Table 1 Classification and properties of hydrogels and their crosslinking modes

Physical crosslinking

Sodium alginate

Biocompatibility, non-toxicity, biodegradability

Ionic crosslinker [10,11,12], chemical crosslinker [10]

Chitosan

Bacteriostatic, pressure resistant, easily modified

Photo crosslinker [13], Michael addition [14], enzyme crosslinker [15]

Hyaluronic acid

Personalized customization, long-term effectiveness, biocompatibility

Chemical crosslinker [16]

Agarose

Antiadhesion, heat reversible, biocompatibility

Thermotropic phase transition [17, 18]

Chondroitin sulfate

Pain relief, promote cell growth, promote cartilage regeneration

Schiff base reaction [19, 20]

Glucan

Blood plasma substitutes, promote cartilage regeneration

Schiff base reaction [21], click chemical reaction [22]

Chemical crosslinking

Gelatin

Thermo-reversible, inexpensive, easy to process

Thermotropic phase transition [23,24,25]

Collagen

Promote cartilage regeneration

Chemical crosslinker [26]

Silk proteins

Mechanical property, biocompatibility, degradability

Photo crosslinker [27]

Sericin protein

Anti-wrinkle, high elasticity, tensile

Enzyme crosslinker [28], photo crosslinker [29]

Albumin

Detoxification, antioxidant, biocompatibility, solubility

Chemical crosslinker [30, 31]

Synthetic hydrogels

NIPAM

Heat sensitivity, degradability, smart-responsive materials

Click chemical reaction [22], thermotropic phase transition [32]

PEG

Solubility, softener, antistatic agent

Michael addition [33]

Acrylic acid

Hydrophilicity

Photo-cross-link [34], free-radical polymerization [35]

Acrylamide

Cytocompatibility, responsiveness, cell adhesion

Chemical crosslinker [36, 37]