Theoretical and experimental aspects of microbicidal activities of hard surface disinfectants: are their label claims based on testing under field conditions?

High-touch environmental surfaces are important in the spread of many nosocomial pathogens. Although such surfaces are routinely disinfected, the testing and label claims of many common disinfectants do not reflect the realities of field use. A study was conducted to determine the influence of several crucial factors on the action of disinfectants in general, and to assess the killing efficiency of selected chemistries against Staphylococcus aureus and Pseudomonas aeruginosa, related to their drying times (i.e., after one application) and label-specified contact times using a quantitative carrier test. The products were also tested for their ability to wet a hydrophobic (epoxy resin) surface. The hard-surface disinfectants (in-use concentration in ppm) tested were: (a) chlorine bleach (500); (b) quaternary ammonium compounds (quat; 600) alone; (c) quat (3000) with 17% isopropanol (v/v); (d) quat (3000) with 60% ethanol (v/v); (e) phenolic (800) alone; (f) quat (2000), phenolic (3000) with 70% ethanol (v/v); and (g) accelerated hydrogen peroxide (AHP; 5000 of H2O2). The arbitrarily set criterion of bactericidal activity was > or = 6 log10 reduction in the viability of both species tested. All surfaces tested with all products dried in < 5 min, with alcohol-based surfaces drying significantly faster. Even though the alcohol-free quat and phenolic claim a contact time of 10 min, they dried in < 4 min after a single application and failed to meet the performance criterion. Bleach (500 ppm) dried in about 3 min and was effective. AHP also dried in about 3 min and met its label claim even at 1 min of contact. Quat (3000) with 17% isopropanol dried at 1 min and was effective. Quat (3000) with 60% ethanol and quat (2000), phenolic (3000) with 70% ethanol dried in < 1 min, and were ineffective. AHP, alcohol-containing quats, and quat-phenolic-alcohol gave acceptable wettability, while quat and phenolic alone, as well as bleach, covered the treated surface unevenly. The findings show that label claims, especially those for contact times, fail to reflect the way many hard-surface disinfectants are used in the field.     

Pseudomonas aeruginosa Biofilm Inactivation: Decreased Cell Culturability, Adhesiveness to Surfaces, and Biofilm Thickness Upon High-Pressure Nonthermal Plasma Treatment

Bacterial biofilms are more resilient to standard killing methods than free-living bacteria. Pseudomonas aeruginosa PAO1 biofilms grown on borosilicate coupons were treated with gas-discharge plasma for various exposure times. Almost 100% of the cells were inactivated after a 5-min plasma exposure. Atomic force microscopy was used to image the biofilms and study their micromechanical properties. Results show that the adhesiveness to borosilicate and the thickness of the Pseudomonas biofilms are reduced upon plasma treatment.     

ZnO Nanocluster as a Potential Catalyst for Dissociation of H2S Molecule

Adsorption of hydrogen sulfide (H₂S) on the external and internal surface of Zn₁₂O₁₂ nanocluster was studied by using density functional calculations. The results indicate that the H₂S molecule is physically adsorbed or chemically dissociated by the nanocluster. It was found that the H₂S molecule can dissociate into –H and–SH fragments, suggesting that the nanocluster might be a potential catalyst for dissociation of the H₂S molecule. Also, dissociation of H₂S to S species in internal surface of the Zn₁₂O₁₂ nanocluster is energetically impossible. The HOMO–LUMO energy gap of H₂S dissociation configuration is changed about 27.68 %, indicating that the electronic properties of the nanocluster by dissociation process have strongly changed.     

Selenium Nanomaterials to Combat Antimicrobial Resistance

The rise of antimicrobial resistance to antibiotics (AMR) as a healthcare crisis has led to a tremendous social and economic impact, whose damage poses a significant threat to future generations. Current treatments either are less effective or result in further acquired resistance. At the same time, several new antimicrobial discovery approaches are expensive, slow, and relatively poorly equipped for translation into the clinical world. Therefore, the use of nanomaterials is presented as a suitable solution. In particular, this review discusses selenium nanoparticles (SeNPs) as one of the most promising therapeutic agents based in the nanoscale to treat infections effectively. This work summarizes the latest advances in the synthesis of SeNPs and their progress as antimicrobial agents using traditional and biogenic approaches. While physiochemical methods produce consistent nanostructures, along with shortened processing procedures and potential for functionalization of designs, green or biogenic synthesis represents a quick, inexpensive, efficient, and eco-friendly approach with more promise for tunability and versatility. In the end, the clinical translation of SeNPs faces various obstacles, including uncertain in vivo safety profiles and mechanisms of action and unclear regulatory frameworks. Nonetheless, the promise possessed by these metalloid nanostructures, along with other nanoparticles in treating bacterial infections and slowing down the AMR crisis, are worth exploring.     

Generation of Asphaltene Deposition Envelope Using Artificial Neural Network

The usefulness of the asphaltene deposition envelope (ADE) is that no asphaltene flocculation occurs at conditions outside the envelope. Since artificial neural network (ANN) is best at identifying patterns or trends in data, it is well suited for prediction or forecasting needs. ANN is also capable of addressing case specific problems that may be encountered in the field such as deposition of asphaltene. In this article, the high pressure, high temperature setup used to perform pressure depletion experiments at three different temperatures on one the Iranian live oils and the ADE generated using ANN.     

Electrospun titania sol–gel‐based ceramic composite nanofibers for online micro‐ solid‐phase extraction with high‐performance liquid chromatography

Titanium(IV) tetraisopropoxide was employed as a metal oxide sol–gel precursor to prepare ceramic composite nanofibers by the electrospinning system. To facilitate this process and obtain the desired nanofibers with higher aspect ratios and surface area, poly(vinylpyrrolidone) was added to the sol of titania. Four ceramic nanofibers sheets based on titania were prepared while each sheet contained different transition metals such as Fe‐Mn, Fe‐Ni, Fe‐Co, and Fe‐Mn‐Co‐Ni. The scanning electron microscope images showed good homogeneity for all the prepared ceramic composites with a diameter range of 100–250 nm. The sorption efficiency was investigated by a micro‐solid‐phase extraction setup in online combination with high‐performance liquid chromatography for the determination of naproxen and clobetasol. All the prepared composites exhibited comparable efficiencies for the desired analytes and the type of metal showed insignificant effect. For the selected composite with Fe‐Mn, the linearity of the analytes was in the range of 1–1000 μg/L and the limit of detection values were found to be 2 and 0.3 μg/L for naproxen and clobetasol, respectively. The developed method was extended to the analysis of urine and blood plasma samples and acceptable relative standard deviations were obtained at two concentration levels.     

Super‐resolution microscopy by movable thin‐films with embedded microspheres: Resolution analysis

Microsphere‐assisted imaging has emerged as an extraordinary simple technique of obtaining optical super‐resolution. This work addresses two central problems in developing this technology: i) methodology of the resolution measurements and ii) limited field‐of‐view provided by each sphere. It is suggested that a standard method of resolution analysis in far‐field microscopy based on convolution with the point‐spread function can be extended into the super‐resolution area. This allows developing a unified approach to resolution measurements, which can be used for comparing results obtained by different techniques. To develop the surface scanning functionality, the high‐index (n ～ 2) barium titanate glass microspheres were embedded in polydimethylsiloxane (PDMS) thin‐films. It is shown that such films adhere to the surface of nanoplasmonic structures so that the tips of embedded spheres experience the objects’ optical near‐fields. Based on rigorous criteria, the resolution ～λ/6‐λ/7 (where λ is the illumination wavelength) is demonstrated for arrays of Au dimers and bowties. Such films can be translated along the surface of investigated samples after liquid lubrication. It is shown that just after lubrication the resolution is diffraction limited, however the super‐resolution gradually recovers as the lubricant evaporates.

     

Adsorption of Thiophene on Aluminum Nitride Nanotubes

Abstract

Thiophene adsorption on pristine (6,0) aluminum nitride nanotubes was studied by using density functional theory calculations, by means of B3LYP and M06-L functionals. We present the nature of the thiophene interaction in different sites of the nanotube. Adsorption energies corresponding to adsorption of thiophene are calculated to be in the range ?18.90 to ?21.06 kJ mol^{? 1} Pablo, P. C., Liprandi, D. A. and Fígoli, N. S. 1996. Ind. Eng. Chem. Res., 34: 3713–3717. [Web of Science ®] , [Google Scholar]. It has been shown that the thiophene molecule has a weak physical adsorption on the pristine models due to weak Van der Waals interaction between the nanotubes and thiophene molecule. The charge transfer between thiophene and the AlNNT is minimal and the electronic properties of the nanotubes are not affected by the thiophene adsorption. Also, with change of tube type, more efficient binding could not be achieved. The results indicate that transition metal nanoclusters are more suitable catalyst with respect to nontransition metal nanotubes in the petroleum industry.     

Numerical investigation of mixed convection heat transfer behavior of nanofluid in a cavity with different heat transfer areas

Journal of Thermal Analysis and Calorimetry - The main purpose of this research is the numerical modeling of laminar mixed convection heat transfer inside an open square cavity with different heat...     

MicroRNA‐2861 and nanofibrous scaffold synergistically promote human induced pluripotent stem cells osteogenic differentiation

Tissue engineering using new strategies has become a growing and promising method for treating large tissue lesions in the body. On the other hand, microRNAs (miRNAs), which are small non‐coding regulatory RNAs, are a new class of genetic materials that can have effective pharmacological roles. The combination of these two themes has created promising prospects for the treatment of diseases. Herein, human induced pluripotent stem cells (iPSCs) were transduced with miRNA‐2861 and then the osteogenic differentiation potential of transduced iPSCs and non‐transduced iPSCs was investigated while cultured on the electrospun poly lactic‐co‐glycolic acid (PLGA) nanofibrous scaffold and culture plate. MiR‐2861‐transduced iPSCs showed a significantly higher viability, mineralization, alkaline phosphatase (ALP) activity, calcium content, and bone‐related gene expression in comparison with those iPSCs that non‐transduced. The results also indicated that this increase is improved when miR‐2861 transduced iPSCs are cultured on the PLGA nanofibrous scaffold synergistically. This synergy was also confirmed by the results obtained from of Western blot analysis. It can be concluded that, miR‐2861, by negative regulation of those proteins that decrease/inhibit osteogenic differentiation and PLGA nanofibrous scaffold by preparation of a suitable artificial extracellular matrix, have a great positive impact in improving iPSCs osteogenic differentiation potential and this blend can be proposed to use in bone tissue engineering application.