title: In SituEvaluation of Calcium Phosphate Nucleation Kinetics and Pathways during Intra- and Extrafibrillar Mineralization of Collagen Matrices.
abstract: We revealed that nucleation sites within collagen fibrils determined pathways for calcium phosphate (CaP) nucleation and its transformation, from amorphous species to crystalline plates, during the biomineralization process. Usingin situsmall-angle X-ray scattering (SAXS), we examined the nucleation and growth of CaP within collagen matrices and elucidated how a nucleation inhibitor, polyaspartic acid (pAsp), governs mineralization kinetics and pathways at multiple length scales. Mineralization without pAsp led initially to spherical aggregates of CaP in the entire extrafibrillar spaces. With time, the spherical aggregates transformed into plates at the outermost surface of the collagen matrix, preventing intrafibrillar mineralization inside. However, mineralization with pAsp led directly to the formation of intrafibrillar CaP plates with a spatial distribution gradient through the depth of the matrix. The results illuminate mineral nucleation kinetics and real-time nanoparticle distributions within organic matrices in solutions containing body fluid components. Because the macroscale mechanical properties of collagen matrices depend on their mineral content, phase, and arrangement at the nanoscale, this study contributes to better design and fabrication of biomaterials for regenerative medicine.
authors.affiliation: Department of Energy, Environmental & Chemical Engineering, Washington University, St. Louis, Missouri 63130, United States.
authors.forename: Doyoon
authors.initials: D
authors.lastname: Kim
authors.affiliation: X-ray Science Division, Argonne National Laboratory, Argonne, Illinois 60439, United States.
authors.forename: Byeongdu
authors.initials: B
authors.lastname: Lee
authors.affiliation: Department of Orthopedic Surgery, Columbia University, New York, New York 10032-3072, United States.
authors.forename: Stavros
authors.initials: S
authors.lastname: Thomopoulos
authors.affiliation: Department of Energy, Environmental & Chemical Engineering, Washington University, St. Louis, Missouri 63130, United States.
authors.forename: Young-Shin
authors.initials: YS
authors.lastname: Jun