The effect of sodium cholate (NaC; concentration 1-16 mM), a biological surfactant, on the aggregation behavior of 1% (w/v, 2.2 × 10-3 M) poly(N-isopropylacrylamide) (PNIPAM) aqueous solutions was studied as a function of temperature. From turbidity, dynamic light scattering, viscosity, and fluorescence measurements, it was observed that (i) there is NaC-induced nanoscale aggregation of PNIPAM in its sol state and (ii) the lower critical solution temperature corresponding to sol-gel transition shifts to a lower temperature by about 2 °C. © 2010 American Chemical Society.

Ashok Kumar Mishra

Department Of Chemistry

Acrylic monomers

Sols

Solutions

Surface active agents

Turbidity

Aggregation behavior

Aqueous solutions

FLUORESCENCE MEASUREMENTS

Lower critical solution temperature

N-isopropylacrylamides

NANOSCALE AGGREGATION

Poly(N-isopropyl acrylamide) (pNIPAM)

SALT-INDUCED AGGREGATION

Sodium Cholate

SOL STATE

Sol-gel transitions

Amides

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Journal of Physical Chemistry B

A new fluorescent cholesterol molecular probe, 3-acetyl-7-(diethylamino)-2H-chromen-2-one attached cholesterol (Cum-Chl), has recently been introduced as a reporter of micro-heterogeneous media. The H-aggregate forming ability of Cum-Chl provides a useful fluorescence parameter, Imonomer/Iaggregate to understand the micro-polarity of anisotropic media. Pluronics are surfactant based polymeric anisotropic media having important applications in therapeutics. Being a sensitive indicator of pluronics micro-polarity Imonomer/Iaggregate can help in selecting pluronics for medicinal purposes. Additionally, temperature and concentration induced sol-gel transition of pluronics (P123, F127) have been successfully investigated by Cum-Chl using its Imonomer/Iaggregate value, along with other conventional fluorescence parameters. Finally, this molecular probe, Cum-Chl emerges as a good sensor of progressive polymeric association and micro-polarity of pluronics. © 2015 The Royal Society of Chemistry.

RSC Advances

Utilizing an aggregate forming microenvironment sensitive coumarin-cholesterol conjugate as a sensor of pluronic organization and micro-polarity

Telmisartan is a poorly soluble drug used in treatment of hypertension. There is a recent interest to use pluronic for improving the solubility and bioavailability of these drugs. In this study the interaction of telmisartan with P123 and F127 has been carried out using steady state and time dependent fluorescence study. Quenching of telmisartan fluorescence by potassium iodide is controlled by interactions arising from collisions and complex formation. A comparison of the fluorescence of telmisartan in pluronics with the well understood fluorescence of 8-anilino-1-naphthalene-sulfonic acid, a known fluorescent molecular probe, indicates that telmisartan is generally present in a relatively polar microenvironment with restricted diffusive motion.© 2013 Elsevier B.V. All rights reserved.

Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy

A fluorescence study on the interaction of telmisartan in triblock polymers pluronic P123 and F127

The photophysical behavior of 8-anilino-1-naphthalenesulphonate (ANS) in vesicles of dipalmitoylphosphatidylcholine (DPPC), a pulmonary surfactant, has been carried out in a detailed manner. ANS shows notable variations in fluorescence intensity, lifetime, and anisotropy parameters as it gets into the vesicle. It was found that ANS partitions well into the DPPC bilayer membrane with an estimated partition coefficient of ∼2.0 × 105. Among the various fluorescence parameters of ANS, fluorescence anisotropy was found to be most responsive to the temperature induced phase change of the bilayer membrane. These interesting fluorescence parameters of ANS were then used to study the hydration of lipid bilayer membrane by submicellar concentration of bile salts. From the steady-state fluorescence intensity and dynamic fluorescence lifetime analyses it is clear that ANS is able to probe the submicellar concentration (≤1 mM) of bile salt induced hydration of lipid bilayer membrane that accompanies expulsion of ANS from the bilayer to the aqueous bulk phase. Lower-temperature shift in the phase transition of DPPC bilayer indicates that fluorescence anisotropy of ANS is sensitive enough to the bile salt induced perturbation in the packed acyl chains of DPPC bilayer and modification in the membrane fluidity. In presence of sodium deoxycholate (NaDC) and sodium cholate (NaC) in DPPC vesicles, ANS experiences restriction in rotational mobility which is evident from the variation in steady-state fluorescence anisotropy and fluorescence anisotropy decay parameters. © 2013 American Chemical Society.

Langmuir

Photophysical behavior of 8-anilino-1-naphthalenesulfonate in vesicles of pulmonary surfactant dipalmitoylphosphatidylcholine (DPPC) and its sensitivity toward the bile salt-vesicle interaction

Excited state prototropism (ESPT) is observed in molecules having one or more ionizable protons, whose proton transfer efficiency is different in ground and excited states. The interaction of various ESPT molecules like naphthols and intramolecular ESPT (ESIPT) molecules like hydroxyflavones etc. with different microheterogeneous media have been studied in detail and excited state prototropism as a probe concept has been gaining ground. The fluorescence of different prototropic forms of such molecules, on partitioning to an organized medium like lipid bilayer membrane, often show sensitive response to the local environment with respect to the local structure, physical properties and dynamics. Our recent work using 1-naphthol as an ESPT fluorescent molecular probe has shown that the incorporation of monomeric bile salt molecules into lipid bilayer membranes composed from dipalmitoylphosphatidylcholine (DPPC, a lung surfactant) and dimyristoylphosphatidylcholine (DMPC), in solid gel and liquid crystalline phases, induce appreciable wetting of the bilayer up to the hydrocarbon core region, even at very low (≤ 1 mM) concentrations of the bile salts. The incorporation and location of fisetin, an ESIPT molecule having antioxidant properties, in lipid bilayer membrane has been sensitively monitored from its intrinsic fluorescence behaviour. © 2012 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).

Progress in Biomedical Optics and Imaging - Proceedings of SPIE

Fluorescent molecular probes based on excited state prototropism in lipid bilayer membrane

Additives like salts and surfactants can alter the phase transition temperature of poly(N-isopropylacrylamide) (PNIPAM). The inclusion of a biological surfactant like sodium cholate (NaC) into PNIPAM could lead a better biocompatibility when the materials are used for biomedical applications. The phase transition behavior of PNIPAM was studied in presence of NaC. DSC study shows that the presence of NaC broadens the phase transition endotherm of PNIPAM, which is also accompanied by a small shift of the critical solution temperature (CST) to lower temperature. The results were compared with the optical measurements like, turbidity, DLS, fluorescence and rheology and it was observed that optical techniques are the best suitable for finding the onset temperature of gelation. The effect of the NaC bile salt is in contrast to the effect of conventional surfactants which are known to shift the CST to higher values, due to mutual solubilization. A study of fluorescence spectroscopic parameters like fluorescence anisotropy, spectral shift, intensity and DLS measurements suggest that a NaC-induced aggregation could be responsible for this unusual observation. © 2008 Elsevier B.V. All rights reserved.

Colloids and Surfaces B: Biointerfaces

The effect of sodium cholate aggregates on thermoreversible gelation of PNIPAM

Polyelectrolytes Engineering Materials

Biological Polyelectrolytes: Solutions, Gels, Intermolecular Complexes and Nanoparticles

Colloidal Phase Separation of Concentrated PNIPAm Solutions

Biomacromolecules

Systematic of Alcohol-Induced Simple Coacervation in Aqueous Gelatin Solutions

Proceedings of the National Academy of Sciences

Nonlinear partial differential equations and applications: Ultrafast surface hydration dynamics and expression of protein functionality:  -Chymotrypsin

Bile-salt-induced aggregation of Poly(N -isopropylacrylamide) and lowering of the lower critical solution temperature in aqueous solutions

Journal	Data powered by TypesetJournal of Physical Chemistry B
Publisher	Data powered by TypesetAmerican Chemical Society
ISSN	15206106
Open Access	No