A novel collagen hydrogel cross-linked by gamma-ray irradiation in acidic pH conditions

Abstract

We made a new type of collagen gel by gamma-ray irradiation of an acidic solution of type-I collagen, and performed comparative studies on a conventional gel and the new type of gel. The neutral gel, a conventional 0.3% (w/v) collagen gel, was formed at neutral pH and then irradiated by gamma-rays. The acidic gel, a 0.3% (w/v) collagen gel, was formed directly from the acidic solution of collagen by y-ray irradiation. Both types of gel were prepared, swollen in water and then dried for the measurement of specific water content. The neutral gel showed a relatively high specific water content and shrunk moderately, depending on the dose, while the acidic gel showed lower specific water content and shrunk clearly by y-ray irradiation. A three-dimensional tangled network of microfibrils was clearly observed in the neutral gels by scanning electron microscopy, but not in the acidic gels. From these results, we concluded that the acidic gel was quite different from a conventional collagen gel. Sodium dodecylsulfate-polyacrylamide gel electrophoresis showed that the alpha1 subunit and alpha2 subunit of the collagen molecule were cross-linked. The triple-helical structure of collagen was only partially perturbed, but not denatured completely, because the circular dichroism spectrum of the collagen solution irradiated at 1.3 kGy was similar to that of native collagen solution. Amino-acid analysis revealed that tyrosine, phenylalanine and histidine decreased by irradiation in the neutral gel. In the case of the acidic gel, these three amino acids and methionine decreased. We considered that these amino acids were cross-linking points between the collagen subunits during the gamma-ray irradiation.

Studies on fish scale collagen of Pacific saury (Cololabis saira)

“…Samples were coated with platinum using ion-sputtering equipment (E1010, Hitachi, Tokyo, Japan). Fine structures on the outer and inner sides of the scales were observed using a Hitachi SU1510 SEM [24,25].…”

“…The gel was wrapped in plastic film, frozen for 10 min at − 80°C in a deep freezer, and lyophilized in a freeze dryer overnight. The sample then was coated with platinum and observed by SEM as described above [24,25].…”

“…CD spectra of the collagen samples were measured using a CD spectrophotometer (J-720, Jasco, Tokyo, Japan) [24]. Collagen was diluted in 0.2 M sodium phosphate buffer (pH 7.4) to a concentration of 0.1% (w/v).…”

“…Mechanical strength of the scale collagen gels seemed to be far lower than that of the porcine collagen gel, because the scale collagen gels were rather soft and fragile. Firm hydrogel was formed when the porcine collagen was used in the same experimental procedure [24,25]. The collagen gels of the red sea bream (Fig.…”

Polymerized Structure and Improved Physical and Biochemical Material Properties of Carboxymethyl Dextran-Conjugated Collagen

“…Irradiation by ultraviolet (UV), 1) -ray, 2) and electron beam, 3) and treatment with watersoluble carbodiimide 4,5) and transglutaminase 5,6) have been applied to increase the mechanical strength and reduce the solubility by cross-linking among collagen molecules. Control of collagen matrix reconstruction with non-collagenous substances interacting with collagen has also been extensively studied to provide combined collagen materials with improved functional properties.…”