Effect of Fe and Co Incorporation on Morphology and Oxygen Evolution Reaction Performance of β‑Co(OH)₂: An In Situ Electrochemical Atomic Force Microscopy Investigation

Cobalt-based hydroxides are widely used as classical electrocatalysts in the oxygen evolution reaction (OER), and their performance is usually regulated by incorporation. It is essential for improving the efficiency of catalysis to track the dynamic changes during the electrochemical process. Here, the different morphological evolution and OER performance variation of incorporation of Fe and Co into β-Co(OH)2 nanosheets under electrochemical conditions were elucidated by in situ electrochemical atomic force microscopy. The production of numerous particles is observed on the initial flat surface of β-Co(OH)2 nanosheets during potential cycling in a Fe2+-spiked electrolyte, while the formation of little flakes is the principally morphological change during potential cycling in a Co2+-spiked electrolyte. This type of discrepancy is due primarily to the fact that the complete irreversible oxidation of β-Co(OH)2 is promoted by Fe incorporation instead of Co incorporation. Additionally, the OER performance of the nanosheets with Fe incorporation presents a more significant improvement compared with that of the nanosheets with Co incorporation. It is on account that the OER performance benefits from Fe incorporation as well as the resulting complete conversion of β-Co(OH)2 into β-CoOOH and the generation of particles with a greater number of highly reactive sites for the OER. Our findings are conducive to gaining an essence of how the incorporation affects the OER properties of β-Co(OH)2 nanosheets through modifying morphological and component evolutions, which are vital for the advancements of cobalt-based hydroxides

Forces and Kinetics of the <i>Bacillus subtilis</i> Spore Coat Proteins CotY and CotX Binding to CotE Inspected by Single Molecule Force Spectroscopy

Spores are uniquely stable cell types that are produced when bacteria encounter nutrient limitations. Spores are encased in a complex multilayered coat, which provides protection against environmental insults. The spore coat of <i>Bacillus subtilis</i> is composed of around 70 individual proteins that are organized into four distinct layers. Here we explored how morphogenetic protein CotE guides formation of the outermost layer of the coat, the crust, around the forespore by focusing on three proteins: CotE, CotY, and CotX. Single molecule force spectroscopy (SMFS) was used to investigate the interactions among CotE, CotY, and CotX at the single-molecule level. Direct interactions among these three proteins were observed. Additionally, the dissociation kinetics was also studied by measuring the unbinding forces of the complexes at different loading rates. A series of kinetic data of these complexes were acquired. It was found that the interaction of CotE and CotY was stronger than that of CotE and CotX

Porous Co₃O₄ Nanorods–Reduced Graphene Oxide with Intrinsic Peroxidase-Like Activity and Catalysis in the Degradation of Methylene Blue

A facile two step process was developed for the synthesis of porous Co₃O₄ nanorods–reduced graphene oxide (PCNG) hybrid materials based on the hydrothermal treatment cobalt acetate tetrahydrate and graphene oxide in a glycerol–water mixed solvent, followed by annealing the intermediate of reduced graphene oxide-supported Co­(CO₃)_0.5(OH)·0.11H₂O nanorods in a N₂ atmosphere. The morphology and microstructure of the composites were examined by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy and Raman spectroscopy. It is shown that the obtained PCNG have intrinsic peroxidase-like activity. The PCNG are utilized for the catalytic degradation of methylene blue. The good catalytic performance of the composites could be attributed to the synergy between the functions of porous Co₃O₄ nanorods and reduced graphene oxide

Revealing the Effect of Photothermal Therapy on Human Breast Cancer Cells: A Combined Study from Mechanical Properties to Membrane HSP70

Hyperthermia-induced overexpression of heat shock protein 70 (HSP70) leads to the thermoresistance of cancer cells and reduces the efficiency of photothermal therapy (PTT). In contrast, cancer cell-specific membrane-associated HSP70 has been proven to activate antitumor immune responses. The dual effect of HSP70 on cancer cells inspires us that in-depth research of membrane HSP70 (mHSP70) during PTT treatment is essential. In this work, a PTT treatment platform for human breast cancer cells (MCF-7 cells) based on a mPEG-NH2-modified polydopamine (PDA)-coated gold nanorod core–shell structure (GNR@PDA-PEG) is developed. Using the force-distance curve-based atomic force microscopy (FD-based AFM), we gain insight into the PTT-induced changes in the morphology, mechanical properties, and mHSP70 expression and distribution of individual MCF-7 cells with high-resolution at the single-cell level. PTT treatment causes pseudopod contraction of MCF-7 cells and generates a high level of intracellular reactive oxygen species, which severely disrupt the cytoskeleton, leading to a decrease in cellular mechanical properties. The adhesion maps, which are recorded by aptamer A8 functional probes using FD-based AFM, reveal that PTT treatment causes a significant upregulation of mHSP70 expression and it starts to exhibit a partial aggregation distribution on the MCF-7 cell surface. This work not only exemplifies that AFM can be a powerful tool for detecting changes in cancer cells during PTT treatment but also provides a better view for targeting mHSP70 for cancer therapy

Single Molecular Recognition Force Spectroscopy Study of a Luteinizing Hormone-Releasing Hormone Analogue as a Carcinoma Target Drug

The luteinizing hormone-releasing hormone-Pseudomonas aeruginosa exotoxin 40 (LHRH-PE40), is a candidate target drug associated with elevated LHRH receptor (LHRH-R) expression in malignant tumor tissue. The capability of LHRH-PE40 to recognize LHRH-Rs on a living cell membrane was studied with single molecular recognition force spectroscopy (SMFS) based on atomic force microscopy (AFM). The recognition force of LHRH-PE40/LHRH-R was compared with that of LHRH/LHRH-R by dynamic force spectroscopy. Meanwhile, cell growth inhibition assay and fluorescence imaging were presented as complementary characterization. The results show that LHRH moiety keeps its capability to recognize LHRH-R specifically, which implies that recombinant protein LHRH-PE40 can be a promising target drug