I need to decrease the temperature of homogeneous gelatin solution nearly 0 before adding cross-linker. But I have trouble. Because at low temperatures gelatin becomes solid and I can't add cross-linker. Could you please help me to cope with this problem?
To achieve this the chemical characteristics of gelatin should appropriately modified. How? It is a research question "if" at least one method hasn't been yet reported by some researchers. Similar strategies has been applied for several other polymers; thus, it would be good to search those papers to see their details.
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In some of the articles they are using acetic acid as a solvent instead of water. Can it be the reason? But mainly they don't mention about it. They are making a homogeneous solution at 50-60 C and decrease the temperature. Then they add crosslinker. But how they are mixing them they don't say.
Regards,
Burcu
The reason of using acetic acid as a solvent is the pH-dependent solubility characteristics of the polymer. Mixing might be performed for the entire solution prior molding in the case of a very slow crosslinking process; if the crosslinking is fast then the crosslinker is introduced into the portion of the solution that is already in the molds. Nevertheless, in my first reply, I meant, reacting the gelatin with another substance to obtain a modified material with tailored solubility features.
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Hi. Once I added glutarhaldehyde to a gelatin solution under stirring at room temperature and immediately quenched the sample in liquid nitrogen. The sample was lyophilized and stored at -80 C. In this way the cross linking was prevented and started only when the sample was thawed again. Quenching must be done very fast but the sample must also be well stirred for homogeneous post cross linking. This was the only critical step, but I reached some good results. Maybe -20 C could be still sufficient for blocking the crosslinking.
May this info be helpful to you?
It is very helpful thank you very much Serena. Also I saw that they are decreasing the temperature of glutaraldehyde to +4 C before adding into gelatin solution. It made me think that they are blocking the activity of glutaraldehyde. But I was not sure. Your answer confirmed my thought.
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Burcu
Clever! I think the cross linking cannot be fully blocked at +4 C but can be slowed down al least. Additional reasons for introducing GTA at +4 C may include the better control of the cross linking kinetics.
:) In one of the article I read that they prepare gelatin and GTA solutions separately. Then they leave them at +4C for 1 hour. After 1 hour they put them at -20 for 5 minutes and then they mix 2 solutions on vortex. I tried to do this but it did not work. Because after 1 hour at +4C gelatin solution became solid. So I skipped that step and only leave it at room temperature as you mentioned. Next I put them at -20C for 5 mins and mixed. It worked better. Other wise they did not mention about how they prepared gelatin solution. They made a solution with the addition of acetic acid. But they did not say anything about heating. Is heating at 50-60C required to prepare a gelatin solution? Or only stirring is enough? Or both? I am also wondering about it.
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Burcu
As you said, you should apply both heating and stirring to get an aqueous solution from gelatin powder (e.g. Sigma). The results also depend on the final gelatin concentration, the higher the more difficult.
You never explained the final goal of your crosslinked solution, if it is to prepare a solid material (a film, a membrane, a scaffold...) you can dry the solution first (eg. freeze-dry) and crosslink the dried gelatin material later by exposure to GTA vapors. If this is your case, I can provide you a paper of ours.
Bye, S.
Yes Serena I am trying to make macroporous scaffold using cryogelation technique. I saw something about crosslinking with GTA vapor. But I am not sure about its applicability to cryogelation.I would be glad if you could provide.
Best
Burcu
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