Sharif Digital Repository

In this research a mathematical model for controlled drug delivery of Ibuprofen has been developed which accounts for physical kinetics based upon variations of the drug concentration, size and release time for a spherical drug pill. Through this model, the drug release for three sizes of the active ingredient including; 213nm (representing existence of only diffusion limitations), 515nm (representing existence of only solubility limitations) and 367nm (representing both diffusion and solubility limitations) was calculated. Theoretical amounts of the drug after two hours of release are calculated to be 95.3, 99.5 and 95.5 percent, respectively. Comparison of theoretical and experimental data... 

The preparation of microcapsules containing perphenazine by solvent evaporation using ethyl cellulose is described. The microparticles are formed after solvent evaporation and polymer precipitation. The drug was dissolved in a polymer solution and emulsified into an aqueous phase to form microcapsules. To study the effects on particle size, encapsulation efficiency and morphology, three different molecular weights of ethyl cellulose (Mw=47000, 71000 and 99000) were used. Covalent bonding of drugs to polymers via hydrolytically or enzymatically cleavable covalent bond was achieved for sustained drug delivery. The release rate of perphenazine from these systems was investigated  

A thorough investigation on different controlled release systems were evaluated. The required devices were constructed simultaneously and the required experiments were performed. The polymeric network and membranes of poly vinyl alcohol with cross-linking agent glutaraldehyde for preparation of hyrogel system was effected. Paraquat, a type of herbicide was introduced as solute in the system. Glutaraldehyde was utilized as cross-linking agent at different concentration. Increase in the concentration of the cross-linking agent will cause a decrease in the extent of release out of the system. The effect of temperature on hydrogel adsorption demonstrates a higher adsorption at lower temperature.... 

Objective: a convenient numerical model has been developed to predict release profile of different types of agents from bulk biodegrading polymer microspheres, including magnitude methods are less accurate than analytical methods. Usually, this study used analytical solutions for the model and compared the analytical results with numerical solution and experimental data. Methods: The objective drug controlled release profiles were modeled based on a four-phase pattern. Then, a specific formulation was considered based on Fick’s second law. After calculating various parameters, the equations were solved using an analytical method. Results: Comparison results showed that analytical solution... 

An exact solution has been obtained for the release kinetics of a solute from a spherical reservoir with the burst effect initial condition into a finite external volume. The exact solution is derived based on the time Laplace transform method. The results presented here indicate that as the external fluid volume increases, the cumulative release at any time and the releasable amount of the solute at infinite time increase. In addition, for a given external volume, as the polymeric coat thickness increases the fractional release at any time decreases, Experimentally, cumulative release profiles of theophylline microspheres coated with ethylene vinyl acetate copolymer into different external... 

Numerical and analytical exact solutions of diffusional release from a cylindrical polymeric matrix into an infinite medium have been developed in which the initial solute loading (A) is greater than solubility limit (Cs). Also, the effects of boundary layers on the drug release rate have been studied. The numerical solution is valid for any initial drug loading whereas analytical solution can be used for high values of drug loading. Comparisons have been made between numerical and analytical exact solutions in upper and lower bounds (A/Cs蠑1 and A/Cs→1) and previously presented approximate solution. The presented results validate the proposed numerical solution  

In this research work, different devices made of glutaraldehyde cross-linked chitosan hydrogels loaded by amoxicillin, have been prepared using freeze-drying method. Effects of system parameters such as cross-linker concentration, pH, and gel structure on the morphology and release behavior of devices have been investigated using standard methods. Morphological studies were performed using SEM instrument and controlled releases are followed via spectrophotometeric method. Reaction of glutaraldehyde with chitosan has been studied using FTIR instrument. SEM micrographs have shown that with increasing cross-linker percentage in hydrogel, pore sizes increased where pore size distribution... 

In the present work a novel multifunctional drug nanocarrier was prepared. Polyglycerol-. g-polycaprolactone was grafted on Mesoporous silica-coated magnetic graphene oxide. Doxorubicin, as anticancer drug, was loaded on this carrier. The in vitro drug release showed the controlled pH responsive behavior. At the endosomal pH (pH 5.5) the amount of drug release enhanced. This nanocarrier would have potential application in the tumor therapy owing to its biodegradability, controlled release and pH responsive behavior  

Lysozyme loaded niosomes containing various molar ratios of two kinds of surfactants were prepared and the properties of these niosomal formulations were studied. The results revealed that the size of niosomes varied between 240.06 ± 32.41 and 895.2 ± 20.84 nm. Formulations with the lowest size and no precipitation had entrapment efficiencies ranging from 60.644 ± 3.310 to 66.333 ± 1.98%. Their controlled release profiles after 48 h were 15.67, 20.67 and 31.50%. After 2 months, the most stable formulation in terms of size, PDI, zeta potential, and entrapment efficiency was used to study the secondary structures of lysozyme in niosomal and free forms. Lysozyme loaded niosome and lysozyme... 

Novel types of highly swelling hydrogels were prepared by grafting crosslinked polyacrylamide-co-poly-2-acrylamido-2-methylpropane sulfonic acid (PAAm-co-PAMPS) chains onto sodium alginate (Na-Alg) through a free radical polymerization method. The superabsorbent formation was confirmed by Fourier transform infrared spectroscopic (FTIR). The controlled release behavior of diclofenac sodium (DS) from superabsorbent polymer was factinvestigated, and shown that the release profiles of DS from superabsorbent polymer were slow in simulated gastric fluid (SGF, pH 1.2) over 3 h, but nearly all of the initial drug content was released in simulated intestinal fluid (SIF, pH 7.4) within 21 h after...