Electrochemically stimulated adenosine 5'-triphosphate (ATP) release through redox switching of conducting polypyrrole films and bilayers

Electrochemically stimulated adenosine 5'-triphosphate (ATP) release from poly(pyrrole adenosine 5'-triphosphate) (PP-ATP) was investigated using cyclic voltammetry. Two separate redox processes at E(1/2) = -0.4 and 0.0 V were clearly elucidated by switching the film in polyelectrolyte solutions and found to correlate with cation and anion dominant transport, respectively. This voltammetric method allows the dominant mobile ionic species to be determined as redox processes associated with the movement of the polyelectrolyte counterion through the film are observed, while redox processes associated with transport of ions having the same charge as the polyelectrolyte are repressed. As such, the more anodic redox process results in ATP release. Spontaneous ATP exchange in a supporting electrolyte was examined at open circuit, revealing that less than 10% of the electrochemically releasable ATP is spontaneously released after 10 days. The ATP release concept was extended to bilayers consisting of PP-ATP as inner layers and poly(N-methylpyrrole) (PNMP) with various dopant anions as outer layers. PP-ATP:poly(N-methylpyrrole chloride) (PP-ATP:PNMP-Cl) bilayers with varied thicknesses of inner and outer films were constructed to examine electrochemically stimulated ATP release during reduction of PP-ATP. PP-ATP:PNMP/ heparin (PP-ATP:PNMP/HPN) bilayers with varied outer film thicknesses, which are were also prepared and their ATP release properties were compared. It was found that the rate of electrochemical ATP release can be controlled by adjusting each film thickness with minimal change of ionic strength of the switching medium.