Thermodynamics of water entry in hydrophobic channels of carbon nanotubes

Experiments and computer simulations demonstrate that water spontaneously fills the hydrophobic cavity of a carbon nanotube. To gain a quantitative thermodynamic understanding of this phenomenon, we use the recently developed two phase thermodynamics method to compute translational and rotational entropies of confined water molecules inside single-walled carbon nanotubes and show that the increase in energy of a water molecule inside the nanotube is compensated by the gain in its rotational entropy. The confined water is in equilibrium with the bulk water and the Helmholtz free energy per water molecule of confined water is the same as that in the bulk within the accuracy of the simulation results. A comparison of translational and rotational spectra of water molecules confined in carbon nanotubes with that of bulk water shows significant shifts in the positions of the spectral peaks that are directly related to the tube radius.     

Nano-structured nickel oxide based DNA biosensor for detection of visceral leishmaniasis (Kala-azar)

Sol-gel synthesized nickel oxide (NiO) film deposited onto indium tin oxide (ITO) coated glass plate has been utilized for the development of sensitive and stable DNA biosensor and demonstrated for diagnosis of visceral leishmaniasis also known as Kala-azar. Leishmania specific sensor is developed by immobilizing 23mer DNA sequence (oligonucleotide) identified from 18S rRNA gene sequences from Leishmania donovani. Characterization studies like X-Ray Diffraction and Scanning Electron Microscopy revealed the formation of nano-structured NiO, while immobilization of single strand (ss)-DNA of Leishmania was supported by UV-visible, Fourier Transform Infrared Spectroscopy and Scanning Electron Microscopy techniques. Response studies of ss-DNA/NiO/ITO bioelectrode are carried out using differential pulsed voltammetry in presence of methylene blue redox dye as a redox mediator. A linear response is obtained in the wide concentration range of 2 pg ml(-1) to 2 μg ml(-1) of complementary target genomic DNA (disease DNA) within the variation of 10% for 5 sets of studies. The observed results hold promise not only for diagnosis of Kala-azar patients but also hold enormous potential of the nano-NiO based probe for development of stable and sensitive biosensors.     

Chitosan nanoparticles of 5-fluorouracil for ophthalmic delivery: characterization, in-vitro and in-vivo study

The aim of this investigation was to develop 5-fluorouracil (5-FU) loaded chitosan nanoparticles (CH-DNPs) for ophthalmic delivery. CH-DNPs were fabricated by ionotropic gelation mechanism using chitosan (CH) and a polyanion (TPP). The nanoparticles were smooth and spherical, confirmed by scanning electron microscopy (SEM) and atomic force microscope (AFM). CH/TPP mass ratio and TPP significantly changed the particles size morphology and encapsulation efficiency. The nanoparticles size ranged from approximately 114 to 192 nm and had a positive zeta potential (30±4 mV). The encapsulation efficiency, loading capacity and recovery of DNPs were 8.12-34.32%, 3.14-15.24% and 24.22 to 67% respectively. Physical characterization was done by Fourier transform infrared (FT-IR) and X-ray diffraction (XRD). No interaction was observed in between drug and polymer and crystallinity of drug was not changed in drug loaded nanoparticles. In-vitro release study of DNPs showed diffusion controlled release. Bioavailability study of batch CS9 was studied in rabbit eye and compare to 5-FU solution. 5-FU level was significantly higher in aqueous humor of rabbit eye. Ocular tolerance was studied in the eye of New Zealand rabbits and tested formulation was non-irritant with no sign of inflammation.     

Multiplex cancer cell detection by SERS nanotags with cyanine and triphenylmethine Raman reporters

SERS nanotags have been prepared to accomplish the multiplex detection of cancer cells. Herein we evaluated the adequacy of lipoic acid-containing cyanine derivatives (Cy3LA and Cy5LA) to function as multiplex partners with a triphenylmethine Raman reporter (B2LA) under a single excitation wavelength. SERS experiments enabled the multiplex recognition of two different cancer cells with antibody-conjugated nanotags that were derivatized with optimized cyanine and triphenylmethine reporters.     

ZrOCl2•8H2O-Catalyzed One-Pot Multicomponent Synthesis of β′-Acetamido-β-dicarbonyl Compounds with Special Reference to pref-Selective β′-Acetamido-β-ketoesters

ZrOCl₂ · 8H₂O catalyzes the one-pot synthesis of β′-acetamido-β-dicarbonyl compounds in high yields from aldehyde, enolizable β-dicarbonyl compound, acetyl chloride, and acetonitrile in solvent as well as in solvent-free conditions. β′-Acetamido-β-ketoesters are formed in moderate to exclusive pref-diastereoselectivity.     

Fluorination of polymers by sulfur hexafluoride gas under electric discharge

Fluorination of low-density polyethylene, polyacetylene, and poly(vinyl alcohol) was carried out using SF₆ gas under electric discharge. The polymers were partially fluorinated and the extent of fluorination was more in the case of poly (vinyl alcohol) than the other two polymers. The fluorinated polymers were characterized by elemental analysis (Fluorine), IR, and x-ray diffraction. Optical transparency of the films was also measured. The fluorinated polymers show better solvent resistance and decreased transparency than the virgin polymer. © 1994 John Wiley & Sons, Inc.     

Synthesis of 3‐aminomethylidenechroman‐2‐carboxamides by a Sequential One‐pot Three Component Reaction and by Post‐Passerini Condensation Modification

3‐Arylaminomethylidenechroman‐2‐carboxamide has been synthesized by a one‐pot three component reaction among 3‐formylchromone, aromatic amine, and cyclohexyl isocyanide. 3‐(N‐alkylsubstitued/unsubstituted)aminomethylidenechroman‐2‐carboxamides were synthesized by heating Passerini products derived from chromone‐3‐carbaldehyde with different aliphatic primary amines. The products obtained from the reactions of aliphatic primary amines readily form chromeno[2,3‐c]pyrrole when heated in acetic acid. Bischromanones have also been synthesized using this methodology.     

Design, synthesis, and delivery properties of novel guanidine-containing molecular transporters built on dimeric inositol scaffolds

We have developed a novel class of synthetic molecular transporters that contain eight residues of guanidine with an inositol dimer as the scaffold. The dimers were prepared by connecting two units of myo- or scyllo-inositol via a carbonate or amide linkage, and the multiple units of the guanidine functionality were constructed on the inositol scaffold by means of peracylation with omega-aminocarboxylate derivatives of varying length. Bioassays based on confocal laser scanning microscopy and fluorescence-activated cell sorter analyses indicated that these transporters display a varying degree of membrane translocating ability, and the intracellular localization and mouse-tissue distribution studies strongly suggested that these transporters undergo substantially different mechanistic processes from those of peptide transporters reported to date. It was also shown that doxorubicin, an anticancer antibiotic, can be efficiently delivered into mouse brain by aid of this type of transporter.     

Spectroscopic probing of bile salt-albumin interaction

Interaction of the bile salts, sodium cholate and sodium deoxy cholate with albumin has been probed by fluorescence and circular dichroism studies. Both covalently and non-covalently labeled protein have been used to follow the aggregation of bile salts in presence of protein and to study bile salt-protein interactions in general. Time resolved studies, in agreement with steady-state fluorescence and circular dichroism studies, indicate alteration of protein secondary structure due to positive co-operative effects in bile salt binding to protein. These studies also indicate that covalent labeling may not always be good for studying proteins as it causes alteration of protein secondary structure.     

Further structure–activity relationships study of substituted dithiolethiones as glutathione-inducing neuroprotective agents

Background

Parkinson’s disease is a neurodegenerative disorder associated with oxidative stress and glutathione depletion. The induction of cellular glutathione levels by exogenous molecules is a promising neuroprotective approach to limit the oxidative damage that characterizes Parkinson’s disease pathophysiology. Dithiolethiones, a class of sulfur-containing heterocyclic molecules, are known to increase cellular levels of glutathione; however, limited information is available regarding the influence of dithiolethione structure on activity. Herein, we report the design, synthesis, and pharmacological evaluation of a further series of dithiolethiones in the SH-SY5Y neuroblastoma cell line.

Results

Our structure–activity relationships data show that dithiolethione electronic properties, given as Hammett σ_p constants, influence glutathione induction activity and compound toxicity. The most active glutathione inducer identified, 6a, dose-dependently protected cells from 6-hydroxydopamine toxicity. Furthermore, the protective effects of 6a were abrogated by the inhibitor of glutathione synthesis, buthionine sulfoximine, confirming the importance of glutathione in the protective activities of 6a.

Conclusions

The results of this study further delineate the relationship between dithiolethione chemical structure and glutathione induction. The neuroprotective properties of analog 6a suggest a role for dithiolethiones as potential antiparkinsonian agents.