Diamines and aminoalcohols: neutral solvents for native collagen

A substantial fraction of interstitial collagens (types I, III, V and VI) can be dissolved from finely divided, connective tissues by homogenization in 0.5-1 M ethylene diamine and certain other organic amines neutralized by hydrochloric or other acids to pH 7-8.5. The amount of collagen solubilized from the tendons and other tissues of young animals is similar to that extracted by dilute acetic acid. In ethylene diamine hydrochloride solutions, native type I collagen denatures at 38 degrees and it has a sedimentation coefficient similar to that measured in acidic citrate solutions. From these amine hydrochloride solutions native collagen fibrils can be regenerated simply by tenfold dilution with water or by dialysis. The form of these precipitates is determined by temperature, pH, enzyme pretreatment of the collagen, and the dialysate salt concentrations and composition. Weak gels can be formed with less than 0.1 mg collagen per ml. Regenerated matrices containing types V and VI collagens, and with different fibril sizes can be used to support cell growth or to form sheets or hydrated gels possibly suitable for prosthetic uses.