Chromone-Based Cd(II) Fluorescent Coordination Polymer Fabricated to Study Optoelectronic and Explosive Sensing Properties

Here, electrical conductivity and explosive sensing properties of multifunctional chromone-Cd(II)-based coordination polymers (CPs) (1-4) have been explored. The presence of different pseudohalide linkers, thiocyanate ions, and dicyanamide ions resulted in 1D and 3D architecture in the CPs. Thin film devices developed from CPs 1-4 (complex-based Schottky devices, CSD1, CSD2, CSD3, and CSD4, respectively) showed semiconductor behavior. Their conductivity values increased under photo illumination (1.37 × 10-5, 1.85 × 10-5, 1.61 × 10-5, and 2.01 × 10-5 S m-1 under dark conditions and 5.06 × 10-5, 8.78 × 10-5, 7.26 × 10-5, and 10.21 × 10-5 S m-1 under light). The nature of the I-V plots of these thin film devices under light irradiation and dark are nonlinear rectifying, which has been observed in Schottky barrier diodes (SBDs). All four CPs (1-4) exhibited highly selective fluorescence quenching-based sensing properties toward well-known explosives, 2,4-dinitrophenol (DNP) and 2,4,6-trinitrophenol (TNP). The limit of detection (LOD) values are 55, 28, 27, and 31 μM for TNP and 78, 44, 32, and 41 μM for DNP for complexes 1-4, respectively. A structure property correlation has been established to explain optoelectronic and explosive sensing properties.

Exploring aryl hydrocarbon receptor (AhR) as a target for Bisphenol-A (BPA)-induced pancreatic islet toxicity and impaired glucose homeostasis: Protective efficacy of ethanol extract of Centella asiatica

The estrogenic impact of Bisphenol-A (BPA), a widely recognized endocrine disruptor, causes disruption of pancreatic β-cell function through estrogen receptors (ERs). While BPA's binding affinity for ERs is significantly lower than that of its natural counterpart, estrogen, recent observations of BPA's affinity for aryl hydrocarbon receptor (AhR) in specific cellular contexts have sparked a specific question: does AhR play a role in BPA's toxicological effects within the endocrine pancreas? To explore this question, we investigated BPA's (10 and 100 μg/ kg body weight/day for 21 days) potential to activate AhR within pancreatic islets and assessed the protective role of ethanol extract of Centella asiatica (CA) (200 and 400 mg/kg body weight/day for 21 days) against BPA-mediated toxicity in mouse model. Our results indicate that BPA effectively triggers the activation of AhR and modulates its target genes within pancreatic islets. In contrast, CA activates AhR but directs downstream pathways differentially and activates Nrf2. Additionally, CA was observed to counteract the disruption caused by BPA in glucose homeostasis and insulin sensitivity. Furthermore, BPA-induced oxidative stress and exaggerated production of proinflammatory cytokines were effectively counteracted by CA supplementation. In summary, our study suggests that CA influenced AhR signaling to mitigate the disrupted pancreatic endocrine function in BPA exposed mice. By shedding light on how BPA interacts with AhR, our research provides valuable insights into the mechanisms involved in the diabetogenic actions of BPA.

Aza-phenol Based Macrocyclic Probes Design for "CHEF-on" Multi Analytes Sensor: Crystal Structure Elucidation and Application in Biological Cell Imaging

Metal bound macrocyclic compounds found in biological systems inspired us to design and synthesize two Robson-type macrocyclic Schiff-base chemosensors, H ₂ L1 (H ₂ L1=1,11-dimethyl-6,16-dithia-3,9,13,19-tetraaza-1,11(1,3)-dibenzenacycloicosaphane-2,9,12,19-tetraene-1,11-diol) and H ₂ L2 (H ₂ L2=1,11-dimethyl-6,16-dioxa-3,9,13,19-tetraaza-1,11(1,3)-dibenzenacycloicosaphane-2,9,12,19-tetraene-1,11-diol). Both the chemosensors have been characterized with different spectroscopic techniques. They act as multianalyte sensor and exhibit "turn-on" fluorescence toward different metal ions in 1X PBS (Phosphate Buffered Saline) solution. In presence of Zn²⁺, Al³⁺, Cr³⁺ and Fe³⁺ ions, H ₂ L1 exhibits ∼6-fold enhancement of emission intensity, while H ₂ L2 shows ∼6-fold enhancement of emission intensity in the presence of Zn²⁺, Al³⁺ and Cr³⁺ ions. The interaction between the different metal ion and chemosensor have been examined by absorption, emission, and ¹H NMR spectroscopy as well as by ESI-MS⁺ analysis. We have successfully isolated and solved the crystal structure of the complex [Zn(H ₂ L1)(NO₃)]NO₃ (1) by X-ray crystallography. The crystal structure of 1 shows 1:1 metal:ligand stoichiometry and helps to understand the observed PET-Off-CHEF-On sensing mechanism. LOD values of H ₂ L1 and H ₂ L2 toward metal ions are found to be ∼10^-8 and ∼10^-7 M, respectively. Large Stokes shifts of the probes against analytes (∼100 nm) make them a suitable candidate for biological cell imaging studies. Robson type phenol based macrocyclic fluorescence sensors are very scarce in the literature. Therefore, the tuning of structural parameters as the number and nature of donor atoms, their relative locations and presence of rigid aromatic groups can lead to the design of new chemosensors, which can accommodate different charged/neutral guest(s) inside its cavity. The study of the spectroscopic properties of this type of macrocyclic ligands and their complexes might open a new avenue of chemosensors.

Selective Low-Level Detection of a Perilous Nitroaromatic Compound Using Tailor-Made Cd(II)-Based Coordination Polymers: Study of Photophysical Properties and Effect of Functional Groups

Three coordination polymers (CPs 1-3) are prepared based on diverse electron-donating properties and coordination arrangements of conjugated ligands. Interestingly, this is also reflected in their photophysical properties. The distinguishable high emissive nature of the luminescent coordination polymer shows its potentiality toward the detection of the perilous substance 2,4,6-trinitrophenol (TNP) or picric acid (PA). TNP has a higher propensity among explosive nitroaromatic compounds (epNACs) due to its significant π···π interaction with the free benzene moieties present in the CPs. Among CPs 1-3, 2 exhibits the highest sensitivity and selectivity toward TNP because of the most favorable π-π stacking with the conjugated organic linker. The calculated limit of detection (LOD) and corresponding quenching constant (K_SV) from the Stern-Volmer (SV) plot for 1, 2, and 3 are found to be 0.68 μM and 7.49 × 10⁴ M^-1, 0.41 μM and 8.01 × 10⁴ M^-1, and 1.18 μM and 8.1 × 10⁴ M^-1, respectively. The fluorescence quenching mechanism is also highly influenced by their structure and coordination arrangement.

Two rhodamine-azo based fluorescent probes for recognition of trivalent metal ions: crystal structure elucidation and biological applications

Two rhodamine and azo based chemosensors (HL1 = (3',6'-bis(ethylamino)-2-((2-hydroxy-3-methoxy-5-(phenyldiazenyl)benzylidene)amino)-2',7'-dimethylspiro[isoindoline-1,9'-xanthen]-3-one) and HL2 = (3',6'-bis(ethylamino)-2-(((2-hydroxy-3-methoxy-5-(p-tolyldiazenyl)benzylidene)amino)-2',7'-dimethylspiro[isoindoline-1,9'-xanthen]-3-one) have been synthesized for colorimetric and fluorometric detection of three trivalent metal ions, Al³⁺, Cr³⁺ and Fe³⁺. The chemosensors have been thoroughly characterized by different spectroscopic techniques and X-ray crystallography. They are non-fluorescent due to the presence of a spirolactam ring. The trivalent metal ions initiate an opening of the spirolactam ring when excited at 490 nm in Britton-Robinson buffer solution (H₂O/MeOH 1 : 9 v/v; pH 7.4). The opening of the spirolactam ring increases conjugation within the probe, which is supported by an intense fluorescent pinkish-yellow colouration and an enhancement of the fluorescence intensity of the chemosensors by ∼400 times in the presence of Al³⁺ and Cr³⁺ ions and by ∼100 times in the presence of Fe³⁺ ions. Such a type of enormous fluorescence enhancement is rarely observed in other chemosensors for the detection of trivalent metal ions. A 2 : 1 binding stoichiometry of the probes with the respective ions has been confirmed by Job's plot analysis. Elucidation of the crystal structures of the Al³⁺ bound chemosensors (1 and 4) also justifies the 2 : 1 binding stoichiometry and the presence of an open spirolactam ring within the chemosensor framework. The limit of detection (LOD) values for both the chemosensors towards the respective metal ions are in the order of ∼10^-9 M which supports their application in the biological field. The biocompatibility of the ligands has been studied with the help of the MTT assay. The results show that no significant toxicity was observed up to 100 μM of chemosensor concentration. The capability of our synthesized chemosensors to detect intracellular Al³⁺, Cr³⁺ and Fe³⁺ ions in the cervical cancer cell line HeLa was evaluated with the aid of fluorescence imaging.

Antibacterial potency of cytocompatible chitosan-decorated biogenic silver nanoparticles and molecular insights towards cell-particle interaction

In the study, leaf extract of Carica papaya was utilized for the biogenic fabrication process of chitosan functionalized silver nanoparticles (Ag-Chito NPs). HRTEM analysis revealed that the fabricated Ag-Chito NPs was spherical in shape, with an average particle size of 13.31 (±0.07) nm. FTIR, UV-Vis, DLS, and other characterizations were also performed to analyze the diverse physicochemical properties of the particles. The antibacterial potency of the synthesized Ag-Chito NPs was tested against the two clinically isolated multidrug resistant uropathogenic bacterial strains, i.e. MLD 2 (Escherichia coli) and MLD 4 (Staphylococcus aureus) through MIC, MBC, time and concentration dependent killing kinetic assay, inhibition of biofilm formation assay, fluorescence and SEM imaging. Significantly, Ag-Chito NPs showed the highest sensitivity against the MLD 2 (MIC value of 12.5 μg/mL) strain, as compared to the MLD 4 (MIC value of 15 μg/mL) strain. From the hemolysis assay, it was revealed that Ag-Chito NPs exerted no significant toxicity up to 50 μg/mL against healthy human blood cells. Additionally, in silico analysis of chitosan (functionalized on the surface of AgNPs) and bacterial cell membrane protein also evidently suggested a strong interaction between Ag-Chito NPs and bacterial cells, which might be responsible for bacterial cell death.

Aza-Crown-Based Macrocyclic Probe Design for "PET-off" Multi-Cu2+ Responsive and "CHEF-on" Multi-Zn2+ Sensor: Application in Biological Cell Imaging and Theoretical Studies

The work represents a rare example of an aza-crown-based macrocyclic chemosensor, H₂DTC (H₂DTC = 1,16-dihydroxy-tetraaza-30-crown-8) for the selective detection of both Zn²⁺ and Cu²⁺ in HEPES buffer medium (pH 7.4). H₂DTC exhibits a fluorescence response for both Zn²⁺ and Cu²⁺ ions. The reversibility of the chemosensor in its binding with Zn²⁺ and Cu²⁺ ions is also examined using a Na₂EDTA solution. H₂DTC exhibits a chelation-enhanced fluorescence (CHEF) effect in the presence of Zn²⁺ ions and a quenching effect (CHEQ) in the presence of paramagnetic Cu²⁺ ions. Furthermore, the geometry and spectral properties of H₂DTC and the chemosensor bound to Zn²⁺ have been studied by DFT and TDDFT calculations. The limit of detection (LOD) values are 0.11 × 10^-9 and 0.27 × 10^-9 M for Cu²⁺ and Zn²⁺, respectively. The formation constants for the Zn²⁺ and Cu²⁺ complexes have been measured by pH-potentiometry in 0.15 M NaCl in 70:30 (v:v) water:ethanol at 298.1 K. UV-vis absorption and fluorometric spectral data and pH-potentiometric titrations indicate 1:1 and 2:1 metal:chemosensor species. In the solid state H₂DTC is able to accommodate up to four metal ions, as proved by the crystal structures of the complexes [Zn₄(DTC)(OH)₂(NO₃)₄] (1) and {[Cu₄(DTC)(OCH₃)₂(NO₃)₄]·H₂O}_n (2). H₂DTC can be used as a potential chemosensor for monitoring Zn²⁺ and Cu²⁺ ions in biological and environmental media with outstanding accuracy and precision. The propensity of H₂DTC to detect intracellular Cu²⁺ and Zn²⁺ ions in the triple negative human breast cancer cell line MDA-MB-468 and in HeLa cells has been determined by fluorescence cell imaging.

Development of Rhodamine 6G-Based Fluorescent Chemosensors for Al3+-Ion Detection: Effect of Ring Strain and Substituent in Enhancing Its Sensing Performance

Four rhodamine 6G-based chemosensors (H ₃ L1-H ₃ L4) are designed for selective detection of Al³⁺ ion. They are characterized using various spectroscopic techniques and X-ray crystallography. All absorption and emission spectral studies have been performed in 10 mM N-(2-hydroxyethyl)piperazine-N'-ethanesulfonic acid (HEPES) buffer solution at pH 7.4 in H₂O/MeOH (9:1, v/v) at 25 °C. In absorption spectra, chemosensors exhibit an intense band around 530 nm in the presence of Al³⁺ ion. Chemosensors (H ₃ L1-H ₃ L4) are nonfluorescent when excited around 490 nm. The presence of Al³⁺ ion enhances the emission intensity (555 nm) many times. The formation of complexes 1-4 is established with the aid of different spectroscopic techniques. The limit of detection value obtained in the nanomolar range confirms the high sensitivity of the probes toward Al³⁺ ion. It has been observed that the presence of aliphatic spacers in the diamine part and different halogen substituents in the salicylaldehyde part strongly influences the selectivity of the chemosensors toward Al³⁺ ion. The propensity of the chemosensors to identify intracellular Al³⁺ ions in triple-negative human breast cancer cell line MDA-MB-468 by fluorescence imaging is also examined in this study.

Vitamin D deficiency in patients with tuberculous meningitis and its relationship with treatment outcome

SETTING

Data on vitamin D deficiency in tuberculous meningitis (TBM) and its relationship with treatment outcomes are limited. Some of the beneficial effects of vitamin D might be mediated through interleukin-1β (IL-1β).

OBJECTIVE

To assess the frequency of vitamin D deficiency among TBM patients, its association with treatment outcomes and correlation between vitamin D and IL-1β levels in cerebrospinal fluid (CSF).

DESIGN

We prospectively studied a consecutive sample of human immunodeficiency virus-negative patients with TBM treated at a hospital in southern India. We defined good outcome as survival without severe neurological disability. Serum total 25-hydroxy vitamin D (25[OH]D) and IL-1β levels in CSF were estimated on pretreatment samples.

RESULTS

We studied 40 patients with TBM; 22 (55%) patients had stage 3 disease. Treatment outcome was poor in 21 (53%) patients: 15 (38%) patients died and 6 (15%) had severe neurological disability. The overall mean serum 25(OH)D level was 32.30 ± 16.38 ng/ml. Ten (25%) patients had vitamin D deficiency (<20 ng/ml), and 12 (30%) patients had vitamin D insufficiency (20-30 ng/ml). However, pretreatment serum 25(OH)D levels did not differ significantly by outcome (good vs. poor outcome: 28.30 ± 14.96 vs. 35.92 ± 17.11 ng/ml, P = 0.141). Moreover, IL-1β levels in CSF did not correlate with serum 25(OH)D levels (Spearman's ρ 0.083, P = 0.609).

CONCLUSION

Vitamin D deficiency/insufficiency is common among patients with TBM. However, serum 25(OH)D levels are not associated with IL-1β levels in CSF or treatment outcome.

An aminoquinoline based biocompatible fluorescent and colourimetric pH sensor designed for cancer cell discrimination

A simple, low cost aminoquinoline based pH sensor,HLwas prepared and it works at a low pH range.HLexhibits cell permeability and used as an effective tool for differentiating between normal and cancer cells.

Novel strain of Shigella dysenteriae serotype 7 from India

We describe a strain of Shigella dysenteriae serotype 7 which had novel biochemical and genetic characters. Unlike other S. dysenteriae, it produced gas, fermented mannitol, was a late-lactose fermenter and harboured the set 1A and set 1B genes. The significance of such atypical strains is that they are difficult to identify. If such strains are missed, they could prove to be a serious public health problem because the infectious dose is very low and they may harbour integrons contributing to drug resistance.

Evaluation of ELISA and dot blots for the serodiagnosis of neurocysticercosis, in children found to have single or multiple enhancing lesions in computerized tomographic scans of the brain

Although human neurocysticercosis (NCC) is being increasingly recognized in children, diagnosis of the disease can be difficult, and the 'gold standard' criteria that indicate an unambiguous case have still to be established. In the present study, the performances of an ELISA and dot-blot assay, for the detection of antibodies against antigens from larval Taenia solium, were investigated and compared, using sera, from children aged 5-12 years, that were diluted to at least 1:400. Eighty of the subjects (20 aged 5-<8 years and 60 older children) each had the signs and symptoms of NCC, including one brain lesion (N=69) or multiple brain lesions (N=11) that were visible by computed tomography. Another 100 sera, from children who had tubercular meningitis (N=20) or a parasitic disease other than taeniasis/cysticercosis (N=20) or, apart from a minor respiratory-tract infection, appeared healthy (N=60), were also investigated. Most (86%) of the cases of NCC had presented with focal seizures. Analysis of antibody response indicated that the optimum threshold titres for seropositivity were 1:800 for the ELISA and 1:6400 for the dot-blot assays. When used with these thresholds, the ELISA gave a sensitivity, specificity, positive and negative predictive values and diagnostic efficacy of 89%, 81%, 79%, 90%, 85%, respectively. The corresponding values for the dot-blot assay were similar, at 89%, 73%, 72.5%, 89%, 82%, respectively. Both assays were more sensitive, in the detection of the specific antibody response, when used among the paediatric cases of NCC who had multiple brain lesions (100%) than when used among the single-lesion cases (87%). As the ELISA gave higher specificity and diagnostic efficacy than the dot-blot assay, it should be considered the better method for the serological confirmation of NCC in children.

Aerobiological investigation and in vitro studies of pollen grains from 2 dominant avenue trees in Kolkata, India

BACKGROUND

Peltophorum pterocarpum and Delonix regia are dominant avenue trees in the city of Kolkata in India. They are well adapted to the humid tropical climate and also grow commonly in different parts of the country. Their pollen grains are reported to be airborne.

OBJECTIVE

The aim of this study was to conduct an aerobiological survey in Kolkata to determine the concentration and seasonal periodicity of pollen grains from P pterocarpum and D regia and to analyze the meteorological factors responsible for their levels in the atmosphere. In addition, we analyzed the prevalence of sensitization due to these grains among patients with seasonal respiratory allergy.

METHODS

An aerobiological survey was conducted with a volumetric Burkard sampler from 2004 to 2006. Correlations between meteorological parameters and pollen grain concentrations were assessed by Spearman correlation test. The protein profile of the pollen extracts was studied by sodium dodecyl sulfate polyacrylamide gel electrophoresis. Finally, the allergenic potential of the pollen extracts was evaluated in patients with respiratory allergy by skin prick test, immunoglobulin (Ig) E enzyme-linked immunosorbent assay, and IgE immunoblotting.

RESULTS

P pterocarpum and D regia pollen grains occur from March to June and April to July, respectively. The pollen concentrations showed statistically significant positive correlations with maximum temperature and wind speed. Positive reactions to P pterocarpum and D regia were observed in 26% and 22% of the patients, respectively. Many protein bands were detected in the pollen extracts over a wide molecular weight range. A total of 5 (P pterocarpum pollen) and 8 (D regia pollen) protein fractions were detected by IgE immunoblotting.

CONCLUSION

P pterocarpum and D regia pollen grains are dominant in the atmosphere of south Kolkata and they are influenced by temperature. The pollen grains release proteins that may be responsible for immediate hypersensitivity reactions in sensitive patients.