Chunhai（樊春海） Fan

Destructive extraction of phospholipids from Escherichia coli membranes by graphene nanosheets

Understanding how nanomaterials interact with cell membranes is related to how they cause cytotoxicity and is therefore critical for designing safer biomedical applications. Recently, graphene (a two-dimensional nanomaterial) was shown to have antibacterial activity on Escherichia coli, but its underlying molecular mechanisms remain unknown. Here we show experimentally and theoretically that pristine graphene and graphene oxide nanosheets can induce the degradation of the inner and outer cell membranes of Escherichia coli, and reduce their viability. Transmission electron microscopy shows three rough stages, and molecular dynamics simulations reveal the atomic details of the process. Graphene nanosheets can penetrate into and extract large amounts of phospholipids from the cell membranes because of the strong dispersion interactions between graphene and lipid molecules. This destructive extraction offers a novel mechanism for the molecular basis of graphenes cytotoxicity and antibacterial activity.

Development of electrochemical immunosensors towards point of care diagnostics

Electrochemical immunosensors (EI) has attracted numerous interests due to its inherent benefits over the other transduction schemes, such as a high sensitivity, ease of use, a possible automation and integration in compact analytical devices, mostly cheap and relatively simple technology of its production. Thus, EIs have great potential in point of care (POC) diagnostics for early detection of diseases. During last decades, numerous efforts have been put into EIs development. Firstly, different fabrication methods and amplification strategies have been employed to achieve high sensitivity. To be pointed, nanotechnology has been involved in the fabrication and signal amplification of EIs, which present great superiority. Secondly, EI arrays have been used for multiparametric analysis. Thirdly, several attempts have been made to construct integrated systems, which showed promising applications for POC test. Several of them are commercially available for POC use. Herein, we will review briefly the recent achievements and progress in developing EIs towards POC diagnostics.

Water‐Dispersed Near‐Infrared‐Emitting Quantum Dots of Ultrasmall Sizes for In Vitro and In Vivo Imaging

Near-infrared (NIR)-fluorescence imaging is widely recognized as an effective method for high-resolution and highsensitivity bioimaging because of its minimized biological autofluorescence background and the increased penetration of excitation and emission light through tissues in the NIR wavelength window (700–900 nm). There have been tremendous efforts to develop high-efficiency fluorescent biological probes for NIR-fluorescence imaging. Semiconductor quantum dots (QDs) have attracted much recent attention as a new generation of fluorescent probes because of their unique optical properties such as strong luminescence, high photostability, and size-tunable emission wavelength. While QDs emitting in the range of 450–650 nm have been well developed, NIR-emitting QDs have been much less explored because of their relatively complicated synthesis and post-treatment manipulations. Furthermore, NIR-emitting QDs are usually prepared in organic phase, and additional surface modification is employed to render them waterdispersible for biological applications. The relatively complicated surface modification often results in an increase in size of the QDs. Only recently, water-dispersed NIRemitting CdTe/CdS QDs with tetrahedral structure were directly prepared in aqueous phase through the epitaxialshell-growth method. Despite these advances, much work is still needed to obtain NIR-emitting QDs that can be facilely synthesized in aqueous phase for high-sensitivity and specific bioimaging. Herein, we report the first example of ultrasmall-sized NIR-emitting CdTe QDs with excellent aqueous dispersibility, robust storage, chemical, and photostability, and strong photoluminescence (photoluminescent quantum yield (PLQY): 15–20%). Significantly, the NIR QDs are directly synthesized in aqueous phase through a facile one-step microwave-assisted method (see the Supporting Information for experimental details and mechanisms) by utilizing several attractive properties of microwave irradiation such as prompt startup, easy heat control (on and off), prompt and homogeneous heating, and so forth. More importantly, highly spectrally and spatially resolved bioimaging was possible, and efficient tumor passive targeting in live mice was shown by using the prepared QDs. QDs with different emission wavelengths in the NIR range (lmax= 700–800 nm) can be readily prepared through fine adjustment of the experimental conditions (e.g., reaction time and temperature). Figure 1a,b displays the normalized ultraviolet photoluminescence (UV-PL) spectra for a series of as-prepared QDs with controllable maximum emission wavelength ranging from 700 to 800 nm in aqueous solution. Such QD solutions are transparent under ambient light conditions, suggesting the as-prepared QDs are well-dispersed in aqueous phase without further treatment (Figure 1c). The excellent aqueous dispersibility of the QDs arises from the surfacecovering mercaptopropionic acid (MPA) that acts as a stabilizer because of the presence of negatively charged carboxylic groups. Under UV irradiation the fluorescence of the as-prepared QDs became darker and the emission wavelength gradually shifted out of the visible region (Figure 1d). The transmission electron microscopy (TEM) and highresolution TEM (HRTEM) images reveal that the NIRemitting QDs are spherical particles with good monodispersibility (Figure 2a,b). The existence of a well-resolved crystal lattice in the HRTEM image further confirms the highly crystalline structures of the QDs (Figure 2b inset). Furthermore, the size distribution histogram (Figure 2c), which was determined by measuring more than 250 particles, shows that the average size and standard deviation of the as-prepared NIR-emitting QDs is (3.74 0.67) nm. Comparatively, the [*] Prof. Y. He, Y. L. Zhong, Dr. Y. Y. Su, Y. M. Lu, Z. Y. Jiang, F. Peng, T. T. Xu, Dr. S. Su Institute of Functional Nano & Soft Materials (FUNSOM) and Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Soochow University Suzhou, Jiangsu 215123 (China) Fax: (+86)512-6588-2846 E-mail: yaohe@suda.edu.cn

Graphene Oxide-Based Antibacterial Cotton Fabrics

Graphene oxide (GO) is an excellent bacteria-killing nanomaterial. In this work, macroscopic applications of this promising nanomaterial by fixing GO sheets onto cotton fabrics, which possess strong antibacterial property and great laundering durability, are reported. The GO-based antibacterial cotton fabrics are prepared in three ways: direct adsorption, radiation-induced crosslinking, and chemical crosslinking. Antibacterial tests show that all these GO-containing fabrics possess strong antibacterial property and could inactivate 98% of bacteria. Most significantly, these fabrics can still kill >90% bacteria even after being washed for 100 times. Also importantly, animal tests show that GO-modified cotton fabrics cause no irritation to rabbit skin. Hence, it is believed that these flexible, foldable, and re-usable GO-based antibacterial cotton fabrics have high promise as a type of new nano-engineered antibacterial materials for a wide range of applications.

Applications of Gold Nanoparticles in the Detection and Identification of Infectious Diseases and Biothreats

Abstract The situation of infectious diseases and biothreats all over the world remains serious. The effective identification of such diseases plays a very important role. In recent years, gold nanoparticles have been widely used in biosensor design to improve the performance for the detection of infectious diseases and biothreats. Here, recent advances of gold‐nanoparticle‐based biosensors in this field are summarized.

Regenerable electrochemical immunological sensing at DNA nanostructure-decorated gold surfaces

A regenerable electrochemical immunosensor with novel 3D DNA nanostructure-decorated gold surfaces was developed by taking advantage of DNA-directed antibody conjugation and high resistance to non-specific protein adsorption.

Highly sensitive fluorescence assay of DNA methyltransferase activity via methylation-sensitive cleavage coupled with nicking enzyme-assisted signal amplification.

Herein, using DNA adenine methylation (Dam) methyltransferase (MTase) as a model analyte, a simple, rapid, and highly sensitive fluorescence sensing platform for monitoring the activity and inhibition of DNA MTase was developed on the basis of methylation-sensitive cleavage and nicking enzyme-assisted signal amplification. In the presence of Dam MTase, an elaborately designed hairpin probe was methylated. With the help of methylation-sensitive restriction endonuclease DpnI, the methylated hairpin probe could be cleaved to release a single-stranded DNA (ssDNA). Subsequently, this released ssDNA would hybridize with the molecular beacon (MB) to open its hairpin structure, resulting in the restoration of fluorescence signal as well as formation of the double-stranded recognition site for nicking enzyme Nt.BbvCI. Eventually, an amplified fluorescence signal was observed through the enzymatic recycling cleavage of MBs. Based on this unique strategy, a very low detection limit down to 0.06 U/mL was achieved within a short assay time (60 min) in one step, which is superior to those of most existing approaches. Owing to the specific site recognition of MTase toward its substrate, the proposed sensing system was able to readily discriminate Dam MTase from other MTase such as M.SssI and even detect the target in complex biological matrix. Furthermore, the application of the proposed sensing strategy for screening Dam MTase inhibitors was also demonstrated with satisfactory results. This novel method not only provides a promising platform for monitoring activity and inhibition of DNA MTases, but also shows great potentials in biological process researches, drugs discovery and clinical diagnostics.

Graphene-templated formation of two-dimensional lepidocrocite nanostructures for high-efficiency catalytic degradation of phenols

Graphene is a two-dimensional nanomaterial with exceptionally interesting physical and chemical properties, which has been actively explored in nanoelectronics, nanodevices and nanoscale catalysis. Here we report a graphene-templated route toward mild, solution-phase synthesis of ultrathin single crystal lepidocrocite (γ-FeOOH) nanosheets with high aspect ratio. We find that when reduced graphene oxide (rGO) was incubated with FeCl3 of 20 wt% at 80 °C and in the presence of reducing reagents (e.g.hydrazine hydrate), close-spaced 2D nanosheets of γ-FeOOH was formed on the surface of rGO, with the average thickness of 2.1 nm. This ultrathin nanomaterial was characterized via a range of complementary techniques, transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), Mossbauer spectroscopy and synchrotron-based scanning transmission X-ray microscopy (STXM), which confirmed the formation of γ-FeOOH 2D nanosheets. Importantly, we explore the application of this novel nanomaterial as an efficient and stable catalyst for phenol treatment in wastewater.

Design and applications of gold nanoparticle conjugates by exploiting biomolecule-gold nanoparticle interactions

Gold nanoparticles (AuNPs) are a type of widely used nanomaterials with unique chemical and physical properties. AuNPs can be readily synthesized, and modified with various chemical or biological molecules, making them promising candidates for catalysis, drug delivery and biological imaging applications. In this review, we mainly focus on recent advances in the design and synthesis of conjugates of AuNPs by exploiting biomolecule-AuNP interactions. We will also discuss a variety of bioapplications of AuNP-based conjugates.

A power-free microfluidic chip for SNP genotyping using graphene oxide and a DNA intercalating dye

We herein report a power-free microfluidic chip for fluorescent DNA detection with high single-nucleotide polymorphism discrimination, using a DNA intercalator and graphene oxide.