Analysis of livestock DNA using nanotechnologies

Traceability of animals and animal products has become a priority for governments of the developed countries, due to consumer demand for comprehensive and integrated animal health and food safety policies. Genetic testing of food and livestock is routinely used in a traceability system for food-borne risk assessment and management. Currently, DNA analyses are carried out with PCR based system, typically a real time PCR which makes use of fluorescent probes. This system allows the identification of species through the amplification of short fragments of mitochondrial DNA whose integrity, due to the high abundance in the cell, is less affected by the treatment in food processing than genomic DNA. We developed an innovative method for species identification using a new type of sensing device based on microfabricated cantilevers. Microcantilevers are silicon beams (500 µm long, 100 µm wide and 1 µm thick) fixed at one end, whose surface is coated (functionalized) with oligonucleotide probes able to hybridize with a specific target molecule. When a solution, containing PCR products complementary to the probes, comes into contact with the sensor surface, the cantilever responds mechanically. Following hybridization, the surface stress, due to electrostatic repulsion or steric interaction, leads to a bending of the cantilever. This effect is optically measured by determining the position of a laser beam reflected by the cantilever surface.The method employs an array of cantilevers, that can be used to test simultaneously up to eight different probes designed against a specific fragment of the mitochondrial cytochrome C oxydase gene for species discrimination. This kind of sensors allows a much higher sensitive detection of a given target compared to traditional systems and, moreover, specific DNA sequences can be detected avoiding fluorescent or radioactive labelling, thus reducing the cost of the analysis. © Copyright 2007 Taylor & Francis Group LLC.