pH-triggered release of vancomycin from protein-capped porous silicon films.
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.
Perelman
Loren A
LA
Nitto Denko Technical Corp, Carlsbad, CA, USA. loren.perelman@gmail.com
Pacholski
Claudia
C
Li
Yang Yang
YY
VanNieuwenhze
Michael S
MS
Vannieuwenhz
Michael S
MS
Sailor
Michael J
MJ
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*
D020099:Coated Materials, Biocompatible; D004337:Drug Carriers; D008567:Membranes, Artificial; D012710:Serum Albumin, Bovine; D014640:Vancomycin; D012825:Silicon