the alginate-based bioink either through the internal (bulky fibers)
or the external (hollow fibers) nozzle [20, 21].
Due to its reversible crosslinking nature, alginate-based bioinks
are generally blended with photocurable biopolymers—such as
gelatin methacrylate (GelMA), hyaluronic acid methacrylate
(HAMA), chondroitin sulfate 2-aminoethyl methacrylate
(CS-AEMA) [17], PEGylated(monoacrylate) fibrinogen [18],
etc.—that can be used to fabricate chemically crosslinked and stable
constructs after a short exposure to mild UV radiation (typically at
365 nm).
In the next sections, we will describe how to formulate tailored
alginate-based bioinks to engineer cartilage and skeletal muscle
tissue in vitro.
2 Materials
The synthesis of photo-crosslinkable derivatives of natural polymers
should be performed in a wet lab equipped with fume hoods and a
freeze drier.
2.1 Synthesis
of Gelatin
Methacrylate (GelMA)
and Hyaluronic Acid
Methacrylate (HAMA)
1. Gelatin (type A, 300 bloom) or hyaluronic acid (see Note 1).
2. Methacrylic anhydride (MA).
3. Round-bottom flasks.
4. Phosphate buffer saline (PBS).
5. Dialysis tubing (MWCO ¼ 2 kDa).
6. Deionized water (DIW).
2.2 Synthesis
of Chondroitin Sulfate
2-Aminoethyl
Methacrylate
(CS-AEMA)
1. Chondroitin sulfate.
2. 2-Aminoethyl methacrylate (AEMA).
3. 1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC).
4. N-Hydroxysuccinimide (NHS).
5. MES buffer: 50 mM 2-(N-morpholino)ethanesulfonic acid,
pH ¼ 6.5.
6. NaCl.
7. Deionized water (DIW).
8. Dialysis tubing (MWCO ¼ 2 kDa).
9. Round-bottom flasks.
2.3 Synthesis of
PEG(Monoacrylate)Fibrinogen
1. Fibrinogen (recombinant human).
2. Phosphate buffer: 50 mM PBS, pH 7.4.
3. PBS/urea solution: 50 mM PBS, 8 M urea.
Photocurable Biopolymers for Coaxial Bioprinting
47