title: pH-triggered release of vancomycin from protein-capped porous silicon films.
abstract: OBJECTIVE
  An in vitro model system for pH-triggered release of the antibiotic vancomycin from porous Si films is studied.
  
  
  METHODS
  Vancomycin is infused into a mesoporous Si film from a mixed aqueous/acetonitrile solution and trapped by a capping layer containing the protein bovine serum albumin (BSA). The protein effectively traps vancomycin in the porous nanostructure at pH 4.0; the protein dissolves and vancomycin is released into solution when the pH increases to 7.4. The surface chemistry of porous Si exerts a substantial effect on the efficacy of drug loading. The amount of drug loading is larger in freshly-etched (hydrophobic, hydrogen-terminated) porous Si and smaller in methyl-modified, undecylenic acid-modified and thermally oxidized samples. The quantity of drug loaded in a freshly etched porous Si chip is proportional to the thickness of the porous layer, which exhibits a constant volume loading efficiency of 31% (v/v). Flow-cell experiments designed to mimic the transition from pH 4 to 7 that occurs when material moves from the stomach to the upper intestinal tract were performed on the freshly etched films and vancomycin- and BSA-release rates were quantified from the effluent of the flow cell by high-pressure liquid chromatography analysis.
  
  
  CONCLUSIONS
  There is a small, constant rate of vancomycin release at pH 4 that is independent of the amount of drug loaded in the pores. This is attributed to diffusion of vancomycin from the BSA-capping layer. The release rate increases five- to tenfold when the pH of the solution in the flow cell increases to 7.4; 100% of the drug is released within 3 h of this increase.
authors.affiliation: Nitto Denko Technical Corp, Carlsbad, CA, USA. loren.perelman@gmail.com
authors.forename: Loren A
authors.initials: LA
authors.lastname: Perelman
authors.forename: Claudia
authors.initials: C
authors.lastname: Pacholski
authors.forename: Yang Yang
authors.initials: YY
authors.lastname: Li
authors.forename: Michael S
authors.initials: MS
authors.lastname: VanNieuwenhze
authors.forename: Michael S
authors.initials: MS
authors.lastname: Vannieuwenhz
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Sailor
mesh_terms: D000042:Absorption; D020099:Coated Materials, Biocompatible / Q000737:chemistry*; D004058:Diffusion; D004337:Drug Carriers / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008422:Materials Testing; D008567:Membranes, Artificial; D011485:Protein Binding; D012710:Serum Albumin, Bovine / Q000737:chemistry*; D012825:Silicon / Q000737:chemistry*; D014640:Vancomycin / Q000008:administration & dosage / Q000737:chemistry*
chemical_list: D020099:Coated Materials, Biocompatible; D004337:Drug Carriers; D008567:Membranes, Artificial; D012710:Serum Albumin, Bovine; D014640:Vancomycin; D012825:Silicon