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Langmuir 2004, 20, 10296-10302
Synthesis and Characterization of Nitric Oxide-Releasing Sol-Gel Microarrays Mary E. Robbins, Erin D. Hopper, and Mark H. Schoenfisch* Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290 Received July 1, 2004. In Final Form: August 30, 2004 Diazeniumdiolate-modified sol-gel microarrays capable of releasing low levels of nitric oxide are reported as a viable means for improving the blood compatibility of a surface without fully modifying the underlying substrate. Several parameters are characterized including: (1) NO surface flux as a function of sol-gel composition and microarray geometry; (2) microstructure dimensions and spacing for optimal blood compatibility; and (3) the effect of sol-gel surface modification on analyte accessibility to platinum electrodes. The sol-gel microarrays release biologically relevant levels of NO under physiological conditions for >24 h. In vitro platelet adhesion assays indicate that a NO surface flux of 2.2 pmol cm-2 s-1 effectively reduces platelet adhesion to glass substrates modified with sol-gel microstructures separated by 50 µm. The blood compatibility observed for these micropatterned surfaces is comparable to NO-releasing sol-gel films. When the separation between NO-releasing microstructures is reduced to 10 µm, the NO surface flux required to reduce platelet adhesion is lowered to 0.4 pmol cm-2 s-1. Finally, the oxygen response of platinum electrodes modified with NO-releasing sol-gel microarrays indicates that selective modification via micropatterning enhances analyte accessibility to the sensor surface.
Introduction Polymers designed to mimic the inner surface (endothelium) of healthy blood vessels through the controlled release of nitric oxide (NO) have emerged as a class of biomaterials well suited for blood-contacting medical device applications due to their ability to resist platelet adhesion and subsequent thrombus (blood clot) formation.1 In the presence of hemoglobin and oxygen, the half-life of NO is
