Search

A sandwich-type photoelectrochemical (PEC) immunosensor was constructed for sensitive detection of prostate specific antigen (PSA). It was based on electrochemically reduced graphene oxide-TiO 2 (ERGO-TiO 2) as photoelectrochemical platform to immobilize capture antibody (Ab 1). Then, quinone-rich polydopamine nanospheres (PDANS) loaded detection antibody (Ab 2) and photocurrent signal label, l -cysteine-coated cadmium sulfide quantum dots (CdSQDs). ERGO-TiO 2 displayed greatly improved photocurrent response to white light. CdSQDs conjugated with PDANS further amplified photocurrent signal because of the good conductivity of PDANS and ERGO. The increased photocurrent showed a linear correlation with PSA in the concentration range from 0.02 pg mL−1 to 200 ng mL−1 with the detection limit of 6.8 fg mL−1. It also revealed high selectivity and good stability. Image 1 • Electrochemically reduced graphene oxide-TiO 2 (ERGO-TiO 2) composite was prepared. • Quinone-rich polydopamine nanospheres (PDANS) was synthesized. • PDANS loaded with cadmium sulfide quantum dots was used as photocurrent signal label. • A photoelectrochemical sensor was constructed for detection of prostate specific antigen. [ABSTRACT FROM AUTHOR]

An electrochemical biosensor based on specific protein-DNA binding and rolling circle amplification (RCA) signal enlargement was developed for transcription factor (TF) detection. The TF biosensor was constructed by three oligo-DNA probes. Probe 1 (P1) was immobilized on gold electrode. Probe 2 (P2) hybridized with P1 to form a partially complementary double-stranded DNA. The complementary part contained a TF binding sequence, while the non-complementary part of P2 integrated a RCA primer sequence. Probe 3 (P3) can displace P2 by hybridizing with P1 to produce a completely complementary double-stranded DNA. When TF protein was introduced, a stable TF-DNA complex would form and the displacement reaction mentioned above was hindered, which made the RCA possible. Finally, the electrochemical redox probe methylene blue (MB) was bound to the RCA product and offered the available detection signal. Using nuclear factor kappa B (NF-κB) p65 as a model target, the fabricated electrochemical biosensor exhibited a wide linear region and a low detection limit. [ABSTRACT FROM AUTHOR]

A nanocomposite of graphene oxide encapsulated multiwalled carbon nanotubes (GO@MWNTs) was produced by a simple method. The composite displayed good dispersibility. An antiaromatic dimesityl-substituted nickel (II) norcorrole complex (NiNC) was noncovalently assembled on the GO@MWNTs to form a novel triad hybrid (GO@MWNTs-NiNC). The hybrid was characterized by different analytical techniques containing AFM, TEM, UV–vis spectroscopy, FT-IR spectroscopy, and TGA. Based on the excellent electrocatalytic properties of the triad hybrid towards dopamine (DA), a new electrochemical sensing platform for the selective and sensitive determination of DA was proposed. Under optimized conditions, the linear response range for determining DA were obtained over the range of 0.03–80 μM with the estimated detection limit of 0.012 μM (S/N = 3). The fabricated sensor also exhibits such features as good stability, selectivity, and reproducibility. [ABSTRACT FROM AUTHOR]

ABSTRCT A three-dimensional graphene oxide/carbon nanotubes-COOH hybrid (GO/CNTs-COOH) consisted of two-dimensional graphene oxide (GO) and one-dimensional carbon nanotubes-COOH (CNTs-COOH) was synthesized. The GO/CNTs-COOH hybrid exhibited excellent water-solubility owing to the high hydrophilicity of GO components and the carboxylation of carbon nanotubes. The cobalt hexacyanoferrate decorated GO/CNTs-COOH (CoHCF/GO/CNTs-COOH) has been prepared using electrostatic adsorption of Co 2+ on GO/CNTs-COOH and K 4 [Fe(CN) 6 ] as an in-situ chemical precipitant. FT-IR, Raman spectroscopy, TEM, SEM, and cyclic voltammetry were utilized to characterize the nanohybrid. The electrochemistry behavior of hydrazine on different modified electrodes was also studied. The CoHCF/GO/CNTs-COOH modified GCE (CoHCF/GO/CNTs-COOH/GCE) exhibited greatly enhanced electrocatalytic performance towards electro-oxidation of hydrazine. The oxidation peak currents showed good linear relationships with concentration of hydrazine. It can be applied to detect hydrazine in samples sensitively. [ABSTRACT FROM AUTHOR]

Highlights: [•] A noncovalent nanohybrid of cobalt tetraphenylporphyrin with chemically reduced graphene oxide was prepared. [•] The nanohybrid was characterized by UV–vis spectroscopy, Raman spectroscopy, and atomic force microscopy. [•] The nanohybrid can be applied to simultaneously detect AA, DA and UA with high sensitivity and low detection limit. [Copyright &y& Elsevier]

Abstract: A nanoscale hybrid of chemically reduced graphene oxide (CRGO) with ferrocene (Fc) was prepared through π–π stacking interaction between Fc and CRGO. FT-IR, Raman spectroscopy, SEM and cyclic voltammetry were utilized to characterize the nanohybrid of Fc with CRGO (Fc-CRGO). Fc-CRGO exhibited good stability and greatly improved electron-transfer behavior. Fc-CRGO and HRP were casted on the surfaces of glass carbon electrode (GCE) with the aid of chitosan for determination of H2O2. The choline oxidase (CHOD) cross-linked with chitosan was further dropped on the surface of modified electrode for detection of choline. The excellent biosensor performance was obtained by combining the advantages of nanohybrid and enzymes. Amperometric determination for choline has been performed at a very low applied potential of −0.10V. The linear response range was of 1.0∼400μM with a detection limit of 0.35μM. The current reached 95% of maximum response within 8s. [Copyright &y& Elsevier]

Graphical abstract Highlights • UV-induced peroxidase-like activity of gold nanoclusters (AuNCs) was prepared with simple method. • A colorimetric assay was developed by integrating the AuNC-chitosan composite membrane with varying colored GNPs serving as output signal. • The extendable colorimetric strategy was used to differentiate pathogenic bacteria and detect SE-B with high sensitivity. Abstract In this study, gold nanoclusters (AuNCs) in the presence of chitosan were prepared assisted by UV irradiation, which exhibit peroxidase-like property tested with H 2 O 2 /3,3,5,5-tetramethylbenzidine (TMB). The chitosan-AuNCs composite membrane also behaves peroxidase-like property and was characterized by TEM, AFM and SEM, which reveal the formed membrane was homogeneous and the AuNCs are predominantly spherical and well-dispersed without agglomeration in the membrane. A colorimetric assay was established by integrating immunoreactions occurred on the enzyme mimicking AuNC-chitosan composite membrane with varying colored GNPs serving as output signal. Three kinds of bacteria were chosen to serve as model bacteria to evaluate the selectivity of this sensor and Staphylococcus aureus (S. aureus), can be easily differentiated from Escherichia coli (E. coli) and Bacillus subtilis (B. subtilis). Such a colorimetric sensing is an extendable strategy due to the recognition element of probe may be replaceable on the catalytic AuNC-chitosan composite membrane. Staphylococcal enterotoxin B (SE-B) as low as 1.0 × 10−12 g/mL may be sensitively detected by naked-eye readout. As a practical application, the developed colorimetric strategy was used for rapid onsite screening strategy for S. aureus and detecting SE-B in food samples. This colorimetric strategy provides promising platform for rapid onsite screening pathogenic bacteria and detection of enterotoxin in food safety and environmental monitoring. [ABSTRACT FROM AUTHOR]

A novel fluorescent chemsensor TBS-protected salicylaldehyde azine (TSAA) for fluoride ion was developed based on aggregation-induced emission (AIE). The probe TSAA was prepared by the reaction of salicylaldehyde azine (SAA) with tert -butyldimethylsilyl chloride (TBS-Cl) via an unusual synthetic methodology and shows only non-emission. Upon treatment with fluoride in aqueous MeCN solution, the TBS protective group of probe TSAA was removed readily and the fluorescence of the probe was switched on, which resulted in a new fluorescence peak around 543 nm. The fluorescent intensity at 543 nm increases linearly with fluoride ion concentration in the range 1–50 μmol L −1 . This proposed probe shows excellent selectivity toward fluoride ion over other common anions and cations. [ABSTRACT FROM AUTHOR]

Abstract: Cryptochromes are blue-light photoreceptors that control many aspects of plant development. In this study, cryptochrome mutants of Arabidopsis were examined to assess the role of cryptchrome-1 (CRY1) in lateral roots growth. When grown in blue light for 12d, mutant seedlings (cry1) showed increased growth of lateral roots, while CRY1-overexpressing transgenic seedlings (CRY1ox) exhibited a marked decrease. Lateral roots growth of CRY1ox could be stimulated by auxin, but expression of PIN1 (efflux carrier of polar auxin transport) was strongly reduced. Contrary, the cry1 mutation showed the opposite effect, indicating that blue light and the auxin-signaling pathway interact in lateral roots growth of Arabidopsis. The free IAA content in CRY1ox roots was half of that in wild type and cry1 mutant roots. Moreover, the content of flavonoids (quercetin, kaempferol, isorhamnetin), which act as endogenous negative regulators of auxin transport, increased in CRY1ox seedlings. Taken together, these results suggest that Arabidopsis CRY1 restrains lateral roots growth by inhibiting auxin transport. [Copyright &y& Elsevier]