A novel in vitro delivery system for assessing the biological integrity of protein upon release from PLGA microspheres.
OBJECTIVE
The development of a novel in vitro system is required to assess the stability and release kinetics of a protein microsphere formulation used for drug delivery to the brain.


METHODS
Microspheres containing lysozyme as model protein were prepared using a (w/o/w) emulsion-solvent evaporation process. Both the active and total (active + inactive) encapsulation efficiencies and release profiles were determined. The biologic activity of lysozyme was measured using bacterial cell lysis; total protein content was measured using a 125I-radiolabel. A novel in vitro apparatus was developed to determine kinetics over a sustained time period (>30 days).


RESULTS
The microencapsulation technique allowed an entrapment of active lysozyme at 80 +/- 4% and a sustained (>42 days) in vitro release. The kinetics study showed that the novel in vitro system was able to detect the release of low amounts (ng) of protein. To improve the stability of the protein within microspheres and allow the release of biologically active lysozyme, a basic additive ( Mg(OH)2 ) was successfully encapsulated.


CONCLUSIONS
This novel in vitro system was appropriate to study protein microsphere release kinetics. In addition, the model is cost-effective and mimes brain physiological conditions more closely than previous models.
Aubert-Pouëssel
Anne
A
INSERM ERIT-M 0104, Ingenierie de la Vectorisation Particulaire, IBT, Angers, France.
Bibby
David C
DC
Venier-Julienne
Marie-claire
MC
Hindré
François
F
Benoît
Jean-Pierre
JP
D002626:Chemistry, Pharmaceutical; D016503:Drug Delivery Systems / Q000295:instrumentation / Q000379:methods*; D004355:Drug Stability; D004356:Drug Storage; D019344:Lactic Acid / Q000008:administration & dosage / Q000737:chemistry / Q000493:pharmacokinetics*; D008863:Microspheres; D009113:Muramidase / Q000008:administration & dosage / Q000737:chemistry / Q000493:pharmacokinetics; D011100:Polyglycolic Acid / Q000008:administration & dosage / Q000737:chemistry / Q000493:pharmacokinetics*; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011108:Polymers / Q000008:administration & dosage / Q000737:chemistry / Q000493:pharmacokinetics*; D011506:Proteins / Q000008:administration & dosage / Q000737:chemistry / Q000493:pharmacokinetics*
D011108:Polymers; D011506:Proteins; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011100:Polyglycolic Acid; D019344:Lactic Acid; D009113:Muramidase