ABSTRACTBiomacromolecules, such as enzymes are widely used for biocatalysis, both at academic and industrial level, due to their high specificity and wide applications in different reaction media. Herein, taking GOx as a representative enzyme, in-situ RAFT polymerization of four different monomers including acrylic acid (AA), methyl acrylate (MA), poly (ethylene glycol) acrylate (PEG-A) and tert-butyl acrylate (TBA) were polymerized directly on the surface of GOx to afford GOx-poly (PEG-A)(GOx-PPEG-A), GOx-poly(MA)(GOx-PMA), GOx-poly(AA)(GOx-PAA), and GOx-poly(TBA)(GOx-PTBA) conjugates, respectively. Thereinto, PAA and PPEG-A represent the hydrophilic polymers, while PMA and PTBA stand for the hydrophobic ones. Effects of different polymer on the properties of GOx were investigated by measuring the bioactivity and stability of the as-prepared and different GOx-polymer conjugates. Higher bioactivity was obtained for GOx modified with hydrophilic polymers compared with that modified with hydrophobic ones. All the tested polymers can enhance the stability of the GOx, while the hydrophobic GOx-polymers conjugates exhibited much better stability than the hydrophilic ones. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 1289–1293

Despite the great achievements been made on the carbon quantum dots (CQDs) investigations, evaluation criteria including simple synthesis unit, speediness capability, green precursor, high quantum yield (QY), stable and excellent physico-chemical properties as well as versatile applicability are still pursued by an ideal preparation method or satisfied products of CQDs. In addition, it is in urgent need but seldom reported to accurately position the utmost QY point for one synthetic cycle using a simple manipulation way. Herein, multifunctional nitrogen doped carbon quantum dots (N-CQDs) were synthesized using various amino acids (AAs) as the precursors via a simple three-electrode electrochemical/electroanalytical system in less than two hours. Most importantly, the optimum reaction time for generating N-CQDs with utmost QY can be straightforwardly and accurately derived via the maximum current value on the amperometric i-t curve recorded during the EC process. The N-CQDs can be well dispersed in aqueous medium with narrow size distribution and average size of 2.95 ± 0.12 nm as evidenced by transmission electron microscopy (TEM). Both the distinct and stable photoluminescent and electrochemiluminescent properties were observed for the as-prepared N-CQDs. The N-CQDs obtained from different AAs have similar optical and ECL features under the same EC conditions, while aspartic acid based N-CQDs exhibited the highest QY of 46.2%. These N-CQDs can be extensively applied in efficient cell imaging, fiber staining and specific sensitive detection towards ferric ion.Controllable electrochemical/electroanalytical approach was developed to generate nitrogen-doped carbon quantum dots (N-CQDs) from varied amino acids. The utmost N-CQDs quantum yields (QYs, 46.2%) can be straightforwardly pinpointed via the maximum current value on the amperometric i-t curve. The N-CQDs were with stable photoluminescent and electrochemiluminescent (ECL) properties and could be extensively applied in fluorescent bioimaging and label-free specific Fe3+ detection.Download high-res image (227KB)Download full-size image

Simultaneously enhancing the catalytic bioactivity and stability of enzyme is still an intractable issue in the enzymatic study. Herein, a facile and effective approach was designed to immobilize and modify laccase on a Cu2+-adsorbed pyrene-terminated block copolymer [poly(acrylic acid)/poly(poly(ethylene glycol) acrylate)] (PAA/PPEGA), which was prepared via well-controlled reversible addition–fragmentation chain transfer polymerization. PAA provided the supporting matrix for firm immobilization of Cu2+, an enzyme bioactivity inducer, onto the microstructure of laccase, while avoiding any contamination of the heavy metal Cu2+ into the following application system. The water-soluble, biocompatible, and nontoxic PPEGA was used as an ideal modifier to improve the laccase stability. Accordingly, the modified laccase exhibited enhanced catalytic bioactivity and stability simultaneously to 447% and 237%, respectively. The modified laccase was immobilized on the highly oriented pyrolytic graphite surface and large-area graphene papers through π–π stacking interactions between the pyrene moiety of PAA/PPEGA and the π-conjugated graphenelike surface. The as-prepared portable solid-state electrochemical laccase biosensor showed lowest detection limit of 50 nM (S/N ≥ 3) and long-term stability for pyrocatechol detection. Besides, the laccase immobilization on graphene paper provided efficient pyrocatechol decontamination platform with convenience and recyclability, which could retain the laccase bioactivity of 176% after 8 consecutive operations.

Carbon nanodots (C-dots), a new type of potential alternative to conventional semiconductor quantum dots, have attracted numerous attentions in various applications including bio-chemical sensing, cell imaging, etc., due to their chemical inertness, low toxicity and flexible functionalization. Various methods including electrochemical (EC) methods have been reported for the synthesis of C-dots. However, complex procedures and/or carbon source-containing electrodes are often required. Herein, solid-state C-dots were simply prepared by bottom-up EC carbonization of nitriles (e.g. acetonitrile) in the presence of an ionic liquid [e.g. 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6)], using carbon-free electrodes. Due to the positive charges of BMIM+ on the C-dots, the final products presented in a precipitate form on the cathode, and the unreacted nitriles and BMIMPF6 can be easily removed by simple vacuum filtration. The as-prepared solid-state C-dots can be well dispersed in an aqueous medium with excellent photoluminescence properties. The average size of the C-dots was found to be 3.02 ± 0.12 nm as evidenced by transmission electron microscopy. Other techniques such as UV-vis spectroscopy, fluorescence spectroscopy, X-ray photoelectron spectroscopy and atomic force microscopy were applied for the characterization of the C-dots and to analyze the possible generation mechanism. These C-dots have been successfully applied in efficient cell imaging and specific ferric ion detection.

Paper-based chips (PB-chips; also referred to as lab-on-paper chips) are using patterned paper as a substrate in a lab-on-a-chip platform. They represent an outstanding technique for fabrication of analytical devices for multiplex analyte assays. Typical features include low-cost, portability, disposability and small sample consumption. This review (with 211 refs.) gives a comprehensive and critical insight into current trends in terms of materials and techniques for use in fabrication, modification and detection. Following an introduction into the principles of PB-chips, we discuss features of using paper in lab-on-a-chip devices and the proper choice of paper. We then discuss the versatile methods known for fabrication of PB-chips (ranging from photolithography, plasma treatment, inkjet etching, plotting, to printing including flexographic printing). The modification of PB-chips with micro- and nano-materials possessing superior optical or electronic properties is then reviewed, and the final section covers detection techniques (such as colorimetry, electrochemistry, electrochemiluminescence and chemiluminescence) along with specific (bio)analytical examples. A conclusion and outlook section discusses the challenges and future prospectives in this field.

•Electron transfer of attached graphene via electrochemical reduction was studied.•The attached graphene was with standing configuration on the electrode.•Ru(bpy)32+ was used as the redox probe to evaluate the electron transfer.•The Electron transfer is much faster than that of tiled graphene modified GCE.•Stable Ru(bpy)32+ ECL sensor was fabricated with the standing graphene.In this study, electron transfer behavior of the graphene nanosheets attachment on glassy carbon electrode (GCE) via direct electrochemical reduction of graphene oxide (GO) is investigated for the first time. The graphene modified electrode was achieved by simply dipping the GCE in GO suspension, followed by cyclic voltammetric scanning in the potential window from 0 V to −1.5 V. Tris(2,2′-bipyridyl)ruthenium(II) [Ru(bpy)32+] was immobilized on the graphene modified electrode and used as the redox probe to evaluate the electron transfer behavior. The electron transfer rate constant (Ks) was calculated to be 61.9±5.8 s−1, which is much faster than that of tiled graphene modified GCE (7.1±0.6 s−1). The enhanced electron transfer property observed with the GCE modified by reductively deposited graphene is probably due to its standing configuration, which is beneficial to the electron transfer comparing with the tiled one. Because the abundant oxygen-containing groups are mainly located at the edges of GO, which should be much easier for the reduction to start from, the reduced GO should tend to stand on the electrode surface as evidenced by scanning electron microscopy analysis. In addition, due to the favored electron transfer and standing configuration, the Ru(bpy)32+ electrochemiluminescence sensor fabricated with standing graphene modified GCE provided much higher and more stable efficiency than that fabricated with tiled graphene.Figure optionsDownload full-size imageDownload as PowerPoint slide