Solid lipid nanoparticles with and without hydroxypropyl-β-cyclodextrin: a comparative study of nanoparticles designed for colonic drug delivery

New solid lipid nanoparticles (SLN), composed of Compritol ATO888 (C) and hydroxypropyl-β-cyclodextrin (HP), were developed in order to study a new colon-specific formulation for diclofenac sodium (D) delivery. The prepared batches differ from each other by the molecular ratio between HP and D and by the composition of the matrix. Nanoparticles composed of an exclusively lipid matrix and nanoparticles with an oligomeric and lipid matrix were compared in order to establish the effect of both components on the drug delivery tests performed. The SLN preparation method was based on the oil/water hot homogenization process. Emulsions produced were cooled at room temperature and lyophilized in order to obtain dried nanoparticles; possible damage to nanoparticle shape and size was avoided by the addition of cryoprotectants to the aqueous dispersion of nanoparticles before exsiccation. An in vitro toxicity study was performed using CaCo(2) cells to establish the safety of the prepared SLN. Data obtained showed that production method studied guarantees emulsions composed of nanosized drops which can be dried by lyophilization into SLN with a size range of 300-600 nm. In vitro and ex vivo tests demonstrated that dried SLN can be considered as colon delivery systems; however, the matrix composition as well as the presence of cryoprotectant on their surface influences the release and permeation rate of D. The in vitro toxicity studies indicated that the SLN are well tolerated.     

Effect of protein concentrations of bovine serum albumin and γ-globulin on the frictional response of a cobalt-chromium femoral head

The study aims to identify the concentration-dependent role of bovine serum albumin (BSA) and γ-globulin in the lubricating ability of a cobalt-chromium femoral head. The frictional coefficients of the cobalt-chromium femoral head decreased with increasing BSA concentrations from 10 to 40 mg/ml and showed statistical differences between any of the BSA concentration groups, except between the 30 and 40 mg/ml concentration groups. In γ-globulin, the frictional coefficients significantly decreased at concentrations of 2.5 and 5.0 mg/ml as compared with the PBS control group, but significant increases were observed at 7.5 and 12.5 mg/ml. These results suggest that the friction of the cobalt-chromium femoral head is dependent on the concentration of both BSA and γ-globulin. However, there is a maximum concentration for BSA to act as an effective boundary lubricant, while the lubricating ability of γ-globulin is most effective in the physiological concentration range within human synovial fluid.     

Ion and molecular recognition effects on the crystallisation of bovine serum albumin–salt mixtures

The effects of various bio-medically important salts Na, K, Li, Mg, Ca, Ni, Co, Cr, Fe and Cl on the dendritic or simple crystallisation of aqueous solutions of Bovine Serum Albumin have been investigated by contact or non-contact mode Atomic Force Microscopy. Four classes of structure are observed depending on the nature of the cation; a) unstructured protein–salt aggregates, b) large scale protein–salt meso-composites, c) mixed salt–protein gels, and d) microscopically phase separated systems.     

Synthesis,characterization and bactericidal activity of silica/silver core–shell nanoparticles

Silica/silver core–shell nanoparticles (NPs) were synthesized by coating silver NPs on silica core particles (size ~300 ± 10 nm) via electro less reduction method. The core–shell NPs were characterized for their structural, morphological, compositional and optical behavior using X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis and UV–Visible spectroscopy, respectively. The size (16–35 nm) and loaded amount of silver NPs on the silica core were found to be dependent upon reaction time and activation method of silica. The bactericidal activity of the NPs was tested by broth micro dilution method against both Bacillus subtilis (gram positive) and Escherichia coli ATCC25922 (gram negative) bacterium. The bactericidal activity of silica/silver core–shell NPS is more against E. coli ATCC25922, when compared to B. subtilis. The minimal inhibitory concentration of the core–shell NPs ranged from 7.8 to 250 μg/mL and is found to be dependent upon the amount of silver on silica, the core. These results suggest that silica/silver core–shell NPs can be utilized as a strong substitutional candidate to control pathogenic bacterium, which are otherwise resistant to antibiotics, making them applicable in diverse medical devices.     

Retention behavior of ionizable isomers in reversed-phase liquid chromatography: a comparative study of porous graphitic carbon and octadecyl bonded silica

The retention behaviors of 36 positional isomers of ionizable substituted benzene compounds have been compared on two different packing materials: porous graphitic carbon (PGC) and octadecyl bonded silica (ODS) using 35% aqueous acetonitrile as the mobile phase. The effect of the mobile phase pH on the solute retention was studied over a range of pH values from pH 2.0 to 7.0. The retention as a function of pH was modeled using equations based on solute ionization. With PGC, the theoretical equations fitted the observed retention data for each class of solute, indicating that the retention mechanism was uniform over the whole pH range. However, with ODS, only the acidic solutes showed agreement with the theoretical model; for the amine-containing compounds, serious deviations from the theory were observed, suggesting that strongly acidic silanols gave added retention at low mobile phase pH. Overall, PGC demonstrated a higher selectivity toward positional isomers than ODS. This was attributed to the greater steric discriminating ability arising from the flat surface of the PGC compared with the more fluid nature of the ODS bonded phase.     

Preparation and characterization of marine sponge collagen nanoparticles and employment for the transdermal delivery of 17β-estradiol-hemihydrate

Background: Transdermal administration of estradiol offers advantages over oral estrogens for hormone replacement therapy regarding side effects by bypassing the hepatic presystemic metabolism. Aim: The objective of this study was to develop nanoparticles of Chondrosia reniformis sponge collagen as penetration enhancers for the transdermal drug delivery of 17β-estradiol-hemihydrate in hormone replacement therapy. Method: Collagen nanoparticles were prepared by controlled alkaline hydrolysis and characterized using atomic force microscopy and photon correlation spectroscopy. Estradiol-hemihydrate was loaded to the nanoparticles by adsorption to their surface, whereupon a drug loading up to 13.1% of sponge collagen particle mass was found. After incorporation of drug-loaded nanoparticles in a hydrogel, the estradiol transdermal delivery from the gel was compared with that from a commercial gel that did not contain nanoparticles. Results: Saliva samples in postmenopausal patients showed significantly higher estradiol levels after application of the gel with nanoparticles. The area under the curve (AUC) for estradiol time–concentration curves over 24 hours was 2.3- to 3.4-fold higher and estradiol levels 24 hours after administration of estradiol were at least twofold higher with the nanoparticle gel. Conclusions: The hydrogel with estradiol-loaded collagen nanoparticles enabled a prolonged estradiol release compared to a commercial gel and yielded a considerably enhanced estradiol absorption. Consequently, sponge collagen nanoparticles represent promising carriers for transdermal drug delivery.     

Preparation and characterization of monodisperse silica nanoparticles via miniemulsion sol–gel reaction of tetraethyl orthosilicate

Monodisperse silica nanoparticles were prepared via miniemulsion sol–gel reaction of tetraethyl orthosilicate (TEOS). Hexadecane (HD) or hexadecyltrimethoxysilane was used as costabilizer to effectively retard the Ostwald ripening process involved in TEOS miniemulsion. The Ostwald ripening behavior was characterized by dynamic light scattering (DLS), and it was adequately described by the modified Kabal’nov equation. The miniemulsion sol–gel reaction of TEOS/HD with a volume fraction (φ _c) of 0.024 at 80 °C is stable in the pH range 6–10. By contrast, gelation of reacting miniemulsions occurs at 70 and 100 min at pH 4 and 5, respectively. The weight-average silica particle size (d _w) of colloidal products prepared at 80 °C and pH 7 decreases from 59 to 36 nm with low polydispersity index (PDI, in the range 1.02–1.03), determined by transmission electron microscopy, when the φ _c of HD increases from 0.024 to 0.23. At constant φ _c (0.024), the resultant silica nanoparticles show larger d _w (83 nm) and PDI (1.35) for the TEOS/HD system at pH 10 as compared to the counterpart of pH 7. Furthermore, for the TEOS/HD system at pH 7 and low φ _c (0.024), d _w increases significantly with temperature being increased from 25 to 80 °C. By contrast, the effect of temperature on silica nanoparticle size becomes insignificant when a high level of HD (φ _c = 0.23) is used. Zeta potential measurements and field emission scanning electron microscopy were used to characterize the surface charge density and morphology of resultant silica nanoparticles.     

Effect of bovine serum albumin on the functionality and structure of catanionic surfactant at air–buffer interface

Interaction of bovine serum albumin (BSA) with the solvent spread monolayer of a catanionic surfactant, octadecyltrimethylammonium dodecylsulfate, (C₁₈TA⁺DS^?) at the air–buffer interface was investigated by measuring the surface pressure with time and change in surface area. Dipalmitoylphosphatidylcholine (DPPC) was used as reference. Kinetics of BSA desorption from the interface to the buffer subphase, that of C₁₈TA⁺DS^? and DPPC through their interaction with BSA, were also studied at different BSA concentrations (in the subphase) and surface pressures. Surface pressure (π)–area (A) isotherms (at pH = 5.4, μ = 0.01, T = 298 K) revealed that the coacervate/DPPC monolayer becomes expanded in the presence of BSA at low π while their protein bound species are released into the subphase at high π. Film morphology, studied by epifluorescence microscopy (EFM) and atomic force microscopy (AFM), reveals that the sizes of the domains of both DPPC and coacervate decrease in the presence of BSA. Presence of BSA in the coacervate and DPPC monolayer was supported from AFM data analysis.     

Synthesis and characterization of pyrochlore-type yttrium titanate nanoparticles by modified sol–gel method

Pyrochlore-type yttrium titanate (Y₂Ti₂O₇) nanoparticles were successfully synthesized by a simple soft-chemistry technique viz. citric acid sol–gel method (CAM). The preparation process was monitored by X-ray diffraction, thermogravimetric–differential thermal analysis and Fourier transform–infrared experiments and the microstructures and average size of as-prepared products were characterized by transmission electron microscopy and high resolution transmission electron microscopy images. It was found that compared with traditional solid state reaction (SSR), Y₂Ti₂O₇ nanopowders were synthesized at a relatively low temperature (750°C) for shortened reaction time. Detailed analysis showed that the as-prepared Y₂Ti₂O₇ with good dispersibility and narrow size distribution were quasi-spherical; the average size was about 20–30 nm, also, the obtained products had higher BET surface area (50 m²/g). These properties are very helpful for a photocatalyst to achieve excellent activity and may result in better behaviour in hydrogen storage.     

The performance of push and pull systems: a simulation and comparative study†

Ideally the just-in-time (pull system) production system holds no buffer inventory so that the production is ‘just in time’. This is achieved only when the stage's operation times are constant and equal; but realistically the variability of operator performance and/or the unequal distribution of task times precludes such an ideal situation. As a result, the production line experiences problems. In this paper we investigate the effects of these variabilities on the performance of push and pull systems and how the manager can decide which production technique to adopt. The implication of the simulation results are reported and openings for future research are identified.     

Preparation and electrochemical characterization of lithium cobalt oxide nanoparticles by modified sol–gel method

Uniformly distributed nanoparticles of LiCoO₂ have been synthesized through the simple sol–gel method in presence of neutral surfactant (Tween-80). The powders were characterized by X-ray diffractometry, transmission electron microscopy and electrochemical method including charge–discharge cycling performance. The powder calcined at a temperature of 900 °C for 5 h shows pure phase layered LiCoO₂. The results show that the particle size is reduced in presence of surfactant as compared to normal sol–gel method. Also, the sample prepared in presence of surfactant and calcined at 900 °C for 5 h shows the highest initial discharge capacity (106 mAh g^?1) with good cycling stability as compared to the sample prepared without surfactant which shows the specific discharge capacity of 50 mAh g^?1.     

Synthesis and characterization of barium ferrite–silica nanocomposites

In this work, we prepared barium ferrite-silica (BaM-SiO₂) nanocomposites of different molar ratios by high-energy ball milling, followed by heat-treatment at different temperatures. The microstructure, morphology and magnetic properties were characterized for different synthesis conditions by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and vibrating sample magnetometry (VSM). The results indicate that 15 h of milling was enough to avoid the generation of hematite phase and to get a good dispersion of barium ferrite particles in the ceramic matrix. For milling periods beyond 15 h and heat treatment above 900 °C, the XRD patterns showed the presence of hematite phase caused by the decomposition of BaM. The agglomerate size observed through SEM analysis was around 150 nm with a good BaM dispersion into the SiO₂ matrix. The highest saturation magnetization (Ms) value obtained was 43 emu/g and the corresponding coercivity (Hc) value of 3.4 kOe for the composition 60BaM-40SiO₂ milled for 15 h and heat treated at 900 °C. This coercivity value is acceptable for the application in magnetic recording media.     

ECAP processing and mechanical milling of Mg and Mg–Ti powders: a comparative study

A study was carried out into the possibility of employing ECAP processing in lieu of mechanical milling for the purpose of developing powder-based hydrogen storage alloys. Mg and Mg–Ti powder compacts were encapsulated in a copper block and were subjected to ECAP deformation to an apparent strain of ε = 4. This resulted in the consolidation of the compacts as well as in the refinement of their structures. The values of coherently diffracting volume size were as small as 70–80 nm, quite comparable to those achieved with mechanical milling. It is, therefore, concluded that ECAP processing can be employed successfully for the purpose of structural refinement. As for material synthesis, however, the ECAP is less efficient in expanding the interfacial area. Therefore, it is necessary to impose relatively heavy strains to able to achieve comparable expansion in the interfacial area. It appears that an advantage of ECAP deformation is the development of structures which have improved ability for milling. It is, therefore, recommended that in the processing of hydrogen storage alloys, the powder mixtures may be first processed with ECAP in open atmosphere and then by mechanical milling of a short duration carried out under protective atmosphere.     

Structural and electronic properties of hydrogen adsorptions on BC₃ sheet and graphene: a comparative study

We have systematically investigated the effect of hydrogen adsorption on a single BC? sheet as well as graphene using first-principles calculations. Specifically, a comparative study of the energetically favorable atomic configurations for both H-adsorbed BC? sheets and graphene at different hydrogen concentrations ranging from 1/32 to 4/32 ML and 1/8 to 1 ML was undertaken. The preferred hydrogen arrangement on the single BC? sheet and graphene was found to have the same property as that of the adsorbed H atoms on the neighboring C atoms on the opposite sides of the sheet. Moreover, at low coverage of H, the pattern of hydrogen adsorption on the BC? shows a proclivity toward formation on the same ring, contrasting their behavior on graphene where they tend to form the elongated zigzag chains instead. Lastly, both the hydrogenated BC? sheet and graphene exhibit alternation of semiconducting and metallic properties as the H concentration is increased. These results suggest the possibility of manipulating the bandgaps in a single BC? sheet and graphene by controlling the H concentrations on the BC? sheet and graphene.     

Comparative study of synthesis and characterization of Pr ：YAG nanoparticles using different precipitator by co-precipitation method

分别采用碳酸氢铵和尿素为沉淀剂用沉淀法制备了Pr掺杂的YAG纳米粉体。并利用XRD、FT-IR、TEM等方法对样品进行了成分、粒度和形貌等性能分析,讨论了不同沉淀剂的反应机理。结果表明,碳酸氢铵沉淀法能够在较低温度下制备颗粒均匀、分散性良好的YAG纳米粉体;而尿素沉淀法所制备的粉体需要较高的煅烧温度,粉体粒径大、团聚较为严重。此外,Pr∶YAG纳米粉体的荧光强度随粉体粒径的增大而加强。     

Optical properties of γ-ferric oxide nanoparticles in a mesoporous silica matrix

Magnetic γ-Fe₂O₃/SiO₂ nanocomposites have been synthesized by impregnating a mesoporous silica matrix with a hexane solution of γ-ferric oxide nanoparticles. The subsequent heat treatment of samples in the course of synthesis influences the optical properties of the final nanostructural material. It is established that an increase in the temperature of annealing (crystallization) leads to a decrease in the energies of both direct and indirect allowed electron transitions to the conduction band.     

Synthesis and characterization of biocomposites with different hydroxyapatite–collagen ratios

Hydroxyapatite (HA)-type I collagen (Col) composite is a tissue-engineered bone graft which can act as a carrier or a template structure for cells or any other agents. In this paper, the effect of Col ratio on the scaffold structure and composition was analyzed. Scaffolds composed by HA/Col with different weight ratios (80:20; 50:50; 20:80, and 10:90) were produced by the precipitation method at pH 8–9, 37°C and 6 h of ripening. Using X-ray diffraction data, the Rietveld structure refinement showed that the size of HA crystals along the c-axis direction (002) decreases significantly in the presence of Col. Thus, the HA crystal shape turned from needle-like in pure HA, into spherical, in the 10:90 composite due to Col fibrillogenesis. The homogeneity of the composite was significantly dependent on the amount of Col in it. HA/Col 20/80 composite presented HA particles in a more homogenous way. Such a biocomposite was successfully produced in a rapid way and it is potentially useful for both small tissue repairs and engineering.     

Preparation and complex characterization of silica holmium sol–gel monoliths

Amorphous, sol–gel derived SiO₂ are known to biocompatible and bioresorbable materials. Biodegradable and inert materials containing radioactive isotopes have potential application as delivery vehicles of the beta radiation to the cancer tumors inside the body. Incorporation of holmium in the sol–gel derived SiO₂ could lead to the formation of a biodegradable material which could be used as carrier biomaterial for the radiation of radioactive holmium to the various cancer sites. The homogeneity of the prepared sol–gel silica holmium monoliths was investigated by Back Scattered Electron Imaging of Scanning Electron Microscope equipped with Energy Dispersive X-ray Analysis, X-ray Induced Photoelectron Spectroscopy and Nuclear Magnetic Resonance Spectroscopy. The biodegradation of the monoliths was investigated in Simulated Body Fluid and TRIS (Trizma pre-set Crystals) solution. The results show that by suitable tailoring of the sol–gel processing parameters holmium can be homogeneously incorporated in the silica matrix with a controlled biodegradation rate.     

Selected variants of a Memetic Algorithm for JSP – a comparative study

The article aims to address a research gap concerning the adequate configuration of a Memetic Algorithm adapted to solve the Job-Shop Scheduling Problem. The goal was accomplished by means of conducting a comparative study of 16 variants of a Memetic Algorithm, characterised with different places of hybridisation and local search methods applied. The study involved the solution of eleven instances of JSP and the comparison of the results with the results achieved with an Evolutionary Algorithm lacking the mechanism of hybridisation and selected local search methods. The utilitarian significance of the problem also involved the use of assessment measures intended for both practical applications and research purposes.     

Synthesis and characterization of NiO nanoparticles by sol–gel method

Nickel oxide nanoparticles have been synthesized in the presence of agarose polysaccharide by sol–gel method. The structure, morphology, optical and magnetic properties of the product was examined by X-ray diffraction, transmission electron microscopy, UV–visible spectrophotometer and superconducting quantum interference device magnetometer. The result of thermogravimetric analysis of the precursor product showed that the proper calcination temperature was 400 °C. X-ray diffraction result revealed that the obtained product was nickel oxide with face-centered cubic structure. TEM image demonstrated that the nickel oxide nanoparticles have spherical shape with size around 3 nm. Analysis of FTIR spectra confirmed the composition of product. The optical absorption band gap of the NiO nanoparticles was estimated to be 3.51 eV. Magnetic measurement showed that the nickel oxide nanoparticles exhibit superparamagnetic behavior at 300 K. Moreover, the nanoparticles show ferromagnetic interactions at 4.2 K owing to the existence of uncompensated moments on the surface of the nanoparticles.