Nitric Oxide Release from Polydimethylsiloxane-based Polyurethanes

Localized nitric oxide (NO) release from polymeric materials holds much promise for the prevention of coagulation often associated with implantable and extracorporeal blood-contacting devices. Films of polyurethane (PU) containing incorporated polyethyleneimine were thus exposed to NO gas to form diazeniumdiolates (NONOates) in situ. Donor incorporation and NO gas exposure did not affect the mechanical properties of the films. The NO release capacity increased with increasing polydimethylsiloxane (PDMS) content in the soft segment of the PU: total capacity could be more than doubled (P<0.05) from 0.093 ± 0.028 to 0.225 ± 0.004 mmol/g when the PDMS content was increased from 0 to 100%. Release kinetics were best approximated using a modified Korsemeyer-Peppas power law (R ² =0.95-0.99). Despite the resultant rapid initial decrease in NO release rates, values above that observed for quiescent endothelial cells (0.83 pmol·cm ⁻² ·s ⁻¹ ) were maintained for extended periods of 5-10 days, while rates above that of a stimulated endothelium (2.7-6.8 pmol·cm ⁻² ·s ⁻¹ ) were achieved for the first 24 hours. This method of NONOate formation may be advantageous, as potential premature NO release by exposure of diazeniumdiolated donors during incorporation, processing and storage, can be avoided by in situ diazoniumdiolation closer to the time of implantation.