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Study of polar and electrical properties of Hydroxyapatite: Modeling and data analysis

Authors:
Anna Bystrova
Anna Bystrova
Anna Bystrova
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Yuri Dekhtyar at Riga Technical University
Yuri Dekhtyar
Alla Sapronova
Alla Sapronova
Vladimir Sergeevich Bystrov at University of Aveiro
Vladimir Sergeevich Bystrov
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Abstract

The results are based on the first principal modeling and calculations for HAP nanostructures as native as well surface modified, charged and having various defects (H and OH vacancies, H inter-nodes). HAP structures were studied using Local Density Approximation (LOA) method with calculations of Density of States (DOS) allow us analyzes the experimental work function data. Molecular modeling by HyperChem is confirmed by photo-electron monochromatic measurements up 6.5 eV and photo-luminescence data from synchrotron DESY experimental data up 30 eV values. Brief analysis of the influence of heating, microwave radiation, hydrogenation, x-rays and synchrotron radiation on Hydroxyapatite (HAP) surface is presented in this work. New data of the structure of hydroxyapatite are obtained.
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 
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         
   
        
       
     
      
       
       
     
           
     
        
  
    

 
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       
         
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      
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         
        
      
       
      
        
        
       
       
         
  
  
     
 
 
    

     
       
           
     
       
       
           
        
        
        
      
   
  
 
        
        
  
   
         
        
       
         
       
       
        
       
       
          
       
        
        
        
 
  
         
       
     
    
  
 
 
       
        
       
     
      
    
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   
  
  
 
  
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
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 
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 
  
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         
        
         
         
           
 
       
        
          
 
        
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        
        
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 
        
          
        
          
      
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  
         
        
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         
       
       
   
    
        
        
     
          
       
   
        

          
      
   
       
         
         
        
       
        
      
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  
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 
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           
       
      
          
       
         
         
 
    
    
          
    
   

 
  
    
        
       
   
      




 

 
   


  


  




 
 
         
        
   
  

        
        
          

        
    
  
    
    
     
   

   
  
  
  
       
        
     

        
       
      

     
  
 

      

    

  
  
        

    
  
  
 
Modified Hydroxyapatite Structure and Properties: Modeling and Synchrotron Data Analysis of Modified Hydroxyapatite Structure
Article
Full-text available
  • Mar 2015
First principle modeling and calculations of hydroxyapatite both native and surface modified and having various defects (OH vacancies, H inter-nodes) were performed. Local Density Approximation method used with calculations of Density of States allows us to analyze the experimental obtained work function data. Molecular modeling was confirmed by photo-electron measurements up to 6.5 eV and photoluminescence experimental data from synchrotron DESY up to 30 eV. Brief analysis of the influence of heating, microwave radiation, hydrogenation, and synchrotron radiation on hydroxyapatite surface is presented in this work. New data on the structure of modified hydroxyapatite are obtained.
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Engineering of the Hydroxyapatite Cell Adhesion Capacity
Article
Full-text available
  • Jan 2013
The general adhesion theory is the fundament to explain cell attachment to a bioimlplant surface in a human body. Electrical potential of the surface could be employed to control attachment. The paper demonstrates that the electrical potential may be engineered due to hydrogenation of hydroxyapatite. Such the procedure enhance attachment of osteoblast and generation of tissue. The Sr and Si doped hydrohyapatite demonstrates higher ability to be engineered by hydrogenation in contrast with undoped and Ag doped materials.
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Application of calcium phosphate nanoparticles in biomedicine J
Article
Full-text available
  • Jan 2010
  • J MATER CHEM
Calcium phosphate has excellent biocompatibility due to its chemical similarity to human hard tissue (bone and teeth). In nanoparticulate dispersed form, it can be used as a carrier in biological systems, e.g. to transfer nucleic acids or drugs. If such nanoparticles are suitably functionalized with fluorescing dyes, they can also be used for imaging or for photodynamic therapy.
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Electronic states spectroscopy of Hydroxyapatite ceramics
Article
Full-text available
  • Jun 2007
Photoluminescence, surface photovoltage spectroscopy and high-resolution characterization methods (Atomic Force Microscopy, Scanning Electron Microscopy, X-ray spectroscopy and DC conductivity) are applied to nanostructured Hydroxyapatite (HAp) bioceramics and allowed to study electron (hole) energy states spectra of the HAp and distinguish bulk and surface localized levels. The measured trap spectra show strong sensitivity to preliminary heat treatment of the ceramics. It is assumed that found deep electron (hole) charged states are responsible for high bioactivity of the HAp nanoceramics.
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Structural Order and Dielectric Behaviour of Hydroxyapatite
Article
  • Jul 2005
Disorder of the OH ion orientation is inherent in the currently accepted structure of hydroxyapatite (HA), hexagonal P63/m. In the case of local ordering in the OH ion orientation, the resulting structure will be a monoclinic P21/b, with an alternate orientation of OH columns in the b-direction. Both of these proposed structures are electrically non polar and fail to explain the polarisation phenomena observed in HA. Here we report some theoretical considerations of structural order in HA and show that in addition to the non polar P21/b phase HA can also exist as a polar phase. Various physical properties including static dielectric constant and polarisation are simulated from empirical interatomic potential calculations and used to explain the observed dielectric anomaly in sintered hydroxyapatite.
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Computational and experimental studies of size and shape related physical properties of hydroxyapatite nanoparticles
Article
  • Feb 2011
In this work, the properties of hydroxyapatite (HAP) nanoparticles (NPs) have been studied both theoretically and experimentally focusing on computational analysis. HAP is widely used to fabricate implants, for drug delivery, etc. The physical properties of the nanosized HAP particles play an important role in the interaction with cells in the human body and are of great interest. Computer simulation was employed to understand the properties of HAP clusters (Ca(5)(PO(4))(3)OH) including formation energies, dipole moments and polarization (surface charges) by molecular mechanics (MM + , OPLS) and mostly by quantum semi-empirical Hartree-Fock (PM3) methods. The size of the simulated cluster is found to affect its dipole moment, polarization, and, finally, the electron work function- ϕ. These parameters depend on the concentration of hydrogen atoms H (or protons) at the surface. Values of ϕ were experimentally estimated via photoelectron emission measurements. The magnitude of ϕ was demonstrated to have a positive correlation on sizes. The NPs demonstrated a capability to be gathered within conglomerates. This property is confirmed by the calculated data for various sizes. Their sizes have a positive correlation on ϕ by the native particles. The main results show that the distributions of dipole moments have very different space orientations (along the OX, OY and OZ axes, the OZ axis is oriented along the OH column) and change with the addition of hydrogen atoms, which saturate the broken hydrogen bonds. This electrical property of NP leads to different behaviors and motions with consequent aggregation: (1) for the case of NPs having dipole moment oriented preferably perpendicular to the OZ axis (with more hydrogen bonds saturated by added H)-the HAP NP aggregates with hexagonal orientation and forms a wider and more spherical shape (sphere-like or bundle-like); (2) for the case of NPs having dipole moment oriented along the OZ axis (as is the case in the absence of added protons or non-saturated hydrogen bonds)-the NPs firstly rotated and oriented along this axis to form the most elongated cylindrical shape (rod-like).
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Interaction of charged hydroxyapatite and living cells. J. Hydroxyapatite polarization properties
  • V S Bystrov
  • N K Bystrova
  • E V Paramonova
  • Yu D Dekhtyar
  • Jan 2007
  • 865
  • D Aronov
D. Aronov, et al. -J. Mater. Sci.: Mater. Med., Vol. 18, p. 865, 2007.
  • Jan 2007
  • 431
  • N Y Mostafa
  • P W Brown
N. Y. Mostafa, P. W. Brown, J.Phys. Chem. Solids, vol. 68, p.431, 2007.