Label-free detection of cupric ions and histidine-tagged proteins using single poly(pyrrole)-NTA chelator conducting polymer nanotube chemiresistive sensor

Novel chemical and biological sensors based on a single poly(pyrrole)-NTA chelator nanotube for sensitive, selective, rapid and real-time detection of histidine-tagged protein and cupric ions are reported. NTA groups on the nanotube surface provided a simple mechanism for metal ion sensing via the high-affinity interaction between NTA and the subsequent detection of histidine-tagged protein through the coordination with metal chelated nanotube. Poly(pyrrole)-NTA chelator nanotubes of 190 nm outside diameter, 35 nm wall thickness and 30 μm long were synthesized by electrochemical polymerization of pyrrole-NTA inside a 200 nm diameter alumina template and assembled as a chemoresistive device by bottom-up contact geometry on a pair of parallel gold electrodes with a gap distance of 3 μm. The chemoresistive sensors based on single poly(pyrrole)-NTA chelator nanotube exhibited detection as low as one-hundredth attomolar (0.6 ppt) cupric ions and 1 ng/ml of penta-histidine tagged syntaxin protein.