Development of a dialysis in vitro release method for biodegradable microspheres

University of Kentucky, Lexington, Kentucky, United States
AAPS PharmSciTech (Impact Factor: 1.64). 02/2005; 6(2):E323-8. DOI: 10.1208/pt060242
Source: PubMed


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 degrees C and 55 degrees 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 degrees C and 55 degrees 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.

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Available from: Patrick P Deluca, Jun 13, 2014
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    • "Thus, modulating particle size is an effective approach to ensure initial burst. Burst release may also be used to provide a loading or bolus dose prior to the slow sustained release of drug from the inner matrix of the microspheres, especially with certain classes of therapeutic agents like LHRH superagonists [23]. Hence, in this study, for a watersoluble peptide like Leuprolide in small sized microspheres, a high surface to volume ratio suggested a strong possibility of initial burst release at the early time point(s). "
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    ABSTRACT: This study explores the mechanistic aspects of in vitro release from biodegradable microspheres with the objective of understanding the effect of the unstirred water layer on polymer degradation and drug release. In vitro drug release experiments on Leuprolide PLGA microspheres were performed under “static” and “continuous” agitation conditions using the “sample and separate” method. At specified time intervals, polymer degradation, mass loss, and drug release were assessed. While molecular weight and molecular number profiles for “static” and “continuous” samples were indistinct, mass loss occurred at a faster rate in “continuous” samples than under “static” conditions. In vitro results describe a fourfold difference in drug release rates between the “continuous” and “static” samples, ascribed to the acceleration of various processes governing release, including elimination of the boundary layer. The findings were confirmed by the fourfold increase in drug release rate when “static” samples were subjected to “continuous” agitation after 11 days. A schema was proposed to describe the complex in vitro release process from biodegradable polymer-drug dosage forms. These experiments highlight the manner in which the unstirred water layer influences drug release from biodegradable microspheres and stress the importance of selecting appropriate conditions for agitation during an in vitro release study.
    Full-text · Article · Jan 2015
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    • "Dialysis technique was used to evaluate drug release from PLGA NPs [14]. A dialysis tube (molecular weight cut-off: 8 kDa) containing 2 mg of nanoparticles suspended in 5 ml PBS (pH = 7.4) was dipped in a medium consisting of 20 ml PBS (pH =7.4) containing 0.1% Tween 80 and was continuously stirred on a shaker incubator for over 14 days at 37°C. "
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    • "Determination of in vitro protein release kinetics 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. "
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