Implication toward a simple strategy to generate pH tunable FRET-based biosensing.

The present contribution depicts a unique approach to generate tunable Förster resonance energy transfer (FRET) emission with variation of pH of the medium. The pH sensitive absorption of Doxorubicin leads to modification of spectral overlap between emission spectra of donor (Pyrazoline) and absorption spectra of acceptor (Doxorubicin) thereby sensing maximum FRET efficiency in an optimum pH (near pK of Doxorubicin). This drug molecule exhibits an instantaneous conformation change at a particular pH, which consequences on abrupt ON-and-OFF FRET efficiency.

Deciphering Block Copolymers as Carriers of a Pyrazoline Derivative through Its Solvatochromic Behavior: A Spectroscopic and Theoretical Exploration.

Many biologically active water-insoluble drug molecules have limited clinical application because of strong hydrophobicity. Recently triblock copolymers have attracted enormous interest as potential drug carriers. For the purpose of delivering the 5-(1-(bromohexa-1,3,5-triyn-1-yl)-3a,4,5,6,7,7a-hexahydro-1H-4,7-methanoindazol-3-yl)-3-methyl-1-phenyl-1H-pyrazole-4-carbonitrile (PYZ) molecule, triblock copolymers are used.

Spectroscopic and theoretical investigation of conformational changes of proteins by synthesized pyrimidine derivative and its sensitivity towards FRET application.

Interest in synthesizing and characterizing (IR, NMR and HRMS spectroscopic methods) a pyrimidine based Schiff-base ligand, 2-(2-(Anthracen-9-ylmethylene) hydrazinyl)-4,6-dimethyl pyrimidine (ANHP) has been developed for its application to ascertain the conformational change of protein and sensitivity towards fluorescence resonance energy transfer (FRET) process. Location of ANHP in bovine serum albumin (BSA) and human serum albumin (HSA) proteins environment has been determined using different spectroscopic techniques. Weakly fluorescent ANHP have shown greater protein induced fluorescence enhancement (PIFE) in case of HSA than BSA, though in both cases energy transfer efficiency are almost same but difference in binding constant values encourages us to find the location of ANHP within the complex protein environment.

Influence of the ionic liquid 1-butyl-3-methylimidazolium bromide on amyloid fibrillogenesis in lysozyme: Evidence from photophysical and imaging studies.

Many proteins can abnormally fold to form pathological amyloid deposits/aggregates that are responsible for various degenerative disorders called amyloidosis. Here we have examined the anti-amyloidogenic potency of an ionic liquid, 1-butyl-3-methylimidazolium bromide, using lysozyme as a model system. Thioflavin T fluorescence assay demonstrated that the ionic liquid suppressed the formation of lysozyme fibrils significantly.

CB7 as a drug vehicle and controlled release of drug through non ionic surfactant: Spectroscopic technique.

A study of the comparative drug carrier properties of cucurbituril[7] (CB7) and β-cyclodextrin (β-CD) with a naphthalimide derivative, [2-(2-aminoethyl)-1H-benzo[deisoquinoline-1,3(2H)-dione] (NAP) and its release in aqueous solution using micellar environment, is the key research interest of this work. The profound changes in the different spectroscopic behavior have been attributed to the formation of a 1:1 inclusion complex for NAP:CB7 system. Several experimental outcomes clearly interpreted that CB7 has better drug carrier properties for NAP compared to β-CD.

Photoinduced Electron Transfer Switching Mechanism of a Naphthalimide Derivative with its Solvatochromic Behaviour: An Experimental and Theoretical Study with In Cell Investigations.

The sole existence of a t-bone-shaped naphthalimide derivative [2-(2-aminoethyl)-1H-benzo[de]isoquinoline-1,3(2H)dione] (NAP), which gives rise to a photoinduced electron transfer (PET) mechanism, has been established using a combination of experimental and theoretical studies. In parallel an in vitro-in cell PET mechanism has also been shown. To understand the photophysics of NAP, solvent studies have been carried out in different solvents.

Binding of ciprofloxacin to bovine serum albumin: Photophysical and thermodynamic aspects.

The present work reveals the study of interaction of a promising chemotherapeutic drug ciprofloxacin (CFX) with a model transport protein bovine serum albumin (BSA). The occurrence of the drug-protein interaction is found to result in significant modulations of the fluorescence excitation and emission spectroscopic properties of CFX following interaction with BSA. However, the major focus of the study underlies a critical insight into the quantitation of the drug-protein interaction phenomenon.

A differential approach towards understanding the enhanced emission induced superior bio-imaging and cytotoxicity within block copolymeric nanomicelles.

Two tri-block copolymers P123 (PEOPPOPEO) and F127 (PEOPPOPEO) have been employed to form polymeric nanomicelles and function as potential nanocarriers for an anticancer pyrazoline derivative (PYZ) in aqueous buffer solution for biological studies. Encapsulation within these nanomicelles considerably enhanced the fluorescence of the PYZ compared to its low fluorescence in aqueous buffer medium. The effect of the micellar structures on the photophysical properties of PYZ have been demonstrated by means of steady state and time resolved fluorescence spectroscopy.

Exploring the interaction of phenothiazinium dyes methylene blue, new methylene blue, azure A and azure B with tRNA: spectroscopic, thermodynamic, voltammetric and molecular modeling approach.

This study focuses on the understanding of the interaction of phenothiazinium dyes methylene blue (MB), new methylene blue (NMB), azure A (AZA) and azure B (AZB) with tRNA with particular emphasis on deciphering the mode and energetics of the binding. Strong intercalative binding to tRNA was observed for MB, NMB and AZB, bound by a partial intercalative mode. AZA has shown groove binding characteristics.

Understanding the effect of size and shape of gold nanomaterials on nanometal surface energy transfer.

Gold Nanomaterials (GNMs) interact with fluorophores via electromagnetic coupling under excitation. In this particular work we carried out (to the best of our knowledge for the first time) a comprehensive study of systematic quenching of a blue emitter 2-Anthracene Sulfonate (2-AS) in the presence of gold nanoparticles of different size and shape. We synthesized gold nanomaterials of four different dimensions [nanoparticle (0D), nanorod (1D), nanotriangle (2D) and nanobipyramids (3D)] and realized the underlying effect on the emitting dipole in terms of steady and time resolved fluorescence.

Deciphering the Role of the Length of the Corona in Controlled NSET within Triblock Copolymers.

Nanometal surface energy transfer (NSET) from 2-anthracene sulfonate (2-AS) to gold nanoparticles in water-soluble triblock copolymers (TBP) P123 (PEO19PPO69PEO19) and F127 (PEO100PPO65PEO100) is systematically investigated. Fluorescence lifetime and anisotropy experiments provide thorough information on the locations of the 2-AS within these micelles. Variation in the size of the micellar corona region of the TBP is found to be the prime factor for different positions of 2-AS in them.

Aggregation-induced fabrication of fluorescent organic nanorings: selective biosensing of cysteine and application to molecular logic gate.

Self-aggregation behavior in aqueous medium of four naphthalimide derivatives has exhibited substitution-dependent, unusual, aggregation induced emission enhancement (AIEE) phenomena. Absorption, emission, and time-resolved study initially indicated the formation of J-type fluorescent organic nanoaggregates (FONs). Simultaneous applications of infrared spectroscopy, theoretical studies, and dynamic light scattering (DLS) measurements explored the underlying mechanism of such substitution-selective aggregation of a chloro-naphthalimide organic molecule.

Spectroscopic and quantum mechanical approach of solvatochromic immobilization: modulation of electronic structure and excited-state properties of 1,8-naphthalimide derivative.

Photophysical and spectroscopic properties of a fluorescent analogue, 2-(5-selenocyanato-pentyl)-6-chlorobenzo- [de]isoquinoline-1,3-dione (NP) in different solvents has been described in this paper using steady-state, time resolved spectroscopy and density functional theory (DFT) calculation. Stoke's shifted emission band in different solvents clearly demonstrate the highly polar character of the excited state, which is also supported by the enhancement of dipole moment of the molecule upon photoexcitation. Spectroscopic studies and multiple linear regression analysis method reveal that the solvatochromic behavior of the probe depends not only on the polarity of the medium but also on the hydrogen bonding interaction with the solvents.

Preferential molecular encapsulation of an ICT fluorescence probe in the supramolecular cage of cucurbit[7]uril and β-cyclodextrin: an experimental and theoretical approach.

Supramolecular interaction between an intramolecular charge transfer (ICT) probe, N,N-dimethylaminonaphthyl-(acrylo)-nitrile (DMANAN), and two well-recognized macrocyclic hosts, cucurbit[7]uril (CB7) and β-cyclodextrin (β-CD), has been studied in aqueous medium by absorption, emission, time-resolved measurements, and (1)H NMR spectroscopic methods. The changes in the profiles of the fluorescence spectra illustrate significant modifications in fluorescence intensity, decay time, and quantum yield upon confinement of probe within the hydrophobic cavity of the hosts. Using the Benesi-Hildebrand relationship, the stoichiometric ratio as well as the binding constant of the host-guest complexation has been estimated.

An efficient, Schiff-base derivative for selective fluorescence sensing of Zn²⁺ ions: quantum chemical calculation appended by real sample application and cell imaging study.

Since zinc ions (Zn(2+)) are involved in numerous biological phenomena and go through subsequent interactions with zinc-binding proteins, we have attempted a sensitive fluorescence based detection of this second most abundant metal ion using an engineered and synthesized Schiff-base ligand, namely 2,4-bis((Z)-2-(1-(pyridin-2-yl)ethylidene)hydrazinyl)pyrimidine (PyHP). The ligand exhibits a zinc-induced fluorescence response when investigated in a MeOH-buffer (10 mM HEPES, pH = 7) (4 : 1) solvent mixture. The presence of zinc ions (λ(ex) = 410 nm, quantum yield, ϕ = 0.

Photophysical aspects of biological photosensitizer Kynurenic acid from the perspective of experimental and quantum chemical study.

In the present contribution, we have explored ground and excited state spectroscopic properties of an antiexcitotoxic and anticonvulsant drug, Kynurenic acid (KA), through steady-state absorption, emission and time-resolved emission spectroscopy and quantum chemical calculations. The main focus of this article is to illustrate the effects of various parameters such as the nature of the solvents and pH of the medium on the spectral properties of KA which confirms the presence of different neutral and ionic species in the ground and excited states. The molecule KA exists mainly as keto- or anionic form in the ground state, whereas the main contribution of its emission is arising from the keto tautomer in the excited state.

Micellization of cetyltrimethylammonium bromide: effect of small chain Bola electrolytes.

Sodium dicarboxylates (or Bola salts) with methylene spacers 0, 2, 4, 6, 8, and 10 were studied in aqueous solution to investigate their influence on the micellization of cetyltrimethylammonium bromide (CTAB). Since bolas with spacer length ≤12 are known not to micellize in general, the herein used sodium dicarboxylates were treated as 2:1 amphiphilic electrolytes which reduced surface tension of water (except sodium oxalate with zero spacer) without self-association. Their concentration dependent conductance was also linear without breaks.

An intriguing pH-triggered FRET-based biosensor emission of a pyrazoline-doxorubicin couple and its application in living cells.

A unique pH-driven Förster resonance energy transfer (FRET) based biosensor emission by a pyrazoline-doxorubicin pair has been deciphered with a bioimaging application in a live HepG2 cell whereas conformational switching of both molecules at elevated pH reveals a fascinating twist (FRET-OFF) via strong fluorescent exciplex formation.

Unveiling the groove binding mechanism of a biocompatible naphthalimide-based organoselenocyanate with calf thymus DNA: an "ex vivo" fluorescence imaging application appended by biophysical experiments and molecular docking simulations.

The present study embodies a detailed investigation of the binding modes of a potential anticancer and neuroprotective fluorescent drug, 2-(5-selenocyanato-pentyl)-6-chloro benzo[de]isoquinoline-1,3-dione (NPOS) with calf thymus DNA (ctDNA). Experimental results based on spectroscopy, isothermal calorimetry, electrochemistry aided with DNA-melting, and circular dichroism studies unambiguously established the formation of a groove binding network between the NPOS and ctDNA. Molecular docking analysis ascertained a hydrogen bonding mediated 'A-T rich region of B-DNA' as the preferential docking site for NPOS.

Photobehavior and docking simulations of drug within macromolecules: binding of an antioxidative isoquinolindione to a serine protease and albumin proteins.

The principal intent of the present contribution is to decipher the binding domain and structural changes of trypsin (TPS), a proteolytic globular enzyme and two serum proteins, namely, bovine serum albumin (BSA), human serum albumin (HSA) association with a newly synthesized bioactive isoquinolindione derivative (ANAP) by employing steady state, time resolved fluorescence and circular dichroism (CD) techniques. Intramolecular charge transfer emission (ICT) of ANAP is found to be responsible for the commendable sensitivity of the probe as an extrinsic fluorescent marker to the protein environments. A sharp distinctive feature of determined micropolarities in proteinous media clearly demarcates the differential extent of hydrophobicity around the encapsulated ANAP.

Self-aggregation of MEGA-9 (N-nonanoyl-N-methyl-D-glucamine) in aqueous medium: physicochemistry of interfacial and solution behaviors with special reference to formation energetics and micelle microenvironment.

Self-aggregation of MEGA-9 (N-nonanoyl-N-methyl-D-glucamine), a nonionic sugar-based surfactant, was studied with respect to the effect of salt (NaCl) and ionic liquid (1-butyl-3-methylimidazolium tetrafluoroborate) on its critical micelle concentration (cmc), aggregation number, hydrodynamic dimensions, energetics of micellization, and micellar microenvironment. Fluorimetry (both steady state and time resolved) was used to understand the microenvironments under the influence of additives. NaCl was found to decrease cmc, increase aggregation number (N), increase micellar size, and decrease enthalpy of micelle formation; the IL effect on the parameters was mostly opposite.

Explicit spectral response of the geometrical isomers of a bio-active pyrazoline derivative encapsulated in β-cyclodextrin nanocavity: a photophysical and quantum chemical analysis.

The existence of two geometrical isomers (cis- and trans-) of a biologically significant pyrazoline derivative [5-(-1'-(4-bromo-phenyl)-3a',7a'-hexahydro-1'H-indazol-3'-yl)-3-methyl-1-phenyl-1H-pyrazole-4-carbonitrile] (PZ) has been established using a combined theoretical and experimental investigation. Solvatochromic analysis of PZ revealed the existence of said cis- and trans- isomers. The unique solvatochromic response of the PZ isomers and their preferential encapsulation within β-cyclodextrin (β-CD) nanocavity clearly shows the difference in the behavioral nature of the isomers of PZ in homogeneous and heterogeneous medium.

Facile room temperature synthesis of lanthanum oxalate nanorods and their interaction with antioxidative naphthalimide derivative.

Polycrystalline lanthanum oxalate (LaOX) nanorods (NRs) were succesfully synthesized using reverse micellar (RM) method. The study espouses the versatility of the reverse micellar method forming monodisperse, stable nanorods at room temperature. The as-synthesized LaOX nanorods were characterised by different techniques.

Differential contribution of Igepal and CnTAB micelles on the photophysics of nonsteroidal drug Naproxen.

Spectroscopic studies of Naproxen (NP), a nonsteroidal drug have been carried out in well characterized, micellar media of cationic surfactants of a homologous series having general formula C(n)TAB (alkyl trimethyl ammonium bromide) and of nonionic surfactants of Igepal (Ig) series (poly(oxyethylene) nonyl phenol). The fluorescence behavior of the drug molecule in C(n)TAB micelles has been found to be opposite to that in Igepal micelles. The binding constants during probe micelle binding have been evaluated from relevant fluorescence data.

Dual intramolecular hydrogen bond as a switch for inducing ground and excited state intramolecular double proton transfer in doxorubicin: an excitation wavelength dependence study.

This paper investigates how solution conditions, especially solvent polarity and hydrogen bonding, influence the fluorescence of an anticancer drug, doxorubicin hydrochloride (DOX). When excited at 480 nm, this molecule shows single fluorescence. However, when excited at 346 nm, it shows dual fluorescence.