Biochemical Analysis Of Surface Functionalized Precious Metal Nanoclusters

Precious metal nanomaterials have attracted a wide range of research interests in materials science,environmental science,electronics,biology,biochemistry and medicine.Metal nanoclusters have become a new research hotspot in recent years because of their unique optical,electrical and magnetic properties.In this paper,the biological small molecules modified on the surface of nano-materials,on the one hand to improve the water-soluble nano-materials;the other hand,its surface functionalization,improve selectivity.In this paper,four different functionalized gold nanomaterials were designed for the specific identification of biomolecules,and the detection methods of sulfide,heparin and phosphate were established respectively.This article focuses on the following aspects:(1)Fluorescence detection of sulfur ions was carried out using glutathione-modified gold nanoclusters based on copper ions.It was found that the functional groups of GSH modified on the surface of gold nanoclusters could react on Cu2+.The divalent copper ions could complex with the mercapto groups in GSH,which caused the spectral changes and accompanied by fluorescence quenching,With the increase of the concentration of sulfur ions,the competition effect of sulfur ions and brine on copper ions,the fluorescence of gold nanoclusters is gradually restored.The change of fluorescence spectrum of GSH-AuNCs,fluorescence intensity and UV absorption spectrum are different in different order of addition of Cu2+ and S2-in Fig.2.4.So as to a switch pattern is designed for the detection of sulfur ions.The concentration of S2-in the range of 2.0 to 24.0 ?M and Cu2+-GSH-AuNCs system showed a good correlation.The detection limit of this method is 0.7 ?M.In addition,this method has been successfully applied to cell imaging and serum detection.(2)Based on heparin(Hep)inhibition of cetyltrimethylammonium bromide(CTAB)to promote the fluorescence enhancement of gold nanoclusters to establish a fluorescence detection of heparin.CTAB acts as a cationic surfactant to enhance the fluorescence enhancement of the gold nanoclusters by electrostatic interaction and hydrophobic self-assembly.Heparin is added to the assay because of its higher affinity for heparin,CTAB nanocomposites,quenching fluorescent signals.From the TEM(Fig.3.3),the particle size of the composite nanomaterials formed by GSH-AuNCs and CTAB was 3.41 nm,and the particle size of GSH-AuNCs was 1.64 nm,indicated that CTAB nanocomposites are formed.At the same time,the infrared spectrum,UV spectrum and Rayleigh scattering spectrum in Fig.3.4 can also show that the spectrum changes corresponding to the addition of CTAB and Hep to GSH-AuNCs.This simple self-assembly and disassembly using nanoclusters has designed a simple,highly selective and sensitive fluorescence assay for Hep.The theoretical detection limit for heparin in the range of 0.1 to 1.6 ?g / mL was 0.075 ?g / m L.(3)The inhibition of AuNPs aggregation by a variety of positively charged polyethyleneimine(PEI)was investigated.The UV energy and fluorescence spectra were used to detect the resonance energy transfer of AuNCs and AuNPs.According to the results of PEI-induced aggregation of AuNPs,AuNPs solution changed from wine red to blue,and a new absorption peak was generated at 610 nm,which overlapped with the emission peak of AuNCs because AuNCs and AuNPs could undergo electrostatic bridging role due to PEI fluorescence resonance energy transfer,resulting in photoluminescence weakened or even disappear;The addition of Hep,a strong electrostatic interaction with PEI,and stronger electrostatic interaction than PEI in Au-NPs and AuNPs do not occur aggregation,fluorescence resonance energy transfer does not occur.This anti-agglutination induced by Hep can be demonstrated by TEM images(Fig.4.3).Figure 4.3A Surface PEI causes aggregation of AuNPs and the ability to find the presence of nanoclusters on its surface.Figure 4.3B shows that Au has good dispersibility when Hep exists,and can clearly see nanoclusters.In the experiment,the qualitative and quantitative analysis of Hep could be achieved by the change of solution color,the change of UV absorption spectrum and the change of fluorescence spectrum.The minimum detection limits of UV and fluorescence in the range of 0 to 187.5 ng / m L were 2.187 ng / m L and 12.2 ng / mL.This method is also used in the detection of Hep in serum.(4)A GSH-AuNCs/PEI/8Q5S composite was synthesized.The emission peak at 620 nm had a red shift of 10 nm compared with GSH-AuNCs and a new weak emission peak at 500 nm.Since 8Q5 S Mg2+ and PO43-are complexed with Mg2+,which is based on the chelating of PO43-,Mg2+ and 8-hydroxyquinoline-5-sulfonic acid(8Q5S)to enhance the fluorescence signal at 500 nm.The minimum detection limit for phosphate ions in the entire system over a range of 0-80 ?M is 0.85 ?M.This method has also been applied in human serum.