Biomimetic fibronectin/mineral and osteogenic growth peptide/mineral composites synthesized on calcium phosphate thin film
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1
Zhejiang Sci-Tech University, College of Life Sciences, China
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2
Yonsei University, Institute of Natural Sciences, Korea
Introduction: Hydroxyapatite (HA) and related calcium phosphates (CaPs) have good osteoconductive properties and bond to living bone through a carbonated hydroxyapatite layer formed on their surfaces. Although HA and CaPs coatings significantly enhance bond strength between tissues and implants, they have several potential drawbacks such as inhibition of osteoblasts in vitro and inadequate new bone formation at the healing site. Osteoinductive properties can be integrated into implants by immobilizing biomolecules to surfaces through processes such as adsorption, covalent binding and coprecipitation. The beauty of the coprecipitation is the ability to prepare mineral layers under mild conditions and the retention of biological activities of biomolecules. In addition, degradation of the precipitated mineral layers in vivo results in gradual exposure and controlled release of incorporated biomolecules.
Materials and Methods: In this study, we developed nano-structured thin calcium phosphate films on titanium substrates and used the deposited films as active layers to biomimetically induce mineral layer by immersing the as-deposited samples in a simple DPBS containing CaCl2. Fibronectin (FN) and osteogenic growth peptide (OGP) were coprecipitated with minerals. The as-deposited thin calcium phosphate film, biomimetically grown mineral, FN/mineral, and OGP/mineral layers were systematically investigated by ATR-FTIR, SEM, and XRD. Cross-sections of OGP spatial distribution were viewed by confocal microscopy at an excitation wavelength of 488 nm. The mechanisms underlying the incorporation of biomolecules into the mineral layer were also investigated.
Results and Discussion: minerals and biomolecule/mineral composites were evenly distributed on the entire surfaces of samples after 24 h in solution. Minerals exhibited plate-like, sharp edged and well-crystallized morphologies, while the FN/mineral and OGP/mineral composites were more rounded and exhibited less growth out of the substrate. The mineral or biomolecule/mineral layers were newly precipitated as two distinct layers, i.e., a dense sub layer of small and curved crystals, and a loose crystal layer that was grown from the under layer. The thicknesses of precipitated layers were 6.30, 3.75, and 4.32 μm for mineral, FN/mineral, and OGP/mineral samples, respectively. Side depth profile, which was obtained by stacking images through confocal microscopy, shows fluorescence throughout the precipitated layer. The patterns of mineral and OGP/mineral layers were indexed to a mixture of apatite and octacalcium phosphate (OCP). The XRD patterns of the FN/mineral coating were encountered with an exclusive apatite phase. The phases of OGP/mineral were partially transformed from OCP to apatite. The Rietveld refinement method provided reliable measurements of lattice parameter changes. The lattice parameter c of apatite was higher in the biomolecule/mineral samples than in the mineral samples. Compared to mineral samples, the lattice parameter a of apatite increased if FN was added to the DPBS, and decreased if OGP was added to the DPBS.
Conclusion: FN/mineral and OGP/mineral composite layers were biomimetically induced on an active calcium phosphate thin film in a rapid and efficient manner. The biomimetic coprecipitation process allowed biomolecules to be incorporated throughout the mineral layer, and influenced its growth as well as its ultimate structure. The percentage of apatite in the precipitated layer increased when biomolecules were added to the DPBS solution.
Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Republic of Korea (2012R1A1A2040717); National Natural Science Foundation of China (51272236, 51502265)
Keywords:
Biomimetic,
Surface modification,
Calcium phosphate,
bioactive interface
Conference:
10th World Biomaterials Congress, Montréal, Canada, 17 May - 22 May, 2016.
Presentation Type:
Poster
Topic:
Surface and interfacial characterization
Citation:
Chen
C,
Yao
C,
Ren
X,
Kong
X and
Lee
I
(2016). Biomimetic fibronectin/mineral and osteogenic growth peptide/mineral composites synthesized on calcium phosphate thin film.
Front. Bioeng. Biotechnol.
Conference Abstract:
10th World Biomaterials Congress.
doi: 10.3389/conf.FBIOE.2016.01.01998
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Received:
27 Mar 2016;
Published Online:
30 Mar 2016.
*
Correspondence:
Dr. Chenxue Yao, Zhejiang Sci-Tech University, College of Life Sciences, Hangzhou, China, Email1
Dr. Xiaoyuan Ren, Zhejiang Sci-Tech University, College of Life Sciences, Hangzhou, China, Email2
Dr. Xiangdong Kong, Zhejiang Sci-Tech University, College of Life Sciences, Hangzhou, China, Email3
Dr. In-Seop Lee, Zhejiang Sci-Tech University, College of Life Sciences, Hangzhou, China, Email4