Characterization of Selenite Reduction by <i>Lysinibacillus</i> sp. ZYM‑1 and Photocatalytic Performance of Biogenic Selenium Nanospheres

This study comprehensively investigated the feasibility of biogenic selenium nanomaterials (Se NMs) as a photocatalyst in dye degradation. The marine selenite-reducing bacterium Lysinibacillus sp. ZYM-1 was isolated. This strain can reduce selenite to Se NMs over a wide range of pH (5–9), selenite concentration (1–25 mM), and temperature (20–50 °C) within 48 h. Draft genome data suggested that sulfite reductase may be responsible for selenite reduction. Biogenic Se NMs generated under different conditions were subsequently characterized. The morphology and size of Se NMs were dependent on medium composition, pH, incubation time, selenite concentration, and temperature. Se nanospheres (Se NSs) exhibited significant visible light-driven photocatalytic activity on Rhodamine B (RhB) with H₂O₂. Three N-deethylation intermediates and phthalic acid were identified as degradation products of RhB by using liquid chromatography-high resolution mass spectrometry (LC-HRMS), indicating the coexistence of chromophore cleavage and the N-deethylation pathway

Bacteria-Mediated Ultrathin Bi₂Se₃ Nanosheets Fabrication and Their Application in Photothermal Cancer Therapy

Bismuth selenide (Bi₂Se₃) attracts a lot of attention nowadays due to its unique electronic and thermoelectric properties. In this study, fabrication of Bi₂Se₃ nanosheets by selenite-reducing bacterium (SeRB) was first reported. Morphology, size, and location of the biogenic Bi₂Se₃ are bacteria-dependent. It is difficult to separate Bi₂Se₃ generated by <i>Bacillus cereus</i> CC-1 (Bi₂Se₃-C) from the biomass because of strong interaction with the cell membrane. However, Bi₂Se₃ produced by <i>Lysinibacillus</i> sp. ZYM-1 (Bi₂Se₃-Z), is highly dispersed in extracellular space with high stability. Further characterization by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM) on Bi₂Se₃-Z indicates that the product is a rhombohedral-phase, ultrathin nanosheet-like structure with an average size of ∼100 nm. Subsequently, the photothermal performance of Bi₂Se₃-Z with the irradiation of 808 nm near-infrared (NIR) laser was determined. When the Bi₂Se₃-Z concentration was 26 mg L^–1, and irradiation power was 2 W, the photothermal conversion efficiency was calculated as 30.7%. At the same condition, 100% of the MCF7 and A549 cancer cells were killed within 10 min of irradiation in vitro. Moreover, using 1% (v/v) PVP as surfactant, a novel nanodumbbell structure of Bi₂Se₃ was obtained. Overall, this bacteria-driven Bi₂Se₃ fabrication paves a new way for biocompatible photothermal nanomaterials

Computer Simulation Studies on the pH-Responsive Self-Assembly of Amphiphilic Carboxy-Terminated Polyester Dendrimers in Aqueous Solution

This paper investigates the pH-responsive self-assembly of an amphiphilic carboxyl-terminated polyester dendrimer, H20–COOH, in aqueous solution using the dissipative particle dynamics method. The electrostatic interactions were described by introducing the explicit interaction between the smeared charges on ionized polymer beads and the counterions. The results show that the self-assemblies could change from unimolecular micelles, microphase-separated small micelles, wormlike micelles, sheetlike micelles, and small vesicles to large vesicles with the decrease in the degree of ionization (α) of carboxylic acid groups. In addition, the detailed self-assembly mechanisms and the molecular packing models have also been disclosed for each self-assembly stages. Interestingly, the wormlike micelles are found to change from linear to branched when α decreases from 0.182 to 0.109. The current work might serve as a comprehensive understanding on the effect of carboxylic acid groups on the self-assembly behaviors of dendritic polymers

A novel two-dimensional polyrotaxane network self-assembled by heterowheel [4]pseudorotaxane

<p>A novel heterowheel pseudorotaxane comprised of one guest, one cucurbit[7]uril and two cucurbit[6]urils was synthesised and characterised by ¹H NMR, single crystal X-ray diffraction analysis and thermogravimetric analysis. Single crystal X-ray diffraction analysis demonstrates that the heterowheel pseudorotaxane self-assembles into two-dimensional polyrotaxane network with the aid of water molecules and hydrogen bonds. Every four heterowheel pseudorotaxanes self-assemble into a parallelogram, which is the basic unit of the 2D network.</p> <p>A novel heterowheel pseudorotaxane consisting of one guest, one cucurbit[7]uril and two cucurbit[6]urils was synthesised. Single crystal X-ray diffraction analysis demonstrates that the heterowheel pseudorotaxane self-assembles into two-dimensional polyrotaxane network with the aid of water molecules and hydrogen bonds. Every four heterowheel pseudorotaxanes self-assemble into a parallelogram, which is the basic unit of the 2D network.</p