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Life Science Div./ All the news/ Scientific results/ Artificial molecule-snaring pores
Monday July 27 2009

Artificial molecule-snaring pores

Bouchet A., Descamps E., Mailley P., Livache T., Chatelain F., Haguet V. Contactless Electrofunctionalization of a Single Pore. Small, en ligne.
CEA
A technique pioneered just a few years ago makes it possible to detect suspended molecules or particles in a sample by gating them through single-pore membranes. However, this technique is still practically unable to identify the group type of the molecules detected. One of the methods that could overcome this issue is to “functionalize the pore”, i.e. fit it with biosensors that specifically recognize the molecules of interest and snare them inside the pore. A research team partnering the Biochips Laboratory (iRTSV/DSV) and the SPrAM molecular architecture properties and structure research laboratory (INAC/DSM) have discovered a new technique enabling ultra-localized organic or inorganic material deposition on the inner pore-wall surface. Thanks to this technique, the biosensors only need to be bonded to the inner pore surface, with no parasitic deposition on the membrane itself. These findings, which have been published online in the academic review Small, pave the way to the production of functionalized pores that can be custom-tailored to separate, purify or capture specifically targeted macromolecules or particles, such as bacteria or cells.


At CEA Grenoble, the inventors of this new electrodeposition technique have christened it ‘contactless electrofunctionalization’: it enables electrosensitive materials such as pyrrole monomers to be etched into the inner surface of a pore that has been engineered inside a dielectric (electrically-insulated) membrane. The functionalization procedure hinges on applying a high electrical field between two electrodes placed just a handful of millimetres from the pore openings. Deposition takes just a few seconds and proves highly robust to changes in the deposition parameters.
Biosensors, such as DNA strands pre-tied to the pyrrole monomers, can then be solidly attached to the inner pore wall. The functionalization process has been demonstrated as effective via DNA/DNA hybridization and fluorescence labelling. This was achieved by covering pores of just a few microns in diameter with DNA probes. As the cDNA strands are gated through the pore, they get stopped and snared by targeted DNA-specific recognition. Fluorescence-labelling the DNA strands leads to the appearance of a fluorescent circle, thus revealing the presence of deposition on the inner pore wall. Observations made on either side of the membrane demonstrate that the functionalization is localized exclusively inside the individual pore.
 

Principle behind trapping molecules of interest exclusively onto the inner pore surface. The membrane, which has been immersed in a solution containing the molecules to be snared, is subjected to a high electrical field (top). The molecules are snared exclusively inside the pore – never on the outer membrane surface (bottom).
  
               
After single-DNA hybridization and fluorescence labelling, only the inner pore wall shows up fluorescent (right: white circle).
The team has demonstrated that the deposition remains stable and that it is possible to reutilize the biofunctionalized pore. This was done by running several successive hybridization/denaturation cycles (here, ‘denaturation’ means detaching target DNA from the DNA snared on the pore wall). The fluorescent ring disappears after the DNA denaturation step, before re-appearing after the next hybridization plus fluorescence-labelling step.
 
This same contactless electrofunctionalization process can also be employed to deposit iridium oxide (IrOx) inside the pore. The pore is partially or fully flushed with this metal oxide, whereas there is no change in the dielectric membrane. This ultra-localized functionalization technique therefore appears equally efficient for a large set of organic or inorganic materials. This biofunctionalization technique is expected to find challenging applications in selective separation, purification, collection and catalysis inside micropores and nanopores.