title: Controlled release of dexamethasone from microcapsules produced by polyelectrolyte layer-by-layer nanoassembly.
abstract: OBJECTIVE
  In an effort to expand the application of core-shell structures fabricated by electrostatic layer-by-layer (LbL) self-assembling for drug delivery, this study reports the controlled release of dexamethasone from microcrystals encapsulated with a polyelectrolyte shell.
  
  
  METHODS
  The LbL self-assembly process was used to produce dexamethasone particles encapsulated with up to five double layers formed by alternating the adsorption of positively charged poly(dimethyldiallyl ammonium chloride), negatively charged sodium poly(styrenesulfonate) and depending on the pH positively or negatively charged gelatin A or B onto the surface of the negatively charged dexamethasone particles. The nano-thin shells were characterized by quartz crystal microbalance measurements, microelectrophoresis, microcalorimetry, confocal microscopy, and scanning electron microscopy. In vitro release of dexamethasone from the microcapsules suspended in water or carboxymethylcellulose gels were measured using vertical Franz-type diffusion cells.
  
  
  RESULTS
  Sonication of a suspension of negatively charged dexamethasone microcrystals in a solution of PDDA not only reduced aggregation but also reduced the size of the sub-micrometer particles. Assembly of multiple polyelectrolyte layers around these monodispersed cores produced a polyelectrolyte multilayer shell around the drug microcrystals that allowed for controlled release depending on the composition and the number of layers.
  
  
  CONCLUSIONS
  Direct surface modification of dexamethasone microcrystals via the LbL process produced monodispersed suspensions with diffusion-controlled sustained drug release via the polyelectrolyte multilayer shell.
authors.affiliation: Institute for Micro-manufacturing and Department of Biomedical Engineering, Louisiana Tech University, Ruston, LA, USA.
authors.forename: Nikhil
authors.initials: N
authors.lastname: Pargaonkar
authors.forename: Yuri M
authors.initials: YM
authors.lastname: Lvov
authors.forename: Ning
authors.initials: N
authors.lastname: Li
authors.forename: Jan H
authors.initials: JH
authors.lastname: Steenekamp
authors.forename: Melgardt M
authors.initials: MM
authors.lastname: de Villiers
mesh_terms: D002214:Capsules / Q000032:analysis / Q000737:chemistry; D002449:Cell Aggregation; D002470:Cell Survival / Q000187:drug effects*; D002626:Chemistry, Pharmaceutical / Q000379:methods; D003460:Crystallization; D003692:Delayed-Action Preparations / Q000008:administration & dosage / Q000493:pharmacokinetics*; D003907:Dexamethasone / Q000008:administration & dosage / Q000032:analysis / Q000493:pharmacokinetics*; D003979:Diazonium Compounds / Q000032:analysis; D004573:Electrolytes / Q000032:analysis / Q000737:chemistry; D006358:Hot Temperature; D008863:Microspheres; D036103:Nanotechnology / Q000379:methods; D010316:Particle Size; D011108:Polymers / Q000032:analysis / Q000737:chemistry; D011208:Powders / Q000032:analysis / Q000737:chemistry; D011725:Pyridines / Q000032:analysis; D013010:Sonication; D055672:Static Electricity; D013678:Technology, Pharmaceutical / Q000379:methods
chemical_list: D002214:Capsules; D003692:Delayed-Action Preparations; D003979:Diazonium Compounds; D004573:Electrolytes; D011108:Polymers; D011208:Powders; D011725:Pyridines; C056729:4-(2'-pyridyldithio)benzyldiazoacetate; D003907:Dexamethasone