Mesoporous MnFe2O4 magnetic nanoparticles as a peroxidase mimic for the colorimetric detection of urine glucose

Cu-BTC Derived Mesoporous CuS Nanomaterial as Nanozyme for Colorimetric Detection of Glutathione

In this paper, Cu-BTC derived mesoporous CuS nanomaterial (m-CuS) was synthesized via a two-step process involving carbonization and sulfidation of Cu-BTC for colorimetric glutathione detection. The Cu-BTC was constructed by 1,3,5-benzenetri-carboxylic acid (H3BTC) and Cu2+ ions. The obtained m-CuS showed a large specific surface area (55.751 m2/g), pore volume (0.153 cm3/g), and pore diameter (15.380 nm). In addition, the synthesized m-CuS exhibited high peroxidase-like activity and could catalyze oxidation of the colorless substrate 3,3',5,5'-tetramethylbenzidine to a blue product. Peroxidase-like activity mechanism studies using terephthalic acid as a fluorescent probe proved that m-CuS assists H2O2 decomposition to reactive oxygen species, which are responsible for TMB oxidation. However, the catalytic activity of m-CuS for the oxidation of TMB by H2O2 could be potently inhibited in the presence of glutathione. Based on this phenomenon, the colorimetric detection of glutathione was demonstrated with good selectivity and high sensitivity. The linear range was 1-20 μM and 20-300 μM with a detection limit of 0.1 μM. The m-CuS showing good stability and robust peroxidase catalytic activity was applied for the detection of glutathione in human urine samples.

Study on the efficiency and recyclability of Fenton-MnFe2O4 for the degumming of hemp fibers

Traditional alkali degumming (TAL) has been widely used for hemp degumming; however, the produced degumming waste liquid pollutes the environment. For this phenomenon, an improved Fenton oxidation degumming process was developed in this study, that is, MnFe2O4 (Fenton-MnFe2O4) was added to the Fenton system. The purpose was to reduce the reaction time and the addition of chemical reagents, and reuse the added MnFe2O4. The effects of the Fenton-MnFe2O4 system on fiber properties (such as residual gum rate, and breaking strength) and the recyclability of MnFe2O4 were studied. The results indicated that the hemp fiber could be separated by Fenton-MnFe2O4 treatment (5.30% H2O2 (w/w), 0.310% FeSO4·7H2O (w/w), 0.040% MnFe2O4 (w/w), 40.0 °C, 40.0 min). The breaking strength of the refined fiber was 18.22 cN per dtex, and the residual gum rate was 5.47%. Compared with the TAL system, the time was shorter, energy consumption was less and pollution was smaller. In addition, the fiber treated with MnFe2O4 after five cycles still showed excellent properties, namely, 15.76 cN per dtex breaking strength and 7.79% residual gum rate, which met the needs of the spinning process. Therefore, Fenton-MnFe2O4 show great development potential in hemp fiber degumming.

Integration of CuS/ZnIn2S4 flower-like heterojunctions and (MnCo)Fe2O4 nanozyme for signal amplification and their application to ultrasensitive PEC aptasensing of cancer biomarker

Vascular endothelial growth factor 165 (VEGF₁₆₅) is a crucial regulator of angiogenesis and works as a major protein biomarker of cancer metastasis. Therefore, its quantitative detection is pivotal in clinic. In this work, CuS/ZnIn₂S₄ flower-like heterojunctions had strong and stable photocurrents, which behaved as photoactive material to construct a photoelectrochemical (PEC) aptasensor for detecting VEGF₁₆₅, combined by home-prepared (MnCo)Fe₂O₄ nanozyme-mediated signal amplification. The interfacial photo-induced electron transfer mechanism was chiefly discussed by UV-vis diffuse reflectance spectroscopy in details. Specifically, the (MnCo)Fe₂O₄ modified VEGF₁₆₅ aptamer was released from the PEC aptasensing platform for its highly specific affinity to target VEGF₁₆₅, which terminated the color precipitation reaction, ultimately recovering the PEC signals. The developed sensor displayed a wider linear range from 1 × 10^-2 to 1 × 10⁴ pg mL^-1 with a smaller limit of detection (LOD) of 0.1 fg mL^-1. This study provides some valuable insights for building other ultrasensitive aptasensors for clinical assays of cancer biomarkers in practice.