title: [Preparation of vanilline cross-linked rhBMP-2/chitosan microspheres and its effect on mesenchymal stem cells].
abstract: OBJECTIVE
  To prepare rhBMP-2/chitosan microspheres (rhBMP-2 CMs) with vanilline as a cross-linking reagent and study the biocompatibility and drug release characteristic of microspheres in vitro.
  
  
  METHODS
  Emulsion cross-linking method was utilized to prepare rhBMP-2 CMs, Scanning electron microscope (SEM) was used to observe the microstructure of microspheres.Leaching solution of microspheres and blank culture medium were designated as experimental and control groups respectively. Both groups were cultured with human mesenchymal stem cells (hMSCs) to determine its cytotoxicity and its effect on the proliferation of hMSCs. Dynamic immersion method was used to examine the in vitro release characteristic of rhBMP-2. And the alkaline phosphatase (ALP) activity of hMSCs was determined to reveal the bioactivity of released rhBMP-2.
  
  
  RESULTS
  The rhBMP-2 CMs were spherical under SEM.After treating with leaching solution for 24 and 48 h, there was no inter-group statistical difference in optical density (OD) values at both timepoints (24 h:0.72 ± 0.07 vs 0.73 ± 0.05, P > 0.05; 48 h:1.19 ± 0.11 vs 1.27 ± 0.06, P > 0.05). After culturing with leaching solution for 1, 3 and 7 days, the number of cells increased with time for both groups. And the OD values were not statistically different at each timepoint. Five milligram rhBMP-2 CMs soaked for 19 days with a gradual release of rhBMP-2. The concentration of rhBMP-2 was 216.1 ± 20.0 ng/ml at Day 19. At Days 3 and 7, the ALP activities of hMSCs were (0.50 ± 0.07) and (0.68 ± 0.06) µmol pNPP·min⁻¹·mg⁻¹ protein respectively and both were higher than that of blank culture medium group (0.14 ± 0.01) (P < 0.05).
  
  
  CONCLUSIONS
  With an excellent biocompatibility, rhBMP-2 CMs may be an ideal carrier for control-released rhBMP-2 and encapsulated rhBMP-2 remains bioactive.
authors.affiliation: Department of Orthopedic Surgery, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100730, China.
authors.forename: Gui
authors.initials: G
authors.lastname: Wu
authors.forename: Hai
authors.initials: H
authors.lastname: Wang
authors.forename: Guixing
authors.initials: G
authors.lastname: Qiu
authors.forename: Xin
authors.initials: X
authors.lastname: Yu
authors.forename: Xinlin
authors.initials: X
authors.lastname: Su
authors.forename: Pei
authors.initials: P
authors.lastname: Ma
authors.forename: Bo
authors.initials: B
authors.lastname: Yin
authors.affiliation: Email: wuzh3000@126.com.
authors.forename: Zhihong
authors.initials: Z
authors.lastname: Wu
mesh_terms: D055396:Bone Morphogenetic Protein 2; D048271:Chitosan; D006801:Humans; D059630:Mesenchymal Stem Cells; D008863:Microspheres; D011994:Recombinant Proteins
chemical_list: C525718:BMP2 protein, human; D055396:Bone Morphogenetic Protein 2; D011994:Recombinant Proteins; D048271:Chitosan