Nanopore and Nanochannel Synthesis for Molecular Interaction Characterisation at the Single-Molecule Level

In aqueous conditions, we monitor in real time the ionic current through individual artificial nanopores under an applied potential. The nanopores are drilled through Si 3 N 4 membranes 30 and 50 nm thick to diameters rangingfrom 2.5 to 6.5 nm. After chemical surface hydroxylation, and addition of bipyridyl, we are able to observe alterations of the ionic current recording when negatively charged surface modified gold nanoparticles are added under an electric field. We recorded the response of 2.5 and 3.2 nm diameter nanopores to 3nm MPSA coated nanoparticles, and compared the signal to that of MUS, MUS:OT 2/1, and MUS:OT ½. The results show that the different surface coatings translate into different current block signatures. At this pore diameter none of the nanoparticles were able to perfuse through the pore. At 4 nm diameter, MPSA nanoparticles generate signals of varied amplitude, by reversing the current, and recapturing particle from the Trans side, we were able to identify the current block amplitude corresponding to a nanoparticle translocating through the nanopore. With the same pore we observed a large increase of the binding time by dsDNA in the presence of Mg ++ ions. The presence of these ions also leads to double amplitude DNA binding events, which suggest that DNA is capable of interacting with the nanopore, before the actual threading event. When the nanopore diameter is 6.5 nm wide, MPSA nanoparticles no longer generate any current block. However, larger MUS particles can cause very small amplitude blocks.