Differential scanning calorimetry

Synthesis of metallic and semiconductor nanoparticles through physical and chemical routes has been extensively reported. However, green synthesized metal nanoparticles are currently in the limelight due to the simplicity, cost-effectiveness and eco-friendliness of their synthesis. This study explored the use of aqueous leaf extract of Costus afer in the synthesis of silver nanoparticles (CA-AgNPs). The optical and structural properties of the resulting silver nanoparticles were studied using UV-visible spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transform infra-red spectrophotometer (FTIR). TEM images of the silver nanoparticles confirmed the existence of monodispersed spherical nanoparticles with a mean size of 20 nm. The FTIR spectra affirmed the presence of phytochemicals from the Costus afer leaf extract on the surface of the silver nanoparticles. The electrochemical characterization of a CA-AgNPs/multiwalled carbon nanot...

Neuronal membrane damage is related to the early impairments appearing in Alzheimer's disease due to the interaction of the amyloid β-peptide (Aβ) with the phospholipid bilayer. In particular, the ganglioside GM1, present with cholesterol in lipid rafts, seems to be able to initiate Aβ aggregation on membrane. We studied the thermodynamic and structural effects of the presence of GM1 on the interaction between Aβ and liposomes, a good membrane model system. Isothermal Titration Calorimetry highlighted the importance of the presence of GM1 in recruiting monomeric Aβ toward the lipid bilayer. Light and Small Angle X-ray Scattering revealed a different pattern for GM1 containing liposomes, both before and after interaction with Aβ. The results suggest that the interaction with GM1 brings to insertion of Aβ in the bilayer, producing a structural perturbation down to the internal layers of the liposome, as demonstrated by the obtained electron density profiles.

A systematic experimental investigation of contact drying operation was carried out in an agitated Charles Thompson filter-dryer. In this study, the effect of process parameters (wall temperature, impeller speed, fill level) on the drying performance in the filter-dryer is quantified as a function of bed temperature and solvent concentration. In addition, the impact of drying conditions on the particle size distribution was also examined. It was found that in the range of parameters investigated, drying rate increased with wall temperature and reduced bed depth. The effect of impeller speed was variable where favorable drying conditions were strongly dependent on the particle properties. Moreover, decrease in the particle size was evident with an increase in impeller speed and decrease in the bed depth due to increased collision frequency and reduction in the fill volume both leading to particle attrition respectively. Besides, the average wall to solid heat transfer coefficient is also estimated for variable operating conditions.

Ion exchange reactions between the Dion-Jacobson-type, triple-layered perovskite RbCa2Nb3O10 and calcium, strontium, and barium cations were investigated. Exchange occurs in all systems, but only the strontium and barium systems form stable compounds. The final products, Rb1−xSrx/2Ca2Nb3O10 (x = 0.45) and Rb1−xBax/2Ca2Nb3O10 (x = 0.55), are isostructural with the parent. Unit cells contract upon replacement of rubidium with the smaller, more highly charged cation. The effect of layer contraction in directing the extent of exchange is discussed.

The aim of this study was to evaluate the effects of preparation method and the type of surfactant on the properties of cephalexin (CPX) microspheres in order to obtain delivery systems suitable for the treatment of dairy mastitis. Microspheres were obtained using various preparation conditions and their physicochemical characteristics such as size, loading efficiency, morphology, and drug crystallinity were investigated. Antibacterial activity of microspheres from the optimum preparation condition was also studied. CPX microspheres were prepared by two different W/O/W emulsion solvent evaporation methods using PLGA as a matrix forming polymer. Several types of surfactants including nonionic, cationic, and anionic at different concentrations were used for preparation of the particles. The type and concentration of surfactant did neither affect the size nor morphology of the microspheres but showed a pronounced effect on the CPX encapsulation efficiency. It was found that Tween 80 showed the highest drug encapsulation efficiency (66.5%). Results from X-ray diffraction diffractograms and differential scanning calorimetry thermograms indicated that CPX entrapped in these microparticles was amorphous. Assessment of antibacterial activity showed that the obtained CPX microspheres exhibited good inhibition with minimum inhibitory concentration and minimum bactericidal concentration values of 128 µg/mL and 2,048 mg/mL against Staphylococcus aureus ATCC 25923, 512 µg/mL and 4,096 mg/mL against Escherichia coli ATCC 25922, respectively.

Carotenoids are a group of phytochemicals that are recognized as playing an important role in the prevention of several degenerative diseases due to their antioxidant activity. The low water-solubility and poor photostability of β-carotene, a potentially important dietary antioxidant, prompted us to investigate β-carotene complexes able to increase its water solubility as well as its photostability in aqueous solution. In this work we have used humic acid in order to synthesize β-carotene–humic acid complexes in different ratios.Complexes were characterized by FT-IR and DSC. β-Carotene determination were performed by HPLC and antioxidant activity of β-carotene, humic acid and the complexes were determined by the TEAC method. The formulation β-carotene–humic acid 2:1 showed the highest photostability and water solubility. The antioxidant activity of the complexes was about 20 times lower than “free” β-carotene, suggesting a decreased chemical reactivity of the carotenoid in the complex. We showed that complexation of β-carotene with humic acids was able to increase its water solubility and photostability, and to affect the antioxidant activity of β-carotene after inclusion in HAs. This work provides a useful tool to avoid antioxidants photodegradation and oxidation by radicals, thus maintaining their biological activity.

A combination of the complex (1-Me-indenyl)(PPh3)NiCCPh and methylaluminoxane (MAO) catalyzes the polymerization of 1-ethynylpyrene to fairly soluble cis-poly(1-ethynylpyrene). The polymers have been characterized by IR, solid state 13C and 1H NMR, and UV-Vis (λmax at 346nm) spectroscopy, and studied by thermogravimetric analysis (T10∼285–392°C), differential scanning calorimetry, and size exclusion chromatography (Mw∼103–104Da; Mw/Mn∼2). The thermal and optical properties of these cis-polymers

The present study aimed to produce verapamil hydrochloride-loaded solid lipid microparticles (SLM) by the w/o/w emulsion solvent evaporation technique, using diethyl ether as solvent phase, glyceryl monostearate as biodegradable polymer and Span 60 as surfactant. SLM of spherical shape were prepared by simple dilution of the emulsion with water. To increase the lipid load the process was conducted at 50 degrees C, and in order to reach sub-micron size, a high-shear homogenizer was used. The encapsulation efficiency of prepared SLM reached 74.29 +/- 0.76%. Particle size (98.55 +/- 1.42 microm), surface morphology (spherical) and drug loading efficiency (18.57 +/- 1.25% w/w) were investigated. And optimization of drug polymer ratio (3:1), nature and concentration of emulsion stabilizer in the external aqueous (0.1%), phase viscosity of external aqueous phase (0.5%), volume of external aqueous phase and stirring rate (1000 rpm) were detected. Analysis of microsphere content after proce...