Argon-plasma-assisted graft polymerization of thick hydrogels with controllable water swelling on Chronoflex

Chronoflex, a polyurethane, is a suitable material for use in polymeric tracheobronchial stents. A controlled release layer on the stent is required for effective localized delivery of cancer drugs to the tumor cells. This paper reports on the investigation of coating Chronoflex with acrylated oligomers by argon plasma assisted UV graft polymerization. Coatings of poly(ethylene glycol) diacrylate (PEGDA) with molecular weight 700 or a 50:50 mixture of PEGDA with poly(propylene glycol) diacrylate (PPGDA) with molecular weight 900 which were tens of micrometers thick were shown to have good adhesion to Chronoflex. No photoinitiator was added. Formulations containing photoinitiator or a trifunctional crosslinker which increases strength and decreases water swelling showed poor adhesion to Chronoflex. The degree of water swelling of grafted PEGDA coating reached about 709%, making it suitable for use as a hydrogel coating for controlled drug release on Chronoflex. Adding PPGDA to PEGDA was shown to decrease the degree of water swelling. Hence, removal of the photoinitiator, use of oligomeric diacrylate with high molecular weight per acrylate group and a clean Chronoflex surface are found to be important factors for ensuring adhesion between the thick hydrogel coating and Chronoflex.