Novel Biosensor Method Based On Gold Nanoparticals And VS2Nanomaterials

Compared to other conventional materials, nano-materials exhibit a series ofunique properties in chemical, electrical, magnetic and optical, due to their surfaceeffect, small size effect, quantum size effect and macroscopic quantum tunneling effect.Therefore, it has attracted extensive attention of experts and scholars in the field ofeach course. In recent years, novel biosensors combined with nano-materials have beenwidely used in medical diagnosis, biomedical research, environmental monitoring andfood industry testing. In this research, we construct several optical biosensor platformbased on gold nanoparticles and VS2ultrathin nanosheets, DNA and peptides asbio-recognition and signal transduction events. They can realize the detection ofenvironmental pollutants sliver ions, protein kinase A related to many diseases, andmercury ions.(1) In chapter2, we developed a label-free, homogeneous SERS platform for therapid, simple and sensitive detection of Ag+by using the unmodified goldnanoparticles (Au NPs). It utilizes the different absorption properties of single-strandDNA (ssDNA) and double-strand DNA (dsDNA) on citrate-coated Au NPs and specificinteractions between Ag+and cytosine-cytosine pairs. The Ag+probe contains twoparts: the cytosine-rich silver-binding sequence and the linker sequence. Au NPs aredecorated through mixed self-assembly with the c-rich DNA and Raman-active dye viaelectrostatic attraction. In the presence of Ag+, silver-mediated base pairs (C–Ag+–C)can be formed between cytosine residues from two Ag-binding sequences to give riseto a hairpin structure. After the addition of NaNO3, the aggregation of Au NPs occursdue to a lack of the protection of ssDNA, resulting in a strong SERS signal because ofthe plasmonic coupling of interparticles and the formation of many SERS “hot spots”.In contrast, in the absence of Ag+, the strong electrostatic attraction of ssDNA withcitrate-coated Au NPs prevents the nanoparticles from salt-induced aggregation,displaying a weak SERS signal. The proposed method shows relatively goodselectivity for Ag+over other metal ions with a detection limit of15nM. Because thisapproach avoids common modification and separation steps usually used, as well as itsrapidity and convenience in the qualitative analysis of Ag+in actual samples, it holdsgreat potential for analytical applications and environmental monitoring.(2) In chapter3, we propose a novel colorimetric platform for sensing the activity and inhibition of protein kinase A based on assembly of phosphorylated substratepeptide modified Au NPs mediated by anti-phosphoserine antibodies without anylabels. In this work, peptide is bio-recognition event and in the presence of proteinkinase A, the substrate peptide is phosphorylated at the serine site. After theintroduction of anti-phosphoserine antibodies, phosphorylated substrate peptide can bespecifically recognized by the antibody. This induces an assembly of peptide decoratedAu NPs and thus triggers an obvious variation in absorption peak along with avisualized color change. The sensor has become a useful platform for activityscreening of protein kinase because of its high sensitivity without the need of labeledantibodies and exquisite capability of visual detection using “naked” eyes.(3) In chapter4, On the basis of that ultrathin VS2nanosheets might serve as ahomogeneous sensing platform for quantitative Hg2+assay due to its high fluorescencequenching ability and discrimination between dsDNA and ssDNA. VS2nanosheetscould adsorb FAM-labeled thymine (T)-rich single-stranded DNA (ssDNA) probe viathe van der Waals force between nucleobases and the basal plane of VS2and thenquench the fluorescence of the dye. After the addition of Hg2+, because of theformation of Hg2+mediated T Hg2+T base pairs, the interaction between the formeddouble-stranded DNA (dsDNA) and VS2is so weak that the FAM-labeled Hg2+probe isaway from the surface of VS2and then the fluorescence of the probe can be retained.Therefore, the sensor can be used to the quantitative detection of Hg2+.