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Drug Release Rate (drug + release_rate)
Selected AbstractsPoly(glutamic acid) poly(ethylene glycol) hydrogels prepared by photoinduced polymerization: Synthesis, characterization, and preliminary release studies of protein drugsJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 1 2002Zhiqiang Yang Abstract A class of new biodegradable hydrogels based on poly(ethylene glycol) methacrylate-graft-poly(glutamic acid) and poly(ethylene glycol) dimethacrylate was synthesized by photoinduced polymerization. Because all the polymeric constituents were highly hydrophilic, crosslinking could be performed in aqueous solutions. This type of crosslinked hydrogel was prepared by modifying a select number of acidic side-groups on poly(glutamic acid) with poly(ethylene glycol) methacrylate. These modified chains were then crosslinked in the presence of poly(ethylene glycol) dimethacrylate under a photoinduced polymerization at a wavelength of 365 nm. Swelling experiments were conducted to study the crosslinking density, pH-responsive behavior, and degradation of the hydrogel. Results showed that the degree of swelling of this type of hydrogels increased as the crosslinker concentration (or density) was reduced. Because of the presence of acidic side chains on poly(glutamic acid), swelling behavior was found to be pH-responsive, increasing at high pH in response to the increase in the amount of ionized acidic side chains. The degradation rate of these hydrogels also varied with pH. More rapid degradation was observed under stronger alkaline conditions because of the hydrolysis of the ester bonds between the crosslinker and the polymer backbone. Practically useful degradation rates could be achieved for such hydrogels under physiological conditions. Drug release rates from these hydrogels were found to be proportional to the protein molecular weight and the crosslinker density; increasing at lower protein molecular weight or crosslinker density. The preliminary findings presented in this article suggest that this class of biodegradable hydrogels could be an attractive avenue for drug delivery applications. The specific photoinduced crosslinking chemistry used would permit hydrogels to be synthesized in existence of the entrapped macromolecular drugs including peptides, proteins, and cells. In addition, the rapid feature of this polymerization procedure along with the ability to perform hydrogel synthesis and drug loading in an aqueous environment would offer great advantages in retaining drug activity during hydrogel synthesis. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 62: 14,21, 2002 [source] Synthesis, Characterization and Drug Release Behavior of pH-Responsive O-carboxymethyl Chitosan-graft-poly(N-vinylpyrrolidone) Hydrogel Beads,ADVANCED ENGINEERING MATERIALS, Issue 12 2009Liwei Ma In this work, the carboxymethyl chitosan (CMCTS) grafted poly(N-vinylpyrrolidone) (PVP) copolymers were synthesized. The hydrogel beads containing VB2 were prepared from the copolymers by an ionic crosslinked. The experimental results shown that VB2 drug release rate from those beads decreased with the increasing grafting percentage, crosslinker concentration and pH value of the medium. Besides, the beads have the better control ability for releasing of model drug than CMCTS does. [source] Hydrophobic Functional Group Initiated Helical Mesostructured Silica for Controlled Drug Release,ADVANCED FUNCTIONAL MATERIALS, Issue 23 2008Lei Zhang Abstract In this paper a novel one-step synthetic pathway that controls both functionality and morphology of functionalized periodic helical mesostructured silicas by the co-condensation of tetraethoxysilane and hydrophobic organoalkoxysilane using achiral surfactants as templates is reported. In contrast to previous methods, the hydrophobic interaction between hydrophobic functional groups and the surfactant as well as the intercalation of hydrophobic groups into the micelles are proposed to lead to the formation of helical mesostructures. This study demonstrates that hydrophobic interaction and intercalation can promote the production of long cylindrical micelles, and that the formation of helical rod-like morphology is attributed to the spiral transformation from bundles of hexagonally-arrayed and straight rod-like composite micelles due to the reduction in surface free energy. It is also revealed that small amounts of mercaptopropyltrimethoxysilane, vinyltrimethoxysilane, and phenyltrimethoxysilane can cause the formation of helical mesostructures. Furthermore, the helical mesostructured silicas are employed as drug carriers for the release study of the model drug aspirin, and the results show that the drug release rate can be controlled by the morphology and helicity of the materials. [source] Encapsulation efficiency and release behaviors of bovine serum albumin loaded in alginate microspheres prepared by sprayingJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2008Jie Zhang Abstract Spraying and spraying with an electrostatic field (SEF) were employed to prepare alginate microspheres for delivering proteins, especially for intestinal digestive enzymes and cytokines. The encapsulation efficiency (EE) of a model protein [bovine serum albumin (BSA)] at a pH value lower than the isoelectric point was 20% higher than that at a natural pH. Moreover, for the microspheres prepared by SEF, EE improved significantly with increasing electric voltage. The interactions between BSA and the alginate microspheres were identified with Fourier transform infrared spectroscopy. The release profiles in vitro showed a controlled and pH-responsive release manner for the encapsulated BSA. A first-order release equation was postulated and modified to describe the release kinetics with an obviously initial burst release related to the eroded porous matrix. The equation fit the release data well when the pH value and composition of the release media were changed. The analysis of the release kinetics indicated that the drug release rate was in an inverse ratio to the diameter of the microspheres. Increasing the gas flow rate or electric voltage decreased both the mean diameter and size distribution of the microspheres significantly and enhanced the release rate of loaded drugs from alginate microspheres. Sodium dodecyl sulfate/polyacrylamide gel electrophoresis analysis revealed that BSA kept its structural integrity during the encapsulation and release process. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Controlled and complete release of a model poorly water-soluble drug, prednisolone, from hydroxypropyl methylcellulose matrix tablets using (SBE)7m -,-cyclodextrin as a solubilizing agentJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 7 2001Venkatramana M. Rao Abstract Sustained-release formulations such as hydroxypropyl methylcellulose (HPMC)-based hydrophilic matrix tablets of poorly water-soluble drugs often result in incomplete release because of the poor solubility and dissolution rate of the drug in the hydrophilic matrix. Sulfobutylether-,-cyclodextrins ((SBE)7M -,-CDs) have been known to improve the solubility of such drugs by forming inclusion complexes. The present paper deals with the modification of drug release from an HPMC-based matrix tablet of a sparingly water-soluble drug, prednisolone (PDL), using (SBE)7M -,-CD as a solubilizing agent. Tablets were prepared by direct compression of a physically mixed PDL, (SBE)7M -,-CD, and polymer. On exposure to water, an in situ PDL:(SBE)7M -,-CD complex was formed in the gel layer, and enhanced drug release relative to a control formulation was observed (lactose used as the excipient instead of (SBE)7M -,-CD ). Other possible changes due to the incorporation of (SBE)7M -,-CD in the formulation were also probed. Incorporation of (SBE)7M -,-CD lead to a higher water uptake relative to the control (lactose) formulation. For a fixed total tablet weight, polymer type, and loading, the drug release rate appeared to depend on the molar ratio of (SBE)7M -,-CD to PDL and not the absolute amount of (SBE)7M -,-CD present in the matrix tablet. This work shows that incorporation of (SBE)7M -,-CD into the matrix tablets could be considered in designing a sustained-release tablet of poorly water-soluble drugs. © 2001 Wiley-Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 90:807,816, 2001 [source] Controlled Delivery Achieved with Bi-Layer Matrix Devices Produced by Co-Injection MouldingMACROMOLECULAR BIOSCIENCE, Issue 8 2004Cláudia M. Vaz Abstract Summary: The aim of this study was to design new soy protein-based bi-layered co-injection moulded matrix systems aimed to achieve controlled drug delivery. The devices consisted of a drug-free outer layer (skin) and a drug-containing core. The systems overcame the inherent disadvantage of non-linear release associated with diffusion-controlled single-layer matrix devices by providing additional releasing area with time to compensate for the decreasing release rate. As expected, the bi-layer devices presented a significant decrease in drug release rate when compared with a correspondent single layer matrix system. The skin thickness and the degree of crosslinking of the core appeared to be very important tools to tailor the release patterns. Furthermore, due to the amphoteric nature of the soy protein, the developed devices evidenced a pH-dependent behaviour. The mechanisms of drug release were also elucidated at two different pH values: i) pH 5.0, near the isoelectric point of soy (low matrix solubility); and ii) pH 7.4, physiological pH (high matrix solubility). Consequently, changing the release medium from pH 5.0 to pH 7.4 after two hours, led to an abrupt increase in drug release and the devices presented a typical controlled drug delivery profile: slow release/fast release. These evidences may provide for the development of individual systems with different release onsets that in combination may exhibit drug releases at predetermined times in a pre-programmed way. Another possibility is the production of three-layer devices presenting bimodal release profiles (fast release/slow release/fast release) by similar technologies. Scanning electron micrograph of a developed bi-layer device. [source] Biodistribution of liposome-entrapped human gamma-globulinBIOPHARMACEUTICS AND DRUG DISPOSITION, Issue 6 2006María A. García-Santana Abstract The present study was aimed at the preparation and performance evaluation of Intacglobin® -loaded liposomes for selective drug presentation to the lungs. Egg phosphatidylcholine- and cholesterol-based liposomes (1:1 and 1:0.25 mol/mol) were prepared by a dehydration,rehydration procedure. A tissue distribution study after single intranasal administration of 0.5 µCi 125I-Intacglobin® -loaded liposomes was conducted in Balb/c mice. The efficiencies of drug entrapment (30%) and the average diameters did not differ significantly between the two liposome formulations. However, liposomes composed of an increased cholesterol amount showed a lower in vitro drug release rate. The airway penetration efficiency of the liposomal formulation was determined by the cumulative percentage of the dose reaching the lungs (AUC) and its sojourn time therein, and were 1.7- and 2.2-times higher compared with the plain 125I- Intacglobin® solution-based formulation, respectively. A significantly greater (p<0.001) drug localization index after 24 h was found at the lungs in comparison with the other tissues (p<0.01), although similar values were detected between groups following administration of either liposomes or control solutions, despite the formulations attributes. In conclusion, it is suggested that longer Intacglobin exposure at the pulmonary region is observed after administration of the liposomal formulation. The results open future perspectives in assessing local passive immunization for the treatment of respiratory infectious diseases. Copyright © 2006 John Wiley & Sons, Ltd. [source] Electrospun starch acetate nanofibers: Development, properties, and potential application in drug deliveryBIOTECHNOLOGY PROGRESS, Issue 6 2009Weijie Xu Abstract Electrospun starch acetate (SA) nanofibers with different degrees of substitution (DS) have been developed using formic acid/water as solvents, and their properties and potential applications in drug delivery have been studied. Although SA is biodegradable, biocompatible, and inexpensive, the mechanical properties and potential applications of SA nanofibers have not been studied. This research studied the effect of the solvent system, SA concentration, annealing time, and DS on the morphology and tenacity of SA nanofibers. The water stability of SA nanofibers and drug release profiles using diclofenac as a model drug with the sorption and the dissolution methods have also been investigated. It has been found that annealing not only increased the mechanical properties of SA nanofibers but also led to a low initial burst and a constant release rate. The results also showed that 90% (v/v) formic acid/water solvent system gave even and fine SA nanofibers and the highest tenacity obtained in this study was 17.9 MPa. The SA nanofibers with DS 2.3 retained about 78.0% and 48.0% of its tenacity after 16 and 32 days exposing to 50°C and 90% relative humidity comparing to 77.0% and 40.2% for SA nanofibers with DS 1.1, respectively. In addition, SA nanofibers with DS 2.3 had a lower initial burst and a more constant drug release rate than those with DS 1.1. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 [source] Small-molecule release from poly(D,L -lactide)/poly(D,L -lactide-co-glycolide) composite microparticlesJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 9 2005Emily J. Pollauf Abstract Addition of biodegradable polymer shells surrounding polymeric, drug-loaded microparticles offers the opportunity to control drug release rates. A novel fabrication method was used to produce microparticles with precise control of particle diameter and the thickness of the polymer shell. The effect of shell thickness on release of a model drug, piroxicam, has been clearly shown for 2- to 15-µm thick shells of poly(D,L -lactide) (PDLL) surrounding a poly(D,L -lactide-co-glycolide) (PLG) core and compared to pure PLG microspheres loaded with piroxicam. Furthermore, the core-shell microparticles are compared to microspheres containing blended polymers in the same mass ratios to demonstrate the importance of the core-shell morphology. Combining PDLL(PLG) microcapsules of different shell thicknesses allows nearly constant release rates to be attained for a period of 6 weeks. © 2005 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 94:2013,2022, 2005 [source] Immediate drug release from solid oral dosage formsJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 1 2005Thomas Schreiner Abstract Fast drug release from solid dosage forms requires a very fast contact of the vast majority of the drug particles with the solvent; this, however, is particularly delayed in tablets and granulations. Starch and cellulose substances favor the matrix disintegration during the starting phase and the generation of the effective dissolution surface of the drug substance, thereby. To investigate the very complex interrelation between the functionality of commonly used excipients and the structural effects of the production processes, wettability, porosity, water uptake, and drug release rates of several ketoprofen-excipient preparations (powder blends, granulations, tablets) were measured. Significant linear correlation between these parameters, however, was not achieved; only qualitative tendencies of the effects could be detected. In consequence, a general mathematical model describing the mechanistic steps of drug dissolution from solid dosage forms in a fully correct way was not realized. However, the time-dependent change of the effective dissolution surface follows stochastic models: a new dissolution equation is based on the differential Noyes-Whitney equation combined with a distribution function, e.g. the lognormal distribution, and numerically solved with the software system EASY-FIT by fitting to the observations. This new model coincides with the data to a considerably higher degree of accuracy than the Weibull function alone, particularly during the starting, matrix disintegration, and end phases. In combination with a procedure continuously quantifying the dissolved drug, this mathematical model is suitable for the characterization and optimization of immediate drug release by the choice and modification of excipients and unit operations. The interdependence of some characteristic effects of excipients and production methods is discussed. © 2004 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 94:120,133, 2005 [source] | ||||||||||