Ultrasensitive and ultraselective detection of the gene requires emergency development to meet the medical demands and infectious disease control. Herein we report a versatile and scalable method based on electrochemical-chemical-cyclic amplification (EC-CA) and fluorescence detection for ultrasensitive gene sensing. The EC-CA is achieved by an electro-Fenton reaction (EFR). The hydroxyl radicals generated at EFR are trapped by terephthalic acid to form highly fluorescent 2-hydroxyterephthalic acid, which can be sensitively detected by a fluorescence spectrophotometer. The method is the first to be able to amplify the signal and reduce the noise simultaneously by using the conventional analytical methods directly. This described method can be used for reliable Fe3+ quantification in the range from 0.1 nM to 0.08 mM. The calculated limit of detection (LOD) is 0.02 nM. Then, hepatitis B virus (HBV) and p53 gene were detected by this proposed method through introducing the Fe3O4 nanoparticles into the gene hybridization system. The LODs for HBV and p53 gene even topped out at 2.6 pM and 1.7 fM, respectively. We demonstrated that the finally recorded signal was triply amplified through the EC cycle, Fe3O4 nanoparticles, and sensitive fluorescence detection. At the same time, the background signal arisen from matrix effects and readout noise was effectively suppressed. This method shows it is simple, convenient, and operational through the detection of Fe3+, HBV, and the p53 gene in blood samples, respectively. We believe our method will make a significant, near-term impact on the development of high-sensitivity methods that are versatile and scalable.

On using magnetic Fe3O4 as the core of nitrogen-doped carbon (NC) matrix composite Fe3C (Fe3C/Fe3O4@NC), it not only shows good peroxide-like and oxidase-like properties but also has excellent Fenton-like degradability. Based on the Fenton-like properties of the core–shell nanocomposites, ciprofloxacin can be degraded by activated peroxo monosulfate. The magnetic core is easy to recover, and the shell has good catalytic performance. The degradation rate using Fe3C/Fe3O4@NC as the catalyst was 7.3 and 2.9 times that of Fe3O4 and Fe3O4@NC as catalysts, respectively, and the sulfate radical was found to be the main active species involved in the degradation. The actual performance of the catalyst was evaluated in simulated wastewater and different water sources. Inorganic anions slightly changed the degradation rate, while common organic compounds in wastewater reduced the degradation rate. The composite materials have excellent catalytic performance, good magnetic response, and repeatability, which are conducive to practical application in wastewater treatment process.

Nucleic acid detection is undoubtedly one of the most important research fields to meet the medical needs of genetic disease diagnosis, cancer treatment, and infectious disease prevention. However, the practical detection methods based on biological amplification are complex and time-consuming and require highly trained operators. Herein, we report a simple, rapid, and sensitive method for the nucleic acid assay by fluorescence or naked eye using chemical cyclic amplification. The addition of hydroxylamine (HA) during the Fenton reaction can continuously generate hydroxyl radicals (•OH) via Fe3+/Fe2+ cycle, termed as “hydroxylamine boosts the Fenton reaction (Fenton-HA system)”. Meanwhile, the reducing substances, such as terephthalic acid or o-phenylenediamine, react with •OH to generate oxidized substances that can be recognized by the naked eye or detected by fluorescence so as to realize the detection of Fe3+. The concentration of Fe3+ has a good linear relationship with fluorescence intensity in the range of 0.1 to 100 nM, and the limit of detection is calculated to be 0.03 nM (S/N = 3). Subsequently, Fe was introduced into the nucleic acid hybridization system after the Fe source was transformed into Fe3+, and the nucleic acids were indirectly determined by this method. This Fenton-HA system was used for sensing HIV-DNA and miRNA-21 to verify the validity of this method in nucleic acid detection. The detection limits were as low as 2.5 pM for HIV-DNA and 3 pM for miRNA-21. We believe that our work has unlocked an efficient signal amplification strategy, which is expected to develop a new generation of highly sensitive chemical biosensors.

Traditional Metal-Organic Frameworks (MOFs), although able to accumulate some chemicals from solution, are usually electrochemical inert. Here, the spherical MIL-53(NiFe) MOFs have been synthesized by a simple solvothermal method. A...