Yajing Yin

Iron phosphate nanostructures synthesized by microwave method and their applications in biosensing.

A fast, simple microwave heating method has been developed for synthesizing iron phosphate (FePO(4)) nanostructures. The nanostructures were characterized and confirmed by transmission electronic microscopy (TEM), scanning electronic microscopy (SEM), energy-dispersive x-ray spectroscopy (EDS), x-ray photoelectron spectroscopy (XPS), x-ray powder diffraction (XRD), Fourier transform infrared (FT-IR), and UV-vis spectroscopy. The morphology and the size of the nanomaterials are significantly influenced by the concentration of the precursors and the kinds of surfactants. The nanostructures have been employed as an electrode substrate to immobilize myoglobin (Mb) and to facilitate the direct electron transfer (DET) reaction of the protein. After being immobilized on the nanomaterials, Mb can keep its natural structure and undergo effective DET reaction with a pair of well-defined redox peaks at - (330 ± 3.0) mV (pH 6.8) and an apparent electron transfer rate constant of 5.54 s(-1). The Mb-FePO(4)/GC electrode displays good features in the electrocatalytic reduction of H(2)O(2), and thus can be used as a biosensor for detecting substrates with a low detection limit (5 ± 1 µM), a wide linear range (0.01-2.5 mM), a high sensitivity (ca. 85 ± 3 µA mM(-1) cm(-2)), as well as good stability and reproducibility. Therefore, FePO(4) nanomaterials can become a simple and effective biosensing platform for the integration of proteins/enzymes and electrodes, which can provide analytical access to a large group of enzymes for a wide range of bioelectrochemical applications.

Aptamer-functionalized graphene oxide for highly efficient loading and cancer cell-specific delivery of antitumor drug

This work reports a novel anticancer drug loading and cell-specific delivery system based on cell type-specific aptamer-functionalized graphene oxide (GO) using decitabine (DAC) and A549 cells as anticancer drug and target cell model, respectively. We conjugated GO with aptamer A1 (a 45-base oligonucleotide that binds to A549 cells with high specificity and affinity) and then loaded DAC onto the surface of GO (A1-GO/DAC complex). The loading capacity of DAC on the GO surface is dependent on pH and initial DAC concentration; the saturated loading capacity, as high as ∼3.0 mg DAC per mg GO (corresponding to the loading efficiency of ∼64%), is attained at physiological pH (7.4) and initial DAC concentration of higher than 0.7 mg mL-1. The release of DAC from the complex is also pH dependent, and DAC is released at a quicker rate at acidic pH conditions (pH 5.5) than at the physiological pH. The complexes can specifically recognize A549 cells from other types of cancer cells and subtypes of lung cancer cells due to the specific binding of the aptamer with the cells. Importantly, cell viability assay results reveal that the complex displays a much higher therapeutic efficacy in inhibiting the growth of the cancer cells by inducing cell membrane damage compared to the DAC-free drug. The high DAC payload and antitumor efficacy render our developed system promising for different biomedical applications.

Indirect electrocatalytic determination of choline by monitoring hydrogen peroxide at the choline oxidase-prussian blue modified iron phosphate nanostructures.

Choline, as a marker of cholinergic activity in brain tissue, is very important in biological and clinical analysis, especially in the clinical detection of the neurodegenerative disorders disease. This work presents an electrochemical approach for the detection of choline based on prussian blue modified iron phosphate nanostructures (PB-FePO(4)). The obtained nanostructures showed a good catalysis toward the electroreduction of H(2)O(2), and an amperometric choline biosensor was developed by immobilizing choline oxidase on the PB-FePO(4) nanostructures. The biosensor exhibited a rapid response (ca. 2s), low detection limit (0.4±0.05 μM), wide linear range (2 μM to 3.2 mM), high sensitivity (~75.2 μAm M(-1) cm(-2)), as well as good stability and repeatability. In addition, the common interfering species, such as ascorbic acid, uric acid and 4-acetamidophenol did not cause obvious interference due to the low detection potential (-0.05 V versus saturated calomel electrode). This nanostructure could be used as a promise platform for the construction of other oxidase-based biosensors.

Nitrogen/carbon atomic ratio-dependent performances of nitrogen-doped carbon-coated metal oxide nanocrystals for anodes in lithium-ion batteries.

We report the hydrothermal synthesis of the N-doped carbon-coated NiO nanocrystals (N-C-NiO NCs) with tunable N/C atomic ratios using the nitrogen-containing ionic liquids (ILs) as new carbon precursor, and the N-doped carbon layer composition-dependent performances of N-C-NiO NCs anode for lithium-ion batteries (LIBs). The results indicate that the N-doped carbon coating can significantly enhance the electronic conductivity, effectively avoid the problems of cracking or pulverization of the NiO, and prevent the aggregation of the active materials upon cycling. These properties make the synthesized material a promising anode material for LIBs. The N-C-NiO NCs with the N/C atomic ratio of 21.2% in the N-doped carbon layer show a high specific capacity of ∼710 mAh g(-1) at a current rate of 0.3 C (very closed to the theoretical capacity of 718 mAh g(-1) for NiO), a high rate capability (still able to deliver a discharge capacity of ∼430 mAh g(-1) at a current density of 10 C), and good capacity retention upon cycling (maintains at 710 mAh g(-1) at least up to the 50th cycle) compared with those of pristine NiO nanoparticles. Moreover, the electrochemical performances of the N-C-NiO NCs depend on the composition (N/C atomic ratios) in the N-doped carbon layer and are enhanced with increasing of the N/C ratios. Our approach offers an effective and convenient technique to improve the specific capacities and rate capabilities of highly insulating electrode materials for batteries and may also provide general and effective approach toward the synthesis of other metal oxides coated with N-doped carbon layer.