title: Effect of co-solvents on the characteristics of enkephalin microcapsules.
abstract: The objective of this project was to study the effect of the presence of co-solvents with dichloromethane on the properties of leu-enkephalin microcapsules. Six co-solvents, including ethyl acetate, methanol, ethanol, acetone, isopropanol and acetonitrile, at three concentrations of 5%, 10% and 20% (v/v), respectively, of dichloromethane were selected for this study. The resulting microcapsules were evaluated for morphology and particle size, surface area, thermal characteristics and efficiency of encapsulation. The analysis of particle size distribution showed bi- and tri-modal distribution of the microcapsules. The median particle size of the microcapsules was between 17 microm and 57 microm. All microcapsules were smaller than 90 microm. Approximately 10% of the microcapsules were smaller than 500 nm. In general, the microcapsules prepared with co-solvents showed relatively smaller median size. The microcapsules were spherical in shape. DSC analysis of the microcapsules showed that there were no significant differences in the glass transition temperatures. There were significant changes in the efficiency of encapsulation due to the addition of co-solvents. Substitution with 20% methanol resulted in 40% increase in the efficiency of encapsulation (12% vs. 17%). Furthermore, substitution with 20% ethyl acetate, isopropanol, or acetonitrile, reduced the efficiency of encapsulation to as low as 6%.
authors.affiliation: College of Pharmacy, Xavier University of Louisiana, 1 Drexel Drive, New Orleans, LA 70125-1098, USA.
authors.forename: Richard A
authors.initials: RA
authors.lastname: Graves
authors.forename: Thomas
authors.initials: T
authors.lastname: Freeman
authors.forename: Sarala
authors.initials: S
authors.lastname: Pamajula
authors.forename: Natalie
authors.initials: N
authors.lastname: Praetorius
authors.forename: Raisa
authors.initials: R
authors.lastname: Moiseyev
authors.forename: Tarun K
authors.initials: TK
authors.lastname: Mandal
mesh_terms: D001672:Biocompatible Materials / Q000737:chemistry*; D001673:Biodegradation, Environmental; D002214:Capsules; D004339:Drug Compounding; D004743:Enkephalin, Leucine / Q000737:chemistry*; D019344:Lactic Acid / Q000737:chemistry*; D008422:Materials Testing; D008752:Methylene Chloride; D008855:Microscopy, Electron, Scanning; D010316:Particle Size; D011100:Polyglycolic Acid / Q000737:chemistry*; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011108:Polymers / Q000737:chemistry*; D012997:Solvents; D013499:Surface Properties; D013816:Thermodynamics
chemical_list: D001672:Biocompatible Materials; D002214:Capsules; D011108:Polymers; D012997:Solvents; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011100:Polyglycolic Acid; D019344:Lactic Acid; D004743:Enkephalin, Leucine; D008752:Methylene Chloride