A sensitive and reagentless electrochemical aptatoxisensor was developed on cobalt (II) salicylaldiimine metallodendrimer (SDD–Co(II)) doped with electro-synthesized silver nanoparticles (AgNPs) for microcystin-LR (L, l-leucine; R, l-arginine), or MC-LR, detection in the nanomolar range. The GCE|SDD–Co(II)|AgNPs aptatoxisensor was fabricated with 5’ thiolated aptamer through self-assembly on the modified surface of the glassy carbon electrode (GCE) and the electronic response was measured using cyclic voltammetry (CV). Specific binding of MC-LR with the aptamer on GCE|SDD–Co(II)|AgNPs aptatoxisensor caused the formation of a complex that resulted in steric hindrance and electrostatic repulsion culminating in variation of the corresponding peak current of the electrochemical probe. The aptatoxisensor showed a linear response for MC-LR between 0.1 and 1.1 µg·L−1 and the calculated limit of detection (LOD) was 0.04 µg·L−1. In the detection of MC-LR in water samples, the aptatoxisensor proved to be highly sensitive and stable, performed well in the presence of interfering analog and was comparable to the conventional analytical techniques. The results demonstrate that the constructed MC-LR aptatoxisensor is a suitable device for routine quantification of MC-LR in freshwater and environmental samples.
Human epidermal growth factor receptor 2 (Her2/neu) is a biomarker that is overexpressed in human breast cancers. A quantum dots (QDs) -based genosensor for Her2/neu oncogene was developed with gallium telluride QDs and amine-terminated probe ssDNA (NH 2 -5 0 -AATTCCAGTGGCCATCAA-3 0 ), that is complementary to the DNA sequence of a section of the ERF gene of HER-2/neu (i.e. 5 0 -GAACATGAAGGACCGGTGGGC-3 0 ). The QDs were highly crystalline, 6 nm (from XRD) in size and had band gap values of 3.3 eV and 3.5 eV calculated from fluorescence emission and UV-visible absorption data, respectively. The sensor sensitivity and limit of detection values were 10.0 mA ng À1 mL À1 and 0.2 pg mL À1 Her2/neu oncogene, respectively.
Copper selenide quantum dot (CuSeQD) materials functionalised with mercaptoalkanoic acids {3-mercaptopropionic acid (3-MPA), 6-mercaptohexanoic acid (6-MHA) and mercaptosuccinic acid (MSA)} were synthesized by a reproducible aqueous colloidal technique at room temperature. The impact of the capping agents on the size and the crystallinity of the CuSeQD materials, were investigated by small angle X-ray scattering (SAXS) and X-ray diffraction (XRD) spectroscopic techniques, respectively. SAXS results confirmed that 6-MHA-CuSeQD had the smallest average particle core size when dried, whereas MSA-CuSeQD had the smallest size in aqueous solution, though with a tendency to aggregate. Dynamic light scattering (DLS) measurements indicated strong bonding of the capping agents to CuSe particles, with MSA being the weakest binding agent, as confirmed by comparatively, low Zeta potential(ζ = À 31.1 mV) and high polydispersity index (0.469) values. UV-Vis absorption studies confirmed a large blue shift of the band gap for the QD compared to the bulk material, with characteristic absorption band (λ) and direct band gap (E gd ) values being (λ = 435 nm, E gd = 8.0 eV), (λ = 400 nm, E gd = 5.6 eV) and (λ = 340 nm, E gd = 4.0 eV), for 6-MHA-CuSeQD, 3-MPA-CuSeQD and MSA-CuSeQD, respectively. As supported by the formal potential values for 6-MHA-CuSeQD (E 0' � 120 mV), 3-MPA-CuSeQD (E 0' � 159 mV) and MSA-CuSeQD (E 0' � 183 mV), the smaller the particle size, the lower the potential required for the application of the quantum dots in an electron transfer process.[a] L.
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