Artificial nanopores have become promising tools for sensing DNA.Here,we report a new technique for sensing DNA through a conical-shaped nanopore embedded in track-etched polyethylene terephthalate(PET)membrane.Two different streptavidin-conjugated monovalent DNA probes were prepared that can bind to two distinct segments(at either end) of the target DNA.The size of target DNA-linked to the two streptavidin-conjugated monovalent DNA probes is double that of the individual probes.By precisely controlling the tip diameter of the conical nanopore embedded in the PET polymer,events due to the translocation of the streptavidin-conjugated monovalent DNA probes through the nanopore can be filtered and purposely undetected,whereas the current pulses due to the translocation of the target DNA-induced selfassembled complexes can be detected.The two streptavidin-conjugated DNA probes cannot be linked by multimismatched DNA.Therefore,multi-mismatched(nonspecific) DNA will not induce any current pulse signatures.The current pulse signatures for the self-assembled complex can be used to confirm the presence of the target DNA.The size-dependent detection of self-assembled complexes on the molecular level shows strong promise forthe detection of biomolecules without interference from the probes.
