with various architectural features within photo cross linkable hydrogel constructs. Using the proposed approach, we were able to successfully embed functional and perfusable microchannels inside methacrylated gelatin (GelMA), star poly (ethylene glycol-co-lactide) acrylate (SPELA), poly (ethylene glycol) dimethacrylate (PEGDMA) and poly (ethylene glycol) diacrylate (PEGDA) hydrogels at different concentrations. In particular, GelMA hydrogels were used as a model to demonstrate the functionality of the fabricated vascular networks in improving mass transport, cellular viability and differentiation within the cell-laden tissue constructs. In addition, successful formation of endothelial monolayers within the fabricated channels was confirmed. Overall, our proposed strategy represents an effective technique for vascularization of hydrogel constructs with useful applications in tissue engineering and organs on a chip.

3D bioprinting for cell culture and tissue fabrication

“…In particular, the functions of the gelatin methacrylate (GelMA) scaffold in mass transport, cell via- (Fig. 1b) [37]. In another work, Fan et al designed a Matrigel and agarose hybrid hydrogel system, where the former was used as microenvironment for cell growth, and the latter undertook the duty for maintaining the 3D printed tubular structure.…”

Advances in bioprinted cell-laden hydrogels for skin tissue engineering

“…Bioprinting technologies are attractive to engineer a vascular tree within thick constructs by the precise layer by layer deposition of multiple cell types and ECMlike bioinks into prescribed spatial locations at high resolution [202]. Promising approaches to generate vascular networks have been reported using inkjet [34,209], laserassisted [203], and extrusion bioprinting [16,92,132]. In general, such approaches are based on four main strategies: (1) direct patterning vascular cells onto a receiving substrate [203], (2) continuous printing of polymeric bioink loaded with endothelial cells followed by polymer removal [96], (3) printing perfusable channels in a 3D construct for subsequent injection of a cell suspension into the empty channel [92], and (4) printing of multicellular spheroids [132].…”

“…The extrusion bioprinting apparatus typically includes a computer-controlled robotic stage, multiple dispensing systems, and a construction platform that collects the printed material. To further improve its versatility and the range of processable biomaterials, additional modules can also be coupled and integrated to the traditional apparatus, serving multiple purposes such as controlling the temperature of reservoirs [93], enabling multimaterial printing [105], and allowing the in situ crosslinking through physical [3] or chemical [16] methods.…”

“…Contrary to bioassembly, where the minimum fabrication units are pre-formed cell building blocks, bioprinting makes use of fabrication units down to molecular level [78]. Bioprinting processes are capable of printing living and non-living materials in a computercontrolled and automated manner with high levels of resolution, accuracy and reproducibility, enabling the generation of biological substitutes with intricate architectures, precise geometrical configurations and biomechanical heterogeneity [16,80,91,92]. Bioprinting technologies can be classified in three main categories: inkjet bioprinting, laser-assisted bioprinting and extrusion bioprinting (Table 1) [111,125,191].…”

“…Larger and complex tissue constructs are obtained through the automated assembly of pre-formed cell-containing fabrication units (e.g., cell aggregates, cell fibres, cell sheets or microtissues) produced by different techniques, such as self-assembled aggregation, microfabrication or microfluidics [10,78,129]. Bottom-up approach addresses some of the limitations of the top-down approach by the creation of tissue constructs with multiple cell types placed in specific 3D locations, with a high cell density and possibility of printing vascular networks [16,121,166]. Bioprinting, one main strategy of biofabrication, is attracting significant interest from researchers working in the field of tissue engineering and regenerative medicine due to their unique ability to print single cells, bioactive molecules, biomaterials or cell-aggregates into structurally organized constructs in a layer-by-layer fashion with high resolution and accuracy [10,78,111,136].…”