Ruirui Qiao

Receptor-mediated delivery of magnetic nanoparticles across the blood-brain barrier.

A brain delivery probe was prepared by covalently conjugating lactoferrin (Lf) to a poly(ethylene glycol) (PEG)-coated Fe(3)O(4) nanoparticle in order to facilitate the transport of the nanoparticles across the blood-brain barrier (BBB) by receptor-mediated transcytosis via the Lf receptor present on cerebral endothelial cells. The efficacy of the Fe(3)O(4)-Lf conjugate to cross the BBB was evaluated in vitro using a cell culture model for the blood-brain barrier as well as in vivo in SD rats. For an in vitro experiment, a well-established porcine BBB model was used based on the primary culture of cerebral capillary endothelial cells grown on filter supports, thus allowing one to follow the transfer of nanoparticles from the apical (blood) to the basolateral (brain) side. For in vivo experiments, SD rats were used as animal model to detect the passage of the nanoparticles through the BBB by MRI techniques. The results of both in vitro and in vivo experiments revealed that the Fe(3)O(4)-Lf probe exhibited an enhanced ability to cross the BBB in comparison to the PEG-coated Fe(3)O(4) nanoparticles and further suggested that the Lf-receptor-mediated transcytosis was an effective measure for delivering the nanoparticles across the BBB.

Lateral flow immunochromatographic assay for sensitive pesticide detection by using Fe3O4 nanoparticle aggregates as color reagents.

Magnetic Fe(3)O(4) particle aggregates were prepared by cross-linking Fe(3)O(4) nanoparticles bearing surface carbonyl groups with poly-L-lysine. Upon further coupling with antiparaoxon methyl polyclonal antibody, the resultant particle aggregate-based probes were used in a lateral flow immunochromatographic assay (LFIA) of pesticide residue of paraoxon methyl. The results were compared with that achieved by using the mother Fe(3)O(4) nanoparticles. More quantitative results on the signal amplification effect endowed by the controlled aggregation of Fe(3)O(4) nanoparticles were extracted by relative optical density analysis. Under optimized conditions, a detection limit of 1.7 ng/mL for paraoxon methyl was achieved by using the particle aggregates, which is almost 40-fold lower than that based on the mother Fe(3)O(4) nanoparticles.

Simultaneous and sensitive determination of multiplex chemical residues based on multicolor quantum dot probes.

Biotinylated denatured bovine serum albumin (Bt-dBSA)-coated cadmium telluride (CdTe) quantum dot (QD) conjugates were prepared and used to develop the multiplexed fluoroimmunoassay for the simultaneous determination of five chemical residues. An immune complex was formed using avidin as the bridge to link the Bt-dBSA-QDs with the antibodies. Primarily, individual quantitative determinations of five representative chemical residues were carried out based on the different emission properties of the QDs. Five antibodies were then conjugated with the corresponding QDs to establish the indirect competition fluorescent-linked immunosorbent assay (ic-FLISA) for the simultaneous detection of five chemicals in one well of a microplate. The linear range for dexamethason (DEX) was from 0.33 microg/kg to 10 microg/kg, 0.28 microg/kg to 10 microg/kg for gentamicin (GM), 0.16 microg/kg to 25 microg/kg for clonazepam (CZP), 0.17 microg/kg to 10 microg/kg for medroxyprogesterone acetate (MPA) and 0.32 microg/kg to 25 microg/kg for ceftiofur (CEF), respectively. The limit of detection (LOD) for the simultaneous determination of DEX, GM, CZP, MPA and CEF were as low as 0.13 microg/kg, 0.16 microg/kg, 0.07 microg/kg, 0.06 microg/kg and 0.14 microg/kg, respectively. This detection method was used to analyze samples of pork muscle and the recoveries ranged from 61.3% to 80.3% for DEX and from 74.0% to 87.2% for MPA. Further more, good correlation between the novel ic-FLISA and traditional ELISA was demonstrated during the determination of DEX and MPA residues in real samples. The QD-based protocol described here is less time consuming than the classical method and it may be sufficiently flexible to be used in other systems for the simultaneous multicolor detection of the drugs.

Polyaniline/Fe3O4 Nanoparticle Composite : Synthesis and Reaction Mechanism

Polyaniline/Fe(3)O(4) nanoparticle composite was prepared by polymerizing aniline in the presence of Fe(3)O(4) nanoparticles upon the use of H(2)O(2) as oxidant. The polymerization was monitored by ultraviolet-visible absorption spectroscopy. The microstructure of the resultant composite was characterized by transmission electron microscopy. The molecular structure of the resultant polyaniline in the composite was investigated by both Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy, while the magnetic property of the composite was characterized by vibrating sample magnetometer. Furthermore, the microwave absorption property of the resultant composite was measured in a frequency range of 2-18 GHz. Systematic investigations revealed that carboxylic acid in the buffer presented a determined role in the polymerization of aniline. To discover the role of carboxylic acid in the polymerization of aniline, more control experiments were designed and carried out by theoretical calculation in combination with electron spin resonance measurements. It was for the first time found out that carboxylic acid such as acetic acid and succinic acid can not only catalyze the polymerization of aniline but also facilitate the generation of hydroxyl radical via the decomposition of H(2)O(2).

Anchoring Group Effects of Surface Ligands on Magnetic Properties of Fe3O4 Nanoparticles: Towards High Performance MRI Contrast Agents

The effect of the anchoring group of surface ligands on the magnetic properties, especially relaxometric properties, of PEGylated Fe₃ O₄ nanoparticles is investigated. Systematic experimental results together with in-depth theoretical analysis reveal that the ligand binding affinity can largely vary the saturation magnetization, whereas conjugated anchoring groups can remarkably enhance the transverse relaxivity, which highlights a novel approach for achieving high-performance MRI contrast agents.

A Novel Type of Dual-Modality Molecular Probe for MR and Nuclear Imaging of Tumor: Preparation, Characterization and in Vivo Application

A novel dual-modality molecular probe composed of biocompatible Fe(3)O(4) nanocrystal, monoclonal antibody and radionuclide was designed and prepared. All functional components in the dual-modality molecular probe, i.e., Fe(3)O(4), PEG, mAb 3H11 and (125)I, were chemically bonded together for forming a stable molecular probe. Systematic in vitro experiments were carried out for evaluating the biological activity of the antibody in the targeting probe. A series of in vivo experiments were performed based on the dual-modality imaging probe for detecting xenografted tumors in nude mice by MRI and gamma-imaging techniques. The pharmacokinetics of the dual-modality molecular probe in tumor-bearing nude mice was studied.

Rapid and sensitive detection of microcystin by immunosensor based on nuclear magnetic resonance.

A stable and sensitive toxin residues immunosensor based on the relaxation of magnetic nanoparticles was developed. The method was performed in one reaction and offered sensitive, fast detection of target toxin residues in water. The target analyte, microcystin-LR (MC-LR) in Tai lake water, competed with the antigens on the surface of the magnetic nanoparticles and then influenced the formation of aggregates of the magnetic nanoparticles. Accordingly, the magnetic relaxation time of the magnetic nanoparticles was changed under the effect of the target analyte. The calibration curve was deduced at different concentrations of the target analyte. The limit of detection (LOD) of MC-LR was 0.6 ng g(-1) and the detection range was 1-18 ng g(-1). Another important feature of the developed method was the easy operation: only two steps were needed (1) to mix the magnetic nanoparticle solution with the sample solution and (2) read the results through the instrument. Therefore, the developed method may be a useful tool for toxin residues sensing and may find widespread applications.

Gelification: An Effective Measure for Achieving Differently Sized Biocompatible Fe3O4 Nanocrystals through a Single Preparation Recipe

Biocompatible Fe(3)O(4) nanocrystals were synthesized through the pyrolysis of ferric acetylacetonate (Fe(acac)(3)) in diphenyl oxide, in the presence of α,ω-dicarboxyl-terminated polyethylene glycol (HOOC-PEG-COOH) and oleylamine. Unusual gelification phenomena were observed from the aliquots extracted at different reaction stages after they were cooled to room temperature. By reaction time, the average size of the Fe(3)O(4) nanocrystals was tuned from 5.8 to 11.7 nm with an equilibrium size around 11.3 nm. By increasing the gelification degree of the stock solution, the equilibrium size of the Fe(3)O(4) nanocrystals was further increased from 11.3 to 18.9 nm. The underlying gel formation mechanism was investigated by using ultraviolet-visible absorption spectroscopy and Fourier transform infrared spectroscopy. The results suggest that the complexation between HOOC-PEG-COOH and Fe(acac)(3), with the help of oleylamine, results in large molecular networks, which are responsible for the gelification of the stock solution, while the interaction between the fragment of the molecular network and Fe(3)O(4) nanocrystal is responsible for the second gelification process observed during the early stage of reflux. To further investigate the particle growth behavior, small molecules released during the preparation were collected and analyzed by using photoelectron spectroscopy/photoionization mass spectroscopy (PES/PIMS). It was demonstrated that the pyrolysis of the Fe precursor is strongly correlated with the particle growth process. Further numerical simulations reveal that the first gelification process induced by the complexation between HOOC-PEG-COOH and Fe(acac)(3) largely alters the pyrolysis behavior of the Fe precursor; consequently, the equilibrium size of the resultant Fe(3)O(4) nanocrystals can effectively be tuned by the gelification degree of the stock solution.

Ultrasensitive immunoassay of 7-aminoclonazepam in human urine based on CdTe nanoparticle bioconjugations by fabricated microfluidic chip

The present paper described a rapid and ultrasensitive detection method using a microfluidic chip for analyzing 7-aminoclonazepam (7-ACZP) residues in human urine. A microfluidic chip-based immunoassay with laser-induced fluorescence (LIF) detection based on the water-soluble denatured bovine serum albumin (dBSA)-coated CdTe quantum dots (QDs) was prepared for the ultrasensitive detection of 7-ACZP. The whole procedure including the chip and the control software was designed and constructed in our own laboratory. The detection of 7-ACZP could be completed within 5 min. The results demonstrated that under the optima conditions, 7-ACZP residues could be detected with a precision of 5% relative standard deviation (RSD), and the linear range and the limit of detection (LOD) for 7-ACZP were 1.1-60.1 and 0.021 ngmL(-1), respectively. This method was compared with ELISA and showed a good correlation. This microfluidic chip with LIF detection was applied to the determination of 7-ACZP residues in positive human urine samples, and the results were confirmed by high-performance liquid chromatography and tandem mass spectrometry (LC/MS/MS). This ultrasensitive detection technique was proved to be practical for clinical use.

Effects of Quantum Dots in Polymerase Chain Reaction

The effects of quantum dots (QDs) on the elimination of nonspecific amplification of the polymerase chain reaction (PCR) were investigated. It was found that QDs could increase the specificity of the PCR at different annealing temperatures and with DNA templates of different lengths. The effects of QDs on the efficiency of the PCR were also studied, and the results showed that there was no enhancement. The mechanisms underlying these effects are discussed. This method could be used to modify the amplification results of the conventional PCR. Furthermore, this technology could make the PCR more widely applicable, especially in the multi-PCR reaction system with different annealing temperatures. This is of great significance for gene diagnosis.