Study on the interaction of methylene blue with cyclodextrin derivatives by absorption and fluorescence spectroscopy

Enhanced Sorption Performance of Natural Zeolites Modified with pH-Fractionated Humic Acids for the Removal of Methylene Blue from Water

This work explores the effect of humic acids (HA) fractionation on the sorption ability of a natural zeolite (NYT)-HA adduct. HA were extracted from compost, fractionated via the pH fractionation method, and characterized via UV-Vis spectroscopy and gel permeation chromatography. The HA samples were immobilized onto NYT via thermal treatment. The resulting adducts (NYT-HA) were tested for their ability to remove methylene blue (MB) from an aqueous solution. It was found that the sorption performance of NYT-HA strongly depends on the chemical characteristics of humic acids. Sorption capacity increased with the molecular weight and hydrophobicity degree of the HA fractions. Hydrophobic and π-π interactions are likely the primary mechanisms by which MB interacts with HA. The sorption kinetic data conform to the pseudo-second-order model. The Freundlich isotherm model adequately described the sorption equilibrium and revealed that the uptake of MB onto NYT-HA is endothermic in nature.

Hybrid Polymer-Silica Nanostructured Materials for Environmental Remediation

Due to the ever-growing global population, it is necessary to develop highly effective processes that minimize the impact of human activities and consumption on the environment. The levels of organic and inorganic contaminants have rapidly increased in recent years, posing a threat to ecosystems. Removing these toxic pollutants from the environment is a challenging task that requires physical, chemical, and biological methods. An effective solution involves the use of novel engineered materials, such as silica-based nanostructured materials, which exhibit a high removal capacity for various pollutants. The starting materials are also thermally and mechanically stable, allowing for easy design and development at the nanoscale through versatile functionalization procedures, enabling their effective use in pollutant capture. However, improvements concerning mechanical properties or applicability for repeated cycles may be required to refine their structural features. This review focuses on hybrid/composite polymer-silica nanostructured materials. The state of the art in nanomaterial synthesis, different techniques of functionalization, and polymer grafting are described. Furthermore, it explores the application of polymer-modified nanostructured materials for the capture of heavy metals, dyes, hydrocarbons and petroleum derivatives, drugs, and other organic compounds. The paper concludes by offering recommendations for future research aimed at advancing the application of polymer-silica nanostructured materials in the efficiency of pollutant uptake.

Solid waste collagen-associated fabrication of magnetic hematite nanoparticle@collagen nanobiocomposite for emission-adsorption of dyes

The strategic utilization of hazardous particulate waste in eliminating environmental pollution is an important research hotspot. Herein, abundantly available hazardous solid collagenic waste of leather industry is converted into stable hybrid nanobiocomposite (HNP@SWDC) comprising magnetic hematite nanoparticles (HNP) and solid waste derived collagen (SWDC) via co-precipitation method. The structural, spectroscopic, surface, thermal, and magnetic properties; fluorescence quenching; dye selectivity; and adsorption are explored via microstructural analyzes of HNP@SWDC and dye adsorbed-HNP@SWDC using ¹H nuclear magnetic resonance, Raman, ultraviolet-visible, Fourier-transform infrared (FTIR), X-ray photoelectron, and fluorescence spectroscopies; thermogravimetry; field-emission scanning electron microscopy; and vibrating-sample magnetometry (VSM). The intimate interaction of SWDC with HNP and elevated magnetic properties of HNP@SWDC are apprehended via amide-imidol tautomerism associated nonconventional hydrogen bondings, disappearance of goethite specific -OH def. in HNP@SWDC, and VSM. The as-fabricated reusable HNP@SWDC is employed for removing methylene blue (MB) and rhodamine B (RhB). Chemisorption of RhB/MB in HNP@SWDC via ionic, electrostatic, and hydrogen bonding interactions alongside dimerization of dyes are realized by ultraviolet-visible, FTIR, and fluorescence studies; pseudosecond order fitting; and activation energies. The adsorption capacity = 46.98-56.14/22.89-27.57 mg g^-1 for RhB/MB is noted using 0.01 g HNP@SWDC within 5-20 ppm dyes and 288-318 K.

Achievement of the Selectivity of Cytotoxic Agents against Cancer Cells by Creation of Combined Formulation with Terpenoid Adjuvants as Prospects to Overcome Multidrug Resistance

Oncological diseases are difficult to treat even with strong drugs due to development the multidrug resistance (MDR) of cancer cells. A strategy is proposed to increase the efficiency and selectivity of cytotoxic agents against cancer cells to engage the differences in the morphology and microenvironment of tumor and healthy cells, including the pH, membrane permeability, and ion channels. Using this approach, we managed to develop enhanced formulations of cytotoxic agents with adjuvants (which are known as efflux inhibitors and as ion channel inhibitors in tumors)-with increased permeability in A549 and a protective effect on healthy HEK293T cells. The composition of the formulation is as follows: cytotoxic agents (doxorubicin (Dox), paclitaxel (Pac), cisplatin) + adjuvants (allylbenzenes and terpenoids) in the form of inclusion complexes with β-cyclodextrin. Modified cyclodextrins make it possible to obtain soluble forms of pure substances of the allylbenzene and terpenoid series and increase the solubility of cytotoxic agents. A comprehensive approach based on three methods for studying the interaction of drugs with cells is proposed: MTT test-quantitative identification of surviving cells; FTIR spectroscopy-providing information on the molecular mechanisms inaccessible to study by any other methods (including binding to DNA, surface proteins, or lipid membrane); confocal microscopy for the visualization of observed effects of Dox accumulation in cancer or healthy cells depending on the drug formulation as a direct control of the correctness of interpretation of the results obtained by the two other methods. We found that eugenol (EG) and apiol increase the intracellular concentration of cytostatic in A549 cells by 2-4 times and maintain it for a long time. However, an important aspect is the selectivity of the enhancing effect of adjuvants on tumor cells in relation to healthy ones. Therefore, the authors focused on adjuvant's effect on the control healthy cells (HEK293T): EG and apiol demonstrate "protective" properties from cytostatic penetration by reducing intracellular concentrations by about 2-3 times. Thus, a combined formulation of cytostatic drugs has been found, showing promise in the aspects of improving the efficiency and selectivity of antitumor drugs; thereby, one of the perspective directions for overcoming MDR is suggested.

Supramolecular detoxification of nitrogen mustard via host-guest encapsulation by carboxylatopillar[5]arene

Nitrogen mustard (NM), a kind of alkylating agent similar to sulfur mustard, remains a threat to public health. However, there is nearly no satisfactory antidote for nitrogen mustard. Herein, we developed a supramolecular antidote to nitrogen mustard through efficient complexation of NM by carboxylatopillar[5]arene potassium salts (CP[5]AK). The cavity of methoxy pillar[5]arene (P5A) is sufficient to encapsulate NM with an association constant of 1.27 × 10² M^-1, which was investigated by ¹H NMR titration, density functional theory studies and independent gradient model studies. NM degrades to the reactive aziridinium salt (2) in the aqueous phase which irreversibly alkylates DNA and proteins, causing severe tissue damage. Considering the size/charge matching with toxic intermediate 2, water-soluble CP[5]AK was selected to encapsulate the toxic aziridinium salt (2), resulting in a high association constant of 4.10 × 10⁴ M^-1. The results of protection experiments of guanosine 5'-monophosphate (GMP) by CP[5]AK indicated that the formation of a complex could effectively inhibit the alkylation of DNA. Besides, in vitro and in vivo experiments also indicated that the toxicity of the aziridinium salt (2) is inhibited with the formation of a stable host-guest complex, and CP[5]AK has a good therapeutic effect on the damage caused by NM. This study provides a new mechanism and strategy for the treatment of NM exposure-induced skin injuries.

Synthesis, characterization and application of high adsorption performance of novel 1,4-polyketone

This study aims to develop an alternating polyketone containing cationic groups in one and four alternating positions for increased functionality. A novel polyarylidene ketone was synthesized using simple condensation polymerization of terephthaldehyde and 2,5-hexane dione (PAK) The physicochemical properties of the resulting polymer were evaluated using Fourier-transform infrared spectroscopy, thermogravimetric analysis, X-ray diffraction, UV-Visible absorbance, fluorescence, and SEM investigations. The findings show that the polymer is amorphous, has good thermal stability, and emits red light. It can also be used as a dye adsorbent in aqueous solutions, with high selectivity for the cationic dye methylene blue (MB). The adsorbent efficiency of PAK was measured as a function of pH, dosage, and initial dye concentration; the greatest dye removal of 96 % was obtained at pH 10, 50 mg dosage, and initial dye concentration of 20 ppm. Kinetics and isotherms were studied, showing that the pseudo-second-order model described kinetic data better than Freundlich and Langmuir and revealed a satisfactory chemisorption process. This study suggests that PAK can purify MB dyeing wastewater, remove Zn²⁺, Cu²⁺, Ni²⁺, Co²⁺, Cd²⁺, Fe³⁺ metal ions well, and is selective for Fe³⁺ and Cu²⁺; ion adsorption is chelating-based.

Sustainable mechanochemical synthesis of β-cyclodextrin polymers by twin screw extrusion

Cyclodextrin nanosponges (CD-NS) are cross-linked cyclodextrin polymers characterized by a nanostructured three-dimensional network. CD-NSs in the last years found many different applications in the pharmaceutical field for the controlled release of drugs and for the absorption of undesired substances from physiological media, food, and wastewater. Most of CD-NS syntheses involve the solubilization of the chosen CD in closed batch, using a suitable organic polar aprotic liquid, which may affect potential environmental or biomedical applications. Since the research is now moving towards more sustainable approaches, new and greener syntheses of CD-NS are now being developed. Here, it is reported a new eco-friendly and efficient synthesis of nanosponges through mechanochemistry. Mechanochemistry involves the application of mechanical forces to drive and control chemical reactions by transferring energy to chemical bonds. The mechanochemical approach involves the use of a twin-screw extruder (TSE) as a chemical reactor: TSE are capable of fine temperature control and, furthermore, TS Extrusion is a continuous process and not a batch process. Among the many available CD-NS syntheses, we tested our solvent-free approach on a β-CD/citric acid (CA) system. Moreover, using TSE, the same polymer was obtained in a considerably shorter time. The so obtained NSs were used for the adsorption and removal of probe molecules, in comparison with NSs prepared by cross-linking β-CD with CA in batch.

Target -responsive host-guest binding-driven dual-sensing readout for enhanced electrochemical chiral analysis

Achieving efficient chiral discrimination by a convenient method remains a challenge in pharmaceutical and biotechnology industries. Our aim in this paper was to develop a dual-signaling enantioselective sensing strategy based on the competitive binding assay. A combination of β-cyclodextrin (β-CD) and methylene blue (MB) was used as an enantioselective discrimination probe to develop a straightforward electrochemical chiral sensor using the drug naproxen (R-and S-NaX) as the representative enantiomers. The principle relied on the difference between two enantiomers in the ability to replace a pre-binding redox probe, which in turn resulted in different dual signals for the two enantiomers. The applicability of the optimized procedure was demonstrated by the analysis of NaX enantiomers in the range of 0.4-6.0 μM. Featuring both signal-on and signal-off elements, the electrode presented significantly enhanced electrochemical activity with a low limit of detection (LOD) of 0.07 μM. We expect that our work will inspire interesting engineering strategies for developing novel enantioselective electrochemical sensors.

Cyclodextrin-Cross-Linked Hydrogels for Adsorption and Photodegradation of Cationic Dyes in Aqueous Solution

Possessing three-dimensional porous structures and tunable mechanical strengths, cyclodextrin-containing polymeric hydrogels are one of the most promising water-based adsorbent materials due to their easy availability, simple chemical modification and environmental friendliness. In this work, two kinds of hydrogels were prepared via the copolymerization with acrylic acid and vinyl-derivatized β-cyclodextrins in water. These two gels have showed good adsorption performance towards cationic dyes through the noncovalent interactions with their anionic backbones and porous network. Meanwhile, pseudo-second-order model was selected to clarify the adsorption kinetics process. Moreover, nano-scaled TiO₂ was doped into these resultant cyclodextrins-based hydrogels to achieve efficient degradation of dyes upon light irradiation. The obtained TiO₂ -loaded hydrogels could exhibit improved adsorption performance and make the adsorbed dyes photo-degraded with the decolorization rates above 95%. It can be envisioned that such cyclodextrin-based soft materials may find applications in dye clearance and water treatment.

Dual-locked spectroscopic probes for sensing and therapy

Optical imaging probes allow us to detect and uncover the physiological and pathological functions of an analyte of interest at the molecular level in a non-invasive, longitudinal manner. By virtue of simplicity, low cost, high sensitivity, adaptation to automated analysis, capacity for spatially resolved imaging and diverse signal output modes, optical imaging probes have been widely applied in biology, physiology, pharmacology and medicine. To build a reliable and practically/clinically relevant probe, the design process often encompasses multidisciplinary themes, including chemistry, biology and medicine. Within the repertoire of probes, dual-locked systems are particularly interesting as a result of their ability to offer enhanced specificity and multiplex detection. In addition, chemiluminescence is a low-background, excitation-free optical modality and, thus, can be integrated into dual-locked systems, permitting crosstalk-free fluorescent and chemiluminescent detection of two distinct biomarkers. For many researchers, these dual-locked systems remain a 'black box'. Therefore, this Review aims to offer a 'beginner's guide' to such dual-locked systems, providing simple explanations on how they work, what they can do and where they have been applied, in order to help readers develop a deeper understanding of this rich area of research.

A Comparative Spectral Study on the Interaction of Organic Dye Congo-Red with Selective Aqueous Micellar Media of CPC, Rhamnolipids and Saponin

The present study is an investigation of the solubilising ability of natural and conventional surfactants saponin (sapindus saponin or reetha saponin), Rhamnolipids (RLs) and N-cetylpyridinium chloride (CPC) respectively via dye-surfactant interaction. The ionic dye Congo Red was examined by absorption spectroscopy method for the study. The dye interacted strongly with oppositely charged surfactant N-cetylpyridinium chloride in the pre-micellar concentration range and formed a stable dye-surfactant complex. The thermodynamic parameter, free energy change for all the systems was calculated at a constant temperature of 25°C. The ΔG0 value for N-cetylpyridinium chloride is found to be −33.269 kJ/mol while for saponin and rhamnolipids the values were −16.084 kJ/mol and −26.006 kJ/mol respectively. The values clearly indicate the efficiency of N-cetylpyridinium chloride surfactant compared to the other two surfactants. The present study aims to understand the dye solubilization in surfactant media in order to develop environmentally friendly, green and cost effective techniques.

Evaluation of Polyethylene Glycol Crosslinked β-CD Polymers for the Removal of Methylene Blue

The environment is at the heart of global worldwide discussion. This study describes the synthesis of ecofriendly polymers by a crosslinking reaction between β-cyclodextrin as the monomer and polyethylene glycol diglycidyl ether (PEDGE) as well as ethylene diglycidyl ether (EDGE) as the crosslinking agents. The studied polymers were characterized by several techniques, such as SEM, FTIR, TGA-TDA and XRD. Their adsorption properties for methylene blue under various conditions of pH, contact time and initial concentration of dye were assessed in order to find the optimal conditions. The results indicate that the polymers are good nominates for methylene blue adsorption with adsorption capacities up to 15 mg/g. The adsorption mechanism was demonstrated to follow the Langmuir model. Finally, the regeneration of the polymers was investigated using Soxhlet extraction with ethanol. The absorption capacities of the adsorbent were stable after three cycles.

Host-guest complexes - Boosting the performance of photosensitizers

In this review, we will show the diversity of supramolecular host-guest complexes of cyclodextrins, cucurbit[n]urils, calix[n]- and pillar[n]arenes with photosensitizers, like porphyrins and phthalocyanines. Host-guest complexes are one of the main building blocks in supramolecular chemistry. For example, they have been widely used to encapsulate hydrophobic drug molecules to enhance the bioavailability in the human body. In these days of multiresistant bacteria and difficulties in cancer therapy, supramolecular host-guest systems with photosensitizers for the photodynamic therapy(PDT) gain more and more interest. In general, photosensitizers with a (large) conjugated aromatic π-system are used, which tend to π-πstacking in aqueous media suppressing the cell toxicity by singletoxygen production quenching. This can be overcome by the formation of host-guest complexes. Besides that, encapsulation of the photosensitizers in host molecules can enhance the solubility, increase cellular uptake, lead to hydrogels, rotaxanes, and switchable systems.

A photodynamic antibacterial spray-coating based on the host–guest immobilization of the photosensitizer methylene blue

An efficient photodynamic antibacterial spray-coating is developed with a very low MB density and high singlet oxygen quantum yield.

Structural transitions and encapsulation selectivity of thermoresponsive polyelectrolyte complex micelles

Polyelectrolyte complex micelles containing thermoresponsive coronas can exhibit varying morphologies and encapsulate multivalently charged therapeutics for drug delivery applications.

Supramolecular fluorescent sensor array for simultaneous qualitative and quantitative analysis of quaternary ammonium herbicides

A supramolecular fluorescent sensor array was firstly used to simultaneously qualitatively and quantitatively analyze quaternary ammonium herbicides.

Molecular dynamics investigations of an indicator displacement assay mechanism in a liquid crystal sensor

Molecular dynamic simulations were applied to address the binding competition mechanism in an IDA based LC sensor system.

Thermodynamic study of β-cyclodextrin-dye inclusion complexes using gradient flow injection technique and molecular modeling

Gradient flow injection technique-diode array spectrophotometry was applied for β-cyclodextrin (β-CD)-dye inclusion complex studies. A single injection of a small amount of mixed β-CD-dye solution (100μl) into the carrier solution of the dye and recording the spectra gave the titration data. The mole ratio data were calculated by calibrating the dispersion pattern using a calibrator dye (rose bengal). Model-based multivariate methods were used to analyze the spectral-mole ratio data and, as a result, estimate stability constants and concentration-spectral profiles. Reliability was tested by applying this method to study the β-CD host-guest complexes with several dyes as guest molecules. Singular value decomposition (SVD) was used to select the chemical model and reduce noise. Molecular modeling provided the ability to predict the guest conformation-orientation (posing) within the cavity of β-CD and the nature of the involved interactions. Among those dyes showing observable spectral variation, the stoichiometric ratio of β-CD: dye (and log Kf) of methyl orange, fluorescein, phenol red, 4-(2-pyridylazo) resorcinol (PAR), and crystal violet were calculated to be 1:1 (4.26±0.01), 1:1 (1.53±0.08), 1:1 (3.11±0.04), 1:1 (1.06±0.12), and 2:1 (5.27±0.03), respectively. Compared with the classical method of titration, this method is simple and fast and has the advantage of needing reduced human interference. Molecular modeling facilitates a better understanding of the type of interactions and conformation of guest molecules in the β-CD cavity. The details of the proposed method are discussed in this paper.

Interaction Mode between Inclusion Complex of Vitamin K3 with γ- Cyclodextrin and Herring-Sperm DNA

Methods including spectroscopy, electronic chemistry and thermodynamics were used to study the inclusion effect between γ-cyclodextrin (CD) and vitamin K3(K3), as well as the interaction mode between herring-sperm DNA (hsDNA) and γ-CD-K3 inclusion complex. The results from ultraviolet spectroscopic method indicated that VK3 and γ-CD formed 1:1 inclusion complex, with the inclusion constant Kf = 1.02 × 10(4) L/mol, which is based on Benesi-Hildebrand's viewpoint. The outcomes from the probe method and Scatchard methods suggested that the interaction mode between γ-CD-K3 and DNA was a mixture mode, which included intercalation and electrostatic binding effects. The binding constants were K (θ)25°C = 2.16 × 10(4) L/mol, and K(θ)37°C = 1.06 × 10(4) L/mol. The thermodynamic functions of the interaction between γ-CD-K3 and DNA were ΔrHm(θ) = -2.74 × 10(4) J/mol, ΔrSm(θ) = 174.74 J·mol(-1)K(-1), therefore, both ΔrHm(θ) (enthalpy) and ΔrSm(θ) (entropy) worked as driven forces in this action.

pH-dependent complexation of hydroxypropyl-beta-cyclodextrin with chlorin e6: effect on solubility and aggregation in relation to photodynamic efficacy

Objectives

The activity of chlorin e6 (Ce6) in photodynamic therapy of cancers is significantly reduced by its propensity to form aggregates. It was postulated that disaggregation of Ce6 could be achieved with the use of hydroxypropyl-beta-cyclodextrin (HP-β-CD) through solubility enhancement.

Methods

An initial phase solubility study of Ce6 was conducted with various concentrations of HP-β-CD at three different pH conditions, i.e. pH 3, pH 5 and pH 7. Solubility-induced disaggregation of Ce6 was illustrated by fluorescence spectroscopy and singlet oxygen generation studies. Interaction between Ce6 and HP-β-CD was further demonstrated by solid-state characterization techniques. Inclusion complex formulations were tested for improved efficacy on squamous cancer cell lines.

Key findings

Increase in Ce6 solubility was observed, especially at pH 7, indicating the formation of inclusion complex between Ce6 and HP-β-CD. This resulted in disaggregation of Ce6 aggregates illustrated by fluorescence spectroscopy. The mode of binding was predominated by H-bonding supported by temperature-dependent binding studies and molecular simulation work. The inclusion complex demonstrated improved photodynamic efficacy through enhanced singlet oxygen generation and phototoxicity on human oral squamous carcinoma cells.

Conclusions

pH-dependent complexation between Ce6- and HP-β-CD-induced disaggregation of Ce6 aggregates and the resultant formulations facilitated improved PDT efficacy on tested cancer cell lines.

Nanospheres based on PLGA/amphiphilic cyclodextrin assemblies as potential enhancers of Methylene Blue neuroprotective effect

Nanospheres of amphiphilic cyclodextrin and PLGA entrapping Methylene Blue are proposed as potential enhancers of drug neuroprotective effect on neuroblastoma cells.

Preparation and characterization of host-guest system between inosine and β-cyclodextrin through inclusion mode

Inosine is a nucleoside that is formed when hypoxanthine is attached to a ribose ring (also known as a ribofuranose) via a β-N₉-glycosidic bond. Inosine is commonly found in tRNAs. Inosine (INS) has been used widely as an antiviral drug. The inclusion complex of INS with β-CDx in solution phase is studied by ground and excited state with UV-visible and fluorescence spectroscopy, respectively. A binding constant and stoichiometric ratio between INS and β-CDx are calculated by BH equation. The lifetime and relative amplitude of INS is increases with increasing the concentrations of β-CDx, confirms the formation of inclusion complex in liquid state. The solid complexes are prepared by kneading method (KM) and co-precipitation method (CP). The solid complex is characterized by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), powder X-ray diffraction (XRD) and differential scanning colorimetry (DSC). CP method gives the solid product with good yield than that of physical mixture and KM method. The structure of complex is proposed based on the study of Patch - Dock server.

A novel set of symmetric methylene blue derivatives exhibits effective bacteria photokilling – a structure–response study

This study focuses on the structure–response relationship of symmetrically substituted phenothiazinium dyes.

Characterization of the interaction of a mono-6-thio-β-cyclodextrin-capped CdTe quantum dots-methylene blue/methylene green system with herring sperm DNA using a spectroscopic approach

Novel, water-soluble CdTe quantum dots (QDs) capped with β-cyclodextrin (β-CD) and ~ 4.0 nm in diameter were synthesized in aqueous solution, and characterized using transmission electron microscopy (TEM). A fluorescence-sensing system based on the photoinduced electron transfer (PET) of (mono-6-thio-β-CD)-CdTe QDs was then designed to measure the interaction of phenothiazine dyes [methylene blue (MB) and methylene green (MG)] with herring sperm DNA (hsDNA). This fluorescence-sensing system was based on a fluorescence "OFF-ON" mode. First, MB/MG adsorbed on the surface of (mono-6-thio-β-CD)-CdTe QDs effectively quenches the fluorescence of (mono-6-thio-β-CD)-CdTe QDs through PET. Then, addition of hsDNA restores the fluorescence intensity of (mono-6-thio-β-CD)-CdTe QDs, because hsDNA can bind with MB/MG and remove it from the as-prepared (mono-6-thio-β-CD)-CdTe QDs. In addition, detailed reaction mechanisms of the (mono-6-thio-β-CD)-CdTe QDs-MB/MG-hsDNA solution system were studied using optical methods, by comparison with the TGA-CdTe QDs-MB/MG-hsDNA solution system.

Complexation, dimerisation and solubilisation of methylene blue in the presence of biamphiphilic ionic liquids: a detailed spectroscopic and electrochemical study

The interactions of methylene blue (MB), a redox active dye with surface active biamphiphilic ionic liquids (BAILs): 1-butyl-3-methylimidazolium dodecylsulfate, [C4mim][C12OSO3] and 1-hexyl-3-methylimidazolium dodecylsulfate [C6mim][C12OSO3] have been investigated in aqueous medium to explore the candidature of surface active ionic liquids (ILs) in the field of dye-surfactant chemistry. Various thermodynamic, spectroscopic and electrochemical techniques such as conductivity, steady-state fluorescence, UV-visible absorption, and cyclic voltammetry (CV) have been used to obtain comprehensive information about MB-BAIL interactions. The presence of MB is seen to enhance the critical micellar concentration (cmc) of BAILs. The extent of interaction between the MB and BAILs varies with the concentration as well as the nature of BAILs. Different interactional phenomena such as the formation of ion-pair complexes, dimers, and solubilisation of monomers of MB have been observed in different concentration regimes of BAILs. A quantitative evaluation of the process of interaction between MB and BAILs has been made in terms of various micellar and binding parameters exploiting UV-visible absorption and CV measurements. Comparatively more hydrophobic [C6mim][C12OSO3] interacts strongly with MB as compared to [C4mim][C12OSO3] via hydrophobic and electrostatic interactions.

Investigation on the interaction between cyclophosphamide and lysozyme in the presence of three different kind of cyclodextrins: determination of the binding mechanism by spectroscopic and molecular modeling techniques

The interactions between cyclophosphamide (CYC) and lysozyme (LYZ) in the presence of different cyclodextrins (CDs) were investigated by UV absorption, fluorescence spectroscopy, circular dichroism (CD), and molecular modeling techniques under imitated physiological conditions. The UV absorption results showed the formation of complexes between CYC and LYZ in the presence of different CDs. Fluorescence data show that CYC has a stronger quenching effect on LYZ, and the red shifts suggested that the microenvironment of Trp residues was changed and became more hydrophilic. The interaction of CYC with LYZ and quenching properties of the complexes caused strong static fluorescence quenching in binary and ternary systems. The binding affinities as well as the number of binding sites were obtained from interaction between CYC and LYZ in the presence of different CDs as binary and ternary systems by modified Stern-Volmer plots. The Resonance Light Scattering (RLS) technique was utilized to investigate the effect of drug and CDs on conformational changes of LYZ as separate and simultaneous. The results suggested that the enhancement of RLS intensity was attributed to the formation of a complex between drug and protein in absence and presence of CDs. The effect of CYC and cyclodextrins on the conformation of LYZ was analyzed using synchronous fluorescence spectroscopy. Our results revealed that the fluorescence quenching of LYZ originated from the Trp and Tyr residues, and demonstrated conformational changes of LYZ with the addition of CYC and CDs. The molecular distances between the donor (LYZ) and acceptor (CYC and CDs) in binary and ternary systems were estimated according to Forster’s theory and showed static quenching for protein with CYC in the presence of CDs. The CD spectra indicated that the binding of the CYC induced secondary structural changes in LYZ in binary and ternary systems. Molecular modeling suggested the binding sites of CYC in the ternary systems differ from those in the binary systems. estimated the distance between CYC and Trp residues in binary and ternary systems in the presence of CDs and confirmed the experimental results.