It was found that DNAs can act as attractive templates for oxidative polymerization of pyrrole and result in novel higher-order superstructures composed of the DNA padding and the conjugate polymer outer layer. Furthermore, the resultant DNA/poly(pyrrole) composite can be deposited on an ITO electrode. The TEM and SEM observations have shown that oxidative polymerization creates a variety of superstructural poly(pyrrole) assemblies such as nanosized rodlike, circular, or supercoiled structures, reflecting the higher-order conformations of DNAs acting as the templates. The findings establish that the morphology of the conjugate polymer assemblies are controllable by a change in the DNA morphology used as their templates. The deposition of DNAs onto the ITO electrode was characterized by (1) ATR IR absorption bands assignable to DNA, (2) XPS binding energy of the phosphate group assignable to DNAs, and (3) binding of ethidium bromide (EB) to DNAs as detected by UV-vis spectroscopy and confocal laser scanning microscope (CLSM), The further detailed examination of the SEM pictures has established that the composite consists of a fibrous structure or its bundled structure, depending on the polymerization conditions. Interestingly, the ITO electrode modified by the DNA/poly(pyrrole) composite showed the CV responsiveness to DNA intercalators, indicating a potential to apply this system to a new amperometric DNA-based sensor.
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