Synthesis Of Biocompatible LaPO₄:Ce,Tb Fluorescent Nanoparticles And Their Application

In recent years, lanthanide-doped luminescent nanomaterials have become a new generation of biomarkers materials due to their unique optical properties, such as large Stokes shift, high fluorescence emission intensity, narrow half emission peaks, long fluorescence lifetime, and so on. What’s more, they have some advantages such as low toxicity and high chemical stability.Therefore, lanthanide-doped luminescent nanomaterials can overcome poor stability of the organic luminescent labeled substance and effectively solve the cytotoxicity and light flashing problem of the quantum dot. Synthesis and application of biocompatible nanomaterials have caught the attention of scholars home and abroad.Here, the LaPO4:Ce,Tb fluorescent nanoparticles were synthesized by hydrothermal method. The results showed that the best conditions to synthesize LaPO4:Ce,Tb nanoparticles were as follows:the mole ratio of lanthanide ions to Na3PO4was5:4; the volume fraction of Copolymer of Phosphono and carboxylic Acid was0.74; the Ce3+doped content was30%; the Tb3+doped content was20%; the pH of the solution was9.0; and the whole reactants reacted at160℃for2h. The fluorescence lifetime of the LaPO4:Ce,Tb nanoparticles was2.63ms, the quantum yield was14%.The prepared LaPO4:Ce,Tb particles were charactered by many methods. From the fluorescence emission spectra we can get that the strong peak at544nm attributed to the5d4-7f5transition of Tb3+; the results of XRD test showed that particles were LaPO4:Ce,Tb Crystal and belong to the hexagonal system; TEM tests showed that the crystallization was spherical and the average particle size was16.6nm; the results of IR showed that the surface of the LaPO4:Ce,Tb nanoparticles were coated with Copolymer of Phosphono and carboxylic Acid.By detecting the resonance rayleigh scattering intensty of LaPO4:Ce,Tb nanoparticles bound and unbound with trypsin, we studied the biocompatibility between LaPO4:Ce,Tb nanopart-icles and biomolecules. The results showed that the LaPO4:Ce,Tb nanoparticles could couple with the trypsin by electrostatic interaction. The best experimental conditions were as follows: the concentrations of NaCl was0.06mol·L-1; reaction temperature was37℃; reaction time was60min and pH value of the disodium hydrogen phosphate-citric acid buffer system was7.0.By the trypsin as a bridge, we have tried to establish the as-prepared LaPO4:Ce,Tb fluorescent nanoparticles and gold nanoparticles to form a new FRET system. Conditions of the reaction were that the concentrations of rare earth nanoparticles、gold nanoparticles and trypsin were2.4×10-3mol·L-1、32μg·mL-1and10μg·mL-1respectively. With increasing the the concentrations of the trypsin, the LaPO4:Ce,Tb fluorescence had a certain declining. The results showed that the resonance energy transfer efficiency was very great.