Methods for Photocrosslinking Alginate Hydrogel Scaffolds with High Cell Viability

Abstract

Methods for seeding high-viability (>85%) three-dimensional (3D) alginate-chondrocyte hydrogel scaffolds are presented that employ photocrosslinking of methacrylate-modified alginate with the photoinitiator VA-086. Comparison with results from several other photoinitiators, including Irgacure 2959, highlights the role of solvent, ultraviolet exposure, and photoinitiator cytotoxicity on process viability of bovine chondrocytes in two-dimensional culture. The radicals generated from VA-086 photodissociation are shown to be noncytotoxic at w/v concentrations up to 1.5%, enabling photocrosslinking without significant cell death. The applicability of these photoinitiators for generating 3D tissue-engineered constructs is evaluated by measuring cell viability in 3D constructs with aggregate moduli in the 10-20 kPa range. Hydrogels with encapsulated bovine chondrocytes were constructed with >85% viability using VA-086. While the commonly used Irgacure 2959 is noncytotoxic in its native state and crosslinks the alginate at weight fractions much lower than VA-086, the cytotoxicity of IRG2959's photogenerated radical leads to viabilities below 70% in the conditions tested.

Structured Macroporous Hydrogels: Progress, Challenges, and Opportunities

“…While UV photopolymerization of (meth)acrylated polymer precursors in many ways does meet these criteria, such processes typically require the use of at least a small fraction of added photoinitiator and, depending on the required duration of UV exposure, may induce toxicity to cells included in the process either directly via DNA damage or indirectly by heating the scaffold. [154,155] Thus, while UV photopoly merization is certainly a viable option for avoiding solvent use is currently used as a water-based structuring chemistry (with notable successes [94,156] ), its limitations should also be recognized. A range of physical mechanisms including hydrophobic self-association, [157] thermogelation, [158,159] charge complexation, [160,161] stereocomplexation, [162] and host-guest interactions [163] have been reported to enable in situ gelation in water.…”

The trend towards in vivo bioprinting

“…This kind of hydrogel precursors can be synthesized by modifying natural or synthetic polymers (gelatin and alginate) with methacrylates or acrylates etc. [34][35][36] . Recent advances indicate that by choosing proper parameters, relatively high viability of the encapsulated cells could be achieved in photo-patterning or bioprinting process [37,38] .…”

Introductory Chapter: Multi-Aspect Bibliographic Analysis of the Synergy of Technical, Biological and Medical Sciences Concerning Materials and Technologies Used for Medical and Dental Implantable Devices

“…Chemical cross-linking hydrogels having convalescent bonds include photo-cross-linkable poly(ethylene glycol)-diacrylate (PEGDA), poly(ethylene glycol)-dimethacrylate (PEGDMA), poly(propylene fumarate) (PPF) and oligo(poly(ethylene glyco) fumarate) (OPF) [481][482][483][484][485], and also natural hydrogels such as dextran, alginate, chitosan and hyaluronic acid synthesised from PEGDA/PEGDMA [486][487][488][489] and Michael-type addition reaction [490][491][492] and Schiff base-cross-linked hydrogels [465,[493][494][495]. In the case of enzyme-mediated cross-linking [458], transglutaminases (including Factor Xllla) and horseradish peroxidases (HRP) [459] are used for the catalysis of star-shaped PEG hydrogels [496] and tissue transglutaminase catalysed PEG hydrogels [497].…”

“…Different synthetic and natural polymers were used for this purpose, including polyethylene glycol (PEG), and copolymers containing PEG [486,510], hyaluronic acid (HA) [511] after an oxidation reaction through HA-tyramine conjugates [505] and as a result of the formation between HA-SH [492,512] and Michael addition [491,513], collagen and gelatin hydrogels mostly cross-linked using glutaraldehyde, genipin or water-soluble carbodiimides [513][514][515], chitosan [516][517][518][519], dextran 192 [520,521] and alginate [522]. Hydrogels were used for reconstruction of the retina [523], ligament [524], fatty tissue [465], kidneys [525], muscles [526], blood vessels [527,528], and also heart, neural cells, invertebral discs, bones and gristle [459].…”