Prasanta K Das

Publications (7)23.36 Total impact

• Article: Structure and Properties of Cholesterol Based Hydrogelators with Varying Hydrophilic Terminals: Biocompatibility and Development of Antibacterial Soft Nanocomposites.

  Sounak Dutta, Tanmoy Kar, Deep Mandal, Prasanta K Das
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  ABSTRACT: The present work demonstrates a rational designing and synthesis of cholesterol based amino acid containing hydrogelators with the aim to improve the biocompatibility of these amphiphilic molecules. A thorough structure-property correlation of these hydrogelators was carried out by varying the hydrophilic terminal from neutral amine to quaternized ammonium chloride. The amphiphiles having cationic polar head as hydrophilic domain and cholesterol as hydrophobic unit showed better water gelation efficiency (minimum gelation concentration (MGC) ~0.9-3.1 %, w/v) than the analogous free amines. Presumably the additional ionic interactions for quaternized amphiphiles might have played the crucial role in gelation as counterions also got involved in hydrogen bonding with solvent molecules. Hence the attainment of desired hydrophilic-lipophilic balance (HLB) of hydrophobic cholesterol in combination with appropriate hydrophilic terminal led to the development of efficient hydrogels. Microscopic investigations revealed the formation of various supramolecular morphologies of hydrogels due to the variation in the molecular structure of the amphiphile. Spectroscopic investigations showed the involvement of hydrogen bonding, hydrophobic and π-π interaction in self-assembled gelation. Importantly, biocompatibility of all the cholesterol based hydrogelators tested against Human hepatic cancer derived HepG2 cells showed increased cell viability than the previously reported alkyl chain based amphiphilic hydrogelators. In order to incorporate broad spectrum antibacterial properties, silver nanoparticles (AgNP) were synthesized in situ within the hydrogels using sunlight. The amphiphile-AgNP soft nanocomposite exhibited notable bactericidal property against both Gram positive and Gram negative bacteria.
  Langmuir 12/2012; · 4.19 Impact Factor
• Article: Covalently functionalized single-walled carbon nanotubes at reverse micellar interface: a strategy to improve lipase activity.

  Moumita Ghosh, Subhabrata Maiti, Sounak Dutta, Dibyendu Das, Prasanta Kumar Das
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  ABSTRACT: The present work reports covalent functionalization of single-walled carbon nanotubes (f-SWNTs) to introduce hydrophilicity to the otherwise amphiphobic nanotubes. The charge and spacer length of the functional moiety were varied by using quaternized ethylene diamine, 6-aminocaproate, quaternized (ethylenedioxy)bis(ethylamine), and a poly(ethylene glycol) (PEG) unit (f-SWNT-1 to f-SWNT-4, respectively). These f-SWNTs with varying degrees of hydrophilicity were incorporated within cetyltrimethyl ammonium bromide (CTAB) reverse micelles to develop stable self-assembled nanohybrids. An optimum hydrophilicity on the SWNT surface led to interfacial localization of f-SWNTs resulting in the augmentation of space at the interface. A surface-active enzyme, lipase, localized at this enhanced interface of f-SWNT-containing CTAB reverse micelles exhibited significant activation (2.5-fold) compared to that in the absence of the nanoconstructs. This improvement in lipase activity was mainly due to the smooth occupancy of lipase and also presumably because of the increase in the concentrations of both substrate and the enzyme at the augmented interface. Interestingly, the f-SWNTs that activate lipase in reverse micelles deactivate the same enzyme in water. The dispersion of f-SWNTs in water and its matching integration at the interface of reverse micelles were confirmed through transmission electron microscopic (TEM) investigations. The interfacial localization of these nanoconstructs was also established from the distinct fluorescence behavior of a hydrophobic fluorescent probe, fluorescein isothiocyanate (FITC), adsorbed onto the f-SWNT surface. In concurrence with the observed lipase activity, the corresponding changes in the enzyme conformation within f-SWNTs integrated reverse micelle as well as in aqueous medium were studied by circular dichroism (CD) and Fourier transform infrared (FTIR) spectroscopy.
  Langmuir 12/2011; 28(3):1715-24. · 4.19 Impact Factor
• Article: Spontaneous formation of biocompatible vesicles in aqueous mixtures of amino acid-based cationic surfactants and SDS/SDBS.

  Anshupriya Shome, Tanmoy Kar, Prasanta K Das
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  ABSTRACT: The spontaneous formation of vesicles by six amino acid-based cationic surfactants and two anionic surfactants (sodium dodecylbenzene sulfonate (SDBS) and sodium dodecyl sulfate (SDS)) is reported. The head-group structure of the cationic surfactants is minutely altered to understand their effect on vesicle formation. To establish the regulatory role of the aromatic group in self-aggregation, both aliphatic and aromatic side-chain-substituted amino acid-based cationic surfactants are used. The presence of aromaticity in any one of the constituents favors the formation of vesicles by cationic/anionic surfactant mixtures. The formation of vesicles is primarily dependent on the balance between the hydrophobicity and hydrophilicity of both cationic and anionic surfactants. Vesicle formation is characterized by surface tension, fluorescence anisotropy, transmission electron microscopy, dynamic light scattering, and phase diagrams. These vesicles are thermally stable up to 65 °C, determined by temperature-dependent fluorescence anisotropy. According to the MTT assay, these catanionic vesicles are nontoxic to NIH3T3 cells, thus indicating their wider applicability as delivery vehicles to cells. Among the six cationic surfactants examined, tryptophan- and tyrosine-based surfactants have the ability to reduce HAuCl(4) to gold nanoparticles (GNPs), which is utilized to obtain in-situ-synthesized GNPs entrapped in vesicles without the need for any external reducing agent.
  ChemPhysChem 02/2011; 12(2):369-78. · 3.41 Impact Factor
• Article: Self-aggregation of synthesized novel bolaforms and their mixtures with sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB) in aqueous medium.

  Kajari Maiti, Debolina Mitra, Rajendra N Mitra, Amiya K Panda, Prasanta K Das, Animesh K Rakshit, Satya P Moulik
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  ABSTRACT: Bolaforms B(1), B(2), and B(3) of the formulas, Br(-)Me(3)N(+)(CH(2))(10)N(+)Me(3)Br(-), Br(-)Me(3)N(+)(CH(2))(10)OH, and Br(-)Me(3)N(+)(CH(2))(10)COO(-)Na(+), respectively, were synthesized, and their properties in the bulk as well as at the air/aqueous NaBr (10 mM) solution interface have been studied. Their interactions with sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB) also have been investigated. Tensiometry, conductometry, spectrophotometry, and microcalorimetry techniques were used for characterization and estimation. Both pure bolaforms and their mixtures with SDS and CTAB have been found to self-aggregate, forming micelles in solution. The mixed systems of bolaform and SDS have been observed to form both micelles and vesicles. Their mutual interactions were synergistic, which at the interface was more spontaneous than in the bulk. The interfacial and bulk compositions of the mixed binary systems (bolaform and SDS or CTAB) with their associated interaction parameters have been estimated from the Rosen interaction model and the regular solution theory of Rubingh, respectively. The formed vesicles have been found to entrap the water-soluble dye, bromophenol blue, and the dye solubilized vesicles of B(1)-SDS and B(2)-SDS completely eluted out of the sephadex column proving their formation. A rough estimation of the size and polydispersity index of the formed micelles and vesicles has been made from DLS measurements.
  The Journal of Physical Chemistry B 06/2010; 114(22):7499-508. · 3.70 Impact Factor
• Article: Bubble Evolution through a Submerged Orifice Using Smoothed Particle Hydrodynamics: Effect of Different Thermophysical Properties

  Arup K. Das, Prasanta K. Das
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  ABSTRACT: Formation of gas bubbles through an orifice under a liquid pool is important as a topic of fundamental research and is relevant in diverse industrial applications. This complex process is influenced by a large number of process parameters including the properties of the liquid and the gas phase. In the present work investigations have been made for bubble evolution at a submerged orifice using a computational simulation. Smoothed particle hydrodynamics is used to model the formation and detachment of the bubble from the orifice mouth. Using the advantage of this particle-based method, effects of density, viscosity, and surface tension of the liquid are investigated by noticing instantaneous bubble contour and the duration of bubble growth. The present simulation has been validated satisfactorily against published results. Finally, the process of neck formation and bubble pinch off has also been studied by varying the specific fluid properties individually. It has been noticed that the effect of surface tension and the effect of viscosity on bubble growth and necking are just the reverse of the effect of density on these processes. Moreover, compared to surface tension and density, the effect of viscosity on bubble evolution is marginal.
  09/2009;
• Article: Simulation of drop movement over an inclined surface using smoothed particle hydrodynamics.

  Arup K Das, Prasanta K Das
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  ABSTRACT: Smoothed particle hydrodynamics (SPH) is used to numerically simulate the movement of drops down an inclined plane. Diffuse interfaces have been assumed for tracking the motion of the contact line. The asymmetric shape of the three-dimensional drop and the variation of contact angle along its periphery can be calculated using the simulation. During the motion of a liquid drop down an inclined plane, an internal circulation of liquid particles is observed due to gravitational pull which causes periodic change in the drop shape. The critical angle of inclination required for the inception of drop motion is also evaluated for different fluids as a function of drop volume. The numerical predictions exhibit a good agreement with the published experimental results.
  Langmuir 09/2009; 25(19):11459-66. · 4.19 Impact Factor
• Source

  Available from: Indranil Chakraborty

  Article: Physicochemical studies on cetylammonium bromide and its modified (mono-, di-, and trihydroxyethylated) head group analogues. Their micellization characteristics in water and thermodynamic and structural aspects of water-in-oil microemulsions formed with them along with n-hexanol and isooctane.

  Debolina Mitra, Indranil Chakraborty, Subhash C Bhattacharya, Satya P Moulik, Sangita Roy, Debapratim Das, Prasanta K Das
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  ABSTRACT: The micellization behavior of cetylammonium bromide and its mono-, di-, and trihydroxyethylated head group analogues and water/oil (w/o) microemulsion formation with them have been studied with detailed thermodynamic and structural considerations. The critical micellar concentration, micellar aggregation number, and behavior of the surfactants at the air/solution interface have been studied in detail. The results have been analyzed and discussed. The formation of the w/o microemulsion stabilized by the aforesaid surfactants in conjunction with the cosurfactant n-hexanol in isooctane has been investigated by the dilution method. The energetics of the transfer of cosurfactant from oil to the interface has been estimated. The structural parameters, namely, droplet dimension, droplet number, and population of surfactant and cosurfactant on the droplet surface, have also been estimated. The efficacy of the surfactants in respect to water dispersion in oil and cosurfactant concentration level at the oil/water interface has been worked out. Such microemulsions are prospective compartmentalized systems to assist enzyme activities. In this respect, the trihydroxyethylated head group analogue in the above series has been found to be a better performer for the preparation and stabilization of microemulsions that has correlated well with its performance than the others in the hydrolysis of p-nitrophenyl-n-hexanoate by the enzyme Chromobacterium viscosum lipase.
  The Journal of Physical Chemistry B 07/2006; 110(23):11314-26. · 3.70 Impact Factor