Joykrishna Dey - Academia.edu (original) (raw)

Papers by Joykrishna Dey

Colloids and surfaces. B, Biointerfaces, 2016

A series of novel two-component organogel systems comprising of amines and anhydrides was develop... more A series of novel two-component organogel systems comprising of amines and anhydrides was developed. These two-component systems in aromatic solvents exhibit instantaneous gelation during mixing at room temperature without the requirement of any external stimulus such as heat, sonication, etc. The corresponding alcohols, however, failed to produce gel under similar condition. The structure-property relationship was investigated. The effect of mixing ratio of the two components as well as the effect of solvents on gelation was studied. A detail characterization of the organogels using electron microscopy, FTIR, (1)H NMR and X-ray diffraction spectroscopy, differential scanning calorimetry and rheology suggested formation of a hydrogen-bonded complex that induces creation of three dimensional entangled network structures which immobilize the solvent showing macroscopic gelation. The packing of hydrocarbon chains of the amines and π-π stacking interaction in aromatic amines were observ...

Journal of colloid and interface science, Jan 16, 2018

Self-assembly of surfactants is influenced by various intermolecular interactions and molecular s... more Self-assembly of surfactants is influenced by various intermolecular interactions and molecular structure, which dictate packing of molecules in the aggregate and its microstructure. Hydrogen-bonding between amide groups plays a key role in the self-assembly process of N-acyl amino acid surfactants (NAAS). The self-assembly properties of two NAAS, sodium N-lauroyl sarcosinate (SLS) and sodium N-lauroyl glycinate (SLG) that differ only in the head-group structure were compared in aqueous and aqueo-organic media by using a number of methods, including surface tension fluorescence, dynamic light scattering, calorimetry, and microscopy. It was observed that aggregate formation is more favoured in SLG. Studies revealed that while SLS formed small spherical micelles, SLG produced unilamellar vesicles in pH 7 buffer above critical micelle concentration at 25 °C. The stability of SLG vesicles with respect to pH and temperature was also investigated. Furthermore, both SLG and SLS were found ...

Journal of Colloid and Interface Science, 2015

The function of a protein depends upon its structure and surfactant molecules are known to alter ... more The function of a protein depends upon its structure and surfactant molecules are known to alter protein structure. For this reason protein-surfactant interaction is important in biological, pharmaceutical, and cosmetic industries. In the present work, interactions of a series of anionic surfactants having the same hydrocarbon chain length, but different amino acid head group, such as L-alanine, L-valine, L-leucine, and L-phenylalanine with the transport protein, bovine serum albumin (BSA), were studied at low surfactant concentrations using fluorescence and circular dichroism (CD) spectroscopy, and isothermal titration calorimetry (ITC). The results of fluorescence measurements suggest that the surfactant molecules bind simultaneously to the drug binding site I and II of the protein subdomain IIA and IIIA, respectively. The fluorescence as well as CD spectra suggest that the conformation of BSA goes to a more structured state upon surfactant binding at low concentrations. The binding constants of the surfactants were determined by the use of fluorescence as well as ITC measurements and were compared with that of the corresponding glycine-derived surfactant. The binding constant values clearly indicate a significant head-group effect on the BSA-surfactant interaction and the interaction is mainly hydrophobic in nature.

Soft Matter, 2018

Sustained release of doxorubicin from a β-aminoacid-containing cytocompatible tripeptidic hydroge... more Sustained release of doxorubicin from a β-aminoacid-containing cytocompatible tripeptidic hydrogel which shows thixotropic behaviour after PVA-induction.

Six L-histidine-based amphiphiles, N-(4-n-alkyloxybenzoyl)-L-histidine of different hydrocarbon c... more Six L-histidine-based amphiphiles, N-(4-n-alkyloxybenzoyl)-L-histidine of different hydrocarbon chain lengths, were designed, synthesized, and examined for their ability to gelate water. Four ofmembers of this family of amphiphiles were observed to form thermoreversible hydrogels in a wide range of pH at room temperature. The structural variations were characterized by critical gelation concentration, gelation time, gel melting temperature (Tgs), rheology, and electron microscopy. Among the amphiphiles, the n-octyl derivative showed better gelation ability in the studied pH range. The amphiphiles were found to have Tgs higher than body temperature (37 C) showing their stability. Also, relatively higher yield stress (>1000 Pa) values of the hydrogels show their higher strength. The effective gelator molecules self-assemble into fibrous structures. Scanning electron microscopic picture of the hydrogels revealed large ribbons with right-handed twist. Small-angle XRD and circular dic...

Aggregation behavior of three N -acyl amino acid surfactants, sodium N -(11-acrylamidoundecanoyl)... more Aggregation behavior of three N -acyl amino acid surfactants, sodium N -(11-acrylamidoundecanoyl)-L-serinate (SAUS), sodium N -(11acrylamidoundecanoyl)-L-asparaginate (SAUAS), and sodium N -(11-acrylamidoundecanoyl)-L-glutaminate (SAUGL), was studied in aqueous solution by use of surface tension, fluorescence, dynamic light scattering, and transmission electron microscopic techniques. The amphiphiles have been shown to initially form flexible bilayer structures, which upon increase of surfactant concentration transform into closed spherical vesicles. The transmission electron micrographs of the aqueous solutions of the surfactants confirmed the existence of spherical vesicles. Dynamic light scattering measurements were performed to obtain hydrodynamic radii of the vesicles. Circular dichroism spectra of the amphiphiles indicated formation of chiral helical aggregates in the case of SAUS. The self-assembly formation of the amphiphiles has been discussed in light of the intermolecular...

Low-molecular-weight organogelators (LMOGs) have received considerable attention over recent deca... more Low-molecular-weight organogelators (LMOGs) have received considerable attention over recent decades because they exhibit interesting self-assembly phenomena, forming threedimensional (3-D) networks. The interest in this area is driven by their unique supramolecular architectures and wide-ranging applications in industrial fields including drug delivery, tissue engineering, synthesis of nanomaterials and devices, sensing and soft lithography. The self-assembly of LMOGs is often driven by one or more noncovalent forces, such as dipolar interaction, van der Waals forces, hydrogen-bonding (Hbonding), and metal-coordination bonds. The self-assembly leads spontaneously to formation of one-dimensional (1-D) aggregates, which either by physical cross-linking or by entanglement produce 3-D network structures that entrap and immobilize a large volume of solvent in the compartments of selfassembled fibrillar networks (SAFINs) having a large solidliquid interface area by surface tension and ca...

RSC Advances, 2020

Correction for ‘Thermodynamically stable vesicle formation of biodegradable double mPEG-tailed am... more Correction for ‘Thermodynamically stable vesicle formation of biodegradable double mPEG-tailed amphiphiles with sulfonate head group’ by Rita Ghosh et al., RSC Adv., 2020, 10, 32522–32531, DOI: 10.1039/D0RA05613H

Langmuir : the ACS journal of surfaces and colloids, Jan 6, 2018

The design and synthesis of biocompatible surfactants are important for a wide range of applicati... more The design and synthesis of biocompatible surfactants are important for a wide range of applications in cosmetics, personal care products, and nanomedicine. This feature article summarizes our studies over the past 8 years on the design, synthesis, surface activity, and self-assembly of a series of unconventional low-molecular-mass amphiphiles containing a poly(ethylene glycol) (PEG) tail or spacer and different ionic or zwitterionic headgroups, including carboxylate, sulfonate, and quaternary ammonium salts. Despite having a so-called polar PEG chain as a tail or spacer, these ionic amphiphiles are found to have a tendency to adsorb at the air/water interface and self-assemble in pH 7.0 buffers at 298 K in the same way that conventional hydrocarbon tail surfactants do. However, they are observed to be relatively less surface-active compared to hydrocarbon tail surfactants. Although these amphiphilic molecules have less surface activity, they do self-assemble in aqueous buffer at 29...

Langmuir, 2017

Monolayer lipid membrane formation based on self-assembly of bolaamphiphiles containing hydrophob... more Monolayer lipid membrane formation based on self-assembly of bolaamphiphiles containing hydrophobic spacer are well-established in the literature, but monolayer vesicle formation by so-called hydrophilic poly(ethylene glycol) (PEG) spacer has not been reported to date. Here, a novel l-cysteine-derived bolaamphiphile with PEG as spacer has been developed and characterized. The interfacial properties and the solution behavior of the amphiphile were investigated in pH 7.0 at 25 °C. The self-assembly properties of the bolaamphiphile in aqueous buffer were investigated by using different techniques, such as surface tensiometry, fluorescence spectroscopy, UV-vis spectroscopy, isothermal titration calorimetry, dynamic light scattering, transmission electron microscopy, and atomic force microscopy. Surprisingly, despite having so-called polar spacer in between two polar head groups, it exhibits formation of microstructures in aqueous buffer as well as in water at 25 °C. The molecule undergoes self-organization leading to the formation of monolayer vesicles with hydrodynamic diameters between 100 and 250 nm in a wide range of concentration. The thermodynamic parameters clearly suggest that the aggregate formation is mainly driven by the hydrophobic effect. The monolayer vesicles were found to form at a very low concentration (≥0.63 mM) and within a wide pH range (2-10). The vesicles exhibit excellent shelf life at physiological temperature.

Journal of colloid and interface science, 2017

Cholesterol (Chol) is a ubiquitous steroidal component of cell membrane and is known to modulate ... more Cholesterol (Chol) is a ubiquitous steroidal component of cell membrane and is known to modulate the packing of phospholipids within the bilayer. Thus, Chol has been frequently used in the formulation and study of artificial "model membranes" like vesicles and liposomes. In this work, we have developed a novel anionic surfactant by conjugating two biomolecules, cholesterol and γ-aminobutyric acid via a urethane linkage. We have studied its physicochemical behavior in aqueous buffer. The surfactant has been shown to spontaneously form small unilamellar vesicles above a very low critical concentration in aqueous neutral buffer at room temperature. The vesicle phase was characterized by use of fluorescence probe, transmission electron microscopy and dynamic light scattering (DLS) techniques. The vesicle bilayer was found to be much less polar as well as more viscous compared to the bulk water. The vesicle stability with respect to change of temperature, pH, and ageing time wa...

Journal of colloid and interface science, 2017

Stimuli-sensitive polymersomes are one of the important vehicles and have been extensively studie... more Stimuli-sensitive polymersomes are one of the important vehicles and have been extensively studied as smart drug delivery system. Polymersomes have added advantage over the micelles because of having the ability to carry not only hydrophobic but also hydrophilic guest in their aqueous core. Among various stimuli, the change of pH and redox reaction is very important for drug delivery purpose especially for anticancer drug. Therefore, in this work, two poly(ethylene glycol) methyl ether methacrylate (mPEG) containing hydrophilic random anionic copolymers, poly[(2-hydroxyethyl methacrylate-3,3'-dithiodipropanoic acid)x-co-(poly(ethylene glycol) methyl ether methacrylate)y], poly[(HEMA-DTDPA)x-co-mPEGy] with different copolymer ratios were designed and synthesized. The self-assembly behaviour of these copolymers were studied by use of various techniques, including fluorescence spectroscopy, light scattering, and electron and optical microscopy. Both the copolymers were observed to ...

Langmuir : the ACS journal of surfaces and colloids, Jan 3, 2017

In our recent reports, we have shown that when a poly(ethylene glycol) (PEG) chain is covalently ... more In our recent reports, we have shown that when a poly(ethylene glycol) (PEG) chain is covalently linked to any ionic group, the resultant molecule behaves like an amphiphile. Depending upon the nature of ionic head groups, they self-assemble to form micelles or vesicles, in which the PEG chain constitutes the micellar core or vesicle bilayer. In this study, we intend to examine what happens when both hydrocarbon (HC) and PEG chains are attached to a carboxylate head group. Therefore, we have synthesized two novel amphiphiles in which a PEG and a HC chain is covalently linked to l-cysteine. The surface activities and the solution behavior of the sodium salts of these amphiphiles were investigated at neutral pH. The amphiphiles self-organize to form large unilamellar vesicles in dilute solutions, which transformed into small micelles at higher concentrations. The HC chains of the molecules have been shown to constitute the bilayer membrane of the vesicles and core of micelles. In acid...

Macromolecular Bioscience, 2016

Stimuli-sensitive polymeric vesicles or polymersomes as self-assembled colloidal nanocarriers hav... more Stimuli-sensitive polymeric vesicles or polymersomes as self-assembled colloidal nanocarriers have received paramount importance for their integral role as delivery system for therapeutics and biotherapeutics. This work describes spontaneous polymersome formation at pH 7, as evidenced by surface tension, steady state fluorescence, dynamic light scattering, and microscopic studies, by three hydrophilic random cationic copolymers synthesized using N,N-(dimethylamino)ethyl methacrylate (DMAEM) and methoxy poly(ethylene glycol) monomethacrylate in different mole ratios. The results suggest that methoxy poly(ethylene glycol) chains constitute the bilayer membrane of the polymersomes and DMAEM projects toward water constituting the positively charged surface. The polymersomes have been observed to release their encapsulated guest at acidic pH as a result of transformation into polymeric micelles. All these highly biocompatible cationic polymers show successful gene transfection ability as nonviral vector on human cell line with different potential. Thus these polymers prove their utility as a potential delivery system for hydrophilic model drug as well as genetic material.

Colloids and Surfaces B: Biointerfaces, 2016

The development of stimuli-responsive biocompatible polymersomes is important for the improvement... more The development of stimuli-responsive biocompatible polymersomes is important for the improvement of drug delivery systems. Herein, we report the spontaneous formation of polymersomes by three random copolymers, l-cys-graft-poly[GMA-co-mPEG300], containing different ratios of l-cysteine (Cys) and methoxy poly(ethylene glycol) (mPEG) covalently linked to the polymer backbone. Cysteine was conjugated to the polymeric backbone through metal free thiol-epoxy 'click' chemistry at final step. The copolymers, without having any typical hydrophobe in the backbone, are sufficiently surface active. The self-assembly formation of the copolymers was studied in aqueous solution by steady-state fluorescence probe technique. Spontaneous polymersomes formation, without any help of stimuli and organic solvent, above a relatively low critical aggregation concentration was confirmed by dynamic light scattering and microscopic techniques. Polymersomes were shown to be able to encapsulate not only hydrophilic dye in their aqueous core but also hydrophobic guest molecules in the bilayer membrane constituted by the mPEG chains. The polymersomes are sufficiently stable under physiological condition. These nano-sized polymersomes exhibit pH-triggered release of encapsulated guest under acidic pH. All three copolymers were found to be completely cell viable and hemocompatible up to very high concentration. Their ability to cross cell membrane was demonstrated by use of a fluorescent dye-tagged polymer. Further, these copolymers did not show any denaturising effect on the secondary structure of the human serum albumin, a transport protein in the blood. Based on the results of this study it is concluded that these spontaneously formed stable and biocompatible polymersomes can have potential use as drug delivery systems.

Journal of Colloid and Interface Science, 2015

Two novel amphiphilic molecules were synthesized by the reaction between poly(ethylene glycol) me... more Two novel amphiphilic molecules were synthesized by the reaction between poly(ethylene glycol) methyl ether (mPEG) of different chain lengths and sodium-2-mercapto ethane sulfonate (mesna). Different techniques, such as surface tensiometry, conductometry, fluorescence spectroscopy, dynamic light scattering, UV-vis spectroscopy, transmission electron microscopy, and isothermal titration calorimetry were employed to investigate the self-assembly properties of the PEG-based single-tailed amphiphiles in aqueous buffer. Despite having so called polar tail the amphiphiles exhibit aggregate formation in aqueous buffer as well as in water. The shorter chain amphiphile was shown to form bilayer vesicles in contrast to small micelles by its longer chain counterpart. The helicity of the PEG chain was taken into consideration to interpret the difference in self-assembled microstructure formation. The thermodynamics of the self-assemblies were also thoroughly examined. The thermodynamic parameters clearly suggested that the hydrophobic interaction among the PEG chains is the main driving force for aggregate formation. The self-assembled microstructures were observed to be fairly stable with respect to increase of surfactant concentration, aging time and temperature.

The Journal of Physical Chemistry B, 2015

The present work reports the pH-induced conformational changes of pepsin in solution at room temp... more The present work reports the pH-induced conformational changes of pepsin in solution at room temperature. The conformational change makes the protein surface active. The protein was found to be present in the partially denatured state at pH 8 as well as at pH 2. The fluorescence probe and circular dichroism (CD) spectra suggested that the most stable state of pepsin exists at pH 5. The binding affinities of pepsin in its native and denatured states for a D,L-carnitine-based cationic surfactant (3-hexadecylcarbamoyl-2-hydroxypropyl)trimethylammonium chloride (C16-CAR) were examined at very low concentrations of the surfactant. The thermodynamics of the binding processes were investigated by use of isothermal titration calorimetry. The results were compared with those of (3-hexadecylcarbamoylpropyl)trimethylammonium chloride (C16-PTAC), which is structurally similar to C16-CAR, but without the secondary -OH functionality near the headgroup. None of the surfactants were observed to undergo binding with pepsin at pH 2, in which it exists in the acid-denatured state. However, both of the surfactants were found to spontaneously bind to the most stable state at pH 5, the partially denatured state at pH 8, and the alkaline denatured state at pH 11. Despite the difference in the headgroup structure, both of the surfactants bind to the same warfarin binding site. Interestingly, the driving force for binding of C16-CAR was found to be different from that of C16-PTC at pH ≥ 5. The steric interaction of the headgroup in C16-CAR was observed to have a significant effect on the binding process.

Journal of the Chemical Society, Perkin Transactions 2, 1998

ABSTRACT Micellar behaviour of the amphiphilic 6-S-alkyl-6-thiocyclomaltooligosaccharid (2) in ch... more ABSTRACT Micellar behaviour of the amphiphilic 6-S-alkyl-6-thiocyclomaltooligosaccharid (2) in chloroform has been measured by use of the fluorescent probe 8-anilinonaphthalene-1-sulfonate (ANS) as guest molecule, as well as by water-chloroform interfacial tension measurements. At low concentrations the amphiphiles show behaviour consistent with their being oligomers of monosaccharide amphiphiles, or `unimolecular micelles'. Thus, with ANS, 1:1 complexes are formed for which the association constants are in proportion to the length of the chains. At higher concentrations, the long-chained (C-16, C-18) alkylthioeyclodextrins form inverted micellar aggregates. The NMR shift changes associated with inclusion of 1-naphthol indicate that even in these aggregates, the carbohydrate cavity plays a part in complexation, while the hydrophobic chains act as extensions of the more hydrophobic primary-hydroxy side of the cavity.

Soft Matter, 2013

Herein we report for the first time fibril formation by pepsin at neutral pH and room temperature... more Herein we report for the first time fibril formation by pepsin at neutral pH and room temperature. Fibril formation was characterized by a number of techniques including fluorescence and circular dichroism spectroscopy, dynamic light scattering, and transmission electron microscopy.

Journal of Colloid and Interface Science, 2011

The interaction of sodium N-lauroylsarcosinate (SLS) with N-cetylpyridinium chloride (CPC) and N-... more The interaction of sodium N-lauroylsarcosinate (SLS) with N-cetylpyridinium chloride (CPC) and N-dodecylpyridinium chloride (DPC) was investigated in aqueous mixtures. A strong interaction between the anionic and cationic surfactants was observed. The interaction parameter, β was determined for a wide composition range and was found to be negative. The mixed systems were found to have much lower critical micelle concentration (cmc) and surface tension at cmc. The surfactant mixtures exhibit synergism in the range of molar fractions investigated. The self-assembly formation in the mixtures of different compositions and total concentrations were studied using a number of techniques, including surface tension, fluorescence spectroscopy, dynamic light scattering (DLS), transmission electron microscopy (TEM), confocal fluorescence microscopy (CFM). Thermodynamically stable unilamellar vesicles were observed to form upon mixing of the anionic and cationic surfactants in a wide range of composition and concentrations in buffered aqueous media. TEM as well as DLS measurements were performed to obtain shape and size of the vesicular structures, respectively. These unilamellar vesicles are stable for periods as long as 3 months and appear to be the equilibrium form of aggregation. Effect of pH, and temperature on the stability was investigated. The vesicular structures were observed to be stable at pH as low as 2.0 and at biological temperature (37°C). In presence of 10 mol% of cholesterol the mixed surfactant vesicles exhibited leakage of the encapsulated calcein dye, showing potential application in pH-triggered drug release.

Colloids and surfaces. B, Biointerfaces, 2016

A series of novel two-component organogel systems comprising of amines and anhydrides was develop... more A series of novel two-component organogel systems comprising of amines and anhydrides was developed. These two-component systems in aromatic solvents exhibit instantaneous gelation during mixing at room temperature without the requirement of any external stimulus such as heat, sonication, etc. The corresponding alcohols, however, failed to produce gel under similar condition. The structure-property relationship was investigated. The effect of mixing ratio of the two components as well as the effect of solvents on gelation was studied. A detail characterization of the organogels using electron microscopy, FTIR, (1)H NMR and X-ray diffraction spectroscopy, differential scanning calorimetry and rheology suggested formation of a hydrogen-bonded complex that induces creation of three dimensional entangled network structures which immobilize the solvent showing macroscopic gelation. The packing of hydrocarbon chains of the amines and π-π stacking interaction in aromatic amines were observ...

Journal of colloid and interface science, Jan 16, 2018

Self-assembly of surfactants is influenced by various intermolecular interactions and molecular s... more Self-assembly of surfactants is influenced by various intermolecular interactions and molecular structure, which dictate packing of molecules in the aggregate and its microstructure. Hydrogen-bonding between amide groups plays a key role in the self-assembly process of N-acyl amino acid surfactants (NAAS). The self-assembly properties of two NAAS, sodium N-lauroyl sarcosinate (SLS) and sodium N-lauroyl glycinate (SLG) that differ only in the head-group structure were compared in aqueous and aqueo-organic media by using a number of methods, including surface tension fluorescence, dynamic light scattering, calorimetry, and microscopy. It was observed that aggregate formation is more favoured in SLG. Studies revealed that while SLS formed small spherical micelles, SLG produced unilamellar vesicles in pH 7 buffer above critical micelle concentration at 25 °C. The stability of SLG vesicles with respect to pH and temperature was also investigated. Furthermore, both SLG and SLS were found ...

Journal of Colloid and Interface Science, 2015

The function of a protein depends upon its structure and surfactant molecules are known to alter ... more The function of a protein depends upon its structure and surfactant molecules are known to alter protein structure. For this reason protein-surfactant interaction is important in biological, pharmaceutical, and cosmetic industries. In the present work, interactions of a series of anionic surfactants having the same hydrocarbon chain length, but different amino acid head group, such as L-alanine, L-valine, L-leucine, and L-phenylalanine with the transport protein, bovine serum albumin (BSA), were studied at low surfactant concentrations using fluorescence and circular dichroism (CD) spectroscopy, and isothermal titration calorimetry (ITC). The results of fluorescence measurements suggest that the surfactant molecules bind simultaneously to the drug binding site I and II of the protein subdomain IIA and IIIA, respectively. The fluorescence as well as CD spectra suggest that the conformation of BSA goes to a more structured state upon surfactant binding at low concentrations. The binding constants of the surfactants were determined by the use of fluorescence as well as ITC measurements and were compared with that of the corresponding glycine-derived surfactant. The binding constant values clearly indicate a significant head-group effect on the BSA-surfactant interaction and the interaction is mainly hydrophobic in nature.

Soft Matter, 2018

Sustained release of doxorubicin from a β-aminoacid-containing cytocompatible tripeptidic hydroge... more Sustained release of doxorubicin from a β-aminoacid-containing cytocompatible tripeptidic hydrogel which shows thixotropic behaviour after PVA-induction.

Six L-histidine-based amphiphiles, N-(4-n-alkyloxybenzoyl)-L-histidine of different hydrocarbon c... more Six L-histidine-based amphiphiles, N-(4-n-alkyloxybenzoyl)-L-histidine of different hydrocarbon chain lengths, were designed, synthesized, and examined for their ability to gelate water. Four ofmembers of this family of amphiphiles were observed to form thermoreversible hydrogels in a wide range of pH at room temperature. The structural variations were characterized by critical gelation concentration, gelation time, gel melting temperature (Tgs), rheology, and electron microscopy. Among the amphiphiles, the n-octyl derivative showed better gelation ability in the studied pH range. The amphiphiles were found to have Tgs higher than body temperature (37 C) showing their stability. Also, relatively higher yield stress (>1000 Pa) values of the hydrogels show their higher strength. The effective gelator molecules self-assemble into fibrous structures. Scanning electron microscopic picture of the hydrogels revealed large ribbons with right-handed twist. Small-angle XRD and circular dic...

Aggregation behavior of three N -acyl amino acid surfactants, sodium N -(11-acrylamidoundecanoyl)... more Aggregation behavior of three N -acyl amino acid surfactants, sodium N -(11-acrylamidoundecanoyl)-L-serinate (SAUS), sodium N -(11acrylamidoundecanoyl)-L-asparaginate (SAUAS), and sodium N -(11-acrylamidoundecanoyl)-L-glutaminate (SAUGL), was studied in aqueous solution by use of surface tension, fluorescence, dynamic light scattering, and transmission electron microscopic techniques. The amphiphiles have been shown to initially form flexible bilayer structures, which upon increase of surfactant concentration transform into closed spherical vesicles. The transmission electron micrographs of the aqueous solutions of the surfactants confirmed the existence of spherical vesicles. Dynamic light scattering measurements were performed to obtain hydrodynamic radii of the vesicles. Circular dichroism spectra of the amphiphiles indicated formation of chiral helical aggregates in the case of SAUS. The self-assembly formation of the amphiphiles has been discussed in light of the intermolecular...

Low-molecular-weight organogelators (LMOGs) have received considerable attention over recent deca... more Low-molecular-weight organogelators (LMOGs) have received considerable attention over recent decades because they exhibit interesting self-assembly phenomena, forming threedimensional (3-D) networks. The interest in this area is driven by their unique supramolecular architectures and wide-ranging applications in industrial fields including drug delivery, tissue engineering, synthesis of nanomaterials and devices, sensing and soft lithography. The self-assembly of LMOGs is often driven by one or more noncovalent forces, such as dipolar interaction, van der Waals forces, hydrogen-bonding (Hbonding), and metal-coordination bonds. The self-assembly leads spontaneously to formation of one-dimensional (1-D) aggregates, which either by physical cross-linking or by entanglement produce 3-D network structures that entrap and immobilize a large volume of solvent in the compartments of selfassembled fibrillar networks (SAFINs) having a large solidliquid interface area by surface tension and ca...

RSC Advances, 2020

Correction for ‘Thermodynamically stable vesicle formation of biodegradable double mPEG-tailed am... more Correction for ‘Thermodynamically stable vesicle formation of biodegradable double mPEG-tailed amphiphiles with sulfonate head group’ by Rita Ghosh et al., RSC Adv., 2020, 10, 32522–32531, DOI: 10.1039/D0RA05613H

Langmuir : the ACS journal of surfaces and colloids, Jan 6, 2018

The design and synthesis of biocompatible surfactants are important for a wide range of applicati... more The design and synthesis of biocompatible surfactants are important for a wide range of applications in cosmetics, personal care products, and nanomedicine. This feature article summarizes our studies over the past 8 years on the design, synthesis, surface activity, and self-assembly of a series of unconventional low-molecular-mass amphiphiles containing a poly(ethylene glycol) (PEG) tail or spacer and different ionic or zwitterionic headgroups, including carboxylate, sulfonate, and quaternary ammonium salts. Despite having a so-called polar PEG chain as a tail or spacer, these ionic amphiphiles are found to have a tendency to adsorb at the air/water interface and self-assemble in pH 7.0 buffers at 298 K in the same way that conventional hydrocarbon tail surfactants do. However, they are observed to be relatively less surface-active compared to hydrocarbon tail surfactants. Although these amphiphilic molecules have less surface activity, they do self-assemble in aqueous buffer at 29...

Langmuir, 2017

Monolayer lipid membrane formation based on self-assembly of bolaamphiphiles containing hydrophob... more Monolayer lipid membrane formation based on self-assembly of bolaamphiphiles containing hydrophobic spacer are well-established in the literature, but monolayer vesicle formation by so-called hydrophilic poly(ethylene glycol) (PEG) spacer has not been reported to date. Here, a novel l-cysteine-derived bolaamphiphile with PEG as spacer has been developed and characterized. The interfacial properties and the solution behavior of the amphiphile were investigated in pH 7.0 at 25 °C. The self-assembly properties of the bolaamphiphile in aqueous buffer were investigated by using different techniques, such as surface tensiometry, fluorescence spectroscopy, UV-vis spectroscopy, isothermal titration calorimetry, dynamic light scattering, transmission electron microscopy, and atomic force microscopy. Surprisingly, despite having so-called polar spacer in between two polar head groups, it exhibits formation of microstructures in aqueous buffer as well as in water at 25 °C. The molecule undergoes self-organization leading to the formation of monolayer vesicles with hydrodynamic diameters between 100 and 250 nm in a wide range of concentration. The thermodynamic parameters clearly suggest that the aggregate formation is mainly driven by the hydrophobic effect. The monolayer vesicles were found to form at a very low concentration (≥0.63 mM) and within a wide pH range (2-10). The vesicles exhibit excellent shelf life at physiological temperature.

Journal of colloid and interface science, 2017

Cholesterol (Chol) is a ubiquitous steroidal component of cell membrane and is known to modulate ... more Cholesterol (Chol) is a ubiquitous steroidal component of cell membrane and is known to modulate the packing of phospholipids within the bilayer. Thus, Chol has been frequently used in the formulation and study of artificial "model membranes" like vesicles and liposomes. In this work, we have developed a novel anionic surfactant by conjugating two biomolecules, cholesterol and γ-aminobutyric acid via a urethane linkage. We have studied its physicochemical behavior in aqueous buffer. The surfactant has been shown to spontaneously form small unilamellar vesicles above a very low critical concentration in aqueous neutral buffer at room temperature. The vesicle phase was characterized by use of fluorescence probe, transmission electron microscopy and dynamic light scattering (DLS) techniques. The vesicle bilayer was found to be much less polar as well as more viscous compared to the bulk water. The vesicle stability with respect to change of temperature, pH, and ageing time wa...

Journal of colloid and interface science, 2017

Stimuli-sensitive polymersomes are one of the important vehicles and have been extensively studie... more Stimuli-sensitive polymersomes are one of the important vehicles and have been extensively studied as smart drug delivery system. Polymersomes have added advantage over the micelles because of having the ability to carry not only hydrophobic but also hydrophilic guest in their aqueous core. Among various stimuli, the change of pH and redox reaction is very important for drug delivery purpose especially for anticancer drug. Therefore, in this work, two poly(ethylene glycol) methyl ether methacrylate (mPEG) containing hydrophilic random anionic copolymers, poly[(2-hydroxyethyl methacrylate-3,3'-dithiodipropanoic acid)x-co-(poly(ethylene glycol) methyl ether methacrylate)y], poly[(HEMA-DTDPA)x-co-mPEGy] with different copolymer ratios were designed and synthesized. The self-assembly behaviour of these copolymers were studied by use of various techniques, including fluorescence spectroscopy, light scattering, and electron and optical microscopy. Both the copolymers were observed to ...

Langmuir : the ACS journal of surfaces and colloids, Jan 3, 2017

In our recent reports, we have shown that when a poly(ethylene glycol) (PEG) chain is covalently ... more In our recent reports, we have shown that when a poly(ethylene glycol) (PEG) chain is covalently linked to any ionic group, the resultant molecule behaves like an amphiphile. Depending upon the nature of ionic head groups, they self-assemble to form micelles or vesicles, in which the PEG chain constitutes the micellar core or vesicle bilayer. In this study, we intend to examine what happens when both hydrocarbon (HC) and PEG chains are attached to a carboxylate head group. Therefore, we have synthesized two novel amphiphiles in which a PEG and a HC chain is covalently linked to l-cysteine. The surface activities and the solution behavior of the sodium salts of these amphiphiles were investigated at neutral pH. The amphiphiles self-organize to form large unilamellar vesicles in dilute solutions, which transformed into small micelles at higher concentrations. The HC chains of the molecules have been shown to constitute the bilayer membrane of the vesicles and core of micelles. In acid...

Macromolecular Bioscience, 2016

Stimuli-sensitive polymeric vesicles or polymersomes as self-assembled colloidal nanocarriers hav... more Stimuli-sensitive polymeric vesicles or polymersomes as self-assembled colloidal nanocarriers have received paramount importance for their integral role as delivery system for therapeutics and biotherapeutics. This work describes spontaneous polymersome formation at pH 7, as evidenced by surface tension, steady state fluorescence, dynamic light scattering, and microscopic studies, by three hydrophilic random cationic copolymers synthesized using N,N-(dimethylamino)ethyl methacrylate (DMAEM) and methoxy poly(ethylene glycol) monomethacrylate in different mole ratios. The results suggest that methoxy poly(ethylene glycol) chains constitute the bilayer membrane of the polymersomes and DMAEM projects toward water constituting the positively charged surface. The polymersomes have been observed to release their encapsulated guest at acidic pH as a result of transformation into polymeric micelles. All these highly biocompatible cationic polymers show successful gene transfection ability as nonviral vector on human cell line with different potential. Thus these polymers prove their utility as a potential delivery system for hydrophilic model drug as well as genetic material.

Colloids and Surfaces B: Biointerfaces, 2016

The development of stimuli-responsive biocompatible polymersomes is important for the improvement... more The development of stimuli-responsive biocompatible polymersomes is important for the improvement of drug delivery systems. Herein, we report the spontaneous formation of polymersomes by three random copolymers, l-cys-graft-poly[GMA-co-mPEG300], containing different ratios of l-cysteine (Cys) and methoxy poly(ethylene glycol) (mPEG) covalently linked to the polymer backbone. Cysteine was conjugated to the polymeric backbone through metal free thiol-epoxy 'click' chemistry at final step. The copolymers, without having any typical hydrophobe in the backbone, are sufficiently surface active. The self-assembly formation of the copolymers was studied in aqueous solution by steady-state fluorescence probe technique. Spontaneous polymersomes formation, without any help of stimuli and organic solvent, above a relatively low critical aggregation concentration was confirmed by dynamic light scattering and microscopic techniques. Polymersomes were shown to be able to encapsulate not only hydrophilic dye in their aqueous core but also hydrophobic guest molecules in the bilayer membrane constituted by the mPEG chains. The polymersomes are sufficiently stable under physiological condition. These nano-sized polymersomes exhibit pH-triggered release of encapsulated guest under acidic pH. All three copolymers were found to be completely cell viable and hemocompatible up to very high concentration. Their ability to cross cell membrane was demonstrated by use of a fluorescent dye-tagged polymer. Further, these copolymers did not show any denaturising effect on the secondary structure of the human serum albumin, a transport protein in the blood. Based on the results of this study it is concluded that these spontaneously formed stable and biocompatible polymersomes can have potential use as drug delivery systems.

Journal of Colloid and Interface Science, 2015

Two novel amphiphilic molecules were synthesized by the reaction between poly(ethylene glycol) me... more Two novel amphiphilic molecules were synthesized by the reaction between poly(ethylene glycol) methyl ether (mPEG) of different chain lengths and sodium-2-mercapto ethane sulfonate (mesna). Different techniques, such as surface tensiometry, conductometry, fluorescence spectroscopy, dynamic light scattering, UV-vis spectroscopy, transmission electron microscopy, and isothermal titration calorimetry were employed to investigate the self-assembly properties of the PEG-based single-tailed amphiphiles in aqueous buffer. Despite having so called polar tail the amphiphiles exhibit aggregate formation in aqueous buffer as well as in water. The shorter chain amphiphile was shown to form bilayer vesicles in contrast to small micelles by its longer chain counterpart. The helicity of the PEG chain was taken into consideration to interpret the difference in self-assembled microstructure formation. The thermodynamics of the self-assemblies were also thoroughly examined. The thermodynamic parameters clearly suggested that the hydrophobic interaction among the PEG chains is the main driving force for aggregate formation. The self-assembled microstructures were observed to be fairly stable with respect to increase of surfactant concentration, aging time and temperature.

The Journal of Physical Chemistry B, 2015

The present work reports the pH-induced conformational changes of pepsin in solution at room temp... more The present work reports the pH-induced conformational changes of pepsin in solution at room temperature. The conformational change makes the protein surface active. The protein was found to be present in the partially denatured state at pH 8 as well as at pH 2. The fluorescence probe and circular dichroism (CD) spectra suggested that the most stable state of pepsin exists at pH 5. The binding affinities of pepsin in its native and denatured states for a D,L-carnitine-based cationic surfactant (3-hexadecylcarbamoyl-2-hydroxypropyl)trimethylammonium chloride (C16-CAR) were examined at very low concentrations of the surfactant. The thermodynamics of the binding processes were investigated by use of isothermal titration calorimetry. The results were compared with those of (3-hexadecylcarbamoylpropyl)trimethylammonium chloride (C16-PTAC), which is structurally similar to C16-CAR, but without the secondary -OH functionality near the headgroup. None of the surfactants were observed to undergo binding with pepsin at pH 2, in which it exists in the acid-denatured state. However, both of the surfactants were found to spontaneously bind to the most stable state at pH 5, the partially denatured state at pH 8, and the alkaline denatured state at pH 11. Despite the difference in the headgroup structure, both of the surfactants bind to the same warfarin binding site. Interestingly, the driving force for binding of C16-CAR was found to be different from that of C16-PTC at pH ≥ 5. The steric interaction of the headgroup in C16-CAR was observed to have a significant effect on the binding process.

Journal of the Chemical Society, Perkin Transactions 2, 1998

ABSTRACT Micellar behaviour of the amphiphilic 6-S-alkyl-6-thiocyclomaltooligosaccharid (2) in ch... more ABSTRACT Micellar behaviour of the amphiphilic 6-S-alkyl-6-thiocyclomaltooligosaccharid (2) in chloroform has been measured by use of the fluorescent probe 8-anilinonaphthalene-1-sulfonate (ANS) as guest molecule, as well as by water-chloroform interfacial tension measurements. At low concentrations the amphiphiles show behaviour consistent with their being oligomers of monosaccharide amphiphiles, or `unimolecular micelles'. Thus, with ANS, 1:1 complexes are formed for which the association constants are in proportion to the length of the chains. At higher concentrations, the long-chained (C-16, C-18) alkylthioeyclodextrins form inverted micellar aggregates. The NMR shift changes associated with inclusion of 1-naphthol indicate that even in these aggregates, the carbohydrate cavity plays a part in complexation, while the hydrophobic chains act as extensions of the more hydrophobic primary-hydroxy side of the cavity.

Soft Matter, 2013

Herein we report for the first time fibril formation by pepsin at neutral pH and room temperature... more Herein we report for the first time fibril formation by pepsin at neutral pH and room temperature. Fibril formation was characterized by a number of techniques including fluorescence and circular dichroism spectroscopy, dynamic light scattering, and transmission electron microscopy.

Journal of Colloid and Interface Science, 2011

The interaction of sodium N-lauroylsarcosinate (SLS) with N-cetylpyridinium chloride (CPC) and N-... more The interaction of sodium N-lauroylsarcosinate (SLS) with N-cetylpyridinium chloride (CPC) and N-dodecylpyridinium chloride (DPC) was investigated in aqueous mixtures. A strong interaction between the anionic and cationic surfactants was observed. The interaction parameter, β was determined for a wide composition range and was found to be negative. The mixed systems were found to have much lower critical micelle concentration (cmc) and surface tension at cmc. The surfactant mixtures exhibit synergism in the range of molar fractions investigated. The self-assembly formation in the mixtures of different compositions and total concentrations were studied using a number of techniques, including surface tension, fluorescence spectroscopy, dynamic light scattering (DLS), transmission electron microscopy (TEM), confocal fluorescence microscopy (CFM). Thermodynamically stable unilamellar vesicles were observed to form upon mixing of the anionic and cationic surfactants in a wide range of composition and concentrations in buffered aqueous media. TEM as well as DLS measurements were performed to obtain shape and size of the vesicular structures, respectively. These unilamellar vesicles are stable for periods as long as 3 months and appear to be the equilibrium form of aggregation. Effect of pH, and temperature on the stability was investigated. The vesicular structures were observed to be stable at pH as low as 2.0 and at biological temperature (37°C). In presence of 10 mol% of cholesterol the mixed surfactant vesicles exhibited leakage of the encapsulated calcein dye, showing potential application in pH-triggered drug release.