title: Inhibition of peptide acylation in PLGA microspheres with water-soluble divalent cationic salts.
abstract: OBJECTIVE
  To test the potential of water-soluble divalent cationic salts to inhibit acylation of octreotide encapsulated in poly(D,L-lactic-co-glycolic acid)-star (PLGA) microspheres.
  
  
  METHODS
  The divalent cationic salts, calcium chloride and manganese chloride, previously shown to disrupt peptide sorption, were introduced in PLGA microspheres prepared by the double emulsion-solvent evaporation method. Peptide stability was monitored by reversed-phase high performance liquid chromatography (RP-HPLC) and identified by liquid chromatography coupled with mass spectrometry (LC-MS) during microsphere degradation under physiological conditions for 4 weeks. Microsphere morphology and salt content were examined by scanning electron microscopy (SEM) and inductively coupled plasma-optical emission spectroscopy (ICP-OES), respectively.
  
  
  RESULTS
  Addition of divalent cationic salts solely to the organic phase did not provide acylation inhibition. However, addition of the salt inhibitors to both the primary emulsion and the outer water phase resulted in improved drug and salt encapsulation efficiency as well as significantly decreased salt leaching and octreotide acylation. After 28 days, the extent of acylation inhibition afforded by divalent cations was > 58% relative to 13% for the NaCl control group.
  
  
  CONCLUSIONS
  Water-soluble divalent cationic salts represent a suitable class of stabilizer of peptide acylation in PLGA microspheres and this study provides an important formulation approach to maximize stabilizer potency.
authors.affiliation: Department of Pharmaceutical Sciences, University of Michigan, Ann Arbor, Michigan 48109, USA.
authors.forename: Ying
authors.initials: Y
authors.lastname: Zhang
authors.forename: Andreas M
authors.initials: AM
authors.lastname: Sophocleous
authors.forename: Steven P
authors.initials: SP
authors.lastname: Schwendeman
mesh_terms: D000215:Acylation; D002413:Cations, Divalent / Q000737:chemistry*; D019344:Lactic Acid / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D008863:Microspheres; D010455:Peptides / Q000737:chemistry*; D011100:Polyglycolic Acid / Q000737:chemistry*; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D012995:Solubility; D013057:Spectrum Analysis / Q000379:methods
chemical_list: D002413:Cations, Divalent; D010455:Peptides; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011100:Polyglycolic Acid; D019344:Lactic Acid