Luqman Ali Shah

Efficient Photocatalytic Degradation of Norfloxacin in Aqueous Media by Hydrothermally Synthesized Immobilized TiO2/Ti Films with Exposed {001} Facets

In this study, a novel immobilized TiO2/Ti film with exposed {001} facets was prepared via a facile one-pot hydrothermal route for the degradation of norfloxacin from aqueous media. The effects of various hydrothermal conditions (i.e., solution pH, hydrothermal time (HT) and HF concentration) on the growth of {001} faceted TiO2/Ti film were investigated. The maximum photocatalytic performance of {001} faceted TiO2/Ti film was observed when prepared at pH 2.62, HT of 3 h and at HF concentration of 0.02 M. The as-prepared {001} faceted TiO2/Ti films were fully characterized by field-emission scanning electron microscope (FE-SEM), X-ray diffraction (XRD), high resolution transmission electron microscope (HR-TEM), and X-ray photoelectron spectroscopy (XPS). More importantly, the as-prepared {001} faceted TiO2/Ti film exhibited excellent photocatalytic performance toward degradation of norfloxacin in various water matrices (Milli-Q water, tap water, river water and synthetic wastewater). The individual influence of various anions (SO42-, HCO3-, NO3-, Cl-) and cations (K+, Ca2+, Mg2+, Cu2+, Na+, Fe3+) usually present in the real water samples on the photocatalytic performance of as-prepared TiO2/Ti film with exposed {001} facet was investigated. The mechanistic studies revealed that •OH is mainly involved in the photocatalytic degradation of norfloxacin by {001} faceted TiO2/Ti film. In addition, norfloxacin degradation byproducts were investigated, on the basis of which degradation schemes were proposed.

VUV-Photocatalytic Degradation of Bezafibrate by Hydrothermally Synthesized Enhanced {001} Facets TiO2/Ti Film

In the present study, a novel TiO2/Ti film with enhanced {001} facets was synthesized by the hydrothermal technique followed by calcination for studying the removal of bezafibrate (BZF), from an aqueous environment. The synthesized photocatalyst was characterized by FE-SEM, XRD, HR-TEM, and PL-technique. The second-order rate constant of (•)OH with BZF was found to be 5.66 × 10(9) M(-1) s(-1). The steady state [(•)OH] was measured as 1.16 × 10(-11) M, on the basis of oxidation of terephthalic acid. The photocatalytic degradation of BZF followed pseudo-first-order kinetics according to the Langmuir-Hinshelwood model (k1 = 2.617 mg L(-1) min(-1) and k2 = 0.0796 (mg L(-1))(-1)). The effects of concentration and the nature of various additives including inorganic anions (NO3(-), NO2(-), HCO3(-), CO3(2-), Cl(-)) and organic species (fulvic acid) and initial solution pHs (2, 4, 6, 9) on photocatalytic degradation of BZF were investigated. It was found that the nature and concentration of studied additives significantly affected the photocatalytic degradation of BZF. The efficiency of the photocatalytic degradation process in terms of electrical energy per order was estimated. Degradation schemes were proposed on the basis of the identified degradation byproducts by ultraperformance liquid chromatography.

Bone cement based on vancomycin loaded mesoporous silica nanoparticle and calcium sulfate composites.

A novel bone cement pellet, with sustained release of vancomycin (VAN), was prepared by mixing VAN loaded mesoporous silica nanoparticle (MSN) and calcium sulfate α-hemihydrate (CS) together. To improve the VAN loading ability, MSN was functionalized with aminopropyltriethoxysilane (APS) to give APS-MSN. The VAN loading content and entrapment efficiency of APS-MSN could reach up to 45.91±0.81% and 84.88±1.52%, respectively, much higher than those of MSN, which were only 3.91% and 4.07%, respectively. The nitrogen adsorption-desorption measurement results demonstrated that most of the VAN were in the pores of APS-MSN. The CS/VAN@APS-MSN composite pellet showed a strongly drug sustained release effect in comparison with CS control pellet. The in vitro cell assays demonstrated that CS/APS-MSN composite was highly biocompatible and suitable to use as bone cement. Furthermore, CS/VAN@APS-MSN pellet showed no pyrogenic effect and meet the clinical requirements on hemolytic reaction. These results imply that CS/VAN@APS-MSN was an ideal candidate to replace CS bone cement in the treatment of open fractures.

Polymer–paclitaxel conjugates based on disulfide linkers for controlled drug release

A novel redox-responsive polymer–drug conjugate (PDC) based on hydrophilic diblock copolymer covalently linked paclitaxel (PTX) via a disulfide linker was prepared and evaluated for intracellular drug delivery. The well-defined hydrophilic diblock copolymer, PEG-b-PHEMA, was synthesized via atom transfer radical polymerization of 2-(trimethylsilyloxyl)ethyl methacrylate (HEMA-TMS), using PEG-Br as a macroinitiator and CuBr/PMDETA as the catalytic system, followed by selectively hydrolyzing the trimethylsilane group to hydroxyl groups. Utilizing the hydroxyl groups as an active reaction site, paclitaxel was covalently conjugated onto the backbone of the diblock copolymer, with a disulfide linker as a spacer to bridge the copolymer and PTX, and the loading content of paclitaxel was 18.4 wt%. Due to the different solubility of segments in the polymer–drug conjugate, the amphiphilic PEG-b-P(HEMA-PTX) could self-assemble into spherical micelles in aqueous solution, with hydrophobic PTX as core and hydrophilic PEG chains as shell. The in vitro cytotoxicity experimental results showed that the diblock copolymer was biocompatible, with no obvious cytotoxicity, whereas the PEG-b-P(HEMA-PTX) conjugate showed glutathione-dependent cytotoxicity with higher cellular proliferation inhibition against glutathione monoester pretreated HeLa cells than that of the nonpretreated HeLa cells. We are convinced that polymer–drug conjugates based on disulfide linkers will be a promising platform for targeted intracellular controlled drug delivery in cancer therapy.

Fabrication of Ag and Au nanoparticles in cross-linked polymer microgels for their comparative catalytic study

Abstract Three dimensional cross-linked polymer microgels with temperature responsive N-isopropyl acrylamide (NIPAM) and pH sensitive methacrylic acid (MAA) were successfully synthesized by free radical emulsion polymerization with different amounts of MAA. Silver and gold nanoparticles with the size of 6.5 nm and 3.5 nm (±0.5 nm), respectively were homogeneously reduced inside these materials by chemical reduction method at pH 2.78 and 8.36 for the preparation of hybrid materials. The samples were characterized by FT-IR, DLS and TEM techniques. The catalytic activity of the hybrid materials was investigated for the reduction of 4-nitrophenol (4-NP) using NaBH4 as reducing agent by UV-Vis spectroscopy. The hybrid polymer network synthesized at pH 8.36 showed enhanced catalytic efficiency compared to the catalysts synthesized at pH 2.78. In this study, it has been stated that the catalyst activity strongly depends on the amount of MAA, pH value during synthesis and the type of entrapped metal nanoparticles.

Degradation of Acetaminophen in Aqueous Media by H2O2 Assisted Gamma Irradiation Process

In the present study, degradation of acetaminophen (ACT) aqueous solution was investigated up to an absorbed γ-irradiation dose of 1000 Gy. The effects of various additives on the degradation efficiency of ACT were also studied. The results showed that ACT degradation was increased with the increase of an absorbed dose. Based on spectrophotometric analysis, 82.5% degradation of the initial ACT concentration (9.98 × 10−5 M) was easily achieved at an absorbed dose of 1000 Gy. The decay of ACT followed pseudo-first order reaction kinetics at different initial concentrations. The radiation chemical yield (G-value) decreased with the increase of an absorbed dose, however at a specific absorbed dose G-values increased with the increase of ACT initial concentration. The addition of H2O2 in the range of 0.1–0.7% was effective for degradation of ACT. The degradation of ACT was inhibited in both acidic and basic solutions while maximium degradation effiency was acheived at nearly neautral solution pH, 7.6. The degradation process was markedly enhanced under oxidative conditions while strongly restrained under reductive conditions, which suggests the key role of oxidative radicals ( ̇OH) in the degradation of ACT.

Micellar Supported Ultrafiltration of Malachite Green: Experimental Verification of Theoretical Approach

Abstract This study pertains to theoretical aspect of membrane and surfactant supported ultrafiltration technique followed by experimental evaluation of rejection percentage (R%) and permeate flux (J). The organic dye malachite green (MG) was removed from water samples with help of micellar solution of sodium dodecyl sulfate (SDS) surfactant on account of effective surfactant-dye interaction. The MG removal from water was result of electrostatic force of attraction between Stern layer of SDS micelles and cationic MG in addition to hydrophobic-hydrophobic interaction. The regenerated cellulose membrane was used to retain enhanced MG-SDS micellar complex from polluted water in stirred ultrafiltration cell. R% of MG increases from 79.3%, 77%, 76% to 97.5%, 95%, 90% for 0.01, 0.1 and 0.2 mM concentrations, respectively. “J” decreases throughout the experiment on account of membrane plugging or concentration polarization. Hydrodynamic radius (Rh) of SDS surfactant was also determined at its post micellar concentrations by dynamic laser light scattering (DLLS) that shows high rejection percentage with increased Rh values.

Degradation of Crystal Violet Dye by Fenton and Photo-Fenton Oxidation Processes

Abstract The oxidative degradation of CV dye in aqueous media has been evaluated using Fenton (Fe2+/H2O2) and photo-Fenton (Fe2+/H2O2/UV) processes. Various operational parameters like H2O2 dosages, Fe2+ dosages and [CV]0 were optimized of both Fenton and photo-Fenton processes for the removal of CV dye from aqueous media. Kinetic results indicated that photo-Fenton process (kobs=0.0097 min−1, t1/2=71.45 min) is more effective than Fenton process (kobs=0.0074 min−1, t1/2=93.66 min). Second order rate constant of ˙OH radical with CV dye was calculated to be 3.96×109 M−1s−1. De-methylated organic intermediates of CV dye detected by LC-MS and some other intermediates like CH3COO−, HCOO−, NH4+ and Cl− were identified by ion-chromatography.

The Role of Non-Ionic Surfactants in Solubilization and Delivery of Sparingly Soluble Drug Naproxen Sodium (NS): A Case Study

Abstract Nonsteroidal anti-inflammatory hydrophobic drugs (NSAIDs) are amongst the most commonly given categories of drugs worldwide in the treatment of pain, irritation and some of them even fever in many conditions. Critical micelle concentration of NSAIDs with Naproxen sodium (NS) and its mixture with non-ionic surfactants i.e. Tween 20, Tween 40 and Tween 60 was investigated at 293 K, 303 K, 313 K and 323 K at different concentrations using surface tension and dynamic laser light scattering (DLS) techniques. Due to amphiphilic behaviour in aqueous solution NS form aggregates at sufficiently high concentration. Thermodynamic/adsorption properties like free energy of micellization (ΔGmic), enthalpy of micellization (ΔHmic), entropy of micellization (ΔSmic), Γmic and area per molecule (A2) of NS in the presence of surfactants were also measured at different temperatures. The results showed that the presence of surfactants favoured the ΔGmic and become more enhanced with increase in temperature. Further the solubility of drug is more favourable with increase in polyethylene chain in basic surfactant molecules i.e. 20–60, which indicates that Tween-60 enhanced the solubility of NS more comparatively to Tween-40 and Tween-20 and may be applied as best additive for solubilisation of NS.