Discovery And Property Studies Of Carbon Nanoparticles In Mature Vinegar

Carbon nanoparticles(CNs)are a type of globoid dots with a size of less than 10 nm.Their skeletal structure is mainly formed by carbon element with plenty of functional groups on the surface of CNs.The CNs has wide-range fluorescence from near ultraviolet to near infrared.They have been widely used in bioinformatics,bioelectronics,biomedicine and other fields due to their good biocompatibility and light photo-stability,which has been become a new research hotspot.In recent years,raw materials of food undergo thermal decomposition and complex chemical reactions,result in the production of nano-scale CNs.Meanwhile,these CNs are different from conventional processing products,which have attracted extensive attention.As one of the traditional condiments in China,mature vinegar is indispensable in daily life of Chinese people.In this paper,the extraction and the physicochemical properties of CNs from mature vinegar were investigated,and the interaction between CNs and biomolecules was conducted to evaluate potential biological effects of CNs.The specific research contents and conclusions are as follows:(1)The water-soluble CNs were extracted from mature vinegar through separation and purification with macroporous resin and dialysis.The CNs aqueous solution emited bright blue fluorescence under ultraviolet light.The morphology of CNs was examined by TEM and found that the CNs were globoid with a particle size less than 5 nm.The fluorescent spectroscopy analysis showed that the fluorescence of CNs prossess the property of excitation-dependent emission.The results of ultraviolet-visable,FT-IR and XPS spectra showed that there was transition of n??* in CNs due to double bond in aromatic rings,and the surface of CNs contains a large number of functional groups such as hydroxyl,carbonyl and carboxyl.Cell proliferation assay showed the low cytotoxicity of CNs.(2)In the study of interaction between CNs and dopamine(DA),the fluorescence of CNs changed gradually from blue to green with increasing dopamine concentration.The size of CNs-FCs conjugate formed by CNs and DA decreased gradually as shown by TEM scanning.In addition,FT-IR and XPS spectra showed that the CNs were reactive towards DA,most likely due to the formation of imine through the Schiff base reaction.The emission spectrum of CNs overlaped with the excition spectrum of DA,and fluorescence decay dynamics revealed that F?rster resonance energy transfer(FRET)occurred between the CNs and polymerized dopamine.(3)In the study of interactions between CNs and human hemoglobin(HHB),fluorescence spectra showed the fluorescence of HHB quenched remarkably by CNs due to a static mode as revealed from temperature dependent and fluorescent lifetime studies.Synchronous fluorescence studies suggested that the alteration of the microenvironment occurred around the tryptophan residues.3-dimentional fluorescence and FT-IR data provided evidence for conformational changes in HHB upon binding with CNs,thus leading to the reduction in the ?-helical content of HHB as confirmed by circular dichroism(CD)spectroscopy.Atomic force microscope(AFM)studies revealed that the essential morphological features of HHB were slightly aggregated.The esterase activity of HHB decreased with the increase of CNs concentration.The binding was driven by large negative enthalpy change,which was favorable negative entropy change thorugh the calculation of thermodynamic parameter.The negative Gibbs energy proposed the reaction between CNs and HHB was spontaneous.Negative enthalpy change corroborated the involvement of hydrogen bonds or van der Waals forces in the binding process.