You may find useful to check: https://www.researchgate.net/post/How_to_dissolve_powder_collagen_with_acetic_acid

Thanks Carlos.

Dear Ratima Suntornnond,

You may try using low concentration of HCl at chiller temperature, 24 hours. Thanks

Thanks Fauzi.

Collagen is completely soluble in 0.1 M acetic acid prepared in sterile H2O after steering 1-3 hrs at room temperature.

Thanks Jasim

hello ratima

the isoelectric point of collagen is 4.7, and 0.1M acetic acid has the pH=2.88, so collagen in this acid has a positive net charge and is completely soluble. put the mixture of acid and collagen powder on stirrer in refrigerator an overnight, this help to solve collagen. but finally i insisted recommend dont use this concentration, and this friendly advise has many reasons. to reduce the errors and increase repeatability use lower concentration of collagen solution. for more information i recommend a useful review paper to you:

Article Review of Collagen I Hydrogels for Bioengineered Tissue Micr...

best regard.