Table 1.
Overview of some commonly used natural and synthetic polymers for cartilage and osteochondral tissue engineering.
| Polymer Type | Polymer Name | Chemical Structure | Existence in Osteochondral Tissue and/or Origin | Advantages | Limitations | References |
|---|---|---|---|---|---|---|
| Natural polymers: Polysaccharide | Hyaluronic acid (HA) |  |
Yes. The most abundant GAG in native cartilage | ECM component (vital in the structural and functional maintenance of cartilage: the morphogenesis and proliferation of chondrocytes, formation of proteoglycans and collagen II, water adsorption and retention, lubrication and compression bearing, immune system modulation), easy to be functionalized | Poor mechanical properties, rapid degradation, week cell adhesion | [[84], [85], [86], [87]] |
| Chondroitin sulfate |
 
|
Yes. A sulfated GAG ubiquitous in native cartilage ECM | ECM component (beneficial in reducing pain and functional limitation associated with knee osteoarthritis, anti-inflammatory activity, role in cell recognition and signaling), easy to be functionalized | Poor mechanical properties, rapid degradation | [[88], [89], [90], [91], [92]] | |
| Alginate |  |
No. A natural unbranched negative polysaccharide obtained from brown algae and bacterial sources |
High functionality, fast cross-linking, low cost, injectable for bioprinting, structural similarity to GAGs | Poor mechanical strength, low cell-matrix interaction, varying levels of purity due to source variability, immunogenicity | [83,[93], [94], [95], [96], [97]] | |
| Agarose |  |
No. A natural neutral polysaccharide found in red algae |
High functionality, thermoreversible gelation, low cost, structural similarity to GAGs | Limited mechanical performance, low bioactivity, poor cell attachment | [[98], [99], [100], [101]] | |
| Chitosan |  |
No. A chemically partial deacetylated derivative of chitin, mainly exploited from two marine crustaceans, shrimps and crabs |
Intrinsic antibacterial ability, pH and temperature responsiveness, cationic characteristic for the electrostatic interactions with the anionic GAGs in ECM, low cost, structural similarity to GAGs | Poor water solubility in physiological conditions, potential allergenic risks, inferior mechanical properties, low cell-matrix interaction | [[102], [103], [104], [105], [106]] | |
| Gellan gum |  |
No. A linear negatively charged polysaccharide produced by the Sphingononas group bacteria |
pH and temperature responsiveness, structural similarity to GAGs | Weak mechanical strength, poor stability, low bioactivity, relatively high gelation temperature, small temperature window | [[107], [108], [109], [110]] | |
| Natural polymers: Protein based materials | Collagen |
 type II collagen |
Yes. The most prevalent protein component constituting the ECM | ECM components, good cell-matrix interaction | Potential of immunogenicity, relatively low mechanical strength, high cost, religious issues, limited sterilizability | [25,[111], [112], [113]] |
| Gelatin |  |
Yes. A derivative of collagen by partial hydrolysis with much lower antigenicity | Biologically active for cellular interaction, low immunogenicity in comparison to collagen, ease of processing and functionalization | Poor mechanical properties, rapid degradation, low thermal stability | [98,[114], [115], [116]] | |
| Silk fibroin |  |
No. The major protein component of natural silk |
High mechanical strength, low immunogenicity, structural similarity to collagen, morphologic flexibility, good sterilizability | Source variability, low biodegradability of the β-sheet crystals | [[117], [118], [119], [120]] | |
| Synthetic polymers |
Poly(ethylene glycol) (PEG) Poly(ethylene oxide) (PEO) |
 |
No | Good biocompatibility, versatility in processing and functionalization, mechanical adjustability, low immunogenicity | Biologically inert for cellular interaction, non-biodegradability | [[121], [122], [123], [124]] |
|
Polylactic acid (PLA) Polyglycolic acid (PGA) Poly(lactic acid-co-glycolic acid) (PLGA) |
 |
No | Good biocompatibility and biodegradability, ease of functionalization, low immunogenicity | Low bioactivity, acidic degradation products eliciting inflammatory response | [[125], [126], [127], [128]] | |
| Polycaprolactone (PCL) |  |
No | Relatively low melting temperature for 3D printing, long-term mechanical stability, ease to manufacture | Poor bioactivity, hydrophobicity | [[129], [130], [131], [132]] | |
| Poly(vinyl alcohol) (PVA) |  |
No | Good water adsorption and retention ability, chemical resistance, good mechanical properties, ease of aqueous processing | Biologically inert, non-degradability | [[133], [134], [135], [136]] | |
| Poly(l-glutamic acid) |  |
No. But its degradation product, l-glutamic acid, is the most abundant amino acid in articular cartilage |
No antigenicity or immunogenicity, good biological and physio-chemical properties, hydrophilicity. | Non-injectability | [[137], [138], [139], [140]] | |
| Poly(propylene fumarate (PPF) |  |
No | High mechanical strength, good degradability, biocompatible degradation products, injectability, thermal and photochemical crosslinkability | Deficient bioactivity | [[141], [142], [143], [144]] | |
| Poly(N-isopropyl acrylamide) (PNIPAAm) |  |
No | Thermoresponsiveness over a wide range of ionic strengths and pH, ease of modification | Poor cell affinity | [[145], [146], [147], [148]] |