Study Of LaPO₄:Ce,Tb Fluorescent Nanoparticles On Determination Of Biological Molecules

In recent years, the analysis and detection technology by using lanthanide-doped luminescent nanoparticles as fluorescent markers has aroused widespread interests due to their unique optical properties, such as low toxicity, large Stokes shift, high fluorescence emission intensity, narrow half emission peaks, long fluorescence lifetime, and so on. It can overcome poor stability of the organic luminescent labeled substance and effectively solve the cytotoxicity and light flashing problem of the quantum dot. Lanthanide-doped luminescent nanoparticles have showed important applications in biological analysis, greatly promoted the progress and the development of biological research.In this paper, the LaPO4:Ce,Tb fluorescent nanoparticles coated with Copolymer of Phosphono and carboxylic Acid were synthesized by hydrothermal method, and were charactered by many methods. The strong excitation peak at278nm and the strong emission peak at545nm can be gotten from the fluorescence spectra; the XRD pattern showed that the as-prepared LaPO4:Ce,Tb particles were hexagon. TEM image indicated that the prepared LaPO4:Ce,Tb nanoparticles was well dispersed and the average particle size was about30nm.Here, LaPO4:Ce,Tb nanoparticles were used as energy donor in the Fluorescence Resonant Energy Transfer (FRET), gold nanoparticles as an energy receptor, and cytochrome C as a "bridge". A new method for quantitative detection of cytochrome C has been found. The results showed that the best experimental conditions were as follows:The pH value of the boric acid-borax buffer solution was7.0, the concentration of LaPO4:Ce,Tb nanoparticles was7.6×10-4mol·L-1, the volume of gold nanoparticles were300μL, the reaction temperature was35℃and reaction time was40min. A good linearity between the relative fluorescence intensity and the concentration of Cytochrome C in the range of0.333～21.0μg·mL-1was obtained. The correlation coefficient was0.9962and the detection limit was0.2μg·mL-1. The content of Cytochrome C in Cytochrome C injection was determined with the method, and the recovery was good. Using Cu2+-modulated POCA-capped LaPO4:Ce,Tb nanoparticals as fluorescent probe, based on the high affinity between Cu2+and histidine, we have established a new method for quantitative detection of Histidine.The pH value of Phosphate buffer solution was7.5, the concentration of LaPO4:Ce,Tb nanoparticles was4.6×10-4mol·L-1, the concentration of Cu2+was1.67×10-5mol·L-1, the reaction temperature was30℃and reaction time was10min. A good linearity between the fluorescence intensity and the concentration of Histidide, the correlation coefficient was0.9945, the detection range was3.33～40.0μg·mL-1and the detection limit was1.4μg·mL-1. The recoveries in Histidine tables by adding standard Histidine solution were between96～103%, which indicated the accuracy was high.