Phenosafranin Research Articles

Wavelength-selective, time-resolved, and visible-light-responsive multicolor switching systems for multistate dynamic information encryption

Visible-light-responsive photoreversible multi-color switching systems (PMCSSs) are attractive to meet the advanced demands in dynamic information encryption. Particularly, PMCSSs with wavelength-selective and time-resolved color switching are highly important but underexplored. Here, a new strategy is proposed to realize wavelength-selective, time-resolved, and visible-light-responsive PMCSSs by integrating acetamide ligand-capping CdS (CdS-NH2) nanoparticles and various redox dyes in solid films for multistate dynamic information encryption. The –NH2 groups of surface-bounded CH3CONH2 act as sacrificial electron donors for scavenging photogenerated holes to endow the CdS-NH2 nanoparticles high photoreductive ability and activity in a broad visible light range from 400 to 515 nm, thus enabling the long-waited wavelength-selective multicolor switching via coupling the wavelength-dependent photoreductivity of CdS-NH2 nanoparticles and the discoloration kinetics of redox dyes, such as methylene blue (MB) and phenosafranine (PS). Moreover, the time-dependent color switching during recoloration process of the color switching system can be modulated by tuning the oxidation kinetics of MB and methylene green (MG), enabling time-resolved dynamic imaging characteristics. Based on the unusual properties of the PMCSSs, a kind of wavelength-selective and time-resolved codes are designed for advanced dynamic information encryption. This work provides new guidance for developing of new PMCSSs for information encryption with high security requirements.

Selective extraction of anionic and cationic dyes using tailored hydrophobic deep eutectic solvents

In this work, eight kinds of hydrophobic deep eutectic solvents (DESs), including four types of ionic and four types of non-ionic DESs, were prepared and applied in vortex-assisted liquid-liquid microextraction (LLME) technology. To explore the extraction ability of the hydrophobic DESs-based vortex-assisted LLME, four types of dyes were selected as analytes, involving anionic tartrazine (TA), amaranth (AM) and cationic phenosafranine (PF), methylene blue (MB). It turned out that the ionic and non-ionic hydrophobic DESs showed selective extraction on anionic and cationic dyes, respectively. In particular, the extraction efficiency of TA could reach 99.3 % when trioctylmethylammonium chloride-thymol ([TMAC][Thy]) was utilized as extraction agent. The partitioning efficiency of PF was up to 99.9 % by using decanoic acid-thymol ([DecA][Thy]) as extraction agent. The limits of detection (LODs) of TA and PF were 0.06 and 0.14 μg mL−1, respectively. The limits of quantification (LOQs) obtained for TA and PF were 0.20 and 0.47 μg mL−1, respectively. Besides, FT-IR and 1H NMR were utilized to investigate the extraction mechanism. The results demonstrated that the hydrogen bonding and electrostatic force were the main driving forces in the extraction process. Furthermore, through separating various anionic and cationic dyes, the selective extraction ability of [TMAC][Thy] and [DecA][Thy] were successfully verified. Hence, the feasible operation, high extraction efficiency and excellent selectivity make the developed hydrophobic DESs-based vortex-assisted LLME attractive in dyes separation.

Excitations of safranin and phenosafranin in aqueous solution: Comparative theoretical analysis

In the present work, the excitations of safranin (SAF) and phenosafranin (PheSAF) in an aqueous solution are analyzed by DFT/TD-DFT, considering the vibronic transitions and hydration. The frontier orbitals, transitions between which cause the absorption and emission of dyes in the visible region of the spectrum, almost do not cover benzene rings and methyl groups of molecules. As a consequence, benzene rings, aromatic hydrogen atoms, as well as SAF methyl groups are not covered by the change in electron density. These features explain the same excitation energies of SAF and PheSAF observed experimentally. At the same time, during relaxation to an excited equilibrium state, the changes in the vast majority of atomic charges again turn out to be different for SAF and PheSAF, which causes a slight difference between the emission energies of dyes. Excitations of both dyes do not lead to twisting of their benzene rings relative to the chromophores - the dihedrals between them are strictly φ = 90°. The thermal twisting of these dihedrals is practically free up to Δφ∼±30°, and then it is sharply hampered. The heights of potential barriers separating their energy minima are very high (∼400 kT). The increase in the dipole moments upon excitation is due to the greatest extent to the significant increase in the electron densities at the N10 atoms of both dyes. All five H-bonds of each of the dyes with water are strengthened upon excitation. The strongest and most enhanced due to excitation are the H-bonds of waters with the N10 atoms. There is a strong photoinduced polarization of water molecules bound to the N10 atoms of the dyes. H-bonds with water of amino groups are stronger in PheSAF, and with the N10 atom, in SAF. The influence of hydrating water molecules leads to significant bathochromic shifts of the maxima of the calculated spectra (23 nm for SAF and 22 nm for PheSAF) relative to the purely implicit specification of the solvent.

ADSORPTIVE MICELLAR FLOCCULATION AND CLOUD POINT EXTRACTION AS PRE-CONCENTRATION METHODS FOR THE DETERMINATION OF PHENOSAFRANINE DYE IN AQUEOUS SOLUTIONS

A micellar-based preconcentration method for the extraction of Phenosafranine (PS) dye was developed by using adsorptive micellar flocculation (AMF) and cloud point extraction (CPE) techniques. In the case of AMF, aluminum sulphate (flocculant) and sodium dodecyl sulphate (SDS) were taken in 1:2 ratios for the extraction of PS dye. The parameters affecting the AMF and CPE were optimized. The calibration range and detection limits were 0.0-8.07 g/mL and 4.182 g/mL respectively for AMF. The calibration range and detection limits were 0.0-9.684 g/mL and 2.272ng/mL respectively for CPE.s The methods presented were used to extract PS dye from aqueous samples.

Effect of Trap Energy on Series Resistance of Phenosafranine Dye Based Organic Diode in Presence of TiO<sub>2</sub> and ZnO Nanoparticles

The series resistance (Rs) controls the device performance significantly and for organic diode, the typical value of Rs is quite high. There are not many reports on the investigation of the high value of resistance in organic diodes. In this paper, we report that the trapping of charge carriers which is an important parameter to control the charge transport mechanism in organic solids is responsible for this high value of series resistance. In this paper effect of trap energy on Rs has been studied in the presence of TiO2 and ZnO nanoparticles on Phenosafranine (PSF) dye-based organic diode. It is already reported that by incorporating nanoparticles, trap energy is reduced which in turn increases the conductivity and efficiency of the device. So it is expected that trap energy has a strong influence on Rs. In this work we have measured Rs by using the Cheung Cheung method and the trap energy is also measured by analyzing the dc current. The value of Rs is related to trap energy. The extracted values of Rs are about 250.8 KΩ, 108.0 KΩ, and 98.4 KΩ respectively for only PSF, PSF+ZnO, and PSF+TiO2. It is also been observed that by incorporating nanoparticles the trap energy is reduced. The estimated values of the trap energy are about 0.090eV, 0.078eV ,0.072eV respectively for only PSF, PSF+ZnO, and PSF+TiO2. It has been observed that lowering of trap energy by incorporating TiO2 and ZnO reduces the value of Rs.

Effect of Zinc Oxide (ZnO) Nanoparticles on Interfacial Barrier Height and Band Bending of Phenosafranin (PSF) Dye-Based Organic Device

In this work, the interfacial barrier height and formation of band bending are studied in a phenosafranin (PSF) dye-based organic device and the effect of zinc oxide nanoparticles on both of these device parameters is estimated. The results show that interfacial band bending influences the barrier height at the metal–organic semiconductor contact. Indium tin oxide (ITO)-coated glass and aluminium are used as front electrode and back electrode, respectively, in the device. Analysis of the current–voltage (I–V) characteristics of the device show that the barrier height is reduced from 0.81 eV to 0.67 eV in the presence of ZnO nanoparticles. The barrier height is also calculated by using the Norde method, which shows a reduction from 0.83 eV to 0.69 eV in the presence of ZnO nanoparticles. Thus the results obtained using the two methods are consistent. The presence of ZnO nanoparticles also reduces the band bending from 0.218 eV to 0.183 eV at the metal—organic dye interface. As both parameters are reduced due to the incorporation of ZnO nanoparticles, it can be concluded that the charge injection process at the interface of the metal–organic layer is improved. The improvement of the charge injection process also results in lowering the threshold voltage of the organic device from 4 V to 3.5 V.

Polyethylene glycols affect electron transfer rate in phenosafranin-DNA complex.

Long distance electron transfer (ET) between small ligands and DNA is a much studied phenomenon and is principally believed to occur through electron (or hole) hopping. Several studies have been carried out in aqueous environments while in real biological milieu the DNA molecules experience a more dense and heterogeneous environment containing otherwise indifferent molecular crowders. It is therefore expected that the ET could get modified in the presence of crowding agent and to investigate that we have made elaborate studies on steady state and time-resolved (picosecond (ps) and femtosecond (fs)-resolved) emission properties of a phenosafranine (PSF) intercalated to calf thymus (CT) DNA in the presence of ethylene glycol (EG) and polyethylene glycols (PEG) of different chain lengths (PEG 200, 400 and 1000). The emission of PSF gets considerably quenched when intercalated to DNA; the quenching is released when PEGs are added into it. The structural integrity of the CT DNA has been established using circular dichroism spectroscopy. CD measurements have evidenced only marginal changes in the DNA structure upon the addition of PEGs. ps-Resolved fluorescence measurements show significant decrease in the contribution of the DNA induced quenched time-constant of PSF upon the addition of PEGs, however, fs-resolved measurements show less noticeable changes in the time constants. Our study shows that the electron hopping rate through the guanine base in DNA core remains unaffected whereas the 'through space' electron transfer process does get affected in the presence of molecular crowders.

Revealing the dynamics and energetics of interaction of a cationic biological photosensitizer within a bile salt aggregate.

The present investigation reports a detailed characterization of the interaction of a cationic photosensitizer, phenosafranin (PSF) with sodium deoxycholate (NaDC) bile salt aggregates based on spectroscopic and calorimetric techniques. Our explicit spectroscopic results not only establish the occurrence of PSF-NaDC binding interaction, but also reveal marked lowering of micropolarity at the interaction site (ET(30) = 55.97 kcal mol-1 in the presence of NaDC as compared to ET(30) = 63.1 kcal mol-1 in bulk aqueous buffer). A thorough mathematical analysis of the fluorescence depolarization results based on the two-step and wobbling in cone model yields critical insight into the complex rotational relaxation dynamics of the bound drug. The impartation of motional restriction on the PSF molecules within the bile salt aggregates is evidenced from enhancement of average rotational correlation time from <τr> = 136 ps in aqueous buffer to 1.11 ns with added NaDC (8.0 mM). This is further supported from a high value of the generalized order parameter (S = 0.81) as well as the diffusion coefficient (Dw = 1.40 × 1012 s-1). Furthermore, our extensive calorimetric investigation unveils the complicated thermodynamics of the interaction process in terms of predominant entropic contribution over the enthalpic part in the lower temperature regime (TΔS = 18.84 ± 1.13 kJ mol-1, ΔH = -5.82 ± 0.35 kJ mol-1 at 288 K) with subsequent reversal of the relative contributions with increasing temperature (TΔS = 7.54 ± 0.39 kJ mol-1, ΔH = - 17.09 ± 0.90 kJ mol-1 at 318 K). The instrumental role of the hydrophobic effect underlying the PSF-NaDC interaction is characterized by a negative heat capacity change (ΔCp = -364 J mol-1 K-1). An intriguing thermodynamic feature in terms of enthalpy-entropy compensation (with increasing temperature ΔG remains almost constant while ΔH and TΔS vary significantly) aptly corroborates the aforesaid argument and establishes an appreciable hydrophobic contribution to the overall binding energies.

Spectrophotometric determination of drug compounds in pure forms and in the pharmaceutical preparations

A “Simple, sensitive and rapid” spectrophotometric method for determination of drug compounds (I) “Dextromethorphan HBr (Dex) and (II) Trimethoprim (Tri)” in both pure forms and pharmaceutical formulations. These methods were based on the oxidation of the studied drugs in presence of acidic medium by a known excess of “N – Bromosuccinimide” as an oxidizing agent and subsequent determination of unreacted oxidant by reacting it with: (I) Phenosafranine (PS) dye [3,7-Diamino-5-phenylphenazin-5-ium chloride] to produce red product at λmax. 532 nm. The linearity range was found to be (6-56)μg/mL and molar absorptivity 4.686×103 L/mol.cm, correlation coefficient 0.9983 and the limit of detection 0.763 μg/ml, with slope, intercept and %RSD were 0.0133, 0.3069 and 0.367 respectively. (II) Crystal Violet (CV) dye [4 [bis [4 (dimethylamino) phenyl] methylidene] cyclohexa-2,5-dien-1-ylidene]-dimethylazanium;chloride to produce blue product at λmax. 590 nm. The linearity range was found to be (5-65)μg/ml and molar absorptivity 8.042×103 L/mol.cm, correlation coefficient 0.9980 and the limit of detection 1.07 μg/ml, with slope, intercept and %RSD were 0.0277, 0.2558 and 0.273 respectively. These methods were successfully applied for the determination of (Dex) and (Tri) in tablets formulations.

Interaction of a phenazinium-based photosensitizer with surface active ionic liquid micelles: Investigating the effect of cyclodextrins on SAIL micelles

The present study depicts a spectroscopic investigation on the binding interaction of a phenazinium-based photosensitizer, phenosafranin (PSF) with a micelle forming surface active ionic liquid (SAIL), 1-butyl-3-methylimidazolium octyl sulfate (Bmim Os). The steady-state as well as time-resolved spectroscopic results reveals the binding of PSF with the micelles of the ionic liquid. The modulations of the spectral properties of PSF on interacting with Bmim Os micelles have been further employed to monitor the effect of various cyclodextrins, αCD, βCD and γCD (with varying dimensions of the hydrophobic cavity), on the Bmim Os micellar aggregates. The effective disruption of the Bmim Os micelles in presence of CDs is confirmed from the reduced size of Bmim Os micelles with added CD as observed from the DLS results.

Binding interaction of phenazinium-based cationic photosensitizers with human hemoglobin: Exploring the effects of pH and chemical structure

The present study demonstrates a spectroscopic study on the interaction of two phenazinium-based cationic photosensitizers, namely, phenosafranin (PSF) and safranin-O (SO) with human hemoglobin (Hb) with particular emphasis on exploring the effects of pH and chemical structures of the dye molecules on the binding phenomenon. The protein (Hb) undergoes complex conformational transitions depending on the medium pH. The dye molecules exhibit a prominent fluorescence quenching following interaction with Hb under various experimental conditions (pH 3.5, 7.4, and 9.0). Our combined steady-state and time-resolved spectroscopic results provide persuasive evidence for static quenching mechanism showing that the dye:Hb interaction proceeds through ground-state complex formation. The meticulous investigations on the pH-dependence of the interaction of the dye molecules with the protein reveal a relatively strong binding of PSF as well as SO with Hb at physiological pH and alkaline pH, while the binding is weaker at acidic pH at which Hb predominantly exists as monomeric units. The binding constant for PSF:Hb interaction is K(PSF:Hb) = (1.09 ± 0.06) × 106 M−1 and that of SO:Hb interaction is K(SO:Hb) = (1.34 ± 0.07) × 105 M−1 at pH 7.4. However, at pH 3.5, the binding constant values are K(PSF:Hb) = (3.58 ± 0.18) × 104 M−1 and K(SO:Hb) = (4.29 ± 0.22) × 104 M−1 and at pH 9.0, the values are K(PSF:Hb) = (8.08 ± 0.40) × 104 M−1 and K(SO:Hb) = (5.07 ± 0.25) × 104 M−1. This depicts a much stronger binding interaction of the dyes with the native Hb at pH 7.4 compared to those at pH 3.5 and 9.0. Our results also unveil the effect of chemical structures of the dyes on the interaction phenomenon in the sense that the binding constant of PSF with Hb is found to be higher than that of SO at pH 7.4 and pH 9.0. The present study also focuses on exploring such important aspects of the interaction phenomena as the effect of binding of the dyes on the protein conformation by circular dichroism spectroscopy and probable binding location of the dyes within the protein scaffolds via micropolarity measurements and molecular docking simulation.

How Does Nanoconfinement within a Reverse Micelle Influence the Interaction of Phenazinium-Based Photosensitizers with DNA?

The major focus of the present work lies in exploring the influence of nanoconfinement within aerosol-OT (AOT) reverse micelles on the binding interaction of two phenazinium-based photosensitizers, namely, phenosafranin (PSF) and safranin-O (SO), with the DNA duplex. Circular dichroism and dynamic light-scattering studies reveal the condensation of DNA within the reverse micellar interior (transformation of the B-form of native DNA to ψ-form). Our results unveil a remarkable effect of the degree of hydration of the reverse micellar core on the stability of the stacking interaction (intercalation) of the drugs (PSF and SO) into DNA; increasing size of the water nanopool (that is, w0) accompanies decreasing curvature of the DNA duplex structure with the consequent effect of increasing stabilization of the drug:DNA intercalation. The marked differences in the dynamical aspects of the interaction scenario following encapsulation within the reverse micellar core and the subsequent dependence on the size of the water nanopool are also meticulously explored. The differential degrees of steric interactions offered by the drug molecules (presence of methyl substitutions on the planar phenazinium ring in SO) are also found to affect the extent of intercalation of the drugs to DNA. In this context, it is imperative to state that the water pool of the reverse micellar core is often argued to approach bulk-like properties of water with increasing micellar size (typically w0 ≥ 10), so that deviation from the bulk water properties is likely to be minimized in large reverse micelles (w0 ≥ 10). On the contrary, our results (particularly quantitative elucidation of micropolarity and dynamical aspects of the interaction) explicitly demonstrate that the bulk-like behavior of the nanoconfined water is not truly achieved even in large reverse micelles.

Interaction of phenazinium-based photosensitizers with the ‘N’ and ‘B’ isoforms of human serum albumin: Effect of methyl substitution

The present work is focused on exploring the interaction of two phenazinium-based biological photosensitizers, phenosafranin (PSF) and safranin-O (SO), with human serum albumin (HSA), with particular emphasis on the physiologically significant NB conformational transition of the protein on the dye:HSA interaction. In addition, the presence of methyl substitution on the planar phenazinium ring in SO paves way for looking into the effect of simple chemical manipulation (that is, methyl substitution on the dye nucleus) on the dye:protein interaction behavior as a function of various (pH-induced) isoforms of HSA. Our results reveal a significantly stronger binding interaction of SO with the B isoform of HSA (at pH9.0) compared to that with the N isoform (at pH7.4). On the contrary, the PSF:HSA interaction is found to be reasonably insensitive to the aforesaid conformational transition of HSA. However, the probable binding location of both the dye molecules (PSF and SO) is found to be within the protein scaffolds (domain IB). This is further quantified from the modulation of fluorescence decay behavior of the dyes within the protein scaffolds. It is important to note that the rotational relaxation behavior of the protein-bound dyes reveals an unusual ‘dip-rise-dip’, an observation not reported earlier. Such unusual anisotropy decay is meticulously analyzed by an associated (or multicomponent) exponential decay model which emphasizes on the fractional contributions from differential classes of fluorophore populations characterized by the fast (due to unbound or solvent exposed part of the fluorophore) and slow (due to embedded or bound part) motions, in combination with their different local mobilities. Furthermore, the translational diffusion of the dye molecules in the presence of the protein in different isoforms (N-form or B-form) at a single molecule level is also measured by Fluorescence Correlation Spectroscopy (FCS).

Endogenous Activation-Induced Delivery of a Bioactive Photosensitizer from a Micellar Carrier to Natural DNA.

The photophysics of phenosafranin (PSF), a member of the photosensitizer phenazinium family, has been explored in nonionic Triton X-165 (TX-165) micelle, calf thymus DNA (ctDNA), and a composite environment consisting of both micelle and DNA, using diverse spectroscopic techniques of both steady-state and time-resolved natures, to divulge the binding interactions of the probe with different hosts. The vivid experimental results demonstrate that PSF binds with both micelle and DNA; however, the binding affinity of the probe is much higher toward the DNA. When micelle-carried PSF comes in proximity to ctDNA, PSF gets released from the micellar environment and intercalates with the DNA base pairs. Endogenous activation, in terms of a higher binding affinity of PSF toward ctDNA relative to that toward the micelle, is ascribed to be responsible for this transfer. Thus, this article demonstrates endogenous transfer of a bioactive molecular probe from a micellar nanocarrier to natural DNA. As the carrier micelle (TX-165) does not perturb the structure of the DNA, this work proposes that it can be used promisingly for the purpose of safe delivery of drugs. The study is expected to stimulate the generation of and/or search for advanced micelle-based carrier systems for delivery of bioactive molecular systems to biological targets like DNA.

Relocation of a biological photosensitizer from non-ionic micellar carrier to DNA: A multispectroscopic investigation

Relocation of a bioactive photosensitizer, namely phenosafranin (PSF), from the phenazinium family, has been demonstrated from non-ionic micellar carrier to the DNA. For the purpose, interaction of micelle-bound PSF with calf thymus DNA (ctDNA) has been investigated vividly exploiting various spectroscopic techniques like absorption, steady state and time resolved emission, fluorescence anisotropy, circular dichroism etc. Experimental outcomes reveal that PSF binds strongly with both the micelle as well as the DNA. In the presence of DNA, however, relocation of the micelle-carried PSF occurs from the micelle to the DNA. Competitive binding of the probe between micelle and the DNA is assigned responsible for this relocation. Circular dichroism spectral measurements reflect that the DNA conformation remains intact in the presence of the micelle advocating that the non-ionic micelles can safely be used for the drug delivery purpose. The work is expected to encourage development of newer carriers for DNA targeted drug delivery.

DNA induced sequestration of a bioactive cationic fluorophore from the lipid environment: A spectroscopic investigation

The effect of calf-thymus DNA (ctDNA) on the lipid bound probe, formed by the cationic phenazinium dye phenosafranin (PSF) and the anionic lipid dimyristoyl-L-α-phosphatidylglycerol (DMPG), has been unearthed exploiting various spectroscopic techniques. Steady state and time-resolved fluorometric studies and measurements of circular dichroism and DNA helix melting temperature reveal that in the presence of DNA the probe is dislodged from the lipid environment and gets intercalated within the DNA helix. The work qualitatively illustrates that the anionic lipid can be used as a potential nanocarrier for delivering the cationic drugs to the most relevant biomacromolecular target, DNA.

A comparative study on the interaction of phenazinium dyes with low pH induced protonated structure and B-form structure of naturally occurring deoxyribonucleic acid

The interaction of two phenazinium dyes namely Phenosafranine (PSF) and Safranin T (ST) with right-handed B-form and left-handed protonated form of Calf Thymus (CT) DNA was investigated using different spectroscopic techniques. Both the dyes have been shown to bind strongly to the right-handed B-form of DNA by the mechanism intercalation as revealed from fluorescence quenching, circular dichroism (CD) and viscosity measurement. From circular dichroic studies it was evidenced that both of them convert the low pH induced left-handed protonated form of DNA back to the bound right-handed form. Scatchard analysis showed that both the dyes bound strongly to B-form of DNA in a non-cooperative manner. In case of protonated form, there was sequential conversion of the polynucleotide from left-handed to the bound right-handed conformation. Our results suggest that the binding environment of the dyes in the two forms of DNA is similar and our data predict that PSF is more effective in the conversion than ST. Experimental data enabled the calculation of the number of base pairs of protonated-form that adopted a right-handed conformation for each bound dye. Our data revealed that PSF is more effective in the conversion compard to that of ST. These results are attributed to greater steric crowd in ST compared to PSF which restricts the former to intercalate between DNA base pairs. The results of these studies allow a better understanding of dye-polymorphic nucleic acid interactions at a molecular level.

Functionalization of cubic mesoporous silica SBA-16 with carboxylic acid via one-pot synthesis route for effective removal of cationic dyes

In this work, we demonstrate that a high density of COOH groups loading, up to 60mol% based on silica, is successfully incorporated into SBA-16 via a one-pot synthesis route, which involves co-condensation of carboxyethylsilanetriol sodium salt (CES) and tetraethylorthosilicate (TEOS) templated by Pluronic F127 and P123 in an acidic medium. A variety of characterization techniques are performed to confirm quantitative incorporation of carboxylic groups into ordered cubic mesostructures. These functionalized materials are used to effectively remove two cationic dyes methylene blue (MB) and phenosafranine (PF) with the maximum adsorption capacities of 561 and 519mgg−1, respectively, at pH 9. The zeta potential results reveal that the electrostatic interactions between cationic dye molecule and negatively charged surface of the adsorbent play a crucial role in their high adsorption capacities. For a binary component system consisting of MB and PF, competitive adsorption of these two dyes is observed with adsorption capacity values slightly lower than those of the corresponding single dye systems. The dye adsorbed material can be easily regenerated by simple acid washing and be reused for five times with MB removal efficiency still up to 98.6%, showing its great potentials in environmental remediation.

Binding interaction of differently charged fluorescent probes with egg yolk phosphatidylcholine and the effect of β-cyclodextrin on the lipid–probe complexes: A fluorometric investigation

Interaction of cationic phenosafranin (PSF), anionic 8-anilino-1-naphthalene sulfonate (ANS) and non-ionic nile red (NR) have been studied with the zwitterionic phospholipid, egg yolk L-α-phosphatidylcholine (EYPC). The study reveals discernible binding interactions of the three fluorescent probes with the EYPC lipid vesicle. Once the binding of the probes with the lipid is established, the effect of cyclic oligosaccharide, β-cyclodextrin (β-CD), on these lipid bound probes has been investigated. Different fluorometric techniques suggest that addition of β-CD to the probe–lipid complexes leads to the release of the probes from the lipid medium through the formation of probe–β-CD inclusion complexes. A competitive binding of the probes between β-cyclodextrin and the lipid is ascribed to be responsible for the effect. This provides an easy avenue for the removal of the probe molecules from the lipid environment. Extension of this work with drug molecules in cell membranes is expected to give rise to a strategy for the removal of adsorbed drugs from the cell membranes by the use of non-toxic β-cyclodextrin.

Ordered cubic mesoporous silica KIT-5 functionalized with carboxylic acid groups for dye removal

Cubic cage-type KIT-5 mesoporous silica functionalized with carboxylic acid (–COOH) groups, ranging from 0 to 45 mol% based on silica, were synthesized via co-condensation of tetraethyl orthosilicate (TEOS) and carboxyethylsilanetriol sodium salt (CES) in the presence of Pluronic F127 in acidic media. The materials thus obtained were characterized by powder X-ray diffraction, nitrogen sorption, transmission electron microscopy, FTIR, thermogravimetric analysis, acid–base titration, and solid-state NMR measurements. The –COOH functionalized KIT-5 was used to adsorb different types of dyes such as phenosafranine (PF), methylene blue (MB), orange II (OII) and rhodamine B (RhB). The –COOH functionalized KIT-5 materials exhibited excellent adsorption capacities for cationic PF and MB, and amphoteric RhB in comparison to pure silica KIT-5, but the opposite for anionic OII. The adsorption was highly dependent on the electrostatic interaction between the adsorbent and the dye molecules. External mass transfer and intra-particle diffusion collectively control the adsorption process.