Development of a dialysis in vitro release method for biodegradable microspheres

Abstract

The purpose of this research was to develop a simple and convenient in vitro release method for biodegradable microspheres using a commercially available dialyzer. A 25 KD MWCO Float-a-Lyzer was used to evaluate peptide diffusion at 37°C and 55°C in different buffers and assess the effect of peptide concentration. In vitro release of Leuprolide from PLGA microspheres, having a 1-month duration of action, was assessed using the dialyzer and compared with the commonly used ''sample and separate'' method with and without agitation. Peptide diffusion through the dialysis membrane was rapid at 37°C and 55°C in all buffers and was independent of peptide concentration. There was no detectable binding to the membrane under the conditions of the study. In vitro release of Leuprolide from PLGA microspheres was tri-phasic and was complete in 28 days with the dialysis technique. With the sample and separate technique, linear release profiles were obtained with complete release occurring under conditions of agitation. Diffusion through the dialysis membrane was sufficiently rapid to qualify the Float-a-Lyzer for an in vitro release system for microparticulate dosage forms. Membrane characteristics render it useful to study drug release under real-time and accelerated conditions.

A model-dependent approach to correlate accelerated with real-time release from biodegradable microspheres

“…15 Briefly, a predetermined amount of microspheres were transferred to the Float-a-Lyzer and suspended in 5 mL of 0.1 M phosphate buffered saline (PBS) pH 7.4. The dialyzer was then introduced into a graduated glass cylinder containing 55 mL buffer at 37-C.…”

“…In a previous study, 15 a novel dialysis technique using a commercially available dialyzer composed of a regenerated cellulose membrane was used to assess peptide diffusion at varying temperatures and release from PLGA microspheres at 37-C. Results from the diffusion and in vitro release studies on peptide-loaded microspheres revealed the advantages of this technique over the commonly used "sample and separate" method including ease of sampling, total buffer replacement, and simulation of in vivo conditions.…”

In Vitro Release Testing of PLGA Microspheres with Franz Diffusion Cells

“…In fact, microspheres move freely inside the dialysis sac at a very low speed, which prevents aggregation. In VDC, though microspheres do not move, they are placed in the buffered donor compartment in contact with a smooth surface, contrary to magnetically agitated dialysis bags (5). In this case, the release is actually a two-step process, the diffusion of LA through the polymer matrix and its subsequent diffusion from donor to receptor chamber.…”

“…This is in accordance with USP recommendations about the suitability of this equipment for delivery systems containing drugs with limited solubility (4). Dialysis tests performed with different devices may be useful for testing biodegradable microspheres (5). Different types of shaking and rotating devices have also been widely used for this purpose (6).…”

Preparation and in vitro characterisation of Ehrlichia ruminantium plasmid DNA and proteins encapsulated into and DNA adsorbed onto biodegradable microparticles

“…A Float-A-Lyzer ® (100 kDa MWCO 3 ml capacity, Spectra/Por ® ) was used for in vitro release kinetic studies (D'Souza and DeLuca, 2005). Preweighed amounts (10-60 mg) of protein-loaded freezedried microparticles were suspended in the release media (12 mM NaH 2 PO 4 ; 75 mM NaCI; 2 mM urea, and 62 mM imidazole pH 8) supplemented with 5 mM SDS as solubilising agent and 0.02% sodium azide as bacteriostatic agent.…”