Xiangling Ren

A practical glucose biosensor based on Fe3O4 nanoparticles and chitosan/nafion composite film

A practical glucose biosensor was developed by combining the intrinsic peroxidase-like activity of Fe(3)O(4) nanoparticles (Fe(3)O(4) NPs) and the anti-interference ability of the nafion film. Glucose oxidase (GOD) was simply mixed with Fe(3)O(4) NPs and cross-linked on the Pt electrode with chitosan (Cs) medium by glutaraldehyde, and then covered with a thin nafion film. The biosensor showed high sensitivity (11.54 microAcm(-2)mM(-1)), low detection limit (6 x10(-6)M), and good storage stability. A linear calibration plot was obtained in the wide concentration range from 6 x10(-6) to 2.2 x10(-3)M. The modified electrode could virtually eliminate the interference during the detection of glucose. Furthermore, the biosensor was successfully applied to detect glucose in human serum sample. This fabrication of glucose biosensor was of considerable interest due to its promise for simple procedure and optimizing conditions in practical application.

A simple and sensitive fluorescence biosensor for detection of organophosphorus pesticides using H2O2-sensitive quantum dots/bi-enzyme

In this paper, we have developed a simple, fast, convenient and sensitive method for determination of organophosphorus pesticides in real samples based on inhibition mechanism of acetylcholinesterase (AChE). The biosensor is composed of enzymes (AChE and ChOx (choline oxidase)), QDs and acetylcholine (ACh), without any complex process of assembly for biosensor. After the experimental conditions are optimized, the limit of detection (LOD) for dichlorvos (DDVP) is found to be 4.49nM. Two linear ranges allow a wide determination of DDVP concentration from 4.49nM to 6780nM. Furthermore, a possible mechanism is put forward to explain the fluorescence quenching of CdTe QDs in the presence of H2O2. More importantly, the obtained biosensor is proven to be suitable for the detection of residues of organophosphorus pesticides (OPs) in real examples. The excellent performance of this biosensor will facilitate future development of rapid and high-throughput detection of organophosphorus pesticides.

Magnetic and fluorescent multifunctional chitosan nanoparticles as a smart drug delivery system

An innovative drug delivery system based on magnetic and fluorescent multifunctional chitosan nanoparticles was developed, which combined magnetic targeting, fluorescent imaging and stimulus-responsive drug release properties into one drug delivery system. Water-soluble superparamagnetic Fe3O4 nanoparticles, CdTe quantum dots (QDs) and pharmaceutical drugs were simultaneously incorporated into chitosan nanoparticles; cross-linking the composite particles with glutaraldehyde tailored their size, morphology, surface properties and drug release behaviors. The system showed superparamagnetic and strong fluorescent properties, and was used as a controlled drug release vehicle, which showed pH-sensitive drug release over a long time. The composite magnetic and fluorescent chitosan nanoparticles are potential candidates as a smart drug delivery system.

Zinc oxide nanoparticles/glucose oxidase photoelectrochemical system for the fabrication of biosensor

Nanosized semiconductor crystals can increase efficiency of photochemical reactions and greatly improve the catalytic activity of enzymes to generate novel photoelectrochemical systems. In this work, glucose oxidase (GOx)/zinc oxide (ZnO) is selected as a model system to assess the photovoltaic effect of semiconductor nanoparticles on the enzyme electrode. UV-spectrum and circular dichroism (CD) results show that the structure of GOx is preserved after conjugation with ZnO nanoparticles. The current response of the enzyme electrode containing ZnO nanoparticles increases from 0.82 to 21 microA cm(-2) in the solution of 10 mM beta-D-glucose. Furthermore, after irradiating the enzyme electrode with UV light for 2 h, the current response can be increased nearly 30% and the detection limit can be lowered about two orders compared with the catalytic reactions in the dark, which indicate that a technique to fabricate a novel photocontrolled enzyme-based biosensor may be developed.

Optical detection of choline and acetylcholine based on H2O2-sensitive quantum dots

In this paper, we have constructed a simple, rapid and sensitive biosensor for detection of choline and acetylcholine (ACh) based on the hydrogen peroxide (H(2)O(2))-sensitive quantum dots (QDs). The detection limit for choline was 0.1 μM and the linear range was 0.1-0.9 μM and 5-150 μM, respectively. The detection limit for ACh was found to be 10 μM and the linear range was 10-5000 μM. The wide linear ranges were shown to be suitable for routine analyses of choline and ACh. Possible mechanism of the fluorescence of QDs quenched by H(2)O(2) was an electron transfer (ET) process. The experimental conditions of biosensors were optimized, and anti-interference ability was also presented. We also detected the choline in milk samples and the linear range was 5-150 μM. The detection linear range of ACh in serum was 10-140 μM. Most importantly, the recovery of choline in milk and ACh in serum samples were both close to 99%. The excellent performance of this biosensor showed that the method can be used in practice detection of choline and ACh.

Amperometric glucose biosensor based on a gold nanorods/cellulose acetate composite film as immobilization matrix.

We report on the utilization of gold nanorods to create a highly responsive glucose biosensor. The feasibility of an amperometric glucose biosensor based on immobilization of glucose oxidase (GOx) in gold nanorod is investigated. GOx is simply mixed with gold nanorods and cross-linked with a cellulose acetate (CA) medium by glutaraldehyde. The adsorption of GOx on the gold nanorods is confirmed by X-ray photoelectron spectroscopy (XPS) measurements. Circular dichroism (CD) and UV-spectrum results show that the activity of GOx was preserved after conjugating with gold nanorods. The current response of modified electrode is 10 times higher than that of without gold nanorods. Under optimal conditions, the biosensor shows high sensitivity (8.4 microA cm(-2) mM(-1)), low detection limit (2x10(-5) M), good storage stability and high affinity to glucose (K(m)(app)=3.84 mM). A linear calibration plot is obtained in the wide concentration range from 3x10(-5) to 2.2x10(-3) M.

An eco-friendly, simple, and sensitive fluorescence biosensor for the detection of choline and acetylcholine based on C-dots and the Fenton reaction.

A simple and novel method is proposed for the preparation of Carbon dots (C-dots) with excellent properties. We firstly demonstrated that the fluorescence of C-dots decreased apparently in the presence of H2O2 and Fe(2+). Based on the this finding, C-dots are successfully adopted as probes for the detection of H2O2. After the experimental conditions are optimized, the limit of detection (LOD) for H2O2 is found to be 0.1 μM. Furthermore, we established an eco-friendly, simple and sensitive biosensor for the detection of choline and acetylcholine (ACh) based on the detection of H2O2 using C-dots as probes. The detection limit for choline is 0.1 μM and the linear range is 0.1-40 μM. The detection limit for ACh is found to be 0.5 μM and the linear range is 0.5-60 μM. The excellent performance of the proposed biosensor shows that this method possesses the potential for practical application.

Preparation of PS/TiO2/UF multilayer core-shell hybrid microspheres with high stability.

In this paper, we report a facile method for preparation of polystyrene/titania/urea-formaldehyde resin (PS/TiO(2)/UF) multilayer core-shell hybrid microspheres with high stability through in situ condensation polymerization. The TEM images show that the thickness of UF shells is about 10 nm. The Zeta potential is close to zero. The density of PS/TiO(2)/UF could be controlled to 1.85 g/cm(3), which matches well with the non-polar dispersant (tetrachloroethylene). They are well dispersed and remain non-agglomerated even over several months, so they could be potential building blocks to fabricate electrophoretic display. Some parameters such as the ratio of urea-formaldehyde prepolymer (UFP) to PS/TiO(2), the pH value, and the temperature are also investigated.

Enzyme biosensor based on NAD-sensitive quantum dots.

A novel quantum dots (QDs) based biosensor has been developed to detect the activity of lactate dehydrogenase (LDH) by the change of fluorescence intensities of the QDs. In this system, the fluorescence intensities of the QDs are quenched by nicotinamide adenine dinucleotide (NAD, the coenzyme of LDH) first and then intensified with increasing amounts of the LDH because of the consumption of the NAD in the biocatalyzed reaction. A linear calibration plot of the activity of LDH is obtained in the wide amounts range from 150 to 1500 U/L and the detection limit is 75 U/L. Furthermore, the effect of several possible interfering substances, such as uric acid (UA), lactose, and glucose on the QDs-based biosensor is also investigated. This enzyme biosensor is of considerable interest due to its promise for simple procedure and the established method has great potential in detection of the physiological level of some biomolecules in clinical diagnostics of various diseases.

Layered MoS2 Hollow Spheres for Highly-Efficient Photothermal Therapy of Rabbit Liver Orthotopic Transplantation Tumors

Combining photothermal therapy (PTT) with clinical technology to kill cancer via overcoming the low tumor targeting and poor therapy efficiency has great potential in basic and clinical researches. A brand-new MoS2 nanostructure is designed and fabricated, i.e., layered MoS2 hollow spheres (LMHSs) with strong absorption in near-infrared region (NIR) and high photothermal conversion efficiency via a simple and fast chemical aerosol flow method. Owing to curving layered hollow spherical structure, the as-prepared LMHSs exhibit unique electronic properties comparing with MoS2 nanosheets. In vitro and in vivo studies demonstrate their high photothermal ablation of cell and tumor elimination rate by single NIR light irradiation. Systematic acute toxicity study indicates that these LMHSs have negligible toxic effects to normal tissues and blood. Remarkably, minimally invasive interventional techniques are introduced to improve tumor targeting of PTT agents for the first time. To explore PTT efficiency on orthotopic transplantation tumors, New Zealand white rabbits with VX2 tumor in liver are used as animal models. The effective elimination of tumors is successfully realized by PTT under the guidance of digital subtraction angiography, computed tomography, and thermal imaging, which provides a new way for tumor-targeting delivery and cancer theranostic application.