Table 2.
Physical properties of hydrogels and their performance as TE scaffolds.
| Physical properties | Materials | Approaches | Applications and performance | References |
|---|---|---|---|---|
| Mechanical strength | GelMA | Chitin nanofibers, Nanoparticles blending | Strain-to-failure increased 200% after chitin nanofiber assembly; stiffness of collagen-based hydrogel increased 10-fold after addition of functionalized nanoparticles. | Jaiswal et al., 2015; Hassanzadeh et al., 2016 |
| PAMPS/PDMAAm | Double network | High strength PAMPS/PDMAAm gel could induce spontaneous hyaline cartilage regeneration in the osteochondral defect. | Yasuda et al., 2009; Fukui et al., 2014 | |
| Stiffness | RGD modified alginate, agarose, and PEGDA | Tuning of Ca2+ or polymer concentration | Intermediate stiffness promoted the osteogenic differentiation of murine MSCs. | Huebsch et al., 2010 |
| Four-arm maleimide-functionalized PEG and four-arm thiol-functionalized PEG | By using different PEG concentration | The proliferation, self-renewal and vascular differentiation of stem cells were enhanced in lower stiffness hydrogel. | Mahadevaiah et al., 2015 | |
| MeHA | Tuning of macromer concentration or UV exposure time | Low stiffness of HA hydrogel promoted chondrogenic differentiation of MSCs. Highly crosslinked HA hydrogel promoted hypertrophic conversion of encapsulated MSCs. | Bian et al., 2013 | |
| Gel-HPA | Altering macromer and/or H2O2 concentration | Medium stiffness showed superior stimulus for maintaining of chondrogenic phenotype, high stiffness promoted collagen type II gene expression. | Wang et al., 2014 | |
| GelMA | Using the same macromer concentration with different methacryloyl substitution | High stiffness environment was beneficial for maintaining of chondrogenic gene expression. | Li et al., 2016 | |
| Stress relaxation | RGD-alginate | Tuning of stress-relaxation by using alginate with different molecular weight or PEG spacer | Fast stress relaxation promoted MSC spreading and osteogenic differentiation. | Chaudhuri et al., 2016 |
| Alginate | Same as above | Slow relaxing environment restricted cell volume expansion, up-regulated the gene related to matrix degradation and cell death. | Lee et al., 2017 | |
| HA, Collagen I | Dynamic crosslinking of HA-ALD and HA-BLD, combined with collagen | Fast relaxation promoted cell spreading and focal adhesion formation. | Lou et al., 2018 | |
| Self-healing | Glycol chitosan, benzaldehyde functioned PEG | Reversible Schiff-base reaction | Self-healing hydrogel could increase proliferation and neural differentiation of neural stem cells, and enhanced capillary inducing capacity of vascular endothelial cells. | Tseng et al., 2015; Hsieh et al., 2017 |
| Dynamic acylhydrazone bond and DA click covalent crosslinking | Increasing the viability, decreasing apoptosis of MSCs and promoting bone regeneration | Lü et al., 2017 | ||
| Degradation | GelMA | Collagenase degradable photocrosslinked gelatin hydrogel | Valvular interstitial cells had more spreading morphology in collagenase treated GelMA hydrogel than untreated hydrogel. | Benton et al., 2009 |
| Sulfated HA | Slowing the degradation of HA hydrogel by sulfated modification | The low degradation was beneficial for chondrogenesis of MSCs. | Feng et al., 2017 | |
| HA functionalized with both maleimide and methacrylate | Thiol-ene crosslinking via MMP degradable crosslinker and photocrosslinking | Differentiation of MSC was directed by degradation-mediated cellular traction. | Khetan et al., 2013 | |
| PEG-derivative | Hydrogel crosslinked by PEG derivative containing nitrobenzyl ether moieties could be degradable by photo exposure. | MSC spreading was enhanced after photodegradation. | Kloxin et al., 2010 | |
| PEG-derivative | Modification of ends of PEG with oligo (lactic acid) and acryloyl, hydrolysis of the ester bonds altered the degradation | The high degradation enhanced osteogenesis of MSCs. | Peng et al., 2018 |