Sumita Roy

Spontaneous formation of vesicles by sodium 2-dodecylnicotinate in water.

The surface activity and aggregation behavior of a synthesized nicotinic acid based anionic surfactant, sodium 2-dodecylnicotinate, were studied in aqueous solution. The self-assembly formation was investigated by use of a number of techniques, including surface tension and conductivity measurements, fluorescence spectroscopy, dynamic light scattering measurement, gel permeation chromatography, and microscopy. The amphiphile exhibits two breaks in the surface tension vs concentration plot, indicating stepwise aggregate formation and thus producing two values of the aggregation concentration. Stepwise aggregation of the amphiphile was further confirmed by steady-state fluorescence spectroscopy using pyrene as a probe molecule, and also the micropolarity of the aggregates was determined. The rigidity of the microenvironment was estimated by determining steady-state fluorescence anisotropy using 1,6-diphenyl-1,3,5-hexatriene as a fluorescence probe molecule. The average hydrodynamic radius and size distribution of the aggregate suggest formation of larger aggregates in aqueous solution. The formation of vesicles in water was established by conductivity measurement and a dye entrapment experiment. The entrapment of a small solute and the release capability have also been examined to demonstrate these bilayers form enclosed vesicles. Transmission electron micrographs revealed the existence of closed vesicles and closed tubules in aqueous solution. Therefore, for the first time, it has been observed that this simple single-chain nicotinic acid based amphiphile spontaneously assembles to vesicles in aqueous solution.

Effect of amide hydrogen bonding on spontaneously formed gel-emulsions by two pyridyl carboxylic acid based amphiphiles, sodium salt of 2-dodecylpyridine-5-carboxylic acid and sodium salt of [2-dodecylpyridine-5-carboxylic]glycine: entrapment and release of vitamin B12

The present study offers the demonstration and rational design of two synthesized single chain pyridyl carboxylic acid (nicotinic acid) based amphiphilic gelators named the sodium salt of 2-dodecylpyridine-5-carboxylic acid (SDDPC) and the sodium salt of [2-dodecylpyridine-5-carboxylic]glycine (SDDPCG). The gelation abilities were tested in a series of organic solvents, by a number of physical methods including X-ray diffraction, FTIR spectroscopy, rheology, DSC, optical and electron microscopy. The minimum gelation concentration and gelation number of the gelators in different solvents were determined. No gelation was observed when pure solvents were employed. The gelation properties of these two compounds found that the gelation depends on H-bonding of the amide linkage. X-ray diffraction study indicates the presence of two recognizable morphologies for SDDPC in a gel-emulsion, whereas for SDDPCG a single type of aggregate is predominant. FTIR spectra suggest that the presence of intermolecular hydrogen bonding facilitates the gelation process. Rheological measurements demonstrated that the gel-emulsions are mechanically stable and exhibit typical viscoelastic properties. Optical microscopy images show a network structure in the gel phase and a fibril structure in the xerogel. SEM images confirmed the presence of network as well as a flex-like thick fibrous network for both the amphiphiles, forming three dimensional (3-D) networks. Both the gelators showed a remarkable response toward external pH. The gel-emulsions were used in the controlled and/or pH triggered release of entrapped (within the gel-emulsions) vitamin B12 at different pHs.

Effect of pH and oxygen atom of the hydrophobic chain on the self-assembly property and morphology of the pyridyl boronic acid based amphiphiles.

The surface activity and aggregation behavior of two synthesized boronic acid based anionic surfactants, sodium salt of 2-dodecyl pyridine-5-boronic acid (SDDPB) and sodium salt of 2-oxydodecyl pyridine-5-boronic acid (SODDPB), were studied in buffer solution at pH 9 and 13 containing carbohydrates. The self-assembly formation was investigated by use of a number of techniques including surface tension, conductivity, fluorescence spectroscopy, dynamic light scattering, X-ray diffraction, and transmission electron microscopy (TEM). Both of the amphiphiles exhibit a single break in the surface tension vs log(concentration) plots, indicating existence of one critical aggregation concentration. Steady state fluorescence spectroscopy was used to determine the polarity indexes using pyrene and the rigidity of the microenvironments of the aggregates using 1,6-diphenyl-1,3,5-hexatriene (DPH) as fluorescence probe molecules. The pKas of both amphiphiles were determined in buffer solutions of different pHs. XRD studies were performed to shed light on the morphology of the self-assemblies. TEM micrographs revealed the existence of vesicles for both the amphiphiles in buffer solution of pH 9, but at pH 13, TEM pictures indicate the existence of closed vesicles in SDDPB solution and at concentrated solution the vesicles are fused to form sponge-like micelles. After aging the vesicular solution of pH 13 of SDDPB, the closed vesicles are destroyed. In contrast, for SODDPB at pH 13, TEM pictures suggest the existence of spherical and complex micelles in solution which were further transformed into crystal-like structure upon aging. The average hydrodynamic radii were determined by dynamic light scattering measurement. Therefore, for the first time, we have successfully synthesized two new surfactants containing pyridyl-boronic acid as a headgroup which shows remarkable tuning of morphology in two different pHs and in the presence of two different carbohydrates.

Synthesis and characterization of biogenic metal nanoparticles and its cytotoxicity and anti-neoplasticity through the induction of oxidative stress, mitochondrial dysfunction and apoptosis

In the present study, we demonstrate a simple, cost-effective and eco-friendly method for biogenic synthesis of silver nanoparticles (AgNPCGs) using ethanolic extract of Calotropis gigantea latex. Attempts were made to characterize these biogenic silver nanoparticles AgNPCGs and also to test its cytotoxic, anti-neoplastic and apoptotic potential through the induction of oxidative stress, mitochondrial dysfunction. AgNPCGs were characterized by UV-vis spectroscopy, dynamic light scattering (DLS) and surface zeta potential measurement, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM) and selected area electron diffraction, scanning electron microscopy (SEM), energy-dispersive X-ray fluorescence spectrometry (EDX). UV visible spectroscopy showed an intense surface plasmon resonance band at 431nm which clearly reflected the formation of silver nanoparticles. FTIR study revealed that latex extract acted as reducing and stabilizing agent for the synthesis of AgNPCGs. Energy dispersive X-ray spectroscopy confirmed the presence of silver as a major component of synthesized AgNPCGs. SEM and TEM studies showed that the synthesized AgNPCGs were nearly spherical in shape with an average size of 2.338nm. The selected area electron diffraction pattern and XRD studies confirmed the crystalline nature of AgNPCGs. AgNPCGs exhibited in-vitro cytotoxic activity against Ehrlichs ascites carcinoma (EAC), Jurkat and MCF-7 cells at respective IC50 doses without producing cytotoxicity to mice and human lymphocytes. Significant chromatin condensation, DNA fragmentation, cell cycle arrest at G2/M phase, up-regulation of Bax and caspase-3 and down-regulation of Bcl-2 were observed in AgNPCGs treated EAC cells. The results suggest that biogenic silver nanoparticles AgNPCGs could be a potential chemotherapeutic formulation for cancer therapy.

Gold nanoparticles from indole-3-carbinol exhibit cytotoxic, genotoxic and antineoplastic effects through the induction of apoptosis

The synthesized gold nanoparticles using indole-3-carbinol (AuNPI3Cs) has been characterized and its antineoplastic activities has been studied here. Several techniques have been used to characterize the AuNPI3Cs. Ultraviolet spectroscopy studies indicated the stability of the synthesized AuNPI3Cs, while FTIR analysis proved that indole-3-carbinol was playing an important role in stabilizing the AuNPI3Cs. TEM analysis study showed that AuNPI3Cs were mostly spherical in shape with an average particle size of 3 nm. The selected area electron diffraction pattern exhibited the crystalline nature of AuNPI3Cs, which was further proved by XRD studies. The present study describes the in vitro antineoplastic efficacy of AuNPI3Cs against Ehrlich ascites carcinoma (EAC) cells. Results showed that the IC50 dose of AuNPI3Cs was significantly capable of elevating intracellular reactive oxygen species. AuNPI3Cs induced apoptosis by increasing the G2/M population, LIVE/DEAD cytotoxicity, chromatin condensation, DNA laddering and TUNEL-positive cells significantly (p < 0.001). Reduction of the mitochondrial potential by AuNPI3Cs was substantiated by JC-1 fluorescent staining. These findings will enlighten future biomedical applications of gold nanoparticles using indole-3-carbinol (AuNPI3Cs) as an antineoplastic agent.

Surface and self-organization of sodium salt of 2-decyl pyridine-5-boronic acid and sodium salt of 2-oxydecyl pyridine-5-boronic acid at two different pHs

This study evaluates the effect of pH and oxygen atom of the hydrophobic chain on the self-assembly property and morphology of the two synthesized pyridyl boronic acid-based amphiphiles in the presence of carbohydrates. Tensiometry measurements confirmed the formation of aggregates in solutions, and all the studied amphiphiles are surface active. Steady-state fluorescence studies established that the microenvironments of the self-assemblies are nonpolar and rigid. DLS measurements suggest the presence of single type of morphology for SDPB at both the pHs. Reversely, the bimodal intensity average size distribution of SODPB at pH 9 indicates the presence of two types of aggregates, and monomodal distribution at pH 13 implies existence of one type of aggregates in solution. TEM micrographs show the presence of vesicles for SDPB at solutions of two different pHs, whereas TEM pictures of SODPB at pH 9 revealed existence of both of complex micelles and vesicles and at pH 13 formation of crystalline structures. The actual arrangement of the hydrocarbon chains in the bilayers has been investigated by XRD studies. The surface activity and self-assembly property of the amphiphiles could be used in surfactant and pharmaceutical purposes.