NANOPORE HYBRID BIOSENSORS FOR SINGLE MOLECULE SELECTIVE SENSING
Large nanopores, realizable by standard lithographic techniques, can be bio-functionalized to obtain a final device with dimensions compatible with single molecule sensing applications, and selective for different kind of interactions between probe and target molecules.
Single molecule sensing with nanopores is a rapidly developing field which exerts a special fascination on the scientific community, both for the potential revolutionary effect it can have on bioanalytics and diagnostics, and for its striking intrinsic interdisciplinary. Starting from the first papers mainly devoted to illustrate the properties of protein pores, much work has been done to realize engineered devices based on solid state nanopores, with specific characteristics and sensing abilities. Nowadays the spectrum of proposed nanopore applications is quite large, most of them being based on electrophoretic current measurements during molecules translocation, i.e. on a simple functioning principle which does not need molecular labeling and optical detection. Nanopore sensing can thus provide a low cost, fast processing and high throughput alternative to current DNA analysis and sequencing techniques.
The specific sensing mechanism merges coulter counting and single current recording (figure 1).: the nanopore conductance is modulated during the passage of single molecules by steric or electrostatic effects. Nevertheless, nanopores properties can be finely tuned by introducing artificial binding and recognition sites or, generally speaking, by chemically modifying their surface properties (figure 2).
Figure 2. Chemically modified nanopores for selective sensing
The single molecule sensing ability of our device was recently demonstrated by registering translocation events of -DNA molecules through a 40 nm diameter FIB drilled nanopore bio-functionalized with 45-mer oligonucleotides (figure 5).
results demonstrate that it will be possible, in a near future, to conceive
and design devices for parallel analysis of biological samples, made
of arrays of nanopores, fabricated by standard lithographic techniques
and finely tuned and resized by bio-functionalization.
We made a step further in this direction with the Polimeric nanochannel device, which is based on chemically modified nanochannels created on a polymeric substrate. The possibility to realize a polymeric nanopore offers many advantages over solid state technologies such as really cheap, rapid and easy fabrication and integrability. Combining nanofabrication and soft lithography it is possible to create a nanochannel device as shown in figure 6 which can be functionalized with oligonucleotides by means of a specifically developed protocol (see figure 7).
Figure 7. Fluorescence image of the microchannels along the inlet and the outlet, where cylindrical pillar are presents, showing the presence of Fitc-labelled DNA
"WHO'S WHO" OF THE PROJECT
 V. Mussi, P. Fanzio, L. Repetto, G. Firpo, S. Stigliani, P. Scaruffi, G.P. Tonini and U. Valbusa, "DNA-functionalized nanopores for single molecule analysis", Nanotecnology, 2009, Proceedings of IEEE-NANO 2009, 9th IEEE Conference, Publication Year: 2009, Pages 682 - 684.
 P. Fanzio, E. Angeli, V. Mussi, U. Valbusa, P. Rivolo, F. Frascella, F. Pirri, "Development of a polymeric device for gene expression profiling", Nanotecnology, 2009, Proceedings of IEEE-NANO 2009, 9th IEEE Conference, Publication Year: 2009, Pages: 613 - 615.
 V. Mussi, P. Fanzio, L. Repetto, G. Firpo, P. Scaruffi, S. Stigliani, GP. Tonini, U. Valbusa, "DNA-functionalized solid state nanopore for biosensing", Nanotechnology 21 (2010) 145102.
 V. Mussi, P. Fanzio, L. Repetto, G. Firpo, P. Scaruffi, S. Stigliani, M. Menotta, M. Magnani, G. P. Tonini and U. Valbusa, "Electrical characterization of DNA-functionalized solid state nanopores for bio-sensing", submitted to Journal of Physics: Condensed Matter.
*Italian Patent # RM2009A000450, 4th September 2009, V. Mussi. P. Fanzio, U. Valbusa, L. Repetto, G. Firpo, S. Stigliani, P. Scaruffi, G.P. Tonini, V. Mussi. P. Fanzio, U. Valbusa, L. Repetto, G. Firpo, S. Stigliani, P. Scaruffi, G.P. Tonini, "Chip nanoforato di nitruro di silicio per l'analisi di profili di espressione genica e relativi biosensori" ("Silicon nitride nanopore chip for gene expression profiling and biosensing");