Hi everyone,

I have a question about accepted definitions of terminologies when it comes to hydrogels such as collagen, gelatin, alginate, etc. I have heard and read the two terms gelation and crosslinking used frequently, and sometimes seemingly interchangeably, and I wanted to know what other people thought. I have worked with several different hydrogels, but I don't think I have ever come to a concise definition for myself about what to call the process that took my hydrogel from solution to a gel. It seems to me that if I could call something a gel, that it arrived to that state via gelation?

When I take an acidic solution of rat tail collagen type I, raise the pH and bring it to above room temperature, I have called that process gelation, but I have been cautious about calling it crosslinking, since in my mind, crosslinking would occur if I added glutaraldehyde or maybe transglutaminase to the solution of collagen, thus creating covalent bonds between the individual collagen fibrils. When I have a solution of gelatin and put it in the fridge to solidify, I have called that gelation, but is it also gelation if I convert that gelatin into gelatin methacrylate and then apply UV in order to photopolymerize ? 

Is crosslinking a subset of gelation? I would appreciate any input. Thank you!