Table 1.
Recent Biodegradable Hydrogels Used in Cell Encapsulation Strategies for Tissue Engineeringa
| Material | Gel precursors | Crosslink mechanism | Degradation mechanism | Cells encapsulated |
|---|---|---|---|---|
| Chitosan | Macromer(s): chitosan grafted with lactic acid and methacrylate | Covalent | Enzymatic (lysozyme) | Chondrocytes12 |
| Initiator: APS/TEMDA | Hydrolyticb | |||
| Macromer(s): chitosan-g-azidobenzoic acid and acryloyl-PEG-RGD | Covalent | Enzymatic (lysozyme) | Cardiomyocytes98 | |
| Alginate-co-Gelatin | Macromer(s): alginate dialdehyde and gelatin | Covalent | Hydrolytic | Hepatocytes90 |
| Crosslinking agent: Boraxc | ||||
| Styrenated gelatin | Macromer(s): styrenated gelatin | Covalent | Enzymatic | Chondrocytes72 |
| Initiator: camphorquinone | ||||
| HA | Macromer(s): methacrylated HA | Covalent | Enzymatic (Hyaluronidase) | Valvular interstitial cells,59 chondrocytes,106,134 fibroblasts135 |
| Initiator: Irgacure 2959 | ||||
| Macromers(s): acrylated HA and PEG-(SH)4 | Covalent | Enzymatic (Hyaluronidase) | Human MSCs26 | |
| Other: triethanolamine (pH 8.0) | ||||
| Macromers(s): thiol-modified HA and PEG diacrylate | Covalent | Enzymatic (Hyaluronidase)b | Adipocyte-stem cells,109 chick dorsal root ganglia110 | |
| Chondroitin sulfate | Macromers(s): methacrylated chondroitin sulfate | Covalent | Enzymatic (Chondroitinase) | Chondrocytes61,62 |
| Initiator: Irgacure 2959 | ||||
| Synthetic ECM analogs | Macromer(s): thiol-modified HA or thiol-modified chondroitin sulfate, thiol-modified gelatin and PEG diacrylate | Covalent | Enzymaticb | Murine fibroblasts,28 MSCs113 |
| PEGylated fibrinogen | Macromers(s): fibrinogen-g-PEGacryloyl and PEG diacrylate | Covalent | Enzymatic (plasmin, MMPs) | Bone marrow stromal cells85 |
| Initiator: Irgacure 2959 | ||||
| Self-assembled peptide gels | Macromer(s): self-assembling peptide | Physical | Dissolution or enzymaticd | Human MSCs,75 preosteoblastes,84 endothelial cells,136 cardiomyocytes,137 embryonic SCs137 |
| Other: electrolyte solutions (e.g., sucrose, DMEM) | ||||
| Elastin-like polypeptide | Macromer(s): genetically engineered ELP | Covalent | Enzymatic | Chondrocytes,77 adipose-derived SCs78 |
| Other: tissue transglutaminase and calcium chloride | ||||
| Macromer(s): PLA-b-PEG-b-PLA dimethacrylate | Covalent | Hydrolytic | Osteoblasts,39 neural precursor cells138 | |
| Initiator: Irgacure 2959 | ||||
| Poly(ethylene glycol) based | Macromer(s): PCL-b-PEG-b-PCL dimethacrylate | Covalent | Enzymatic (lipase) Hydrolytic | Chondrocytes139 |
| Initiator: Irgacure 2959 | ||||
| Macromer(s): PEG-(poly(glycerol succinic acidmethacrylate4))2 | Covalent | Hydrolytic | Chondrocytes37 | |
| Initiator: Eosin-Y, NVP, triethanolamine | ||||
| Macromer(s): OPF and NVP | Covalent | Hydrolytic | Chondrocytes126 | |
| Initiator: Irgacure 2959 | ||||
| Polyfumarate based | Macromer(s): poly(lactide-co-ethylene oxide-co-fumarate) and MMP-diacrylate | Covalent | Hydrolytic Enzymatic (MMPs) | Bone marrow stromal cells133 |
| Initiator: APS/TEMDA | ||||
| Macromer(s): poly(ethylene glycol) di-[ethyl phosphatidyl (ethylene glycol) methacrylate] | Covalent | Hydrolytic | Goat MSCs51 | |
| Initiator: Irgacure 2959 | ||||
| Phosphoester | Macromer(s): poly(6-aminohexyl propylene phosphate)-acrylate | Covalent | Hydrolytic | Goat MSCs125 |
| Initiator: Irgacure 2959 |
Studies published prior to 2005 were not included.
Degradation may also occur via hydrolysis.
In addition to Borax, gel also forms crosslinks between amine groups on gelatin and dialdehyde groups on alginate.
Not confirmed.
APS: ammonium persulfate; TEMDA: N,N,N′,N′-tetramethylethylenediamine; PEG: poly(ethylene glycol); HA: hyaluronic acid; Irgacure 2959: 2-hydroxy-1-[4-(hydroxyethoxy) phenol]-2-methyl-1-propanone; ECM: extracellular matrix; MSCs: mesenchymal stem cells; MMPs: metalloproteinases; DMEM: Dulbecco's modified Eagle's medium; ELP: Elastin-like peptides; PLA: poly(lactic acid); PCL: poly(8-caprolactone); NVP: N-vinylpyrrolidone; OPF: oligo(polyethylene glycol) fumarate.