Influence Of Various Experimental Factors Research Articles

Insulin nanoparticles for transdermal delivery: preparation and physicochemical characterization and in vitro evaluation

Aim: This work is aimed to study the feasibility of insulin nanoparticles for transdermal drug delivery (TDD) using supercritical antisolvent (SAS) micronization process. Methods: The influences of various experimental factors on the mean particle size (MPS) of insulin nanoparticles were investigated. Moreover, the insulin nanoparticles obtained were characterized by scanning electron microscopy (SEM), dynamic light scattering (DLS), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and thermogravimetric (TG) analyses. Results: Under optimum conditions, uniform spherical insulin nanoparticles with a MPS of 68.2 ± 10.8 nm were obtained. The Physicochemical characterization results showed that SAS process has not induced degradation of insulin. Evaluation in vitro showed that insulin nanoparticles were accorded with the Fick's first diffusion law and had a high permeation rate. Conclusion: These results suggest that insulin nanoparticles can have a great potential in TDD systems of diabetes chemotherapy.

Role of phase behavior in micronization of lysozyme via a supercritical anti-solvent process

Abstract Ultra-fine particles of protein lysozyme were prepared with a supercritical anti-solvent (SAS) apparatus by using dimethyl sulfoxide (DMSO) as solvent and carbon dioxide as anti-solvent. The influences of various experimental factors on the morphology and the mean size of particulate products were investigated. As evidenced from the experimental results, phase behavior of the mixtures in precipitator during the particle formation stage played a crucial role in the SAS processes. Uniform networked nano-particles were obtained when the precipitations were conducted in the supercritical region of carbon dioxide + DMSO mixture. Several different types of morphologies were produced simultaneously as the precipitations were operated near the critical region. Spherical micron-scale clusters were formed in the superheated vapor region, while submicron-particles were aggregated as dense cake when lysozyme precipitated in the vapor–liquid coexistence region. The wide angle X-ray scattering (WAXS) patterns indicated that both the raw lysozyme and the processed particulate samples were amorphous. The differential scanning calorimeter (DSC) thermograms showed that the dehydration peak was disappeared after SAS treatment. Moreover, the networked primary particles could be disintegrated and dispersed well in water through ultrasonication, which were confirmed by analysis with dynamic laser scattering (DLS). A continuous stirred tank reactor (CSTR) model was used to calculate the dynamic composition variations of the mixtures in precipitator during the particle formation period.

Colloidal oxide nanoparticles for the photocatalytic degradation of organic dye

In this work, easily processable and highly crystalline ZnO and TiO2 nanoparticles, with a narrow size distribution, obtained by using novel non-hydrolytic synthetic approaches were both tested for the photocatalyzed degradation of an organic dye, methyl red (2-(4-Dimethylamino-phenylazo)-benzoic acid)—C.I. 13020) and their behaviour comparatively examined with respect to TiO2 and ZnO commercial powders. The experiments were carried out using semiconducting oxides under UV and visible light illumination. Preliminary studies on the influence of various experimental factors as pH and dye concentration were performed. The obtained results demonstrated a high photocatalytic efficiency of nanosized semiconducting particles.

Bromodeoxyuridine labelling as an alternative method to identify 6-thioguanine-resistant mutant lymphocytes in humans

6-Thioguanine-resistant (TG R) mutant lymphocytes in human blood are usually enumerated by the cloning assay which allows the molecular characterisation of the HPRT mutations to be detected. A “short-term” alternative approach is provided by the anti-bromodeoxyuridine (anti-BrdU) technique in which TG R lymphocytes are identified immunocytochemically by their ability to synthesise DNA in the presence of 6-thioguanine (TG). We have evaluated the influence of various experimental factors that could affect the frequency of TG R lymphocytes. A standard protocol is proposed, based on 24-h cold storage of isolated lymphocytes at 4°C and 40-h culture with and without TG, the last 16 h with BrdU. The harvested cells are treated with hypotonic (0.075 M) KCl, fixed with methanol:acetic acid (3:1) and put on microscopic slides. For the TG cultures, all cells are prepared on the slides, while slides from the control cultures are made by a 1/50 dilution. DNA is denatured by formamide, and the BrdU label is identified by anti-BrdU antibody detected by immunoperoxidase staining using a peroxidase-conjugated secondary antibody with diaminobenzidine as substrate. In 10 donors, the frequency of TG R lymphocytes (variant frequency, V f) detected by this protocol ranged from 69.65×10 −6 to 83.45×10 −6, and split measurements showed a relatively small intra-assay variation in V f values of each donor. BrdU in DNA was also detected by immunofluorescence using a fluorescein-conjugated anti-BrdU monoclonal antibody. This method, facilitating easy identification of positive cells and rapid microscopic scoring, may serve as a basis for an automated analysis of TG R lymphocytes. V f values detected by the anti-BrdU assay are higher than mutant frequencies obtained by the cloning assay, which has been assigned to the presence of non-mutant phenocopies considered to represent spontaneously cycling lymphocytes. Although the anti-BrdU assay is rapid and easy and has been shown to respond to genotoxic exposures, its true value could be evaluated only when it can be ascertained that phenocopies do not significantly contribute to the V f values obtained.

Electrocatalytic reduction of carbon dioxide by nickel cyclam2+ in water: study of the factors affecting the efficiency and the selectivity of the process

The electrocatalytic properties of Ni cyclam/sup 2 +/ in CO/sub 2/ reduction have been studies. The influence of various experimental factors on the course of the reaction has been investigated. Under given conditions, Ni cyclam/sup 2 +/ is remarkably efficient and selective for electroreduction of CO/sub 2/ into CO, even in water. The stability of the system has been tested in long range electrolysis, showing that even after thousands of catalytic cycles no deactivation occurs. The mechanistic investigation presently described points to the importance of molecular species adsorbed on the cathode surface. The contribution of reduced species in the bulk is marginal. In addition, during the electrocatalytic process, a nickel(I) carbonyl complex is present: (Ni(cyclam)(CO))/sup +/. The latter complex may be involved in the catalytic reaction leading to CO evolution. Surprisingly, the behavior of Ni cyclam/sup 2 +/ as electrocatalyst is unique. Among the numerous complexes investigated, only Ni cyclam/sup 2 +/ shows such a large selectivity for the electroreduction of CO/sub 2/ over the electroreduction of water. The size of the cyclam ligand and the presence of secondary amine groups (NH) might account for the very special properties of the electrocatalyst.

Immobilization of yeast by adhesion to a support without use of a chemical agent

Yeast Saccharomyces cerevisiae has been immobilized by adhesion to plate supports of glass or polycarbonate after a suitable pretreatment, and sedimentation on the support, followed by washing the non-adhering cells. The pretreatment consists of starving the cells in pure water. Its efficiency is related to both a release of substances, decreasing the electrostatic repulsion between the particles involved, and a modification of the cell wall itself. A single layer of immobilized cells is obtained and a large fraction of the cells keep the capacity to reduce methylene blue and to multiply. The influence of various experimental factors (pretreatment, harvesting time, time of contact with the support) is discussed.