It is important to develop methods to determine cylindrospermopsin (CYN) at trace levels since CYN is a kind of widespread cyanobacterial toxin in water sources. In this study, a label-free impedimetric aptasensor has been fabricated for detecting CYN. In this case, the amino-substituted aptamer of CYN was covalently grafted onto the surface of the thionine–graphene (TH–G) nanocomposite through the cross-linker glutaraldehyde (GA). The reaction of the aptamer with CYN was monitored by electrochemical impedance spectroscopy because the CYN induced conformation change of the aptamer can cause a remarkable decrease of the electron transfer resistance. Under optimum conditions, the aptasensor exhibits high sensitivity and a low detection limit for CYN determination. The CYN can be quantified in a wide range of 0.39 to 78 ng mL−1 with a good linearity (R2 = 0.9968) and a low detection limit of 0.117 ng mL−1. In addition, the proposed aptasensor displays excellent stability, reusability and reproducibility.

Herein, we present the synthesis and application of a new type of graphene-based magnetic and plasmonic nanocomposite for magnetic-field-assisted drug delivery and chemo-photothermal synergistic therapy. The nanocomposites were prepared via conjugation of the PEGylated Fe2O3@Au core/shell nanoparticles (Fe2O3@Au NPs) with reduced graphene oxide (rGO). The hybrid nanostructures (rGO–Fe2O3@Au NPs) are superparamagnetic and show great photothermal conversion efficiency under 808 nm near-infrared (NIR) laser irradiation and high drug loading ability (1.0 mg mg−1). MTT cell viability assay demonstrates that the chemotherapeutic drug, doxorubicin loaded rGO–Fe2O3@Au NPs (DOX–rGO–Fe2O3@Au NPs) have synergistic interaction between photothermal therapy (PTT) and chemotherapy. Furthermore, in vitro studies using HeLa cells show that the chemo-photothermal therapeutic efficacy of DOX–rGO–Fe2O3@Au NPs can be dramatically improved by the assistance of magnetic-field-guided drug delivery.

•A simple way of preparing GO–AgNPs nanohybrids based on electrostatic interactions was developed.•Different densities, sizes and shapes of AgNPs have been conjugated to GO sheets easily.•AgNPs anchored on GO sheets showed better stability than that of colloidal AgNPs.•GO–AgNPs exhibited enhanced antibacterial activities towards both G+ and G− bacterial strains than that of AgNPs.A simple method based on electrostatic interactions was utilized to assemble silver nanoparticles (AgNPs) to graphene oxide (GO) sheets. This method allows conjugation of AgNPs with desired morphologies (densities, sizes and shapes) onto GO. In this process, poly(diallyldimethylammonium chloride) (PDDA) was introduced as an adhesive agent. The as-prepared graphene oxide–AgNPs composites (GO–AgNPs) have enhanced colloid stability and photo-stability than that of AgNPs. After conjugating to GO sheets, the antibacterial activities of AgNPs against Gram negative (G−) bacterial strain (Escherichia coli, E. coli) and Gram positive (G+) bacterial strain (Bacillus subtilis, B. subtilis) have been improved significantly. The antibacterial activity of GO–AgNPs is dependent on the size of AgNPs, i.e. the small AgNPs modified GO sheets show more effective antibacterial capability than that of large AgNPs modified GO sheets. Compared with AgNPs, the enhanced antibacterial activity of GO–AgNPs might not only be due to high stability of AgNPs anchored on GO sheets, but also the positive charged surface of hybrids which increases the electrostatic interaction of bacterial cell membrane with nanohybrids.

•A conducting hydrogel-based electrochemical sensor was developed for rapid detection of copper (II) ions.•High selective recognition of copper (II) ions down to 1 nmol L−1 is demonstrated.•The polyacrylamide-phytic acid-polydopamine conducting hydrogel was synthesized for the first time.•The conducting hydrogel presents a great removal capacity toward copper (II) ions.In this work, a conducting porous polymer hydrogel-based electrochemical sensor has been developed for rapid detection of copper (II) ions (Cu2+). The polymer (termed as PAAM/PA/PDA) hydrogel is prepared through multi-interactions of the monomers dopamine (DA), acrylamide (AAM) and phytic acid (PA) under mild ambient conditions: the AAM polymerizes through free-radical polymerization, DA occurs poly coupling reaction, and PA crosslinks polydopamine (PDA) and polyacrylamide (PAAM) by hydrogen bonds. The three dimensional (3D) network nanostructured PAAM/PA/PDA hydrogel not only provides a large surface area for increasing the amount of immobilized molecules/ions, but also exhibits a good conductivity. The PAAM/PA/PDA hydrogel-based electrochemical sensor exhibits a low detection limit (1 nmol L−1, S/N=3) and wide linear range (from 1 nmol L−1 to 1 µmol L−1) for Cu2+ detection in aqueous samples. Furthermore, the Cu2+ can be sensitively detected by the electrochemical sensor in different sample matrices, indicating that the electrochemical sensor could be used to monitor Cu2+ with reasonable assay performance in practical samples. The PAAM/PA/PDA hydrogel also exhibits a good capacity to remove Cu2+(231.36±4.70 mg g−1), which is superior to those of other adsorption materials reported in the literature. The facile synthesized PAAM/PA/PDA hydrogel provides a novel and regenerable platform for monitoring and removing Cu2+ in real samples.