title: Preparation, characterization, and in vivo evaluation of insulin-loaded PLA-PEG microspheres for controlled parenteral drug delivery.
abstract: OBJECTIVE
  The aim of this study was to prepare insulin-loaded poly(lactic acid)-polyethylene glycol microspheres that could control insulin release at least for 1 week and evaluate their in vivo performance in a streptozotocin-induced diabetic rat model.
  
  
  METHODS
  The microspheres were prepared using a water-in-oil-in-water double emulsion solvent evaporation technique. Different formulation variables influencing the yield, particle size, entrapment efficiency, and in vitro release profiles were investigated. The pharmacokinetic study of optimized formulation was performed with single dose in comparison with multiple dose of Humulin 30/70 as a reference product in streptozotocin-induced diabetic rats.
  
  
  RESULTS
  The optimized formulation of insulin microspheres was nonporous, smooth-surfaced, and spherical in structure under scanning electron microscope with a mean particle size of 3.07 microm and entrapment efficiency of 42.74% of the theoretical amount incorporated. The in vitro insulin release profiles was characterized by a bimodal behavior with an initial burst release because of the insulin adsorbed on the microsphere surface, followed by slower and continuous release corresponding to the insulin entrapped in polymer matrix.
  
  
  CONCLUSIONS
  The optimized formulation and reference were comparable in the extent of absorption. Consequently, these microspheres can be proposed as new controlled parenteral delivery system.
authors.affiliation: School of Pharmaceutical Sciences, Universiti Sains Malaysia, Minden, Penang, Malaysia. ravigdk2002@yahoo.co.uk
authors.forename: Ravi
authors.initials: R
authors.lastname: Sheshala
authors.forename: Kok Khiang
authors.initials: KK
authors.lastname: Peh
authors.forename: Yusrida
authors.initials: Y
authors.lastname: Darwis
mesh_terms: D000818:Animals; D001786:Blood Glucose / Q000032:analysis; D003692:Delayed-Action Preparations; D003921:Diabetes Mellitus, Experimental / Q000097:blood / Q000188:drug therapy*; D004337:Drug Carriers / Q000737:chemistry*; D004339:Drug Compounding / Q000379:methods*; D005260:Female; D007004:Hypoglycemic Agents / Q000008:administration & dosage* / Q000493:pharmacokinetics / Q000627:therapeutic use; D007279:Injections, Subcutaneous; D007328:Insulin / Q000008:administration & dosage* / Q000493:pharmacokinetics / Q000627:therapeutic use; D007773:Lactates / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D008863:Microspheres; D010316:Particle Size; D011092:Polyethylene Glycols / Q000737:chemistry*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012995:Solubility; D013311:Streptozocin; D013499:Surface Properties
chemical_list: D001786:Blood Glucose; D003692:Delayed-Action Preparations; D004337:Drug Carriers; D007004:Hypoglycemic Agents; D007328:Insulin; D007773:Lactates; C088513:poly(lactic acid-ethylene glycol); D011092:Polyethylene Glycols; D013311:Streptozocin