Preparations Of Gold And Silver Functional Nanomaterials And Their Applications In Sensing

The various research reports towards the nanomaterials indicate that they can open many good opportunities in an extremely multidisciplinary environment for promoting the rapid developments of different research fields. For example, silver nanoparticles broaden potential ways use as a fertile ground for analytical purpose due to the character of strong surface plasmon resonance scattering and surface-enhanced fluorescence, and gold/silver nanoclusters have molecule-like characteristics which make it give rise to unique and size dependent fluorescence properties. Therefore, considering their satisfactory optical charaters, in this study we attempt to develop sensing for heavy metal ions, medicine, and biologically important molecules based on gold and silver nanomaterials. The main contains are listed as follows:1. Copper ions are well known as the third essential transition metal in human bodies, whereas over-intake of copper ions could seriously result in various diseases. Lidocaine hydrochloride (LC-HC1), a clinical anesthetic, is widely used in topical anesthesia, intradermal infiltration, and peripheral nerve blocks. LC-HC1can easily cross the blood-brain barrier, and systemic administration of LC-HC1leads to neurological effects when its concentration exceeds the threshold level. Therefore, simple, selective, sensitive methods to detect Cu2+and LC-HC1remain necessary and valuable. In this study, homocysteine-functionalized silver nanoparticles (Hcys-AgNPs), prepared by reducing AgNO3with sodium borohydride in the presence of homocysteine, played an important role in this strategy. Aggregation of Hcys-AgNPs was induced in the presence of Cu2+ions, yielding a dramatic color change from deep brown to bright yellow. In contrast, once both Cu2+ions and LC-HC1existed together, the Hcys-AgNPs showed little aggregation, leading to much less color change compared with that in the presence of Cu2+ions alone. It is apparent that there exists a-SH group in homocysteine, which can be easily modified onto the surface of AgNPs through S-Ag bond. Furthermore, the-COOH group of homocysteine exhibits strong affinity to the Cu2+, thus forming carboxylate-Cu2+-carboxylate bridges. However, under alkaline conditions, the coordination compound formed by Cu2+and LC-HC1can prevent most parts of Cu2+from binding to the Hcys-AgNPs. Consequently, based on the fact that AgNPs modified with homocysteine aggregated in the presence of Cu2+due to the ion-templated chelation and dispersed in the presence of Cu2+and LC-HC1together because of the complexation between Cu2+and LC-HC1. Depending on this mechanism, capped AgNPs can display colorimetric response to Cu2+and LC-HC1. Additionally, the Hcys-AgNPs bound by Cu2+represented excellent selectivity compared to other metal ions (Fe2+, Mg2+, Mn2+, Hg2+, Zn2+, Ni2+, Co2+Pb2+, Ba2+, Ca2+, Cd2+, Al3+, Fe3+, Cr3+and K+), and Procaine hydrochloride (PC-HC1) indicated no interference to LC-HC1. Finally, the method was applied to detect Cu2+ions of water samples and LC-HC1in rat serum and human urine with low interference compared with HPLC, suggesting we provided a simple and reliable method towards detecting both Cu2+ions and LC-HC1.2. Surface-enhanced fluorescence on metal nanostructures (SEF) is that fluorescence enhancement occurs while a fluorophore is localized near the surface of metallic nanoparticles. Nevertheless, fluorescence is also quenched once the fluorophore is excessively close to the metal core, and the maximum enhancement occurs at about10nm from the metal surface. Herein, a novel high-sensitive enhanced-fluorescence immunoassay for detection of superoxide dismutase (SOD) is established by combining surface-enhanced fluorescence (SEF) with immuno-magnetic separation. Based on a sandwich-type immunoassay, analytes in samples are first captured by magnetic beads coated with a monoclonal antibody and then "sandwiched" by another monoclonal antibody on silver nanoparticles labeled with fluorescein-labeled oligonucleotides in the presence of magnet. Subsequently, the immune complex is enriched by exposure to a magnetic field. Lastly, the fluorescence intensity is measured according to the number of dissociated fluorescein. The increased fluorescence intensity permits high-sensitive detection of SOD in a linear range of10-8×105pg/mL, with a detection limit of4pg/mL at a signal-to-noise ratio of3.3. Deoxyribonuclease Ⅰ, considered mainly to be a digestive enzyme, hydrolyzes phosphodiester bonds of single-strand DNA (ssDNA) or double-strand DNA (dsDNA) to generate oligonucleotides and nucleotides with5’-phospho and3’-hydroxy termini. It is well known that the concentration of extracellular DNA is related to the pathogenesis of several diseases. Specifically, events related to DNA concentrations are being reported in cancer patients. Additionally, DNase I has also been found in nondigestive tissues such as human kidney and liver. Blood plasma DNase activity protects host cells from DNA effluent from foreign cells after opsonization, and degrades endogenous DNA appearing in blood after degradation of cells, so as to maintain the physiological level of DNA in the blood. In view of the biological significance of DNase Ⅰ, development of a simple, highly sensitivity and cost-effective method for quantifying this enzyme is necessary in the fields of drug discovery, clinical diagnostics and bioanalysis. Herein, fluorescent DNA-templated gold/silver nanoclusters (DNA-Au/Ag NCs) are presented as a novel probe for sensitive detection of deoxyribonuclease Ⅰ (DNase Ⅰ). The procedure is based on quenching fluorescence of DNA-Au/Ag NCs by DNase Ⅰ digestion of the DNA (5’-CCCTTAATCCCC-3’) template. Furthermore, the practicality of this probe for detection of DNaseⅠin human serum and saliva samples was validated, demonstrating its advantages of simplicity, selectivity, sensitivity and low cost. Importantly, satisfactory agreement between results obtained by the fluorescent method described here and high performance liquid chromatography (HPLC) further confirmed the reliability and accuracy of this approach. The decrease in fluorescence intensity permitted sensitive detection of DNaseⅠin a linear range of0.013-60μg mL-1, with a detection limit of3ng mL-1at a signal-to-noise ratio of3.In summary, we suppose that the research results describes above would be beneficial for us to understand deeply their characters of this two kinds of nanomaterials, and it is significant for us to enlarge their applications in pharmaceutical analysis.