Photocatalytic degradation of antibiotics and antimicrobial and anticancer activities of two-dimensional ZnO nanosheets.

Active pharmaceutical ingredients have emerged as an environmentally undesirable element because of their widespread exploitation and consequent pollution, which has deleterious effects on living things. In the pursuit of sustainable environmental remediation, biomedical applications, and energy production, there has been a significant focus on two-dimensional materials (2D materials) owing to their unique electrical, optical, and structural properties. Herein, we have synthesized 2D zinc oxide nanosheets (ZnO NSs) using a facile and practicable hydrothermal method and characterized them thoroughly using spectroscopic and microscopic techniques. The 2D nanosheets are used as an efficient photocatalyst for antibiotic (herein, end-user ciprofloxacin (CIP) was used as a model antibiotic) degradation under sunlight. It is observed that ZnO NSs photodegrade ~ 90% of CIP within two hours of sunlight illumination. The molecular mechanism of CIP degradation is proposed based on ex-situ IR analysis. Moreover, the 2D ZNO NSs are used as an antimicrobial agent and exhibit antibacterial qualities against a range of bacterial species, including Escherichia coli, Staphylococcus aureus, and MIC of the bacteria are found to be 5 µg/l and 10 µg/l, respectively. Despite having the biocompatible nature of ZnO, as-synthesized nanosheets have also shown cytotoxicity against two types of cancer cells, i.e. A549 and A375. Thus, ZnO nanosheets showed a nontoxic nature, which can be exploited as promising alternatives in different biomedical applications.

Ionosomes: Observation of Ionic Bilayer Water Clusters.

Emulsification of immiscible two-phase fluids, i.e., one condensed phase dispersed homogeneously as tiny droplets in an outer continuous medium, plays a key role in medicine, food, chemical separations, cosmetics, fabrication of micro- and nanoparticles and capsules, and dynamic optics. Herein, we demonstrate that water clusters/droplets can be formed in an organic phase via the spontaneous assembling of ionic bilayers. We term these clusters ionosomes, by analogy with liposomes where water clusters are encapsulated in a bilayer of lipid molecules. The driving force for the generation of ionosomes is a unique asymmetrical electrostatic attraction at the water/oil interface: small and more mobile hydrated ions reside in the inner aqueous side, which correlate tightly with the lipophilic bulky counterions in the adjacent outer oil side. These ionosomes can be formed through electrochemical (using an external power source) or chemical (by salt distribution) polarization at the liquid-liquid interface. The charge density of the cations, the organic solvent, and the synergistic effects between tetraethylammonium and lithium cations, all affecting the formation of ionosomes, were investigated. These results clearly prove that a new emulsification strategy is developed providing an alternative and generic platform, besides the canonical emulsification procedure with either ionic or nonionic surfactants as emulsifiers. Finally, we also demonstrate the detection of individual ionosomes via single-entity electrochemistry.

Scanning Electrochemical and Photoelectrochemical Microscopy on Finder Grids: Toward Correlative Multitechnique Imaging of Surfaces.

Scanning electrochemical microscopy (SECM) is a powerful technique for mapping surface reactivity and investigating heterogeneous processes on the nanoscale. Despite significant advances in high-resolution SECM and photo-SECM imaging, they cannot provide atomic scale structural information about surfaces. By correlating the SECM images with atomic scale structural and bonding information obtained by transmission electron microscopy (TEM) techniques with one-to-one correspondence, one can elucidate the nature of the active sites and understand the origins of heterogeneous surface reactivity. To enable multitechnique imaging of the same nanoscale portion of the electrode surface, we develop a methodology for using a TEM finder grid as a conductive support in SECM and photo-SECM experiments. In this paper, we present the results of our first nanoscale SECM and photo-SECM experiments on carbon TEM grids, including imaging of semiconductor nanorods.

Highly Crystalline Mesoporous C60 with Ordered Pores: A Class of Nanomaterials for Energy Applications.

Highly ordered mesoporous C60 with a well-ordered porous structure and a high crystallinity is prepared through the nanohard templating method using a saturated solution of C60 in 1-chloronaphthalene (51 mg mL-1 ) as a C60 precursor and SBA-15 as a hard template. The high solubility of C60 in 1-chloronaphthalene helps not only to encapsulate a huge amount of the C60 into the mesopores of the template but also supports the oligomerization of C60 and the formation of crystalline walls made of C60 . The obtained mesoporous C60 exhibits a rod-shaped morphology, a high specific surface area (680 m2 g-1 ), tuneable pores, and a highly crystalline wall structure. This exciting ordered mesoporous C60 offers high supercapacitive performance and a high selectivity to H2 O2 production and methanol tolerance for ORR. This simple strategy could be adopted to make a series of mesoporous fullerenes with different structures and carbon atoms as a new class of energy materials.

Electrochemical Approach for Effective Antifouling and Antimicrobial Surfaces.

Biofouling, the adsorption of organisms to a surface, is a major problem today in many areas of our lives. This includes: (i) health, as biofouling on medical device leads to hospital-acquired infections, (ii) water, since the accumulation of organisms on membranes and pipes in desalination systems harms the function of the system, and (iii) energy, due to the heavy load of the organic layer that accumulates on marine vessels and causes a larger consumption of fuel. This paper presents an effective electrochemical approach for generating antifouling and antimicrobial surfaces. Distinct from previously reported antifouling or antimicrobial electrochemical studies, we demonstrate the formation of a hydrogen gas bubble layer through the application of a low-voltage square-waveform pulses to the conductive surface. This electrochemically generated gas bubble layer serves as a separation barrier between the surroundings and the target surface where the adhesion of bacteria can be deterred. Our results indicate that this barrier could effectively reduce the adsorption of bacteria to the surface by 99.5%. We propose that the antimicrobial mechanism correlates with the fundamental of hydrogen evolution reaction (HER). HER leads to an arid environment that does not allow the existence of live bacteria. In addition, we show that this drought condition kills the preadhered bacteria on the surface due to water stress. This work serves as the basis for the exploration of future self-sustainable antifouling techniques such as incorporating it with photocatalytic and photoelectrochemical reactions.

Electrochemically stimulated drug release from flexible electrodes coated electrophoretically with doxorubicin loaded reduced graphene oxide.

The electrochemically triggered release of doxorubicin (DOX) from flexible electrodes modified electrophoretically with reduced graphene oxide (rGO)-DOX is reported. The release is driven by a positive potential pulse that decreases the pH of the rGO-DOX surface locally, which is confirmed by scanning electrochemical microscopy (SECM) in situ. In vitro cell viability tests confirms that the delivery system meets therapeutic needs.

Correction: Ambient temperature deposition of gallium nitride/gallium oxynitride from a deep eutectic electrolyte, under potential control.

Correction for 'Ambient temperature deposition of gallium nitride/gallium oxynitride from a deep eutectic electrolyte, under potential control' by Sujoy Sarkar et al., Chem. Commun., 2016, 52, 6407-6410.

Ambient temperature deposition of gallium nitride/gallium oxynitride from a deep eutectic electrolyte, under potential control.

A ternary, ionically conducting, deep eutectic solvent based on acetamide, urea and gallium nitrate is reported for the electrodeposition of gallium nitride/gallium indium nitride under ambient conditions; blue and white light emitting photoluminescent deposits are obtained under potential control.

Escherichia coli O8-antigen enhances biofilm formation under agitated conditions.

Bacterial surface components have a major role in the development of biofilms. In the present study, the effect of Escherichia coli O8-antigen on biofilms was investigated using two E. coli K-12 derived strains that differed only in the O8-antigen biosynthesis. In the presence of O8-antigen both bacterial adhesion and biofilm formation slightly decreased under static conditions whereas a substantial increase in adhesion and biofilm formation was observed under agitated conditions. It was noted that, irrespective of the O8-antigen status, the hydrophobic interactions played an important role in bacterial adhesion under both static and agitated conditions. However, under agitated conditions, the extent of bacterial adhesion in the O8-antigen bearing strain was predominantly determined by the electrostatic interactions. Results showed that the presence of O8-antigen decreases the surface hydrophobicity and surface charge. Moreover, O8-antigen facilitates adhesion on hydrophilic and hydrophobic surfaces as revealed through tests with modified substrata. Our results indicate that O8-antigen, which appears dispensable for biofilm formation under static conditions, actually enhances E. coli biofilm formation under agitated conditions.

Study on assessment of renal function in chronic liver disease.

INTRODUCTION: Renal dysfunction is common in chronic liver disease. The cause of this renal dysfunction is either multi-organ involvement in acute conditions or secondary to advanced liver disease. OBJECTIVES: The study was undertaken to assess the renal function in chronic liver diseases and find out the association of alteration of renal function with gradation of liver disease. (assessed by child-pugh criteria) and to find out the association of alteration of renal function among the cases of chronic liver disease of different aetiology. MATERIALS AND METHODS: This cross-sectional, observational study was undertaken in Department of General Medicine, Calcutta National Medical College & Hospital, Kolkata during March 2012 to July 2013 with 50 admitted patients of chronic liver disease after considering the exclusion criteria. The patients were interviewed with a pre-designed and pre-tested schedule, examined clinically, followed by some laboratory investigations relevant to diagnose the aetiology of chronic liver disease, and to assess the severity of liver and renal dysfunction. Data was analysed by standard statistical method. RESULTS: Eighty six percent of the patients were male and the mean age of study population was 43.58 y, 68% patients suffered from alcoholic liver disease, followed by 14% patients had chronic Hepatitis-B, 10% patients developed acute kidney injury, 20% had hepato renal syndrome and 14% had IgA deposition. The distribution of serum urea and creatinine across the categories of Child Pugh classification tested by Mann-Whitney test and the distribution was statistically significant. CONCLUSION: The present study has found significant association between severity of liver dysfunction and certain parameters of renal dysfunction.

Equiatomic ternary chalcogenide: PdPS and its reduced graphene oxide composite for efficient electrocatalytic hydrogen evolution.

The layered ternary chalcogenide, palladium phosphorous sulphide (PdPS), and its composite with reduced graphene oxide are shown to be efficient hydrogen evolution electrocatalysts. The Tafel slope and the exchange current density values associated with hydrogen evolution reaction are determined to be 46 mV dec(-1) and 1.4 × 10(-4) A cm(-2) respectively.

Multiple resistance mechanisms acting in unison in an Escherichia coli clinical isolate.

The emergence of multiple-resistant isolates poses a serious problem in the hospital environment making it important to evaluate the responsible factors. This work ascertains the mechanisms responsible for the development of resistance in enterobacterial clinical isolates. The major resistance mechanisms have been explored. The presence of target mutations, drug hydrolyzing enzymes, active efflux pump, and drug-resistance genes were elucidated experimentally employing standard methods. One of the clinical isolates was resistant to five classes of structurally unrelated antibiotics and showed involvement of multiple resistance mechanisms. Here, we report the simultaneous presence of multiple drug-resistance mechanisms in an Escherichia coli clinical isolate.

Vivax malaria presenting with myelitis: a rare complication.

Neurological complications may occur with the Plasmodium falciparum infection. However, the association of neurological manifestations with vivax malaria remains doubtful. Of late, there are isolated case reports/studies which have implicated P. vivax in the pathogenesis of severe malaria which is characterized by the features of different organ dysfunctions, which were previously thought to be caused by P. falciparum alone. Though several case studies have mentioned the association of the P. vivax infection with cerebral malaria, a causal correlation has yet to be established. Dorsal cord myelitis (which leads to paraplegia) during the febrile illness, is rarely described in association with vivax malaria, though there are reports on the Post Malaria Neurological Syndrome (PMNS) and acute disseminated encephalomyelitis following vivax malaria. We are reporting a case of P. Vivax malaria which presented with myelitis, which responded well to the antimalarial treatment.

Sub-inhibitory cefsulodin sensitization of E. coli to ß-lactams is mediated by PBP1b inhibition.

The combination of antibiotics is one of the strategies to combat drug-resistant bacteria, though only a handful of such combinations are in use, such as the ß-lactam combinations. In the present study, the efficacy of a specific sub-inhibitory concentration of cefsulodin with other ß-lactams was evaluated against a range of Gram-negative clinical isolates. This approach increased the sensitivity of the isolates, regardless of the ß-lactamase production. The preferred target and mechanism of action of cefsulodin were identified in laboratory strains of Escherichia coli, by examining the effects of deleting the penicillin-binding protein (PBP) 1a and 1b encoding genes individually. Deletion of PBP1b was involved in sensitizing the bacteria to ß-lactam agents, irrespective of its O-antigen status. Moreover, the use of a sub-inhibitory concentration of cefsulodin in combination with a ß-lactam exerted an effect similar to that one obtained for PBP1b gene deletion. We conclude that the identified ß-lactam/cefsulodin combination works by inhibiting PBP1b (at least partially) despite the involvement of ß-lactamases, and therefore could be extended to a broad range of Gram-negative pathogens.

Effects of lactoferricin B against keratitis-associated fungal biofilms.

Biofilms are considered as the most important developmental characteristics in ocular infections. Biofilm eradication is a major challenge today to overcome the incidence of drug resistance. This report demonstrates the in vitro ability of biofilm formation on contact lens by three common keratitis-associated fungal pathogens, namely, Aspergillus fumigatus, Fusarium solani, and Candida albicans. Antifungal sensitivity testing performed for both planktonic cells and biofilm revealed the sessile phenotype to be resistant at MIC levels for the planktonic cells and also at higher concentrations. A prototype lens care solution was also found to be partially effective in eradication of the mature biofilm from contact lenses. Lactoferricin B (Lacf, 64 µg/ml), an antimicrobial peptide, exhibited almost no effect on the sessile phenotype. However, the combinatory effect of Lacf with antifungals against planktonic cells and biofilms of three fungal strains that were isolated from keratitis patients exhibited a reduction of antifungal dose more than eightfold. Furthermore, the effect of Lacf in lens care solution against biofilms in which those strains formed was eradicated successfully. These results suggest that lactoferricin B could be a promising candidate for clinical use in improving biofilm susceptibility to antifungals and also as an antibiofilm-antifungal additive in lens care solution.

Deletion of penicillin-binding protein 1b impairs biofilm formation and motility in Escherichia coli.

The major bifunctional transpeptidases/transglycosylases of Escherichia coli, penicillin-binding proteins (PBPs) 1a and 1b, were evaluated for their influence on biofilm formation. While the PBP1a mutant was unaffected, the PBP1b mutant exhibited significantly decreased biofilm formation and motility. Interestingly, the extracellular indole concentration was higher in the PBP1b mutant, and similar phenotypic defects were replicated in the wild-type upon addition of exogenous indole. Expression of PBP1b in trans substantially decreased indole production and restored normal phenotypes. Results further suggest that rpoS deletion has a counteracting effect on the mrcB mutant. These findings indicate that PBP1b deletion influences biofilm formation and motility, possibly through indole.

PBP5, PBP6 and DacD play different roles in intrinsic ß-lactam resistance of Escherichia coli.

Escherichia coli PBP5, PBP6 and DacD, encoded by dacA, dacC and dacD, respectively, share substantial amino acid identity and together constitute ~50 % of the total penicillin-binding proteins of E. coli. PBP5 helps maintain intrinsic ß-lactam resistance within the cell. To test if PBP6 and DacD play simlar roles, we deleted dacC and dacD individually, and dacC in combination with dacA, from E. coli 2443 and compared ß-lactam sensitivity of the mutants and the parent strain. ß-Lactam resistance was complemented by wild-type, but not dd-carboxypeptidase-deficient PBP5, confirming that enzymic activity of PBP5 is essential for ß-lactam resistance. Deletion of dacC and expression of PBP6 during exponential or stationary phase did not alter ß-lactam resistance of a dacA mutant. Expression of DacD during mid-exponential phase partially restored ß-lactam resistance of the dacA mutant. Therefore, PBP5 dd-carboxypeptidase activity is essential for intrinsic ß-lactam resistance of E. coli and DacD can partially compensate for PBP5 in this capacity, whereas PBP6 cannot.

Deletion of penicillin-binding protein 5 (PBP5) sensitises Escherichia coli cells to beta-lactam agents.

Escherichia coli penicillin-binding protein 5 (PBP5), a dd-carboxypeptidase encoded by the dacA gene, plays a key role in the maintenance of cell shape. Although PBP5 shares one of the highest copy numbers among the PBPs, it is not essential for cell survival. To determine the effect of this redundant PBP on beta-lactam antibiotic susceptibility, PBP5 was deleted from O-antigen-negative E. coli K-12 (CS109) and O8-antigen-positive E. coli 2443, thus creating strains AM15-1 and AG1O5-1, respectively. Compared with the parent strains, both mutants were four- to eight-fold more susceptible to all the beta-lactam antibiotics tested. Reversion to beta-lactam resistance was observed in the mutants upon complementing with cloned PBP5, indicating the involvement of PBP5 in maintaining an O-antigen-independent intrinsic beta-lactam resistance in E. coli cells. To check whether other dacA homologues were able to substitute this behaviour of E. coli PBP5, AG1O5-1 was complemented with its nearest dacA homologues (Salmonella enterica serovar Typhimurium LT2, Vibrio cholerae and Haemophilus influenzae). All of the cloned homologues were capable of restoring the lost beta-lactam resistance in AG1O5-1, either completely or at least partially. Therefore, apart from maintaining cell shape, involvement of PBP5 in maintaining intrinsic beta-lactam resistance is an important physiological observation and we speculate that such a strategy of deleting PBP5 may be helpful to introduce beta-lactam susceptibility in the laboratory.

Chromium and nickel migration study through fine grained soil.

A comprehensive laboratory-scale investigation was carried out to explore the toxic metal attenuation capacity of a field clay sample collected from adjoining areas of an ash pond site of a Super Thermal Power Plant in West Bengal, India. The existence of two major elements viz., Cr6+ and Ni2+ in excess to permissible limit was observed in soil and water samples collected from the site. Batch kinetic performance results exhibited reasonable Cr6+ and Ni2+ uptake capacity of soil in equilibrium condition. The experimental data also fitted well in Freundlich isotherm model. The adsorption behaviour of above pollutants in both vertical and horizontal directions through soil was explored. The results showed that more than 80% of Ni and 72% of Cr were found to be sorbed by the soil. Breakthrough adsorption study also showed a good metal adsorption capacity of soil.

Involvement of O8-antigen in altering beta-lactam antibiotic susceptibilities in Escherichia coli.

In spite of being dispensable, O-antigens are believed to facilitate various cellular processes and alter antibiotic sensitivities. Escherichia coli K-12 (CS109) strains are lacking in O-antigens and are reported to be sensitive to antibiotics. To our surprise, E. coli 2443 (expressing O8-antigen) manifested two- to fourfold higher sensitivities toward penicillin and its derivatives than strain CS109. However, sensitivities toward other structurally unrelated antibiotics remained unchanged. To understand the rationale behind such observations, we replaced the rfb locus of strain 2443 with that of E. coli K-12. The beta-lactam sensitivities of 2443 cells with replaced rfb locus appeared to be identical to those for CS109. Therefore, it is quite reasonable to hypothesize the possible involvement of O8-antigen in beta-lactam sensitization.