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1.
Langmuir ; 37(6): 2065-2078, 2021 02 16.
Artigo em Inglês | MEDLINE | ID: mdl-33529530

RESUMO

Modulating the structures and properties of biomembranes via permeation of small amphiphilic molecules is immensely important, having diverse applications in cell biology, biotechnology, and pharmaceuticals, because their physiochemical and biological interactions lead to new pathways for transdermal drug delivery and administration. In this work, we have elucidated the role of dimethyl sulfoxide (DMSO), broadly used as a penetration-enhancing agent and cryoprotective agent on model lipid membranes, using a combination of fluorescence microscopy and time-resolved fluorescence spectroscopy. Spatially resolved fluorescence lifetime imaging microscopy (FLIM) has been employed to unravel how the fluidity of the DMSO-induced bilayer regulates the structural alteration of the vesicles. Moreover, we have also shown that the dehydration effect of DMSO leads to weakening of the hydrogen bond between lipid headgroups and water molecules and results in faster solvation dynamics as demonstrated by femtosecond time-resolved fluorescence spectroscopy. It has been gleaned that the water dynamics becomes faster because bilayer rigidity decreases in the presence of DMSO, which is also supported by time-resolved rotational anisotropy measurements. The enhanced diffusivity and increased membrane fluidity in the presence of DMSO are further ratified at the single-molecule level through fluorescence correlation spectroscopy (FCS) measurements. Our results indicate that while the presence of DMSO significantly affects the 1,2-dimyristoyl-rac-glycero-3-phosphocholine (DMPC) and 1,2-dipalmitoyl-rac-glycero-3-phosphatidylcholine (DPPC) bilayers, it has a weak effect on 1,2-dimyristoyl-sn-glycero-3-phospho-rac-glycerol (DMPG) vesicles, which might explain the preferential interaction of DMSO with the positively charged choline group present in DMPC and DPPC vesicles. The experimental findings have also been further verified with molecular dynamics simulation studies. Moreover, it has been observed that DMSO is likely to have a differential effect on heterogeneous bilayer membranes depending on the structure and composition of their headgroups. Our results illuminate the importance of probing the lipid structure and composition of cellular membranes in determining the effects of cryoprotective agents.

2.
Langmuir ; 36(26): 7634-7647, 2020 07 07.
Artigo em Inglês | MEDLINE | ID: mdl-32525679

RESUMO

The extensive and diversified applications of the well-known plasmonic nanoparticle systems along with their easy and environment-friendly synthesis strategies drive us to investigate in-depth this important research field. In the current scenario, our present study deals with an important plasmonic nanomaterial, i.e., globular protein, and human serum albumin (HSA)-conjugated gold nanoparticle (HSA-Au NP) system. The well-known chemical denaturants, urea and guanidine hydrochloride (GdnHCl or GnHCl), are investigated to show detrimental effects toward the formation of gold nanoparticles; however, the effect of GdnHCl is observed to be much prominent compared to that of urea. The synthesized nanoparticle system is found to be highly biocompatible from the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT)-based cytotoxicity assay, and therefore, the applications of encapsulation of the well-known anticancer drug molecule, doxorubicin hydrochloride (Dox), in the nanoparticle system are further studied. In this drug encapsulation study, drug-metal complexation between Dox and HAuCl4·3H2O has been discussed elaborately. Similar to the nanoparticle formation, the effects of denaturants on drug encapsulation have also been discovered, and interestingly, it has been observed that urea plays a positive role, whereas GdnHCl plays a negative or detrimental role toward drug encapsulation in the synthesized gold nanoparticle system. The detailed photophysical mechanisms behind the drug encapsulation in the synthesized plasmonic nanosystem at every stage have also been explored. Overall, this study will conclusively explain the influences of the extensively used chemical denaturants on the synthesis and drug encapsulation behaviors of a well-known protein-conjugated gold nanoparticle, and as a consequence, it can be highly useful and acceptable to the biomedical and pharmaceutical research communities.

3.
Langmuir ; 36(9): 2459-2473, 2020 03 10.
Artigo em Inglês | MEDLINE | ID: mdl-32073868

RESUMO

One of the congenital flaws of metabolism, phenylketonuria (PKU), is known to be related to the self-assembly of toxic fibrillar aggregates of phenylalanine (Phe) in blood at elevated concentrations. Our experimental findings using l-phenylalanine (l-Phe) at millimolar concentration suggest the formation of fibrillar morphologies in the dry phase, which in the solution phase interact strongly with the model membrane composed of 1,2-diacyl-sn-glycero-phosphocholine (LAPC) lipid, thereby decreasing the rigidity (or increasing the fluidity) of the membrane. The hydrophobic interaction, in addition to the electrostatic attraction of Phe with the model membrane, is found to be responsible for such phenomena. On the contrary, various microscopic observations reveal that such fibrillar morphologies of l-Phe are severely ruptured in the presence of its enantiomer d-phenylalanine (d-Phe), thereby converting the fibrillar morphologies into crushed flakes. Various biophysical studies, including the solvation dynamics experiment, suggest that this l-Phe in the presence of d-Phe, when interacting with the same model membrane, now reverts the rigidity of the membrane, i.e., increases the rigidity of the membrane, which was lost due to interaction with l-Phe exclusively. Fluorescence anisotropy measurements also support this reverse rigid character of the membrane in the presence of an enantiomeric mixture of amino acids. A comprehensive understanding of the interaction of Phe with the model membrane is further pursued at the single-molecular fluorescence detection level using fluorescence correlation spectroscopy (FCS) experiments. Therefore, our experimental conclusion interprets a linear correlation between increased permeability and enhanced fluidity of the membrane in the presence of l-Phe and certifies d-Phe as a therapeutic modulator of l-Phe fibrillar morphologies. Further, the study proposes that the rigidity of the membrane lost due to interaction with l-Phe was reinstated-in fact, increased-in the presence of the enantiomeric mixture containing both d- and l-Phe.


Assuntos
Amiloide/química , Lipossomos/química , Fenilalanina/química , Fluidez de Membrana/efeitos dos fármacos , Permeabilidade/efeitos dos fármacos , Fosfatidilcolinas/química , Estereoisomerismo
4.
Photochem Photobiol Sci ; 18(6): 1359-1372, 2019 Jun 12.
Artigo em Inglês | MEDLINE | ID: mdl-30916109

RESUMO

Literature reports provide ample evidence of the dynamical studies of various fluorophores in different room-temperature ionic liquid (RTIL)-cosolvent mixtures. However, most of the experimental and simulation studies reveal that ∼50% of the spectral relaxation dynamics is fast and cannot be resolved using traditional time correlated single photon counting (TCSPC) measurements. Our group has also investigated the dynamics of a solvatochromic probe coumarin 153 (C153) in a RTIL-cosolvent mixture using a TCSPC setup (S. Sarkar, R. Pramanik, C. Ghatak, P. Setua and N. Sarkar, J. Phys. Chem. B, 2010, 114, 2779-2789). Consequently, a major portion of the solvation dynamics remained undetected and moreover we could not monitor the dynamics beyond 0.4 mole fraction of the cosolvents. Thus in this study, we have rekindled our interest to sufficiently capture the rotational anisotropy and solvation dynamics of C153 beyond 0.4 mole fraction of the cosolvents in the RTIL-cosolvent mixture employing femtosecond fluorescence upconversion measurements. Additionally, we have utilized another RTIL with a higher alkyl chain length and viscosity to obtain a comprehensive and quantitative picture of the role of viscosity on the dynamics of the probe molecule. The most interesting observation of the present work is that the viscosities of different RTIL-cosolvent mixtures can efficiently control the cis-trans isomerization kinetics of the anionic fluorophore merocyanine 540 (MC 540) and the translational diffusion of a hydrophobic probe. The optimization of geometrical structures of [EmimOs]- and [EmimOs]-cosolvent mixtures followed by frequency analyses in both gas and solution phases have been carried out using quantum chemical calculations with the aid of density functional theory (DFT) methods. The computation based on the bond distances, electron densities and non-covalent interactions (NCI) has also been used to investigate the existence of the hydrogen-bond (H-bond). Again to comprehend van der Waals interactions and the conventional hydrogen-bond, the evolution of NCI plots are simulated. Therefore, the detailed experimental and theoretical studies presented in this manuscript lead to the inference that addition of the conventional solvents finely tunes the physicochemical properties of RTILs and broadens their scope of applications in the fields of chemistry and biology.

5.
Langmuir ; 34(10): 3296-3306, 2018 03 13.
Artigo em Inglês | MEDLINE | ID: mdl-29474788

RESUMO

In this article, we have unveiled the aggregation behavior of a potent chemotherapeutic drug, doxorubicin hydrochloride (Dox) in a well-known imidazolium based surface active ionic liquid (SAIL), 1-octyl-3-methylimidazolium chloride (C8mimCl). The aggregates formed by Dox in C8mimCl have been characterized using dynamic light scattering (DLS), fluorescence lifetime imaging microscopy (FLIM), high-resolution transmission electron microscopy (HR-TEM), analytical transmission electron microscopy (analytical TEM), field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), and Fourier-transform infrared spectroscopy (FTIR) measurements. It is found that Dox forms large spherical aggregates in the presence of C8mimCl SAIL. We have also explored the driving force behind this aggregation behavior of Dox in C8mimCl. Furthermore, it is observed that in the presence of a common bile salt, sodium cholate (NaCh), Dox/C8mimCl spherical aggregates disrupt to form rodlike fibrillar aggregates. Therefore, formation of spherical aggregates and also its disruption into rodlike fibrillar aggregates have been performed, and this is expected to open a new scope for the design of a new generation smart drug delivery system where the drug itself aggregates to form the delivery system.

6.
Langmuir ; 33(38): 9811-9821, 2017 09 26.
Artigo em Inglês | MEDLINE | ID: mdl-28849933

RESUMO

In this article, anionic lipophilic dye merocyanine 540(MC540) and cationic surface-active ionic liquid (SAIL) 1-octyl-3-methylimidazolium chloride (C8mimCl) are employed to construct highly ordered fibrillar and vesicular aggregates exploiting an ionic self-assembly (ISA) strategy. It is noteworthy that the concentration of the counterions has exquisite control over the morphology, in which lowering the concentration of both the building blocks in a stoichiometric ratio of 1:1 provides a vesicle to fibril transition. Here, we have reported the concentration-controlled fibril-vesicle transition utilizing the emerging fluorescence lifetime imaging microscopy (FLIM) technique. Furthermore, we have detected this morphological transformation by means of other microscopic techniques such as field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and cryogenic-transmission electron microscopy (cryo-TEM) to gain additional support. Besides, multiwavelength FLIM (MW-FLIM) and atomic force microscopy (AFM) techniques assist us in knowing the microheterogeneity and the height profile of the vesicles, respectively. We have replaced the SAIL, C8mimCl, by an analogous traditional surfactant, n-octyltrimethylammonium bromide (OTAB), and it provides a discernible change in morphology similar to that of C8mimCl, whereas 1-octanol is unable to exhibit any structural aggregation and thus reveals the importance of electrostatic interaction in supramolecular aggregate formation. However, the SAILs having the same imidazolium headgroup with different chain lengths other than C8mimCl are unable to display any structural transition and determine the importance of the correct chain length for efficient packing of the counterions to form a specific self-assembly. Therefore, this study reveals the synergistic interplay of electrostatic, hydrophobic, and π-π stacking interactions to construct the self-assembly and their concentration-dependent morphological transition.

7.
Langmuir ; 33(23): 5891-5899, 2017 06 13.
Artigo em Inglês | MEDLINE | ID: mdl-28514858

RESUMO

In this article, we have reported the synthesis and physicochemical characterization of a novel l-glycine amino acid derived cholesterol based surface active ionic liquid (SAIL). This SAIL has been explored for the preparation of ionic liquid (IL)-in-oil microemulsions and vesicles. The formation of IL-in-oil microemulsion is characterized by construction of a ternary phase diagram, dynamic light scattering (DLS) measurement, proton nuclear magnetic resonance (1H NMR) study, fluorescence measurement using coumarin 480 (C-480) as a molecular probe, and also by recording the diffusion behavior of the molecular probe rhodamine 6G (R6G) in microemulsion droplets through the fluorescence correlation spectroscopy (FCS) technique. Similarly, the spontaneous vesicle formation from the SAIL in water has been established using DLS, transmission electron microscopy (TEM), cryogenic-transmission electron microscopy (cryo-TEM), field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), FCS, and fluorescence lifetime imaging microscopy (FLIM) measurements. These aggregates may potentially serve as good biomimicking models and possible drug carriers.

8.
ACS Sens ; 9(7): 3660-3670, 2024 Jul 26.
Artigo em Inglês | MEDLINE | ID: mdl-38968930

RESUMO

DNA-based tension sensors have innovated the imaging and calibration of mechanosensitive receptor-transmitted molecular forces, such as integrin tensions. However, these sensors mainly serve as binary reporters, only indicating if molecular forces exceed one predefined threshold. Here, we have developed tandem tension sensor (TTS), which comprises two consecutive force-sensing units, each with unique force detection thresholds and distinct fluorescence spectra, thereby enabling the quantification of molecular forces with dual reference levels. With TTS, we revealed that vinculin is not required for transmitting integrin tensions at approximately 10 pN (piconewtons) but is essential for elevating integrin tensions beyond 20 pN in focal adhesions (FAs). Such high tensions have emerged during the early stage of FA formation. TTS also successfully detected changes in integrin tensions in response to disrupted actin formation, inhibited myosin activity, and tuned substrate elasticity. We also applied TTS to examine integrin tensions in platelets and revealed two force regimes, with integrin tensions surpassing 20 pN at cell central regions and 13-20 pN integrin tensions at the cell edge. Overall, TTS, especially the construct consisting of a hairpin DNA (13 pN opening force) and a shearing DNA (20 pN opening force), stands as a valuable tool for the quantification of receptor-transmitted molecular forces within living cells.


Assuntos
Integrinas , Integrinas/metabolismo , Humanos , Vinculina/metabolismo , Adesões Focais , Técnicas Biossensoriais/métodos , Animais , DNA/química , Plaquetas/citologia , Plaquetas/metabolismo
10.
J Phys Chem Lett ; 13(30): 7016-7022, 2022 Aug 04.
Artigo em Inglês | MEDLINE | ID: mdl-35900114

RESUMO

Dopamine (DA) and 3,4-dihydroxy-l-phenylalanine (L-Dopa or DPA), a marker and medicine for the neurological disorder Parkinson's disease (PD), lead to the formation of polymeric fluorescent nanoparticles (F-Poly NPs or F-NPs or simply, NPs). The interaction study between proteins and NPs shows prominent interaction with strong specificity toward albumin type proteins for DPA derived and mixed NPs. Furthermore, encapsulation of the anticancer drug doxorubicin hydrochloride (Dox) inside the NP-protein conjugates results in excellent white light emission with pronounced specificity toward albumin proteins for F-PDPA and F-Mix NPs. Finally, the use of BSA protein fibril resulting in strong binding with NPs along with Dox assisted white light emission has also been studied.


Assuntos
Portadores de Fármacos , Nanopartículas , Albuminas , Doxorrubicina/química , Portadores de Fármacos/química , Nanopartículas/química , Polímeros
11.
J Phys Chem Lett ; 12(51): 12411-12418, 2021 Dec 30.
Artigo em Inglês | MEDLINE | ID: mdl-34939822

RESUMO

Trimethylamine N-oxide (TMAO), a choline-containing dietary supplement obtained from red meat, egg, and other animal resources, on excess accumulation is known to cause cardiovascular diseases (CVDs) like atherosclerosis. To understand the molecular mechanism of the pathogenesis of TMAO-induced CVDs, we have set up 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) membrane in water that mimicked the endothelial cell membrane-blood interface of the artery wall and investigated the effect of an elevated concentration of TMAO on the membrane. We found that TMAO exerts an "action at a distance" mechanism through electrostatic force of attraction that significantly alters various properties of the membrane, like hydrophobicity, lateral organization, and interfacial water dynamics, which elevates the rigidity of the membrane. Such an effect was found to be further amplified in the presence of known causes of CVDs, i.e., high content of cholesterol (Chol). Therefore, TMAO-induced membrane rigidity may restrict the intrinsic elasticity of an artery membrane, expected to be introducing "hardening of the arteries", which makes the membrane atherosclerotic.


Assuntos
Doenças Cardiovasculares/metabolismo , Bicamadas Lipídicas/metabolismo , Metilaminas/efeitos adversos , Metilaminas/metabolismo , Nutrientes/metabolismo , Fosfolipídeos/metabolismo , Animais , Doenças Cardiovasculares/induzido quimicamente , Doenças Cardiovasculares/patologia , Suplementos Nutricionais , Humanos , Bicamadas Lipídicas/química , Metilaminas/administração & dosagem , Nutrientes/administração & dosagem , Nutrientes/efeitos adversos , Fosfolipídeos/química , Eletricidade Estática
12.
J Phys Chem B ; 125(46): 12637-12653, 2021 11 25.
Artigo em Inglês | MEDLINE | ID: mdl-34784202

RESUMO

The physiologically important biomolecule, dopamine (DA), shows strong self-oxidation and aggregation behaviors, which have been controlled and modulated to result in fluorescent polydopamine (F-PDA) nanoparticles. On the other hand, the simultaneous binding of two diverse deoxyribonucleic acid (DNA) binding probes, 4',6-diamidino-2-phenylindole dihydrochloride (DAPI) and ethidium bromide (EtBr), has been elaborately established to follow the Förster-based resonance energy transfer (FRET) pathway. The comparative understanding of this DNA-mediated FRET in three media, phosphate buffer saline (PBS) of pH 7.4, DA, and F-PDA, has concluded that the FRET efficiency in the three media follows the order: PBS > DA > F-PDA. This controlled FRET in the fluorescent F-PDA matrix serves a pivotal role for efficient white light (WL) generation with excellent Commission Internationale de l'Eclairage (CIE) parameters that match well with that of pure WL emission. The obtained WL emission has been shown to be very specific with respect to concentrations of different participating components and the excitation wavelength of the illuminating source. Furthermore, the optical properties of the WL emitting solution have been observed to be retained excellently inside the well-known agarose gel matrix. Finally, the mechanistic pathway behind such a FRET-based WL generation has been established in detail, and to the best of our knowledge, the current study offers the first and only report that discloses the influence of a fluorescent polyneurotransmitter matrix for successful generation of WL emission.


Assuntos
Transferência Ressonante de Energia de Fluorescência , Nanopartículas , DNA , Luz
13.
J Phys Chem B ; 124(11): 2065-2080, 2020 03 19.
Artigo em Inglês | MEDLINE | ID: mdl-32081003

RESUMO

"Mother nature" utilizes molecular self-assembly as an efficient tool to design several fascinating supramolecular architectures from simple building blocks like amino acids, peptides, and nucleobases. The self-assembling behavior of various biologically important molecules, morphological outcomes, molecular mechanism of association, and finally their applications in the real world draw broad interest from chemical and biological point of views. In this present Feature Article, the amyloid hypothesis is extended to include nonproteinaceous single metabolites that invoke a new paradigm for the pathology of inborn metabolic disorders. In this scenario, we dedicate this paper to understanding the morphological consequences and mechanistic insight of the self-assembly of some important amino acids (e.g., l-phenylalanine, l-tyrosine, glycine, etc.) and nucleobases (adenine and eight uracil moiety derivatives). Using proper spectroscopic and microscopic tools, distinct assembling mechanisms of different amino acids and nucleobases have been established. Again, lanthanides, polyphenolic compounds such as crown ethers, and a worldwide drink, beer, are elegantly employed as inhibitors of the resulting fibrillar aggregated structures. As a consequence, this study will cover literally a vast region in the self-assembling outcomes of single biologically important molecules, and therefore, we expect that a detailed understanding of such morphological outcomes using spectroscopic and microscopic approaches may open a new paradigm in this burgeoning field.


Assuntos
Aminoácidos , Peptídeos , Amiloide , Nanotecnologia , Análise Espectral
14.
ACS Appl Bio Mater ; 3(7): 4282-4293, 2020 Jul 20.
Artigo em Inglês | MEDLINE | ID: mdl-35025428

RESUMO

Gold nanoclusters (Au NCs) are an emerging class of fluorescent nanomaterials due to their fascinating chemical or physical properties and atomically precise structures; hence, they have been widely used in the field of biosensing and bioimaging. In this article, we demonstrate the green synthesis of orange, yellow, green, and cyan emitting Au NCs by core etching and ligand exchange methodology. Our investigation reveals that the chain length of the mercaptan acids, which are present on the surface of the Au NCs, controls the optical and electronic properties of the synthesized NCs. The steady-state and time-resolved spectroscopic data suggest that the emission properties of Au NCs mainly originate from the ligand to metal charge transfer (LMCT) transition. Alterations of the optical properties of these Au NCs can be proposed due to the difference in the core size of the Au NCs, which is strongly influenced by the surface-capping ligands. These NCs are highly biocompatible and nontoxic as evidenced by the cell viability and cellular uptake studies. By virtue of this, our as-synthesized NCs have been successfully used as excellent intracellular fluorescent imaging probes. Interestingly, fluorescence properties of Au NCs can efficiently probe the protein amyloids associated with several neurodegenerative diseases. To facilitate research in the field of amyloidosis, we have demonstrated fluorescence lifetime imaging microscopy (FLIM) and fluorescence correlation spectroscopy (FCS) as two advanced tools to probe the aggregation of proteins and to monitor the physical interactions between proteins and NCs. It has been observed that the hydrophobicity of the NC surface can trigger the amyloid detection capability of Au NCs. Owing to these unique optical and attractive biological properties coupled with the imaging capability, these ultrasmall-sized Au NCs may enable in vivo detection of amyloids in the near future.

15.
J Phys Chem B ; 123(1): 117-129, 2019 01 10.
Artigo em Inglês | MEDLINE | ID: mdl-30543430

RESUMO

It is well reported that sugar molecules provide different types of stabilization to biomembranes both in vitro as well as in vivo. In the present article, our focus is to investigate the interactions of two sugar molecules (sucrose and sucralose) with the lamellar structures of aerosol OT (AOT). We have attempted the structural characterization of the lamellae in the presence and absence of sugars with the aid of dynamic light scattering (DLS), small-angle X-ray scattering (SAXS), Fourier transformed infrared spectroscopy (FTIR), polarized optical microscopy (POM), and cryogenic-transmission electron microscopic (cryo-TEM) techniques. In this study, we have chosen three Coumarin dyes, which show a wide variation of hydrophobicity and performed a combination of steady-state and time-resolved fluorescence measurements to unveil the inner detail of the location of the sugars and their specific interactions with the lamellar structures. Our study reveals that sucrose molecules are present in the interfacial region with a major population whereas the most probable location of sucralose is the interior of the AOT bilayer. Therefore, sucralose molecules probably penetrate the bilayer by decreasing the efficient packing of AOT. The important essence of this study is the location and the interactions of sucralose with the lamellae which may provide a future direction to the transportation of the drug molecules in the biomembrane.


Assuntos
Cumarínicos/química , Corantes Fluorescentes/química , Simulação de Dinâmica Molecular , Sacarose/análogos & derivados , Sacarose/química , Aerossóis/química , Estrutura Molecular , Fatores de Tempo
16.
ACS Omega ; 3(1): 314-328, 2018 Jan 31.
Artigo em Inglês | MEDLINE | ID: mdl-31457894

RESUMO

In this article, we have investigated the excited-state intramolecular double proton transfer dynamics of [2,2'-bipyridyl]-3,3'-diol, BP(OH)2, in three alcohol-water binary mixtures, namely, ethanol (EtOH)-water, n-propanol (PrOH)-water, tert-butyl alcohol (TBA)-water, and dimethyl sulfoxide (DMSO)-water utilizing the femtosecond fluorescence upconversion technique. We have found that in alcohol-water binary mixtures the proton transfer (PT) pathway of BP(OH)2 is sequential and the anomalous slowdown in PT dynamics is observed in mole fraction (χ) ranges χEtOH = 0.04-0.07, χEtOH = 0.23-0.28, χPrOH = 0.17-0.30, χTBA = 0.12-0.21, and χTBA = 0.40-0.46. Our study sheds light on the involvement of water network in the PT dynamics. Reduction in water accessibility due to the involvement of water molecules in cluster formation results in hindered PT dynamics, and this retardation is more for the TBA-water binary mixture compared to that for the other two mixtures. Additionally, we have found two anomalous regions for the DMSO-water binary mixture in ranges χDMSO = 0.12-0.16 and χDMSO = 0.26-0.34. However, most interestingly, beyond χDMSO = 0.40, we do not find any growth component in the femtosecond fluorescence upconversion trace, which may be due to the change in the PT mechanism from a sequential water-mediated pathway to a concerted intramolecular pathway.

17.
J Colloid Interface Sci ; 522: 63-73, 2018 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-29574270

RESUMO

Studying the self-assembly of uracil derivatives has great importance in biochemistry and nanotechnology. Now, in order to architect unique and interesting nucleobase nanostructures, herein, we report a simple, yet robust uracil moiety based platform which is potentially capable to self-assemble into fibrils. The system is validated using eight uracil moiety derivatives and the effect is examined via fluorescence lifetime imaging microscopy (FLIM), field emission scanning electron microscopy (FESEM), steady state DCM fluorescence and fluorescence correlation spectroscopy (FCS). FLIM and FESEM give qualitative information regarding the fibril formation of different morphologies including string, rod, flower, needles etc. Steady state DCM fluorescence and FCS establish a quantitative estimation of the extent of fibril formation. The involvement of hydrogen bonding interaction between NH and CO groups in the fibrillar growth of 5-IU is evoked from the crystallographic study. Again, the key role of different functional groups behind the formation of fibrillar network is investigated through blocking the COO- group of orotic acid with lanthanides. Finally, esterification and N,N'-dimethylation exquisitely explore the role and priority of different groups in the fibril formation of pyrimidine analogues. The results may be useful for understanding the processes of self-assembly of the uracil derivatives and the rationalized design of the uracil based supramolecular structures with specific properties.

18.
ACS Omega ; 2(11): 7637-7646, 2017 Nov 30.
Artigo em Inglês | MEDLINE | ID: mdl-30023559

RESUMO

We have introduced new niosome formulations using sucrose monolaurate, vitamin E and n-octanol as independent additives. Detailed characterization techniques including turbidity, dynamic light scattering, transmission electron microscopy, ξ potential, and proton nuclear magnetic resonance measurements have been introduced to monitor the morphological transition of the carbohydrate-based micellar assembly into niosomal aggregates. Moreover, microheterogeneity of these niosomal aggregates has been investigated through different fluorescence spectroscopic techniques using a hydrophobic probe molecule coumarin 153 (C153). Further, it has been observed that vitamin E and octanol have an opposing effect on the rotational motion of C153 in the respective niosome assemblies. The time-resolved anisotropy studies suggest that incorporation of vitamin E and octanol into the surfactant aggregates results in slower and faster rotational motion of C153, respectively, compared to the micellar assemblies. Moreover, the ability to entrap a probe molecule by these niosomes is utilized to encapsulate and deliver the anticancer drug doxorubicin inside the mammalian cells which is monitored through fluorescence microscopic images. Interestingly, the niosome composed of vitamin E demonstrated better cytocompatibility toward primary chondrocyte cell lines compared to the octanol-forming niosome.

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