Assembly of collagen fibrillar networks in the presence of alginate

This study reports in vitro reconstitution of collagen–alginate blends with a wide range of alginate/collagen ratios, aiming at revealing the nanostructured fibrillar networks assembled at high collagen concentrations. The aggregation states of collagen monomeric solutions at varying concentrations from 1 to 7 mg/ml, in the absence or presence of alginate, were examined by using scanning electron microscopy and atomic force microscopy. Compared with collagen, the blends with increasing alginate/collagen ratios assembled into looser three-dimensional fibrillar networks interlaced by larger twisted fibrils which were irregular and dense aggregates of smaller fibrils with the normal banding periodicity. Typical turbidimetric assays revealed the different kinetics in presence of alginate and alginate-eluted quantitation further confirming the capturing of alginate in the collagen–alginate fibrillar networks. The electrostatic complexation between collagen and alginate was postulated to play a crucial role in this abnormal aggregation of collagen–alginate blends.