The interaction of submicellar concentrations of various physiologically important unconjugated [sodium deoxycholate (NaDC), sodium cholate (NaC)] and conjugated [sodium glycodeoxycholate (NaGDC), sodium glycocholate (NaGC), sodium taurodeoxycholate (NaTDC), sodium taurocholate (NaTC)] bile salts with dipalmitoylphosphatidylcholine (DPPC) and dimyristoylphosphatidylcholine (DMPC) small unilamellar vesicles in solid gel (SG) and liquid crystalline (LC) phases was investigated using the excited-state prototropism of 1-naphthol. Steady-state and time-resolved fluorescence of the two excited-state prototropic forms of 1-naphthol indicate that submicellar bile salt concentration induces hydration of the lipid bilayer membrane into the core region. This hydration effect is a general phenomenon of the bile salts studied. The bilayer hydration efficiency of the bile salt follows the order NaDC > NaC > NaGDC > NaTDC > NaGC > NaTC for both DPPC and DMPC vesicles in their SG and LC phases. © 2011 American Chemical Society.

Ashok Kumar Mishra

Department Of Chemistry

Monalisa Mohapatra

1-NAPHTHOL

Bi-layer

BILE SALTS

CORE REGION

DIMYRISTOYLPHOSPHATIDYLCHOLINE

Dipalmitoyl phosphatidylcholine

HYDRATION EFFECTS

LIPID BILAYER MEMBRANES

LIQUID-CRYSTALLINE

Small unilamellar vesicle

Sodium Cholate

SODIUM DEOXYCHOLATE

SODIUM TAURODEOXYCHOLATE

TAUROCHOLATE

Time-resolved fluorescence

Body fluids

Excited states

Hydration

Lipid bilayers

Phenols

Salts

bile acid

article

chemistry

Crystallization

Fluorescence

Lipid bilayer

micelle

Bile Acids and Salts

Micelles

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

Langmuir

This study demonstrates that significant perturbation of tween20:cholesterol(1:1) niosome membrane takes place even at premicellar concentration of bile salts. Here, 1-naphthol (1-NpOH), a known and sensitive excited state proton transfer (ESPT) probe, was used to understand the nature of perturbation of the membrane in an unbuffered medium. The significant decrease in 1-NpOH fluorescence intensity in niosome-bile salt mixed system at both lower (10 °C) and higher (50 °C) temperatures indicates the bile salts [sodium cholate (NaC) and sodium deoxycholate (NaDC)] induce perturbation of niosome membranes. Variations in the fluorescence lifetime values of both the prototropic emissions (neutral and anionic species) along with the proton transfer rate of 1-NpOH confirm the bile salts perturb up to the hydrophobic core domain of the niosomal membranes. Bile salts induce size change of the niosomal membrane is confirmed through dynamic light scattering study. © 2019 Elsevier B.V.

Fulltext

Colloids and Surfaces B: Biointerfaces

Significant bile salt induced perturbation of niosome membrane: A molecular level interaction study using 1-Naphthol fluorescence

Bio-molecules are principal building blocks of living species and their inter-play is the cause of bio-activities. Various sophisticated experimental techniques as well as theoretical studies have been carried out for decades to understand the functions of bio-molecules. Fluorescence, one of the popular spectroscopic techniques has been used rigorously to follow various bio-events. However, fluorescence suffers from certain limitations due to the insufficient availability of fluorescent bio-molecules. Covalent attachment of fluorophores with different bio-molecules provides a way of overcoming this problem. Lipid, steroid, sugar, nucleic, and amino acid are the 5 main classes of bio-molecules although there are many other sub-classes. This review demonstrates the applications of such conjugated fluorescent molecular probes in different domains of biological activities. This also brings out the advantages and disadvantages of this particular type of fluorophores with the insight to the future perspectives. © 2018, © 2018 Taylor & Francis Group, LLC.

Applied Spectroscopy Reviews

Fluorophore tagged bio-molecules and their applications: A brief review

Successful applications of solid lipid nanoparticles (SLNs) rely on their physicochemical properties which are mainly governed by their comprising materials (e.g., lipids, emulsifiers) and preparation methods. We have prepared biocompatible solid lipid nanoparticles with glycerol monostearate as lipid and varying combinations of bile salts sodium deoxycholate and sodium cholate (bile salts to lipid ratio 8% w/w) as emulsifiers. The detailed characterization of solid lipid nanoparticles was performed using a combination of light scattering, microscopic, calorimetric, and spectroscopic techniques. It was seen that different compositions of bile salts yield nanoparticles with different sizes. The use of only sodium deoxycholate (8% w/w) produces nanoparticles with average sizes ∼487 nm. The average particle size increases with increasing cholate fraction. A higher average particle size around ∼652 nm is obtained with 8% (w/w) sodium cholate. All the SLNs show good physical stability at room temperature and do not show polymorphic transformation during the storage. In order to study the microenvironments, solid lipid nanoparticles are loaded with an external fluorescent-probe fisetin (probe to lipid ratio 1% w/w). Photophysical properties of fisetin loaded SLNs indicate the micro-heterogenicity inside the nanoparticles. © 2018 Elsevier B.V.

Physicochemical characterization of solid lipid nanoparticles comprised of glycerol monostearate and bile salts

Pluronics are polymeric surfactants that undergo sol-gel phase transition as a function of both temperature and concentration and have a high impact on therapeutics. An excited state proton transfer (ESPT) fluorescent molecular probe, 4-chloro-1-naphthol, has been employed to explore the sol-gel transition of pluronics in aqueous media. In aqueous homogeneous media, 4-chloro-1-naphthol shows anionic emission, whereas in heterogeneous media, it results in dual emission of its neutral and anionic forms. Moreover, variations in the intensity (I) ratio, Ineutral/Ianion, and area (A) ratio under the two individual curves, Aneutral/Aanion, faithfully reflect the progressive changes in the medium heterogeneity. The values of both Ineutral/Ianion and Aneutral/Aanion increase with increasing temperature during sol-gel phase transition and reach maxima at the phase transition temperature. Moreover, the higher values of Ineutral/Ianion and Aneutral/Aanion in 10% P123 compared to those in F127 signify a lower micro-polarity of the P123 medium compared to that of F127. Evidence of progressive dehydration is obtained from the excited state decay dynamics. It shows that the proton transfer rate decreases remarkably up to the sol-gel transition temperature and after that it remains almost constant. In the present study, thermo-reversible sol-gel transition of pluronics (P123, F127) along with the dehydration of micelles has been monitored with 4-chloro-1-naphthol. © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2016.

New Journal of Chemistry

Monitoring thermo-reversible dehydration of the pluronic microenvironment using 4-chloro-1-naphthol as an ESPT fluorescent molecular probe

This work focuses on the membrane perturbation, solubilisation and thermotropic phase transition process of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) MLVs induced by a glucose-triazole-hydrogenated cardanol conjugate (GTHCC). GTHCC is a recently introduced non toxic sugar derivative. Differential scanning calorimetry (DSC) and fluorescence molecular probe based techniques have been used to understand the concentration dependent membrane perturbation, solubilisation and thermotropic phase transition process of DPPC MLVs. The phase transition temperature of DPPC MLVs decreases with increase in mol% of GTHCC. At higher concentration above 10 mol%, GTHCC was significantly perturbed the membrane organization. The intrinsic fluorescence of GTHCC is also found to be sensitive towards phase behaviour and changes in membrane organization of DPPC MLVs. © 2014 Elsevier B.V. All rights reserved.

Journal of Molecular Structure

Effect of a glucose-triazole-hydrogenated cardanol conjugate on lipid bilayer membrane organization and thermotropic phase transition

A detailed photophysical study of the plant flavonoid fisetin in a dimyristoylphosphatidylcholine (DMPC) bilayer membrane has been carried out. Fisetin is found to partition well into the membrane (Kp = (4.6 ± 0.5) × 105 in solid gel phase and (5.1 ± 0.5) × 105 in liquid crystalline phase). A fluorescence quenching study using cetylpyridinium chloride (CPC) as the quencher suggests that fisetin molecules are generally present near the head group region of the lipid bilayer membrane. The temperature dependence of the fluorescence lifetime indicates a local heterogeneity in the distribution of fisetin within the bilayer membrane. The phototautomer form of fisetin, which is the primary emitting species from the lipid membrane, has a large Stoke's shift (175 nm) and fluoresces with an intense green fluorescence, which can make the molecule a good dye for marker and bioimaging applications. Membrane-bound fisetin shows sensitive variations of fluorescence intensity, lifetime, and anisotropy parameters in cholesterol-containing DMPC membranes, in mixed phospholipids, and as a function of temperature. This suggests that fisetin can be an efficient fluorescent molecular probe for sensing lipid bilayer membrane related changes. The location of fisetin in the membrane and the observed cholesterol-induced expulsion of fisetin may possibly have implications in the antioxidant activity of fisetin. © 2011 American Chemical Society.

Journal of Physical Chemistry B

Photophysical behavior of fisetin in dimyristoylphosphatidylcholine liposome membrane

In this study, 1-naphthol has been used as a sensitive ESPT fluorescent molecular probe to investigate the interaction of submicellar concentrations of two physiologically important bile salts, sodium deoxycholate and sodium cholate, with dipalmitoylphosphatidylcholine small unilamellar vesicles in solid gel and liquid crystalline phases. Steady-state and time-resolved fluorescence of the two excited state prototropic forms of 1-naphthol indicate that the incorporation of monomeric bile salt molecules in the lipid bilayer membrane induces appreciable wetting of the bilayer up to the hydrocarbon core region, even at very low (≤1 mM) concentrations of the bile salts. © 2010 American Chemical Society.

1-naphthol as a sensitive fluorescent molecular probe for monitoring the interaction of submicellar concentration of bile salt with a bilayer membrane of DPPC, a lung surfactant

Effects of two bile salts, namely sodium deoxycholate (NaDC) and sodium cholate (NaC), on DPPC small unilamellar vesicles have been investigated using the steady-state fluorescence anisotropy (rss) of diphenylhexatriene (DPH) as a tool. It was found that the variation of rss is sensitive enough to monitor different stages of interaction of bile salts with DPPC vesicles. NaDC induced significant changes in the membrane well below its CMC (6 mM). Even at 4 mM, which is still lower than the CMC, the phospholipids were completely solubilised by the NaDC micelles. The effect of NaC on DPPC vesicles, however, was much less significant, especially in the sub-micellar concentration regime. Being more hydrophilic NaC does not interact with the membrane efficiently. Complete solubilisation of phospholipids took place only when the concentration of NaC was above its CMC (16 mM). The experiments also showed that the bile salt-induced changes of vesicle structure were strongly dependent on the concentration of the bile salt and not on the molar ratio of lipid and bile salt. © Indian Academy of Sciences.

Journal of Chemical Sciences

Effect of sodium deoxycholate and sodium cholate on DPPC vesicles: A fluorescence anisotropy study with diphenylhexatriene

Biochimica et Biophysica Acta (BBA) - Biomembranes

The vesicle-to-micelle transformation of phospholipid–cholate mixed aggregates: A state of the art analysis including membrane curvature effects

Journal of Chemical Theory and Computation

Simulating the Transition between Gel and Liquid-Crystal Phases of Lipid Bilayers: Dependence of the Transition Temperature on the Hydration Level

Effect of submicellar concentrations of conjugated and unconjugated bile salts on the lipid bilayer membrane

Journal	Langmuir
ISSN	07437463
Open Access	No