Sodium Alginate Bioprinting

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Sodium alginate is a naturally derived biomaterial that can be chemically crosslinked with calcium chloride to create cell-laden hydrogels. These reagents are used in a variety of applications including bioprinting. The recommended preparation provided in the user instruction below yields a streamlined matrix bioink that supports 3D printed cell-laden constructs. As sodium alginate cannot support itself before it is crosslinked, we recommend using Pluronic F127 as a sacrificial support. However, users can modify the preparation to suit their needs. Read on to learn the methods of sodium alginate bioprinting.

Figure 1: Live/dead images of human neonatal dermal fibroblasts encapsulated in 2% alginate (left) and a piece of a bioprinted cell-laden 2% alginate ring after 7 days of culture (right).

Storage and Handling

  • Sodium Alginate should be stored at 4ºC in an airtight container.
  • Calcium Chloride should be stored at room temperature in a dry environment.

You Will Need

Instructions for Use

Prepare the Sodium Alginate

  1. Dissolve 2% or 5% (w/v) sodium alginate in media without calcium or magnesium under stirring at 60°C. Regularly check and mix with spatula to speed up process. (Sodium alginate may be dissolved up to 24-48 hours in advance of use.)
  2. *Sterile filter sodium alginate with a 0.45 µm filter into a sterile container.
  3. Allow solution to reach 37°C. Mix in desired cell type and concentration. Be sure to pipette vigorously to achieve a homogenous solution.

Prepare Calcium Chloride solution

  1. Dissolve 100 mM (0.011 g/ml) concentration of calcium chloride in deionized water. (Calcium chloride solution may be made 24-48 hours in advance of use.)
  2. You will need enough calcium chloride to be able to submerge your samples.
  3. *Sterile filter calcium chloride solution with a 0.22 µm filter into a sterile container.

Prepare FRESH

For use with alginate, you will suspend FRESH in 0.1 wt% CaCl₂ solution as noted in our protocol on how to prepare FRESH.

Print Settings

Layer Height (mm)Speed (mm/s)Pressure (PSI)Temperature (°C)NeedleCrosslinking
Alginate (2%)0.1567.5RT0.25″ straight 30GChemical (CaCl2)
Alginate (5%)0.15615RT0.25″ straight 30GChemical (CaCl2)

Post-print settings

  1. While printing, heat the sterilized solution of CaCl2 to 40-50°C.
  2. After the printing has finished, crosslink the finished structures in the heated solution. Crosslink for 15 minutes at room temperature. This will melt the FRESH while chemically crosslinking the alginate.
  3. After crosslinking samples, wash each structure 3 times with PBS, then add media.
  4. Incubate as needed.

* If not using cells, sterile filtering steps may be skipped.

Notes

  1. Adjust gelation time and gel stiffness by varying the concentration of alginate and calcium chloride as well as the crosslinking time. For help adjusting print parameters please contact [email protected].
  2. A fill volume change of more than 2 mL may affect pressure settings.

Further Information

For further questions about sodium alginate bioprinting or information about these products, please contact [email protected].

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