Table 1.

Various natural and synthetic hydrogels with their type, advantages, and disadvantages

Hydrogel	Type	Advantages	Disadvantages	Cell type used	References
Agarose	Natural	High mechanical strength, low cost	Low cell adhesion	Human neural stem cells, porcine BMSCs	27, 28, 29
Alginate	Natural	Fast gelation, low cost, good stability	Poor cell attachment, easily clogs at high concentrations	Human neural stem cells, porcine BMSCs	27, 28, 30
Chitosan	Natural	Antibacterial & antifungal	Slow gelation, poor mechanical properties	Human neural stem cells, human ADSCs	27, 29, 31
Collagen I	Natural	Promotes cell attachment, good printing abilities, have RGD sequencea	Poor mechanical stability, slow gelation, easily clogs	Human amniotic fluid stem cells, human BMSCs	29, 32
Fibrin	Natural	Promotes angiogenesis, fast gelation	Poor mechanical stability, easily clogs	Human amniotic fluid stem cells, human BMSCs	32, 33
Gelatin	Natural	Reversible, promotes cell adhesion	Unstable/fragile, poor abilities without modification	Human cardiac progenitor cells	34
Hyaluronic acid (HA)	Natural	Promotes proliferation and angiogenesis, fast gelation	Rapid degradation, poor mechanical stability	Human cardiac progenitor cells, human BMSCs	34, 35
Matrigel	Natural	Promotes differentiation	Clogs easily, made from tumor cells	Human epithelial cells	36
Methacrylated gelatin/gelatin methacryloyl (GelMA)	Synthetic	Easily degradable, high mechanical strength	Slow gelation, requires ultraviolet (UV) light which causes cell damage	Porcine BMSCs, human BMSCs	28, 37
Pluronic	Synthetic	Reversible (good sacrificial ink)	Poor mechanical stability, rapid degradation, requires thermal control	Human endothelial cells, bovine chondrocytes	39, 40
Polyethylene glycol (PEG)	Synthetic	Good when combined with other components	Low cell proliferation & adhesion, poor mechanical strength, UV causes cell damage	Porcine BMSCs, human BMSCs	28, 40

^aRGD = tripeptide Arg‐Gly‐Asp sequence which mediates cell attachment.

Abbreviations: ADSCs, adipose derived stem cells; BMSCs, bone marrow stem cells.