Biomimetic hydroxyapatite nanocrystals in composites with C60 and Au-DNA nanoparticles: IR-spectral study

Due to growing interest towards development so-called 'smart biomaterials'-mainly composites with targeted biological action consisting of inorganic nanoparticles and organic compounds-the primary tasks in this field include synthesis of proper nanoparticles and studying chemical interaction between them and organic constituents. Exactly such kind of research is the object of this study - synthesis of composites in the system HAP:DNA:Au:C60:H2O including components of this system-composites HAP:DNA:Au:H2O, DNA:Au:H2O, HAP:C60:H2O, HAP:BSF, C60:H2O and studying chemical interaction in this system by comparison of IR spectra. All materials in this system are typical ingredients of smart biomaterials. The HAP nanocrystals were synthesized by chemical synthesis in a biomimetic route, all other materials were acquired on the market. We chose the simplest method of the composite synthesis-by mixing at room temperature. Comparative study of IR spectra of these composites revealed the considerable distortion, shifting or full disappearance of some absorption bands of the components of the composites. The largest alterations were found in the range of deformation vibrations and they are different for different modes of vibrations. In the range of valence vibrations the components' absorption bands are mostly preserved. These features are the ample evidence of chemical interaction between these components. Identification of the absorption bands that were changed most of all indicates the chemical bonds which directly participate in the chemical interaction. For example loss of the DNA absorption band at wave number 1704 cm-1 can serve as indication of new chemical bond with this part of the DNA molecule, namely C=O bond in thymine. The spectra alteration and their dependence vs. components concentration in the system HAP-DNA reveal that the HAP nanoparticles supposably are localized due to interaction with DNA molecules and that results in significant alteration of the spectra of DNA deformation vibrations. When DNA concentration increases the surplus of DNA molecules cannot interact with HAP and their spectrum is not changed. Thus there is something like threshold effect for the spectra's dependence vs. HAP concentration. The obtained results proved high efficiency of IR spectroscopy to study such kind of composite materials but unambiguous identification of every absorption band in the composites' spectra demands special experiments coupled with thorough calculations.