title: Drug delivery to the skin from sub-micron polymeric particle formulations: influence of particle size and polymer hydrophobicity.
abstract: OBJECTIVE
  To investigate the influence of particle size and polymer properties on the topical delivery of a lipophilic "active" species (Nile Red (NR)) from sub-micron polymeric particles.
  
  
  METHODS
  Three poly-(epsilon-caprolactone) (CAPA) formulations were examined to assess the impact of particle size. Three other formulations, based on cellulose acetate butyrate (CAB), CAPA and polystyrene were studied to address the role of polymer hydrophobicity. In vitro skin permeation, and confocal microscopy and stratum corneum (SC) tape-stripping were used to evaluate the cutaneous disposition of NR.
  
  
  RESULTS
  NR delivery into the SC was greater from the larger particles, the overall smaller surface area of which enhanced the "leaving tendency" of the lipophilic "active". Skin uptake of NR (measured as "%payload released") from polystyrene, CAPA and CAB particles increased with decreasing polymer hydrophobicity (polystyrene > CAPA > CAB) as expected. Confocal microscopy revealed that NR released from the particles accumulated in, and penetrated via, lipid domains between the SC corneocytes. The particles showed affinity for hairs, and concentrated on the skin surface at the follicular openings.
  
  
  CONCLUSIONS
  Delivery of a model drug to the skin from sub-micron polymeric particle formulations is sensitive to the particle size and the relative hydrophobicity of the carrier.
authors.affiliation: Department of Pharmacy & Pharmacology, University of Bath, Claverton Down, Bath, BA2 7AY, UK.
authors.forename: Xiao
authors.initials: X
authors.lastname: Wu
authors.forename: Bruno
authors.initials: B
authors.lastname: Biatry
authors.forename: Colette
authors.initials: C
authors.lastname: Cazeneuve
authors.forename: Richard H
authors.initials: RH
authors.lastname: Guy
mesh_terms: D000818:Animals; D016503:Drug Delivery Systems; D018613:Microscopy, Confocal; D010316:Particle Size; D010539:Permeability; D010599:Pharmacokinetics; D011108:Polymers / Q000737:chemistry*; D012867:Skin / Q000378:metabolism*; D013552:Swine
chemical_list: D011108:Polymers