The reaction of glutaraldehyde with dilute solutions of an acid-precursor gelatin
Curt Thies, Shirley Cuthbertson and Noble Yoshida
Materials Research, Central Research Division, The National Cash Register Co., Dayton, Ohio 45409, USA
Received 8 February 1968. Available online 6 July 2004.
The reaction of glutaraldehyde with acid-precursor gelatin has been studied at 40°C under dilute solution conditions ( 1.0% by weight gelatin) which yield watersoluble reaction products. An iodometric technique established that in 0.05 M acetate buffer, 0.90 ± 0.05 mmoles glutaraldehyde were consumed per gram gelatin over a pH range of 3.7–6.5. The initial reaction was rapid, but equilibrium glutaraldehyde uptake required several days. Glutaraldehyde consumption was reduced to 0.58–0.82 mmoles/gm gelatin by 0.05 M phthlate buffer and neutral salt ions.
Several physical characteristics of glutaraldehyde-gelatin reaction products were examined in order to characterize them more fully. Spectra of such products may have absorption maxima at 264, 436, and 526 mμ, but which of these three maxima are observed in a given case varied with pH and neutral salt ion concentration. Specific optical rotations of the reaction products were consistently only slightly less levorotatory (by +4 to +9°) than the original gelatin sample. Reduced viscosity of a glutaraldehyde-gelatin reaction mixture (40°C, pH 4.5) decreased initially. This decrease paralleled glutaraldehyde consumption determined directly and indicated a lack of intermolecular crosslinking. The constant viscosity observed after the decrease implies that the reaction product is resistant to hydrolytic degradation under the specified test conditions. Preliminary ultracentrifugation data indicate that reaction products formed at 40°C in phthalate buffer chemically crosslink when stored at 24°C in the presence of excess glutaraldehyde. This is not observed for reaction products formed in acetate buffer.