Synthesis and Characterization of Nitric Oxide-Releasing Sol-Gel Microarrays

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 um. 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 um, 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.