Inas H. Hafez

Unusually Large Hysteresis of Temperature-Responsive Poly(N-ethyl-2- propionamidoacrylamide) Studied by Microcalorimetry and FT-IR

We reported here the full characterization of the hysteresis of the phase transition behavior of an aqueous solution of poly(N-ethyl-2-propionamidoacrylamide) (PNEPA), which has a unique alpha,alpha-disubstituted structure, by using microcalorimetry and FT-IR. Phase transition temperatures near the thermodynamic equilibrium were determined by extrapolating the scanning rate of the microcalorimetry to zero. The calculated hysteresis from the phase transition temperature was unusually very large (approximately 8 degrees C). FT-IR analysis indicated that the large hysteresis of PNEPA resulted from a coupling of intra-/intermonomeric unit hydrogen bonds, which is known to occur in a beta-sheet of proteins but has never been reported in temperature-responsive polymers. The effects of the molecular weight and polymer concentration on the hysteresis were studied by using fractionated PNEPAs and it was found that a low molecular weight and a low concentration enhanced the hysteresis.

Design of a multifunctional nanohybrid system of the phytohormone gibberellic acid using an inorganic layered double-hydroxide material.

To offer a multifunctional and applicable system of the high-value biotechnological phytohormone gibberellic acid (GA), a nanohybrid system of GA using the inorganic Mg-Al layered double-hydroxide material (LDH) was formulated. The ion-exchange technique of LDH was applied to synthesize the GA-LDH hybrid. The hybrid structure of GA-LDH was confirmed by different spectroscopic techniques. The nanohybrid size was described by SEM to be ∼0.1 μm. The GA-LDH nanohybrid structure was the key parameter that controlled GA properties. The layered molecular structure of LDH limited the interaction of GA molecules in two-dimensional directions. Accordingly, GA molecules did not crystallize and were released in an amorphous form suitable for dissolution. At various simulated soil solutions, the nanohybrids showed a sustained release process following Higuchi kinetics. The biodegradation process of the intercalated GA showed an extended period of soil preservation as well as a slow rate of degradation.

Tuning surface accessibility and catalytic activity of Au nanoparticles through immobilization within porous-organic polymers

Herein, we outline a facile and promising approach in which microporous organic polymer matrices were constructed from their molecular building blocks, in the presence of surface-functionalized Au nanoparticles (AuNPs) as one component of the system. This approach permitted the construction of microporous networks around AuNPs and consequently allowed controlling access of small guest molecules to the surface of the AuNPs. Gas sorption measurements confirmed the permanent microporosity of the composites, and furthermore demonstrated interdependence between the size and degree of connectivity of the molecular linkers, the amount of AuNPs added to the initial reaction mixture, and porosity of the composites. A clear electrocatalytic activity dependence on the molecular size of the substrate and pore system of the host matrix is demonstrated. Of special significance is the enhanced catalytic activity of the investigated composites towards borohydride oxidation (mass activity of 8.8–12 mA mg−1) as compared to flat Au electrode (1.6 mA mg−1). These results show a versatile pathway to utilize decorated AuNPs, as functionalized building units, in construction of porous solids with hybrid composition and tunable properties.

FORMULATION OF POLYACRYLIC ACID-LAYERED DOUBLE HYDROXIDE COMPOSITE SYSTEM AS A SOIL CONDITIONER FOR WATER MANAGEMENT

An efficient strategy of soil-conditioner application was offered by incorporating a high molecular weight organic polymer (polyacrylic acid; PAA) into a soil-friendly inorganic material (layered double hydroxide; LDH). The prepared materials were characterized by different spectroscopic techniques to confirm the formed nanocomposite structure. The SEM images captured the morphological ability of PAA-LDH nanocomposites to absorb and keep water molecules during soil-water application. The IR analysis indicated an electrostatic grafting process between PAA units and LDH moieties. The platform of PAA-LDH nanocomposite formulation stabilized the soil aggregates and improved the water-stability.

Versatile Nanocomposite Formulation System of Non-Steroidal Anti-Inflammatory Drugs of the Arylalkanoic Acids

Nanotechnology has shown tremendous promise in target-specific delivery of drugs in the body. Although passive and active targeted-drug delivery has addressed a number of important issues, additional properties that can be included in nanocarrier systems to enhance the bioavailability of drugs at the disease site, and especially upon cellular internalization, are very important. Upon the support of nanotechnology, scientists in hybrid research field could deal with the combination of different substances from macroscopic to molecular level, and create novel materials with intentional functionalities. Thus, the hybridization technology can be adapted to create efficient drug nanocarriers. Hybridized drug-carriers can be made from a variety of organic and inorganic materials including biodegradable polymers and inorganic clays. The selection of material for development of nanoparticle carriers is mainly dictated by the desired diagnostic or therapeutic goal, type of payload, material safety profile, and the route of administration. Among the various approaches for exploiting developments in drug nanotechnology, layered double hydroxide (LDH) materials offer some unique advantages, as their medical properties support their different pharmaceutical applications. By the introduction of drugLDH nanocomposite platform, the delivery system becomes an active participant rather than passive vehicle in the optimization of drug-therapy. In this chapter, we are going to focus on the intercalation chemistry of LDH, the different LDH nanocomposites formulation strategies, and the physical and chemical properties of drug-LDH nanocomposites. In addition, we discuss the different drug-LDH pharmaceutical applications such as drug solubility, dissolution behavior, and the delivery of some nonsteroidal anti-inflammatory drugs (NSAIDs) to its active target-sites.

Tailoring of a Potential Nanoformulated Form of Gibberellic Acid: Synthesis, Characterization, and Field Applications on Vegetation and Flowering

Nanoformulation of agrochemicals has become a potential choice to improve the physicochemical properties, enhance the utilization efficiency, and reduce the side effects and ecotoxicity of many hazardous chemicals. Here, we tailored a new formulation platform for gibberellic acid (GA) using the layered double hydroxides (LDH) as a potential carrier. Typically, we synthesized, characterized, and potentially applied the newly nanoformulated form of GA on the quantity and quality properties of Dendranthema grandiflorum cultivar. We also evaluated the synergetic effect of the carrier LDH on the release behavior of GA, showing a remarkable impact on the utilization efficiency of GA. The nanohybrid structure of GA also showed an enhanced thermal stability and safe preservation for the incorporated moieties. Taking into account the hazardous effect of free GA on the environment and human health, the hybrid technique of GA is one of the best choices among all of the studied protocols.

ADVANCED NANOHYBRID FORMULATION OF THE SPARINGLY SOLUBLE DRUG SULINDAC FOR CONTROLLED RELEASE STUDIES

We offered an advanced nanohybrid formulation system of Sulindac (SUL) based on layered double hydroxide (LDH) nanoparticles. The formulated materials were characterized by X-rays, Infrared and SEM techniques to confirm the nanohybrid structure. The drug incorporation ratio was determined to be 45%. The drug solubility was improved after the LDH nanohybrid formation. The anion-exchange mechanism of LDH supported the dissolution process for the intercalated SUL.

INTERACTION BETWEEN DRUGS AND BIOMEDICAL MATERIALS I: BINDING POSITION OF BEZAFIBRATE TO HUMAN SERUM ALUBMIN

The interaction between bezafibrate (BZF) and human serum albumin (HSA) was investigated by equilibrium dialysis. Since the binding constant of BZF to HSA was independent of ionic strength and decreased with the addition of fatty acid, the interaction between BZF and HSA was considered to be due to hydrophobic mechanism. Chemical shifts in 1H-NMR spectra of BZF were independent of the concentration of BZF and addition of HSA. Spin-lattice relaxation time (T1) and spin-spin relaxation time (T2) of respective protons of BZF were independent of the concentration, but depended on the concentration of HSA added. The binding position of BZF to HSA was considered to involve the hydrophobic aromatic moiety of BZF from the ratio of spin-spin relaxation rates (1/T2) of BZF bound to HSA and free BZF.

CONTROL OF NANOPARTICLE SIZE, CRYSTAL STRUCTURE AND GROWTH OF LAYERED DOUBLE HYDROXIDE BY HYDROTHERMAL TREATMENT

Here, we showed the effect of hydrothermal treatment and aging process of urea hydrolysis on crystal structure, particle size and particle size distribution of Mg-Al layered double hydroxide (LDH) materials. The obtained materials were characterized by X-ray crystallography and scanning electron microscopy. The studied synthetic parameters showed a great influence on the physicochemical properties of the selected LDH materials. At insufficient conditions of hydrothermal treatments, the formed LDH particles were amorphous and the non-LDH phases dominated the X-ray diffraction chart. The crystal growth increased with increasing hydrothermal temperature. Aging process improved the crystal morphology up to18 hours, while further aging destroyed the LDH particles. The increase of hydrothermal aging led to a wide particle size distribution.