title: Ca2+-induced self-assembly ofBombyx morisilk sericin into a nanofibrous network-like protein matrix for directing controlled nucleation of hydroxylapatite nano-needles.
abstract: Bone biomineralization is a well-regulated protein-mediated process where hydroxylapatite (HAP) crystals are nucleated with preferred orientation within self-assembled protein matrix. Mimicking this process is a promising approach to the production of bone-like protein/mineral nanocomposites for bone repair and regeneration. Towards the goal of fabricating such nanocomposites from sericin, a protein spun byBombyx mori(B.mori) silkworm, and bone mineral HAP, for the first time we investigated the chemical mechanism underpinning the synergistic processes of the conformational change/self-assembly ofB.morisericin (BS) as well as the nucleation of HAP on the resultant self-assembledBSmatrix. We found thatBS, rich in anionic amino acid residues, could bind Ca2+ions from the HAP precursor solution through electrostatic attraction. The Ca2+binding drove the conformational change ofBSfrom random coils into β-sheets and its concomitant self-assembly into interconnected nanofibrous network-like protein matrix, which initiated the nucleation and growth of HAP crystals. HAP crystals directed by the resultant self-assembledBSmatrix grew preferentially along their crystallographic c-axis, leading to the formation of HAP nano-needles. The HAP nano-needles in the self-assembledBSmatrix were subsequently aggregated into globules, probably driven by the hydrogen bonding between C=O groups ofBSand O-H groups of HAP nano-needles. The present work sheds light on the chemical mechanisms ofBSself-assembly and the controlled mineralization directed by the self-assembled matrix. We also found that the resultant nanocomposites could promote the osteogenic differentiation of human bone marrow-derived mesenchymal stem cells. Thus our work also generates a biomimetic approach to bone-like silk protein/mineral nanocomposite scaffolds that can find potential applications in bone repair and regeneration.
authors.affiliation: Institute of Applied Bioresource Research, College of Animal Science, Zhejiang University, Yuhangtang Road 866, Hangzhou, Zhejiang 310058, China.
authors.forename: Mingying
authors.initials: M
authors.lastname: Yang
authors.affiliation: Institute of Applied Bioresource Research, College of Animal Science, Zhejiang University, Yuhangtang Road 866, Hangzhou, Zhejiang 310058, China.
authors.forename: Guanshan
authors.initials: G
authors.lastname: Zhou
authors.affiliation: Institute of Applied Bioresource Research, College of Animal Science, Zhejiang University, Yuhangtang Road 866, Hangzhou, Zhejiang 310058, China.
authors.forename: Yajun
authors.initials: Y
authors.lastname: Shuai
authors.affiliation: Institute of Applied Bioresource Research, College of Animal Science, Zhejiang University, Yuhangtang Road 866, Hangzhou, Zhejiang 310058, China.
authors.forename: Jie
authors.initials: J
authors.lastname: Wang
authors.affiliation: Institute of Applied Bioresource Research, College of Animal Science, Zhejiang University, Yuhangtang Road 866, Hangzhou, Zhejiang 310058, China.
authors.forename: Liangjun
authors.initials: L
authors.lastname: Zhu
authors.affiliation: Department of Chemistry & Biochemistry, Stephenson Life Sciences Research Center, University of Oklahoma, 101 Stephenson Parkway, Norman, Oklahoma 73019-5300, United States.
authors.forename: Chuanbin
authors.initials: C
authors.lastname: Mao