Background: Magnetic vehicles are very attractive for delivery of therapeutic agents as they can be targeted to specific locations in the body through the application of a magnetic field gradient. The magnetic localization of a therapeutic agent results in the concentration of the therapy at the target site consequently reducing or eliminating the systemic drug side effects. Objective: The aim of this review is to provide an update on the progress made in the development of the magnetic targeting technique addressing characteristics of the magnetic carriers and limitations of the current targeting magnet systems. Methods: This review discusses fundamental requirements for the optimal formulation of the magnetic carrier, current applications and potentially new approaches for the magnetically mediated, site-specific localization of therapeutic agents, including drugs, genes and cells. Results/conclusion: More efficient targeting magnetic systems in combination with prolonged circulation lifespan and carrie...

Magnetic targeting for site-specific drug delivery: applications and clinical potential

The effects of drug physico-chemical properties on release from copoly (lactic/glycolic acid) matrix

Porous biodegradable microparticles for delivery of pentamidine

The objective was to develop a microencapsulation process suitable for the controlled release of an active protein drug. beta-glucuronidase was selected as a model protein and a combination of complex coacervation (gelatin/sodium alginate, gelatin/acacia and albumin/acacia) and spray drying was investigated. Coacervates were either spray dried or glutaraldehyde crosslinked to form microcapsules. Polyvinylpyrrolidone (PVP) and polyethylene glycol were investigated as potential coacervate enhancers and stabilizers. beta-glucuronidase/polymer mixtures were spray dried to determine any polymer protective effects on protein activity. A BUCHI 190 Spray Drier was used, beta-glucuronidase activity was determined using a Sigma Kit and microcapsule particle size was measured by Accusizer analysis (light blockage). All non-crosslinked coacervates investigated, with the exceptions of albumin/acacia and albumin/acacia/beta-glucuronidase/PVP, were unsuitable for spray drying as they rapidly phase separated and blocked the spray drier nozzle. beta-glucuronidase activity in the albumin/acacia coacervates approximated to 99% prior to and 80% following spray drying. This can be compared to activities of approximately 30% and 68% when spray dried alone and with albumin, respectively, and of 18% in albumin/acacia microcapsules crosslinked with glutaraldehyde. Microcapsule particle size was affected by coacervation pH, additives and spray drying. In vitro beta-glucuronidase release was biphasic, with an initial burst release followed by a zero order release phase and continued over the 12 day study period. In conclusion, the spray drying albumin/acacia/PVP method described is useful for the preparation and collection of controlled release microcapsules with minimal loss of beta-glucuronidase activity.

β-Glucuronidase activity following complex coacervation and spray drying microencapsulation

Fluconazole-loaded ethyl cellulose microspheres were prepared by alginate facilitated (water-in-oil)-in-water emulsion technology and the effects of various processing variables on the properties of microspheres were investigated. Scanning electron microscopy revealed spherical nature and smooth surface morphology of the microspheres except those prepared at higher concentration of emulsifiers and higher stirring speeds. The size of microspheres varied between 228 and 592 μm, and as high as 80% drug entrapment efficiency was obtained depending upon the processing variables. When compared up to 2 h, the drug release in pH 1.2 HCl solution was slower than in pH 7.4 phosphate buffer saline solution. However, this trend was reversed at high shear conditions. The microspheres provided extended drug release in alkaline dissolution medium and the drug release was found to be controlled by Fickian-diffusion mechanism. However, the mechanism shifted to anomalous diffusion at high shear rates and emulsifier concentrations. The aging of microspheres did not influence the drug release kinetics. However, the physical interaction between drug and excipients affected the drug dissolution behaviors. X-ray diffractometry (X-RD) and differential scanning calorimetry (DSC) analysis revealed amorphous nature of drug in the microspheres. Fourier transform infrared (FTIR) spectroscopy indicated stable character of fluconazole in the microspheres. The stability testing data also supported the stable nature of fluconazole in the microspheres. The fluconazole extracted from 80% drug-loaded formulation showed good in vitro antifungal activity against Candida albicans. Thus, proper control of the processing variables involved in this modified multiple emulsion technology could allow effective incorporation of slightly water soluble drugs into ethyl cellulose microspheres without affecting drug stability.

/pdf/investigation-on-processing-variables-for-the-preparation-of-nmm6yefayg.pdf

Investigation on Processing Variables for the Preparation of Fluconazole-Loaded Ethyl Cellulose Microspheres by Modified Multiple Emulsion Technique

Sustained release biodegradable microcapsules of AZT were prepared using different concentrations of copolymer of poly(lactic/glycolic) acid (PLGA 50:50 and PLGA 90:10). Solid microcapsules were co...

Preparation of biodegradable microcapsules containing zidovudine (AZT) using solvent evaporation technique.

Biodegradable microcapsules of zidovudine (AZT) were prepared using poly-(lactide/glycolide) by the solvent evaporation technique. The objective of this project was to focus on the effect of several formulation and processing factors on the efficiency of encapsulation, surface morphology, and drug release profiles. When the drug was incorporated as powder or as aqueous suspension containing a high amount of insoluble particles, to the organic phase the surface of the microcapsules was appeared to be wrinkled. The efficiency of encapsulation decreased when AZT powder was dispersed directly into the organic solvent instead of adding as an aqueous solution. When the relative volume of the aqueous phase containing 1% PVA was changed from 25 up to 125% of the volume of the organic phase, the efficiency of encapsulation, surface morphology, and release profiles did not change significantly. The efficiency of encapsulation decreased from 9 to 3.8% when the drug loading was increased from 10 to 50% of the weight of the polymer.

Effect of formulation and processing factors on the characteristics of biodegradable microcapsules of zidovudine

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Preparation of biodegradable microcapsules containing zidovudine (AZT) using solvent evaporation technique.

Effect of formulation and processing factors on the characteristics of biodegradable microcapsules of zidovudine