Table 1 Natural polymeric hydrogel scaffolds

HA

Produced by the fermentation of Streptococcus, extracted from corpus cavernosum, umbilical cord, and synovial vitreous humor, abundant in the ECM of human embryonic and connective tissues

Nourishes, lubricates, and dampens joints; exhibits excellent biocompatibility, cellular affinity, immunomodulatory ability; and inhibits the inflammatory cytokine expression

Poor mechanical properties and high internal degradation rate

[35,36,37,38, 43, 44]

Chitosan

Chitin is formed via deacetylation

Biocompatibility, adhesion, and degradability

Low solubility, high viscosity, and low mechanical strength

[46, 47, 51, 52]

Alginate

Obtained from brown algae and Pseudomonas mucosa

Highly hydrophilic and water soluble

Poor gel stability, low mechanical strength, rapid drug release, and poor degradation properties

[55,56,57, 61, 62]

Collagen

Synthesized from fibroblasts and present in organic matter and connective tissues of articular cartilage, tendons, and bones

Physicochemical properties, immunological properties, biodegradability, good biocompatibility, and promotion of cell growth

Insufficient mechanical strength and poor heat resistance

[11, 64,65,66, 69]

Silk fibroin

Hydrophobic silk cardiac protein and hydrophilic silk glue protein composition

Excellent mechanical properties, biodegradability, biocompatibility, resistance to oxidation, and antibacterial properties

Low mechanical strength

[70, 71, 76]

Gelatin

Present in skin, tendons, ligaments, and bones and extracted via hydrolysis or acid–base reactions

High thermal stability with degradation times up to several weeks. Facilitates ECM deposition and new cartilage tissue formation

Low mechanical strength, poor thermal stability, and high degradation rate

[78, 82, 83]