Silver Nanoparticles Enhanced Terbium Fluorescence To Determine Dopamine

Dopamine (4-(2-aminoethyf)-benzen-l,2-diol DA) is one of the crucial catecholamines. As a neurotransmitter in the brain, DA plays a major role in the central and peripheral nervous systems. An abnormality of DA in the human body can cause health issues, such as Parkinson’s disease, anorexia, HIV, neuroblastoma etc. Therefore, studied and found the rapid, sensitive and selective method which determined DA concentration in biological fluids (urine, serum etc.) and pharmaceutical formulation is of great importance for the life science, pharmacological studying and the clinic application.In this paper, silver nanoparticles (AgNPs) were selected as enhanced base. The fluorescence of the system of Tb3+-DA was enhanced by metal enhanced fluorescence of AgNPs and the effect of co-luminescence. In order to improve the selectivity of the system, co-ligand was selected by the recognition function. Based on these, we established new potential value fluorescence method of determination of DA. Particularly, the mechanism of the system was discussed. The main conclusions are listed as follows:In the first section, we summarized the recent development of the analytical method of DA, the mechanism of metal enhanced fluorescence of AgNPs and the rare earths co-luminesce nee effect.In the second section, different of silver nanoparticles (AgNPs) were prepared by chemical reduction. The metal enhanced fluorescence of AgNPs was utilized to determination of DA. From the research, we found that the co-luminescence (Tb3+ and Gd3+) effect of rare earth was enhanced by DA in the presence of the cit-AgNPs. The effect of rare earth co-luminescence ions (Gd3+, Y3+, Sm3+, La3+, Er3+, Eu3+, Tm3+etc) were also studied, it was found that Gd3+ and Y3+ have co-luminescence effect. In this section, we discussed the co-luminescence effect of Tb3+-Gd3+-DA which was enhanced by AgNPs. What is more, there was a good linear relationship between the fluorescence intensity and the concentration of DA. Under the optimal conditions, the linear range was 5.0-100 nM, the limit of determination (S/N=3) was calculated to be 1.7 nM. The method was applied for the determination of DA in pharmaceutical preparations with good accuracy. The mechanism of enhanced fluorescence by AgNPs was also discussed.In the third section, the fluorescence properties of the system of Tb3+-AgNPs-Y3+-DA were studied. In this work, DA can remarkably enhance the luminescence intensity of the Tb3+ ion by Y3+ in the colloidal solution of AgNPs, forming a new co-luminescence system. Furthermore, based on the metal enhanced fluorescence (MEF), AgNPs can sensitize the co-luminescence effect of the complex of Tb3+-Y3+-DA. In a neutral buffer solution (pH 7.50), the luminescence intensity of the system was linearly related to the concentration of DA in the range of 2.0-100 nM, with a limit of detection as low as 0.57 nM. The proposed method was applied for the determination of DA in dopamine hydrochloride injections and human serum samples with good accuracy and satisfactory recovery. Comparing to other methods, this method was simple, wide linear range and high sensitivity. And the co-luminescence effect was also discussed.In the fourth section, a new spectrofluorimetric method with high sensitivity and selectivity was developed for the determination of dopamine (DA) based on silver nanoparticles resonance signal amplification by HCOO-bridge action. HCOO- acts as a bridge ligand between Tb3+ and AgNPs to enhance the fluorescence. The enhanced fluorescence also resulted from the coupling of the emission of HCOO--Tb3+-DA complexes with the broadened localized surface plasmon resonance (LSPR) of aggregates of AgNPs. DA was selectively determined by the steric hindrance effect of metal-oxo clusters. Under the optimized condition, the enhanced fluorescence intensity was linearly related to the concentration of the DA with a range of 0.5-100 nM (R2=0.998) and with a limit of detection as low as 0.15 nM. The method was applied for the determination of DA in pharmaceutical preparations and human serum samples with good accuracy and satisfactory recovery (97-103.3%). The mechanism of enhanced fluorescence by HCOO" bridge action was discussed.The chief characteristics of this thesis are as follows:1. The vast majority of co-luminescence-based analytical methods require that surfectants must exist in the system. However, these methods were bad for the application to the determination of DA in the human. The analytical method based on RE-columin sensitized by metallic nanoparticles alone without surfactant in aqueous solution has not been reported yet. What is more, the sensitivity was high and the detection limit for DA was very low (down to nM).2. In this method, buffer solution was Tris-HCl or HEPES-NaOH which was good biocompatibility. Furthermore, the experiment was conduced in a neutral buffer solution which was similar to human body fluids. The sensitive methods were important for the pharmacological studying and the clinic application.3. The selectivity and sensitivity were obviously improved by the bridge action of HCOO". The method was successfully applied for the determination of DA in human serum samples. This work provided new insight in developing highly selective and sensitive sensors for reactive species detection by bridge action.