Aceclofenac (ACF) is a kind of antipyretic, analgesic, and antiarthritic drug, which is clinically suitable for the treatment of rheumatoid arthritis. However, the morphology of ACF produced in the crystallization process is easily regulated by different solvents, which has a significant effect on the powder properties of the ACF crystals. Therefore, the study of crystal habits is needed for producing ACF with a better performance. In this study, the effects of different solvents on the growth of the ACF crystal were studied by analyzing the morphology of ACF in various solvents and comprehensive simulation calculations. It was found that the ACF crystals in ethanol (EAL) and acetonitrile (ACE) were quadrangular in shape. In methyl acetate (MA), acetone (ACT), and n-propanol (NPL), the lateral aspect of the (101̅) facet is clearly prominent. More interestingly, pentagonal crystals are found only in methanol (MEL), and the (002) facet eventually disappears as they grow. Through molecular dynamics simulations, we have found that the attachment energy Eatt of crystal facets, the Connolly surface coefficient R, and solvent effects Es are the main factors influencing the growth of ACF crystals. The competitive adsorption of ACF and solvent molecules onto crystal facets accounts for morphology change during the growth process. By establishing a strong link between experimental observations and simulation results, this study favors the morphology control of the ACF crystal.
Pollutant degradation is present mainly in the surface layer of biofilms, and the surface layer is the most vulnerable to impairment by toxic pollutants. In this work, the effects of nanosized TiO2 (n-TiO2) on the average thicknesses of Bacillus subtilis biofilm and on bacterial attachment on different surfaces were investigated. The binding mechanism of n-TiO2 to the cell surface was also probed. The results revealed that n-TiO2 caused biofilm dispersal and the thicknesses decreased by 2.0 to 2.6 μm after several hours of exposure. The attachment abilities of bacteria with extracellular polymeric substances (EPS) on hydrophilic surfaces were significantly reduced by 31% and 81% under 10 and 100 mg/liter of n-TiO2, respectively, whereas those of bacteria without EPS were significantly reduced by 43% and 87%, respectively. The attachment abilities of bacteria with and without EPS on hydrophobic surfaces were significantly reduced by 50% and 56%, respectively, under 100 mg/liter of n-TiO2. The results demonstrated that biofilm dispersal can be attributed to the changes in the cell surface structure and the reduction of microbial attachment ability.IMPORTANCE Nanoparticles can penetrate into the outer layer of biofilm in a relatively short period and can bind onto EPS and bacterial surfaces. The current work probed the effects of nanosized TiO2 (n-TiO2) on biofilm thickness, bacterial migration, and surface properties of the cell in the early stage using the surface plasmon resonance waveguide mode. The results demonstrated that n-TiO2 decreased the adhesive ability of both cell and EPS and induced bacterial migration and biofilm detachment in several hours. The decreased adhesive ability of microbes and EPS worked against microbial aggregation, reducing the effluent quality in the biological wastewater treatment process.
The crystal habit of pentaerythritol (PE) crystals is usually rod-shaped, which may lead to low bulk density and bad flowability compared with low aspect ratio crystals. In this study, dipentaerythritol (DPE), methylcellulose (MC), and hydroxypropyl methylcellulose (HPMC) were selected as additives to modify the morphology of PE crystals. In the presence of DPE, the bulk density of PE crystals was improved, and the aspect ratio was decreased. The modified attachment energy (AE) model was conducted to analyze changes in PE crystal habits in the presence of DPE, which characterizes the intensity of the interaction between DPE molecules and PE crystal faces. Spherical pentaerythritol crystals can be successfully prepared by adding MC and HPMC solution, and the formation mechanism can be divided into five steps.
危险品化学品经营许可证（带存储）