[Background and Purpose] Atelocollagen (AC) is obtained by protease treatment of type I collagen, yielding a highly biocompatible, low-immunogenicity product that has been widely used as a scaffold for cell culture and transplantation. In previous work, we have reported that AC is as an excellent vehicle for the delivery of nucleic acids to cultured cells. AC solutions possess appealing gel-forming properties under physiological conditions, giving such solutions a high capacity for retention of physiologically active substances.

In our previous report at the 89th Annual Meeting of the Japanese Biochemical Society, we showed that the difference in binding force between AC and peptides with a variety of isoelectric points (pIs) correlates with sustained-release properties; notably, molecules with lower pIs were released more slowly from AC gels. In the present study, we investigated the sustained-release from AC gel of proteins with a variety of molecular weights (Mws) and of peptides with various pIs. The results of these analyses enhance our understanding of potential applications of AC as a carrier for physiologically active substances.

[Methods] Proteins were mixed with 0.1%, 0.5%, and 1.0% atelocollagen solution. The mixtures were gelated under physiological conditions and the release of proteins from the AC gel was measured over time.

[Results and Discussion] Under the electron microscope, higher concentrations of AC gel exhibited thicker network structures. These higher-concentration AC gels possessed increased capacity for protein retention. In parallel, proteins with similar pIs but higher Mw tended to be retained in the AC gel. This trend may reflect a molecular sieving effect by the network structure of the AC gel. These results suggested that the sustained release of proteins from atelocollagen gel can be estimated based on pI and Mw; proteins with collagen binding domains are expected to be retained for extended time periods. We believe that the sustained-release property of AC can be regulated, potentially making this product an effective carrier for use in cell culture, transplantation, and drug formulation.