Development of a dialysis in vitro release method for biodegradable microspheres

University of Kentucky College of Pharmacy, Lexington, KY 40536, USA.
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.

Download full-text


Available from: Patrick P Deluca, Jun 13, 2014
  • Source
    • "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). "
    [Show abstract] [Hide abstract]
    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.
    01/2015; 2015:1-12. DOI:10.1155/2015/823476
  • Source
    • "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. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Poly lactic-co-glycolic acid (PLGA) based nanoparticles are considered to be a promising drug carrier in tumor targeting but suffer from the high level of opsonization by reticuloendothelial system due to their hydrophobic structure. As a result surface modification of these nanoparticles has been widely studied as an essential step in their development. Among various surface modifications, human serum albumin (HSA) possesses advantages including small size, hydrophilic surface and accumulation in leaky vasculature of tumors through passive targeting and a probable active transport into tumor tissues. PLGA nanoparticles of docetaxel were prepared by emulsification evaporation method and were surface conjugated with human serum albumin. Fourier transform infrared spectrum was used to confirm the conjugation reaction where nuclear magnetic resonance was utilized for conjugation ratio determination. In addition, transmission electron microscopy showed two different contrast media in conjugated nanoparticles. Furthermore, cytotoxicity of free docetaxel, unconjugated and conjugated PLGA nanoparticles was studied in HepG2 cells. Size, zeta potential and drug loading of PLGA nanoparticles were about 199 nm, -11.07 mV, and 4%, respectively where size, zeta potential and drug loading of conjugated nanoparticles were found to be 204 nm, -5.6 mV and 3.6% respectively. Conjugated nanoparticles represented a three-phasic release pattern with a 20% burst effect for docetaxel on the first day. Cytotoxicity experiment showed that the IC50 of HSA conjugated PLGA nanoparticles (5.4 mug) was significantly lower than both free docetaxel (20.2 mug) and unconjugated PLGA nanoparticles (6.2 mug). In conclusion surface modification of PLGA nanoparticles through HSA conjugation results in more cytotoxicity against tumor cell lines compared with free docetaxel and unconjugated PLGA nanoparticles. Albumin conjugated PLGA nanoparticles may represent a promising drug delivery system in cancer therapy.
    DARU-JOURNAL OF FACULTY OF PHARMACY 07/2013; 21(1):58. DOI:10.1186/2008-2231-21-58 · 1.64 Impact Factor
  • Source
    • "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. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Four E. ruminantium 1H12 open reading frames and their proteins known to protect sheep against heartwater needle challenge were encapsulated into, or adsorbed onto poly(d,l-lactide-co-glycolide) microparticles. Microspheres with smooth surface and smaller than 5 μm diameters were produced, with high adsorption and encapsulation efficiencies. Gel electrophoresis showed that neither encapsulation nor adsorption affected the stability of the DNA or proteins. Cationic microparticles released ∼40% of plasmid DNA on day 1 while PLGA 50:50-COOH microparticles co-encapsulating plasmid DNA and polyvinyl alcohol only started to release from days 12-28. Recombinant proteins were released from PLGA 85:15 and homopolymer R 203 S microparticles in a biphasic manner with a high initial burst release (∼45-80%). In contrast, PLGA 50:50 microparticles had low (15-65%) initial burst release followed by (25-80%) release by days (days 28-42). A cocktail of these microparticles could therefore be used as single-dose auto-booster vaccine.
    Ticks and Tick-borne Diseases 12/2010; 1(4):186-93. DOI:10.1016/j.ttbdis.2010.08.001 · 2.72 Impact Factor
Show more