A novel immunosensor based on cobalt oxide nanocomposite modified single walled carbon nanohorns for the selective detection of aflatoxin B1.

We developed a novel, sensitive, and selective platform for the specific determination of aflatoxin B1 (AFB1). Single-walled carbon nanohorns decorated by a cobalt oxide composite and gold nanoparticles were created to provide facile electron transfer and improve the sensor's sensitivity. In addition, we attributed the selectivity of the proposed sensor to the specific binding property of the anti-aflatoxin B1 antibody. We clarified the specific interaction of the proposed immunosensor to AFB1 using homology modeling combined with molecular docking. In the presence of AFB1, the current signal of the modified electrode reduced; this involved specific antibody-antigen binding, including hydrophobic hydrogen bonding and pi-pi stack interactions. The new AFB1 sensor platform showed two linearity ranges of 0.01-1 ng mL-1 and 1-100 ng mL-1, with the limit of detection at 0.0019 ng mL-1. We investigated the proposed immunosensor in real samples, including peanuts, certified reference material of a peanut sample (labeled 206 µg kg-1 AFB1), corn, and chicken feed. The sensor's accuracy was 86.1-104.4% recovery, which agrees with the reference HPLC technique using paired t-test analysis. The present work shows excellent performance for AFB1 detection and could be applied for food quality control or modified to detect other mycotoxins.

An electrochemical sensor for the voltammetric determination of artemisinin based on carbon materials and cobalt phthalocyanine.

An electrochemical sensor for the determination of artemisinin has been developed based on a glassy carbon electrode modified with hybrid nanocomposites of cobalt phthalocyanine, graphene nanoplatelets, multi-walled carbon nanotubes and ionic liquids (IL). To improve the sensitivity and selectivity of the sensor, cobalt phthalocyanine (CoPc) was used as an effective redox mediator to promote and catalyze the artemisinin reduction. Furthermore, the graphene nanoplatelets and multi-walled carbon nanotubes were used as excellent conducting supporting materials to improve the sensitivity of the electrochemical sensor. Moreover, IL with a surface charge was also employed to prevent aggregation of the graphene nanoplatelets and multi-walled carbon nanotubes. The analytical signal was generated from the reduction of Co(III)Pc generated by artemisinin. The proposed electrochemical sensor was applied to the detection of artemisinin using differential pulse voltammetry and provided a signal with wide linearity ranging from 1.5-60 µM and 60-600 µM and a detection limit of 0.70 µM (3SD/m). Furthermore, the proposed sensor displayed good repeatability and reproducibility of 2.9-3.0 and 3.1-4.4% RSD, respectively. Applications of the sensor to drug and plant samples demonstrated accuracy in a range of 105-116% recoveries. In addition, the results were in good agreement with those obtained from the HPLC method as a reference technique. Thus, the proposed electrochemical sensor provides a new alternative platform for sensitive and selective determination of artemisinin in the analysis of pharmaceuticals with good precision and accuracy.

A portable selective electrochemical sensor amplified with Fe3O4@Au-cysteamine-thymine acetic acid as conductive mediator for determination of mercuric ion.

Mercury ion (Hg2+) is considered to be one of the most toxic heavy metal ions and can cause adverse effects on kidney function, the central nervous system, and the immune system. Therefore, it is important to develop a fast and simple method for sensitive and selective detection of Hg2+ in the environment. This research proposes a portable electrochemical sensor for rapid and selective detection of Hg2+. The sensor platform is designed based on thymine acetic acid anchored with cysteamine-conjugated core shell Fe3O4@Au nanoparticles (Fe3O4@Au/CA/T-COOH) immobilized on a sensing area of a screen-printed carbon electrode (SPCE) with the aid of an external magnetic field embedded in a homemade electrode holder for ease of handling. In the presence of Hg2+, the immobilized thymine combines specifically with Hg2+ and forms a thymine-Hg2+-thymine mismatch (T-Hg2+-T). The resulting amount of Hg2+ was determined by differential pulse anodic stripping voltammetry (DPASV). Under optimal conditions, the sensor exhibited two wide linearities in a range from 1 to 200 µg L-1 and 200-2200 µg L-1 with the reliability coefficient of determination of 0.997 and 0.999, respectively. The detection limit (LOD) and the quantification limit (LOQ) were also determined to be 0.5 µg L-1 and 1.0 µg L-1, respectively. The sensor was further applied for determination of Hg2+ in water samples, a certified reference material and fish samples. The results were compared with flow injection atomic spectroscopy-inductively coupled plasma-optical emission spectroscopy (FIAS-ICP-OES) systems as a reference method. Results obtained with the proposed sensor were relatively satisfactory, and they showed no significant differences at a 95% confidence level by t-test from the standard method. Therefore, considering its fast and simple advantages, this novel strategy provides a potential platform for construction of a Hg2+ electrochemical sensor.