The traditional nucleic acid-modified electrode in room-temperature manner suffers from the drawback of time-consuming and uneven distribution. In this work, we adopted the freeze-thawing method to construct a nicking enzyme-powered DNA walking machine on the gold electrode. In the absence of kanamycin, the intact substrate strand can trigger the self-assembly and form G4 nanowires on the electrode surface. After adding hemin, a significant catalytic current of the TMB oxidization can be observed. By contrast, once the specific binding between aptamer and kanamycin occurs, the activated walking strand processes a consecutive binding-cleavage cycle with the substrate strand on the electrode surface. The residue substrate fragment is unable to trigger the subsequent G-quadruplex assembly, resulting in a decrease in catalytic current. Under optimal experimental conditions, a linear relationship between the kanamycin concentration and current decrease was obtained in the range from 5 to 100 pM, and the limit of detection was 1.44 pM. This method has also demonstrated practical performance in the spiked milk and honey with satisfactory recoveries of 107.1 % to 114.3 % and 94.3 % to 101.5 %, respectively.
Cancer cells require higher ROS levels to maintain their growth state of rapid division and spread·H 2 O 2 , as a kind of usual ROS molecule, is monitored by designing a new in-situ growth G4-nanowire-driven electrochemical biosensor, which is further used for probing H 2 O 2 released by rat astroglioma cell. In this process, the electrocatalytic performance to H 2 O 2 of G4-nanowire (containing G-quadruplex/hemin nanostructures) is employed as signal output, which is constructed by terminal deoxynucleotidyl transferase (TdT)-mediated polymerization in the dNTPs pool of dTTP and dGTP (4: 6). Then, the method is applied for H 2 O 2 monitoring in the range of 0.0003 ∼ 6 mM and the detection limit is estimated to be 0.075 μM (S/N = 3). More importantly, the content of H 2 O 2 generated in rat astroglioma cell is also calculated roughly, displaying an excellent feasibility for the related physiological and pathological studies. Later, TdT activity and its inhibitors are also probed orderly, and a wide linear range is presented with a detection limit of 0.81 mU/mL. It is hoped that the designed platform will provide a reference for exploring new ways to continuous dynamic surveillance of diseases in diagnosis and treatment stage.
Photodynamic therapy (PDT) is a light triggered therapy by producing reactive oxygen species (ROS), but traditional PDT may suffer from the real-time illumination that reduces the compliance of treatment and cause phototoxicity. A supramolecular photoactive G-quartet based material is reported, which is self-assembled from guanosine (G) and 4-formylphenylboronic acid/1,8-diaminooctane, with incorporation of riboflavin as a photocatalyst to the G4 nanowire, for post-irradiation photodynamic antibacterial therapy. The G4-materials, which exhibit hydrogel-like properties, provide a scaffold for loading riboflavin, and the reductant guanosine for the riboflavin for phototriggered production of the therapeutic H 2 O 2 . The photocatalytic activity shows great tolerance against room temperature storage and heating/cooling treatments. The riboflavin-loaded G4 hydrogels, after photo-irradiation, are capable of killing gram-positive bacteria (e.g., Staphylococcus aureus ), gram-negative bacteria (e.g., Escherichia coli ), and multidrug resistant bacteria (methicillin-resistant Staphylococcus aureus ) with sterilization ratio over 99.999%. The post-irradiated hydrogels also exhibit great antibacterial activity in the infected wound of the rats, revealing the potential of this novel concept in the light therapy.
危险品化学品经营许可证（带存储）