Asad Muhammad Khan

Redox Behavior of Anticancer Chalcone on a Glassy Carbon Electrode and Evaluation of its Interaction Parameters with DNA

The interaction of anticancer chalcone [AMC, 1-(4′-aminophenyl)-3-(4-N,N-dimethylphenyl)-2-propen-1-one] with DNA has been explored using electrochemical, spectroscopic and viscometric techniques. A shift in peak potential and decrease in peak current were observed in cyclic voltammetry and hypochromism accompanied with bathochromic shift were noticed in UV-Vis absorption spectroscopy. These findings were taken as evidence for AMC –DNA intercalation. A binding constant (K) with a value of 6.15 × 105 M−1 was obtained from CV data, which was also confirmed by UV-Vis absorption titration. Moreover, the diffusion coefficient of the drug with and without DNA (Db and Du), heterogeneous electron transfer rate constant (ko) and electron affinity (A) were also calculated from electrochemical data.

New catanionic surfactants with ionic liquid properties

A systematic study of the physico-chemical properties of a series of new catanionic surfactants with ionic liquid properties is reported. Importantly, by avoiding environmentally unfriendly halide and imidazolium based moieties highly tunable surfactant ionic liquids have been prepared.

Separation and recycling of nanoparticles using cloud point extraction with non-ionic surfactant mixtures

A viable cost-effective approach employing mixtures of non-ionic surfactants Triton X-114/Triton X-100 (TX-114/TX-100), and subsequent cloud point extraction (CPE), has been utilized to concentrate and recycle inorganic nanoparticles (NPs) in aqueous media. Gold Au- and palladium Pd-NPs have been pre-synthesized in aqueous phases and stabilized by sodium 2-mercaptoethanesulfonate (MES) ligands, then dispersed in aqueous non-ionic surfactant mixtures. Heating the NP-micellar systems induced cloud point phase separations, resulting in concentration of the NPs in lower phases after the transition. For the Au-NPs UV/vis absorption has been used to quantify the recovery and recycle efficiency after five repeated CPE cycles. Transmission electron microscopy (TEM) was used to investigate NP size, shape, and stability. The results showed that NPs are preserved after the recovery processes, but highlight a potential limitation, in that further particle growth can occur in the condensed phases.

A UV-Visible Study of Partitioning of Pyrene in an Anionic Surfactant Sodium Dodecyl Sulfate

The interaction of hydrophobic dye pyrene with sodium dodecyl sulphate (SDS), an anionic surfactant, was studied in the process of solubilization. Difference UV-Visible spectroscopy was used to carry out the study. The partition coefficient (Kx), and number of dye molecules incorporated per micelle (n) was calculated. High Kx value shows that pyrene is partitioned strongly from polar to nonpolar environment. Steady-state fluorescence spectroscopy is used to check the environment of the pyrene as it is a well-known fluorescent probe. Onset of slope in curves is used to determine the critical micelle concentration (CMC).

THERMODYNAMIC CHARACTERIZATION OF DEXAMETHASONE SODIUM PHOSPHATE AND ITS COMPLEX WITH DNA AS STUDIED BY CONDUCTOMETRIC AND SPECTROSCOPIC TECHNIQUES

Electrical conductivities were measured to calculate critical aggregation concentration (cac) of dexamethasone sodium phosphate (DSP) at various temperature from 298-313K with an increment of 5 K and in this way its thermodynamic parameters like Gibbs energy of aggregation ( ° ∆ agg G ) , enthalpy of aggregation ( ° ∆ agg H ) and entropy of aggregation ( ° ∆ agg S ) were estimated. The results demonstrate that DSP forms enthalpy driven aggregates through open association process. Furthermore, its interaction with DNA was studied by UV-Vis spectroscopy. The binding constant of DSP-DNA interaction was evaluated at 298 K and

Electrochemical behavior of 1-ferrocenyl-3-phenyl-2-propen-1-one on glassy carbon electrode and evaluation of its interaction parameters with DNA

The electrochemical behavior of 1-ferrocenyl-3-phenyl-2-propen-1-one (ferrocenylone) and its interaction with DNA was studied by a glassy carbon electrode using cyclic voltammetry (CV) technique. The results from CV were supported by UV-Visible spectroscopy performed under the similar conditions. The positive peak potential shift in CV and the bathochromic shift in the UV-Vis absorption spectra suggested an intercalative mode of binding. The binding constant (K = 1.39 ± 0.02 × 104 mol-1 L) and the binding site size (0.53 bp) were obtained from voltammetric data which leads to a standard Gibbs free energy change (ΔGo= -RT lnK) of -23.64 kJ mol-1 and hence indicated the spontaneity of the binding interaction. The values of binding constants obtained from UV-Vis absorption and CV measurements, 1.26 ± 0.01 × 104 and 1.39 ± 0.02 × 104 mol-1 L respectively, were in close agreement.

Association Behavior of 3,4-Dihydroxy-9,10-dioxo-2-anthracenesulfonic Acid Sodium Salt in Cationic Surfactant Medium Under Different pH Conditions

Ultraviolet (UV)-visible behavior of 3,4-dihydroxy-9,10-dioxo-2-anthracenesulfonic acid sodium salt (ARS) has been studied at pH 4.0, aqueous medium, and at pH 10.0. The effects of cetyl trimethylammoniumbromide (CTAB) on the UV-visible spectra of ARS have been evaluated qualitatively as well as quantitatively in the different concentration regions of CTAB. The shift in the UV-visible spectrum of ARS, due to CTAB, at its low concentration is comparable to the shift shown by the same at pH 10.0. In acidic and basic pH, effect of CTAB is significantly lowered on the UV-visible spectra than ARS in the purely aqueous medium. In aqueous and basic medium, lower values of partition and binding constant are obtained compared to the one obtained in acidic medium. Conductivity studies show that increasing dye concentrations have no effect on its partitioning behavior nevertheless critical micelle concentration of CTAB is lowered.

The effects of counterion exchange on charge stabilization for anionic surfactants in nonpolar solvents

HYPOTHESIS Sodium dioctylsulfosuccinate (Aerosol OT or NaAOT) is a well-studied charging agent for model poly(methyl methacrylate) (PMMA) latexes dispersed in nonpolar alkane solvents. Despite this, few controlled variations have been made to the molecular structure. A series of counterion-exchanged analogs of NaAOT with other alkali metals (lithium, potassium, rubidium, and cesium) were prepared, and it was expected that this should influence the stabilization of charge on PMMA latexes and the properties of the inverse micelles. EXPERIMENTS The electrophoretic mobilities of PMMA latexes were measured for all the counterion-exchanged AOT analogs, and these values were used to calculate the electrokinetic or ζ potentials. This enabled a comparison of the efficacy of the different surfactants as charging agents. Small-angle scattering measurements (using neutrons and X-rays) were performed to determine the structure of the inverse micelles, and electrical conductivity measurements were performed to determine the ionized fractions and Debye lengths. FINDINGS Sodium AOT is a much more effective charging agent than any of the other alkali metal AOTs. Despite this, the inverse micelle size and electrical conductivity of NaAOT are unremarkable. This shows a significant non-periodicity in the charging efficiency of these surfactants, and it emphasizes that charging particles in nonpolar solvents is a complex phenomenon.

pH Induced Partitioning and Interactions of Ciprofloxacin Hydrochloride with Anionic Surfactant Sodium Dodecyl Sulfate Using Ultraviolet and Fourier Transformed Infrared Spectroscopy Study

Ultraviolet (UV) and Fourier transformed infrared (FTIR) spectra of ciprofloxacin hydrochloride (Cpf) were studied under different pH conditions. The effect of aqueous, strong acidic, (pH 0.5–1.0) and a basic (pH 9.2) conditions on spectral behavior of Cpf was investigated in aqueous as well as in micellar environment of sodium dodecyl sulfate (SDS). Cpf shows partitioning from aqueous to micellar phase in a strong acidic as well as in a basic environment. Cpf shows no partitioning or binding to micelle in aqueous phase. Conductivity studies show that critical micelle concentration of SDS is increased with increasing concentration of Cpf. Different sites are responsible for binding under different pH conditions.

Biofilms in Endodontics—Current Status and Future Directions

Microbiota are found in highly organized and complex entities, known as biofilms, the characteristics of which are fundamentally different from microbes in planktonic suspensions. Root canal infections are biofilm mediated. The complexity and variability of the root canal system, together with the multi-species nature of biofilms, make disinfection of this system extremely challenging. Microbial persistence appears to be the most important factor for failure of root canal treatment and this could further have an impact on pain and quality of life. Biofilm removal is accomplished by a chemo-mechanical process, using specific instruments and disinfecting chemicals in the form of irrigants and/or intracanal medicaments. Endodontic research has focused on the characterization of root canal biofilms and the clinical methods to disrupt the biofilms in addition to achieving microbial killing. In this narrative review, we discuss the role of microbial biofilms in endodontics and review the literature on the role of root canal disinfectants and disinfectant-activating methods on biofilm removal.