Browsing by Author "Cui, Daxiang"

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    A Graphene Oxide Coated Gold Nanostar Based Sensing Platform for Ultrasensitive Electrochemical Detection of Circulating Tumor DNA
    (Analytical Methods, 2020) Rahman, Mahbubur; Cui, Daxiang; Zhou, Shukui; Zhang, Amin; Chen, Di
    A high-performance electrochemical sensing platform inspired by a functional ‘green’ electrochemical reduction pathway was developed to identify and detect circulating tumor DNA (ctDNA) of gastric carcinoma in peripheral blood. The assembly of the biosensor, consisting of graphene oxide-wrapped gold nanostars (GO-AuNSs), was fabricated on a glassy carbon electrode using the surface chemistry of ‘layer-by-layer’ modification via an electrochemical route. The electrodeposition of the GO-AuNS nanocomposite on the electrode's surface effectively improved its electrochemical response and enhanced its immobilization pathway. At the same time, it demonstrated the electrochemical phenomena caused by DNA immobilization and hybridization events sans complex labelling or other indicators. The immobilization of the probe DNA occurred due to the π–π (weak) interactions between the GO-AuNS composite and the DNA bases. The hybridization of the probe DNA with ctDNA resulted in the formation of a helix structure, which precipitated the release of the resulting dsDNA from the electrode's surface. The immobilization and hybridization events caused a ‘signal off’ and ‘signal on’ model by respectively decreasing and increasing the signal current. The prepared composite nanostructure and the subsequently modified electrodes were characterized using Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). The electrochemical response of the biosensor was elucidated using Differential Pulse Voltammetry (DPV), Cyclic Voltammetry (CV), and Electrochemical Impedance Spectroscopy (EIS). A linear relationship was established between the oxidation peak currents (DPV) and the different concentrations of ctDNA within the range of 1.0 × 10−20 M to 1.0 × 10−12 M (R2 = 0.998), with a detection limit (LOD) of 1.0 × 10−20 M (S/N = 3). The developed method shows translational prospects in ctDNA detection.
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    Extraction, Radical Scavenging and Antimicrobial Activity of Essential Oils of Root of Dryopteris Marginalis
    (Asian Journal of Chemistry, 2019) Islam, Md. Zahidul; Foisal, Jannat Al; Rahman, Mahbubur; Mimi, Mst. Afsana; Islam, Faridul; Habib, Rasel; Khan, Nowshin Farzana; Rahman, Md. Atiqur; Parvin, Tanzima; Cui, Daxiang
    The aim of the study was to characterize the chemical constituents and determine antibacterial and antioxidant activities of essential oils and three different extracts of Dryopteris marginalis. The root had essential oil yield of 0.36 % (w/w) in which 12 organic compounds representing 97.22% of the root oils were identified. Tyranton was found as the most abundant component with 77.571 % of the total concentration in the essential oil. The zones of inhibition of different organic extracts against the tested bacteria were found in the range of 6.5-15 mm. Pseudomonas was the most vulnerable with MICs of 15.62 μg/mL by both ethyl acetate and petroleum ether extract producing 3.8 mm zone of inhibition. The essential oils extracted from roots of Dryopteris marginalis showed maximum 85.29 % inhibition of radical scavenging at 2 mg/mL concentration. Among all root extracts, methanol extract exhibited 41.11 % inhibition at 2 mg/mL concentration.