Kehua Xu

Bio: Kehua Xu is an academic researcher from Shandong Normal University. The author has contributed to research in topics: Fluorescence & Nanoprobe. The author has an hindex of 27, co-authored 69 publications receiving 2563 citations. Previous affiliations of Kehua Xu include Ohio University.

A New Nanobiosensor for Glucose with High Sensitivity and Selectivity in Serum Based on Fluorescence Resonance Energy Transfer (FRET) between CdTe Quantum Dots and Au Nanoparticles

Abstract: A novel assembled nanobiosensor QDs-ConA-beta-CDs-AuNPs was designed for the direct determination of glucose in serum with high sensitivity and selectivity. The sensing approach is based on fluorescence resonance energy transfer (FRET) between CdTe quantum dots (QDs) as an energy donor and gold nanoparticles (AuNPs) as an energy acceptor. The specific combination of concanavalin A (ConA)-conjugated QDs and thiolated beta-cyclodextrins (beta-SH-CDs)-modified AuNPs assembles a hyperefficient FRET nanobiosensor. In the presence of glucose, the AuNPs-beta-CDs segment of the nanobiosensor is displaced by glucose which competes with beta-CDs on the binding sites of ConA, resulting in the fluorescence recovery of the quenched QDs. Experimental results show that the increase in fluorescence intensity is proportional to the concentration of glucose within the range of 0.10-50 muM under the optimized experimental conditions. In addition, the nanobiosensor has high sensitivity with a detection limit as low as 50 nM, and has excellent selectivity for glucose over other sugars and most biological species present in serum. The nanobiosensor was applied directly to determine glucose in normal adult human serum, and the recovery and precision of the method were satisfactory. The unique combination of high sensitivity and good selectivity of this biosensor indicates its potential for the clinical determination of glucose directly and simply in serum, and provides the possibility to detect low levels of glucose in single cells or bacterial cultures. Moreover, the designed nanobiosensor achieves direct detection in biological samples, suggesting the use of nanobiotechnology-based assembled sensors for direct analytical applications in vivo or in vitro.

A near-infrared reversible fluorescent probe for real-time imaging of redox status changes in vivo

Abstract: Alterations of cellular redox status are closely associated with physiological and pathological processes. Glutathione (GSH) and H2O2 should be the most representative redox couple in living cells. However, up to now, there is no way to reversibly detect GSH/H2O2. In this report, a near-infrared (NIR) fluorescent probe (Cy-O-Eb) for monitoring the changes of GSH/H2O2 levels in vivo was developed based on switching on–off a five-membered ring involved in ebselen. This probe could reversibly respond to GSH and H2O2 with high selectivity, sensitivity and mitochondrial targeting. It was successfully used to monitor the changes of redox status during apoptosis and the H2O2 changes at the wound margin in zebrafish larvae. Thus, the probe would provide an ideal tool for monitoring redox status changes and studying molecular events involved in redox regulation.

A highly sensitive acidic pH fluorescent probe and its application to HepG2 cells

Abstract: A novel acidic fluorescent probe 1 has been designed, synthesized, characterized and evaluated in vivo as optical imaging of intracellular H+ The design strategy for the probe is based on the change in structure between spirocyclic (non-fluorescent) and ring-open (fluorescent) forms of rhodamine dyes The probe exhibits high sensitivity, good photostability, excellent cell membrane permeability and strong pH dependence The pH titration indicates that the fluorescence intensity increases more than 100-fold within the pH range of 42–60 with the pKa value of 485, which is valuable for studying acidic organelles in living cells The fluorescent imaging of HepG2 cells also demonstrates that the designed probe has great value in monitoring intracellular H+ within living cells

Gold nanoparticles in chemical and biological sensing.

Abstract: Detection of chemical and biological agents plays a fundamental role in biomedical, forensic and environmental sciences1–4 as well as in anti bioterrorism applications.5–7 The development of highly sensitive, cost effective, miniature sensors is therefore in high demand which requires advanced technology coupled with fundamental knowledge in chemistry, biology and material sciences.8–13 In general, sensors feature two functional components: a recognition element to provide selective/specific binding with the target analytes and a transducer component for signaling the binding event. An efficient sensor relies heavily on these two essential components for the recognition process in terms of response time, signal to noise (S/N) ratio, selectivity and limits of detection (LOD).14,15 Therefore, designing sensors with higher efficacy depends on the development of novel materials to improve both the recognition and transduction processes. Nanomaterials feature unique physicochemical properties that can be of great utility in creating new recognition and transduction processes for chemical and biological sensors15–27 as well as improving the S/N ratio by miniaturization of the sensor elements.28 Gold nanoparticles (AuNPs) possess distinct physical and chemical attributes that make them excellent scaffolds for the fabrication of novel chemical and biological sensors (Figure 1).29–36 First, AuNPs can be synthesized in a straightforward manner and can be made highly stable. Second, they possess unique optoelectronic properties. Third, they provide high surface-to-volume ratio with excellent biocompatibility using appropriate ligands.30 Fourth, these properties of AuNPs can be readily tuned varying their size, shape and the surrounding chemical environment. For example, the binding event between recognition element and the analyte can alter physicochemical properties of transducer AuNPs, such as plasmon resonance absorption, conductivity, redox behavior, etc. that in turn can generate a detectable response signal. Finally, AuNPs offer a suitable platform for multi-functionalization with a wide range of organic or biological ligands for the selective binding and detection of small molecules and biological targets.30–32,36 Each of these attributes of AuNPs has allowed researchers to develop novel sensing strategies with improved sensitivity, stability and selectivity. In the last decade of research, the advent of AuNP as a sensory element provided us a broad spectrum of innovative approaches for the detection of metal ions, small molecules, proteins, nucleic acids, malignant cells, etc. in a rapid and efficient manner.37 Figure 1 Physical properties of AuNPs and schematic illustration of an AuNP-based detection system. In this current review, we have highlighted the several synthetic routes and properties of AuNPs that make them excellent probes for different sensing strategies. Furthermore, we will discuss various sensing strategies and major advances in the last two decades of research utilizing AuNPs in the detection of variety of target analytes including metal ions, organic molecules, proteins, nucleic acids, and microorganisms.

Luminescent chemodosimeters for bioimaging.

Abstract: Yuming Yang,†,§ Qiang Zhao,‡,§ Wei Feng,† and Fuyou Li*,† †Department of Chemistry and State Key Laboratory of Molecular Engineering of Polymers and Institutes of Biomedical Sciences, Fudan University, Shanghai 200433, P. R. China ‡Key Laboratory for Organic Electronics and Information Displays (KLOEID) and Institute of Advanced Materials (IAM), Nanjing University of Posts and Telecommunications, Nanjing 210046, P. R. China.

Metals in Neurobiology: Probing Their Chemistry and Biology with Molecular Imaging

Abstract: The brain is a singular organ of unique biological complexity that serves as the command center for cognitive and motor function. As such, this specialized system also possesses a unique chemical composition and reactivity at the molecular level. In this regard, two vital distinguishing features of the brain are its requirements for the highest concentrations of metal ions in the body and the highest per-weight consumption of body oxygen. In humans, the brain accounts for only 2% of total body mass but consumes 20% of the oxygen that is taken in through respiration. As a consequence of high oxygen demand and cell complexity, distinctly high metal levels pervade all regions of the brain and central nervous system. Structural roles for metal ions in the brain and the body include the stabilization of biomolecules in static (e.g., Mg2+ for nucleic acid folds, Zn2+ in zinc-finger transcription factors) or dynamic (e.g., Na+ and K+ in ion channels, Ca2+ in neuronal cell signaling) modes, and catalytic roles for brain metal ions are also numerous and often of special demand.

Fluorescent chemosensors based on spiroring-opening of xanthenes and related derivatives.

Abstract: Fluorescent Chemosensors Based on Spiroring-Opening of Xanthenes and Related Derivatives Xiaoqiang Chen, Tuhin Pradhan, Fang Wang, Jong Seung Kim,* and Juyoung Yoon* Departments of Chemistry and Nano Science and of Bioinspired Science (WCU), Ewha Womans University, Seoul 120-750, Korea State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemistry and Chemical Engineering, Nanjing University of Technology, Nanjing 210009, China Department of Chemistry, Korea University, Seoul 136-701, Korea