Use of magnetically disentangled thiolated carbon nanotubes as a label-free impedimetric genosensor for detecting canine Leishmania spp. infection

We discuss the development of a thiolated carbon nanotube (ThNT) transducer for femtomolar detection of Leishmania spp. (CL) DNA based on the use of electrical impedance spectroscopy. Aminated short single strands probes of the chosen DNA target were covalently linked to carboxyl-functionalized ThNTs, anchored upon ultrathin Au films. The genosensors exhibit a less resistive behavior when an external magnetic field was applied to forcefully disentangle the ThNTs during their covalent immobilization, than when immobilized in their natural randomly oriented form. Under disentangled conditions the sensors presented a linear detection of parasite DNA in the 0.1 to 98.3 fg/μL range. The lower limit corresponds to a CL DNA concentration of 15 fM in canine genomic samples extracted directly from the blood of infected animals. The covalent immobilization of the ThNTs at the electrode surface reduces their tendency to peeling off. As a result, one could recycle the sensors after each experiment by rinsing them with hot water and use them for at least 5 successive times, with a relative standard deviation lower than 5%. Since no amplification of the target DNA is required, we suggest that use of these genosensors can represent a simple and yet accurate approach for the fast-molecular diagnosis of canine leishmaniasis.

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