For diffusion modelling of calcium crosslinking in the MGS-1 alginate gel, we will measure the difference in weight and calculate absorbed calcium chloride volume over different crosslinking times.
Materials & Methods
Materials
100 mM calcium chloride
3wt% alginate solution
20wt% 425 µm MGS-1
3.5wt% CMC
Spatula
2 x 1 mL syringe
12 x 5 mL glass vials
red food colouring
disposable transfer pipette Methods
Make 10 mL of 20wt% earth sand, 3.5wt% CMC and 3wt% alginate gel by following procedure listed in Bioink Composition Testing
Load 1 mL of the MGS-1 gel into a 1 mL syringe and extrude into 6 vials
ensure there are no bubbles, tap the vial down after extruding to ensure the top surface is flat
Label each vial with 2, 5, 10, 15, 20, and 60 minutes respectively
Repeat steps 1-3 but load pure 3wt% alginate
In 15 mL of 100 mM calcium chloride solution, add ~2 drops of red food colouring and mix
Weigh each vial and record the initial mass
Pipette 1 mL of the red 100 mM calcium chloride solution into each vial
Start a timer for crosslinking based on the labelled time
Remove the calcium chloride solution using a disposable transfer pipette after 2, 5, 10, 15, 20, and 60 minutes of crosslinking (based on the vial)
ensure not to disturb the gel
Weigh the vial again and record the final mass
Calculate the volume of calcium chloride absorbed for each time point by using the below formula and a calcium chloride density of 1.007 g/mL
Graph crosslinking time vs. volume of calcium chloride absorbed
Volume=pCaCl2Final weight - Initial weight
Results
Figure 1. Vials containing 1 mL MGS-1 gel and 1 mL red calcium chloride solution
Table 1. Weight measured in grams.
Time (minutes)
MGS-1 gel initial mass
MGS-1 gel final mass
2
7.1689
7.1956
5
7.1273
7.1598
10
7.2991
7.3387
15
7.2609
7.3018
20
7.2654
7.3165
60
7.2181
7.2703
Figure 2. Resulting graph for MGS-1 gel calcium chloride volume absorbed.
20 mins vs 60 mins crosslinking have very minimal volume difference
Red solution observed on the surface of the gel, but no visible diffusion
Summary
Seeing a trend of increased volume absorbed with increasing crosslinking time
No significant difference in volume absorbed in 20 mins vs 60 mins crosslinking, suggesting that longer than 20 minutes of submerging in calcium chloride may not make a difference in crosslinking
MGS-1 composition may be hindering calcium diffusion as volume absorbed is a lot less than earth sand and pure alginate gels
Hand off
The obtained data will be fitted against our theoretical diffusion model
