Sol–gel derived nitric oxide-releasing oxygen sensors

Abstract

An amperometric sol–gel derived sensor that both releases nitric oxide (NO) and measures physiologically relevant concentrations of oxygen (PO₂) is described. The sensor consists of a platinum electrode coated with an aminosilane/ethyltrimethoxysilane hybrid xerogel film. Hydrophilic polyurethane (HPU) is doped into the hybrid film to reduce sensor hydration time and increase oxygen permeability. Diazeniumdiolate NO donors are formed within the polymer matrix by exposing the cured film to high pressures of NO. These coatings release up to 7.2 pmol s⁻¹ cm⁻² of NO over the first 12 h and maintain detectable levels of NO release through 48 h. Sensors modified with HPU-doped, NO-releasing xerogels exhibit a linear response to O₂ within 30 min of polarization at −0.65 V vs. Ag/AgCl, and have a sensitivity of ∼6 nA/mmHg O₂. The xerogel coating is stable in buffer solution with minimal fragmentation over 48 h. In vitro biocompatibility studies indicate that these materials effectively reduce platelet adhesion.