Plasmonic Imaging Of Real Time Protein Interactions With Single Multi-walled Carbon Nanotubes

The peculiar geometry of carbon nanotubes gives it many unique properties,such as extraordinary stiffness,tensile strength,high electric conductivity,cell penetration and biocompatibility,which makes carbon nanotubes have a broad range of applications in electronics and medical field.As nanomedicine develop rapidly in recent years,there has been an explosion of interest in use of carbon nanomaterials in molecular transporters as its natural match to biomolecules,applied it in the transportation of drug molecules.When nanomaterials enter the body,once contact with biological milieu,such as blood,it will interact with various blood constituents,then it changes the property of nanomaterials itself due to the self-assembly and layering of proteins onto nanomaterials surface,eventually forms the structure of bio-corona spontaneously.This'bio-transformation' of nanomaterials on surface modulates their overall pharmacological and toxicological profile and their potential therapeutic or diagnostic functionality in a rather unpredictable manner.At present,the research on the interaction between carbon nanotubes and proteins is still in the basic stage.The analysis of its kinetic process mostly uses conventional SPR spectroscopy,which is based on the average kinetics process of a large number of carbon nanotubes.The individual differences between different carbon nanotubes are ignored and real-time imaging analysis is impossible to achieve by this method.For the study of the interaction between single carbon nanotube and protein,the most common technique is the total internal reflection microscope(TIRF)which uses the fluorescent labelled analyte molecules combine to the surface receptor.The combination of situation is determined by observing the intensity of the surface fluorescent complexes.However,due to the use of fluorescent labels,the preparation process is cumbersome.the fluorescent label also affects the actual binding of the molecules,and there is the disadvantage that the fluorescence may be quenched under long-term observation.Above all,we applied surface plasmon resonance imaging technique on microscopy to research real-time label-free the binding process of two different modified groups(COOH?NH2)on single carbon nanotubes with wheat germ agglutinin(WGA),bovine serum albumin(BSA)and immunoglobulin G(IgG)in phosphate buffered saline(PBS)and record the sequential images of surface plasmon resonance.The results show that there is discrepancy on binding kinetics in different single carbon nanotubes interacting with same protein.This phenomenon usually get neglected by conventional surface plasmon resonance spectrum,which usually just reveals the average level of a large amount of carbon nanotubes.We determine the binding rate constant,dissociation rate constant and equilibrium constant of different single carbon nanotubes;Aimed to the same modified group on carbon nanotubes(MWNT-COOH),we conclude that binding rates with different protein has big difference,usually BSA>WGA>IgG;Besides,aimed to the WGA binding on carbon nanotubes,the modified groups on carbon nanotubes also influence the binding of protein,usually with c:arboxyl group quicker than amino group,which may affected by hydrophobicity and charges on surface of carbon nanotubes.In addition,for the amino carbon nanotube SPR chip,the two parameters of amplitude and power spectral density are used to analyze in qualitative the random vibration of MWNT-NH2 in PBS solution,water and protein solution,and we also explore the factor of ionic strength on MWNT-NH2 vibration.The results show that the slope of the power spectral density in the aqueous solution is-0.7-0.9,and the vibration amplitude of the amino carbon nanotubes in the solution becomes smaller after the addition of the protein solution.As the ionic strength increases,the amplitude also increases.In conclusion,the work in this essay emphasizes the functionality and reliability of applying surface plasmon resonance imaging technique on the detection and analysis of protein interactions with single nanotubes,and provide the supporting information of analyzing 'bio-transformation' of nanomaterials on surface in toxicology from dynamic process perspective.In addition to prove the high speed and simplicity of label-free surface plamon resonance imaging technique on detection and analysis,which offers us a big prospect on pharmaceutical industry.