Photobinding of [gamma-(32)P] ATP gamma-benzophenone to the surface of a polyurethane membrane in the preparation of a beta-particle-emitting balloon catheter.

Abstract

The goal of this study was to photochemically bind 5'-[gamma-(32)P]-azido-ATP gamma-benzophenone ((32)P-ATP-BPA) to a polyurethane surface. Expandable balloon catheters composed of (32)P-coated polyurethane have the potential for preventing restenosis following percutaneous transluminal coronary angioplasty. After extensive preparation and cleaning of polyurethane disks, 10 microL of the radioactive ATP-BPA reagent (specific activity = 9.4 Ci/mmol) was applied to the surface. After drying, the membrane disks were exposed ultraviolet radiation (254 nm; 6,000 microwatts/cm(2)) for up to 2 h and subsequently washed. The amount of (32)P bound to the membrane disks was determined by Cerenkov counting in a liquid scintillation counter. The effect of the labeling solution composition (solvent, presence of potassium or manganese ions, addition of surfactants, etc.) on photobinding efficiency was determined. The efficiency of attaching the (32)P-ATP-BPA reagent to the polyurethane surfaces was markedly dependent upon the cleaning and pretreatment conditions. Following detailed washing and rinsing steps, a photobinding efficiency of 36.4+/-3.6% was obtained with 10 min UV exposure time using (32)P-ATP-BPA solutions that were 95/5 methanol/water by vol. Increasing the concentration of the (32)P-ATP-BPA reagent did not improve the photobinding efficiency; however, the total amount of (32)P bound to the disks was increased. Photochemical methods can be employed to attach beta(-)-emitting radionuclides to polymers that are employed as balloon catheters. The preparation of the polymeric material (washing, rinsing, and drying) is critically important in maximizing the amount of (32)P-ATP-BPA that can be bound to the polymer.