Synergistic intrafibrillar/extrafibrillar mineralization of collagen fibrils and scaffolds enhanced by introducing polyacrylamide to PILP for osteogenic differentiation

Mineralization can help improve the mechanical properties and degradation rates of collagen scaffolds while ensuring good biocompatibility, thereby providing a suitable microenvironment for osteogenic differentiation. Intrafibrillar/extrafibrillar mineralization of collagen is promoted by polymer-induced liquid precursors (PILP). In this study, polyacrylamide (PAM) was introduced to PILP which synergistically mineralized collagen scaffold intrafibrillarly and extrafibrillarly. PAM and polyacrylic acid (PAA) can stabilize the amorphous calcium phosphate (ACP), to form a PILP of PAM and PAA/ACP. As a control, another scaffold material was formed using the conventional mineralization method, that is, soaking collagen in a simulated body fluid. Collagen mineralization was characterized using SEM and TEM. After 7 days of mineralization with PILP, intrafibrillar crystallization of collagen was significantly higher than that in the control group, and the stiffness and modulus of this scaffold material significantly increased. Cellular experiment results indicated that the PILP-mineralized collagen scaffold was biocompatible and promoted the osteogenic differentiation of MC3T3-E1 pre-osteoblasts. Biomimetic mineralization by PILP will assist the fabrication of mineralized collagen scaffold for bone repair applications.