Fabrication of Hollow Structures in Photodegradable Hydrogels Using a Multi-Photon Excitation Process for Blood Vessel Tissue Engineering

Abstract

Engineered blood vessels generally recapitulate vascular function in vitro and can be utilized in drug discovery as a novel microphysiological system. Recently, various methods to fabricate vascular models in hydrogels have been reported to study the blood vessel functions in vitro; however, in general, it is difficult to fabricate hollow structures with a designed size and structure with a tens of micrometers scale for blood vessel tissue engineering. This study reports a method to fabricate the hollow structures in photodegradable hydrogels prepared in a microfluidic device. An infrared femtosecond pulsed laser, employed to induce photodegradation via multi-photon excitation, was scanned in the hydrogel in a program-controlled manner for fabricating the designed hollow structures. The photodegradable hydrogel was prepared by a crosslinking reaction between an azide-modified gelatin solution and a dibenzocyclooctyl-terminated photocleavable tetra-arm polyethylene glycol crosslinker solution. After assessing the composition of the photodegradable hydrogel in terms of swelling and cell adhesion, the hydrogel prepared in the microfluidic device was processed by laser scanning to fabricate linear and branched hollow structures present in it. We introduced a microsphere suspension into the fabricated structure in photodegradable hydrogels, and confirmed the fabrication of perfusable hollow structures of designed patterns via the multi-photon excitation process.

Stimuli-Responsive Hydrogels: The Dynamic Smart Biomaterials of Tomorrow

“…They used a microfluidic setup to design blood vessels with a specific structure and size in the tens of micrometer scale. The obtained structures sustained the adhesion and growth of vascular endothelial cells (HUVECs) . Furthermore, photodegradable hydrogels can be used in wound-healing applications .…”

“…Moreover, light-triggered methods are increasingly based on visible light sources instead of UV-light to avoid cell damage. , In addition, light-based printing methods are attracting more attention. Recent papers report high precision and high resolution by targeted laser irradiation that does not affect the surrounding cells. ,, …”

“…One promising method is based on the autonomous rolling-up of anisotropic hydrogel gels under the influence of a temperature or (de)­hydration trigger. ,− , Alternatively, photoerosion has been investigated for the formation of thin hollow channels in hydrogels. This method is either based on the use of photomasks (downward erosion) or very precise multiphoton laser irradiation. , Furthermore, postprinting shrinking procedures are very interesting candidates to reduce the dimensions of a printed construct. Both temperature and charge compensation triggers have been reported in the literature. ,,, With all three techniques (self-rolling sheets, photoerosion, and printing-shrinking), the formation of hollow channels in the tens of micrometer range has been reported. ,, The smallest features have been reached by means of pulsed laser irradiation.…”

Emerging Roles of Microfluidics in Brain Research: From Cerebral Fluids Manipulation to Brain-on-a-Chip and Neuroelectronic Devices Engineering

“…Other on-the-fly changes using MPL technology include selective material removal and spatiotemporal functionalization of biomaterials. Selective removal of materials such as collagen and PEG-based hydrogels on-chip has been achieved using photoablation ,,− or photodegradation, ,− with the latter being favored for its amenability to 2PA, bioorthogonality, and minimal risk to material and cellular integrity. The Anseth group demonstrated in 2010 the utility of two-photon photodegradable PEG-based hydrogels for spatiotemporal cell studies and characterized the dynamics of cell detachment upon scaffold degradation .…”

Biofabricating the Vascular Tree in Engineered Bone Tissue

“…Another relevant application of microfabrication approaches is the creation of microfluidic devices, which allow for the highly controlled perfusion of microchannels, and can more closely mimic cellular microenvironments. Since their introduction, microfluidic devices have been produced via soft lithography [93,94], additive manufacturing [95], photolithography [96][97][98] and micro-molding [92] processes, which are often limited to planar microfluidic networks. While initial microfluidic devices were limited to non-biodegradable poly(dimethylsiloxane) (PDMS) [99] and silicone [92], which do not permit native tissue remodelling throughout the construct to take place, recent work has shifted towards more biocompatible and biodegradable elastomers for the generation of microcapillary-like networks [100][101][102].…”