title: Nanostructured hydroxyapatite surfaces-mediated adsorption alters recognition of BMP receptor IA and bioactivity of bone morphogenetic protein-2.
abstract: Highly efficient loading of bone morphogenetic protein-2 (BMP-2) onto carriers with desirable performance is still a major challenge in the field of bone regeneration. Till now, the nanoscaled surface-induced changes of the structure and bioactivity of BMP-2 remains poorly understood. Here, the effect of nanoscaled surface on the adsorption and bioactivity of BMP-2 was investigated with a series of hydroxyapatite surfaces (HAPs): HAP crystal-coated surface (HAP), HAP crystal-coated polished surface (HAP-Pol), and sintered HAP crystal-coated surface (HAP-Sin). The adsorption dynamics of recombinant human BMP-2 (rhBMP-2) and the accessibility of the binding epitopes of adsorbed rhBMP-2 for BMP receptors (BMPRs) were examined by a quartz crystal microbalance with dissipation. Moreover, the bioactivity of adsorbed rhBMP-2 and the BMP-induced Smad signaling were investigated with C2C12 model cells. A noticeably high mass-uptake of rhBMP-2 and enhanced recognition of BMPR-IA to adsorbed rhBMP-2 were found on the HAP-Pol surface. For the rhBMP-2-adsorbed HAPs, both ALP activity and Smad signaling increased in the order of HAP-Sin<HAP<HAP-Pol. Furthermore, hybrid molecular dynamics and steered molecular dynamics simulations validated that BMP-2 tightly anchored on the HAP-Pol surface with a relative loosened conformation, but the HAP-Sin surface induced a compact conformation of BMP-2. In conclusion, the nanostructured HAPs can modulate the way of adsorption of rhBMP-2, and thus the recognition of BMPR-IA and the bioactivity of rhBMP-2. These findings can provide insightful suggestions for the future design and fabrication of rhBMP-2-based scaffolds/implants.
  
  
  CONCLUSIONS
  This study provides strong evidences that nanoscaled HAPs yield extraordinary influence on the adsorption behaviors and bioactivity of rhBMP-2. It has been found that the surface roughness and crystallinity played a crucial role in governing the way of rhBMP-2 binding to HAPs, and thus the conformation, recognition of BMPR-IA and bioactivity of adsorbed rhBMP-2. It is also for the first time to correlate numerical modeling and experimental results of the bioactivity of rhBMP-2 on nanostructured HAPs. This work can pave an avenue for the wider uses of rhBMP-2 in clinical applications and arouse broad interests among researchers in the fields of nano-biotechnology, biomaterials and bone tissue engineering.
authors.affiliation: The State Key Laboratory of Bioreactor Engineering and Key Laboratory for Ultrafine Materials of Ministry of Education, East China University of Science and Technology, Shanghai 200237, PR China; School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology, 2 George St, Brisbane, QLD 4001, Australia.
authors.forename: Baolin
authors.initials: B
authors.lastname: Huang
authors.affiliation: The State Key Laboratory of Bioreactor Engineering and Key Laboratory for Ultrafine Materials of Ministry of Education, East China University of Science and Technology, Shanghai 200237, PR China. Electronic address: yyuan@ecust.edu.cn.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Yuan
authors.affiliation: The State Key Laboratory of Bioreactor Engineering and Key Laboratory for Ultrafine Materials of Ministry of Education, East China University of Science and Technology, Shanghai 200237, PR China.
authors.forename: Sai
authors.initials: S
authors.lastname: Ding
authors.affiliation: Institute of Nano- and Bio-polymeric Materials, School of Material Science and Engineering, Tongji University, Shanghai 200092, PR China.
authors.forename: Jianbo
authors.initials: J
authors.lastname: Li
authors.affiliation: Institute of Nano- and Bio-polymeric Materials, School of Material Science and Engineering, Tongji University, Shanghai 200092, PR China.
authors.forename: Jie
authors.initials: J
authors.lastname: Ren
authors.affiliation: Key Laboratory of Advanced Technologies of Materials, Ministry of Education, School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu 610031, PR China.
authors.forename: Bo
authors.initials: B
authors.lastname: Feng
authors.affiliation: School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology, 2 George St, Brisbane, QLD 4001, Australia.
authors.forename: Tong
authors.initials: T
authors.lastname: Li
authors.affiliation: School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology, 2 George St, Brisbane, QLD 4001, Australia.
authors.forename: Yuantong
authors.initials: Y
authors.lastname: Gu
authors.affiliation: The State Key Laboratory of Bioreactor Engineering and Key Laboratory for Ultrafine Materials of Ministry of Education, East China University of Science and Technology, Shanghai 200237, PR China. Electronic address: liucs@ecust.edu.cn.
authors.forename: Changsheng
authors.initials: C
authors.lastname: Liu
mesh_terms: D000327:Adsorption; D001665:Binding Sites; D055396:Bone Morphogenetic Protein 2 / Q000008:administration & dosage* / Q000737:chemistry*; D052005:Bone Morphogenetic Protein Receptors, Type I / Q000737:chemistry*; D020099:Coated Materials, Biocompatible / Q000138:chemical synthesis*; D004058:Diffusion; D017886:Durapatite / Q000737:chemistry*; D008422:Materials Testing; D062105:Molecular Docking Simulation; D056004:Molecular Dynamics Simulation; D053769:Nanocapsules / Q000737:chemistry* / Q000648:ultrastructure; D010316:Particle Size; D011485:Protein Binding; D013499:Surface Properties
chemical_list: C525718:BMP2 protein, human; D055396:Bone Morphogenetic Protein 2; D020099:Coated Materials, Biocompatible; D053769:Nanocapsules; D017886:Durapatite; D052005:Bone Morphogenetic Protein Receptors, Type I
keywords: Adsorption; BMP-2; Bioactivity; Hydroxyapatite; Molecular dynamics