Interaction of carbon nanoparticles to serum albumin: elucidation of the extent of perturbation of serum albumin conformations and thermodynamical parameters.

Carbon nanoparticles continuously generated from industries and vehicles due to incomplete combustion of fuels is one of the potent causes of air pollution. The exposure of this polluted air with carbon nanoparticles, introduced into the bloodstream of animals in the course of respiration, motivated us to study their interaction with plasma proteins, bovine serum albumin and human serum albumin. Carbon nanoparticles with very small size and high purity were synthesized by dehydration of d-glucose using concentrated sulphuric acid as dehydrating agent. These were characterized by transmission electron microscopy, atomic force microscopy, X-ray diffraction, Raman spectroscopy, FTIR spectroscopy and UV-visible spectroscopy. Carbon nanoparticles-protein interactions were studied by fluorescence spectroscopy, circular dichroism spectroscopy and isothermal titration calorimetry. The fluorescence quenching constants and thermodynamic parameters such as enthalpy change (ΔH°), entropy change (ΔS°) and free energy change (ΔG°) were calculated, which indicated a strong static quenching and primary electrostatic interaction between the carbon nanoparticles and blood proteins. Circular dichroism spectra provided the information about the secondary structure alteration of the proteins in presence of carbon nanoparticles. These findings have shed light towards an understanding of the interactions between carbon nanoparticles and serum proteins which may clarify the potential risks and undesirable health effects of carbon nanoparticles, as well as the related cellular trafficking and systemic translocation.