Table 3.

Common Materials Used To Construct Hydrogel Scaffolds

Material	Source	Inherently cell adhesive	Injectable	Gelation mechanism	Comments
Matrigel™	Mouse tumor cells	Yes	Yes	pH and temperature changes	Primarily used as a cell carrier but unlikely to be approved for human use
Collagen	Animals	Yes	Sometimes	Chemical crosslinking,pH and temperature changes	Highly biocompatible and used to mimic the natural ECM
Hyaluronic acid	Animals, bacteria	No	Yes	Electrostatic interaction	Often chemically derivatized to form injectable gels and has mostly been used for brain injuries
Fibrin	Blood	No	Yes	Enzymatic crosslinking	Extensively tested in vivo and shown to be suitable for cell and biomolecule delivery
Alginate	Algae	No	Sometimes	Ionic crosslinking	Used as a preformed scaffold for cell transplantation and regeneration studies
Agarose	Seaweed	No	No	Temperature change	Mostly used as a preformed scaffold and has shown promise in promoting regeneration
Chitosan	Insects and crustaceans	Sometimes	Sometimes	Ionic or chemical crosslinking	Material is widely available in nature and has been extensively derivatized to form both crosslinked and injectable gels
Dextran	Bacteria	No	Sometimes	Chemical crosslinking	Recently developed into macroporous scaffolds
Peptide Amphiphiles	Synthetic	No	Yes	pH, temperature, and ionic strength changes	Easily produced, modified with peptide domains, and formed into gels
PEG	Synthetic	No	Sometimes	Chemical and photo-crosslinking	Used for controlled studies of scaffold degradation and cell adhesivity
PHEMA	Synthetic	No	No	Chemical crosslinking	Supports biomolecule delivery and has highly tunable mechanical properties
PHPMA	Synthetic	No	No	Chemical crosslinking	Can be functionalized with peptide domains and has similar mechanical properties to CNS tissue