Tracking food poison
doi:10.1038/nindia.2008.136 Published online 7 March 2008
Researchers have devised a bioactive electrode that can seek out traces of toxic chemicals in food. The electrode is highly sensitive in detecting Ochratoxin A (OTA), a fungal toxin. This could have significant potential in real time detection of toxic chemicals in different types of food products.
Despite being a non-toxic biopolymer and having excellent film-forming ability, Chitosan (CS) is poorly biocompatible. This prevents it from holding biomolecules on its surface. Earlier, nanoparticles of zinc oxide and gold have been added to CS to overcome this problem. During the present work, researchers added titanium dioxide nanoparticles to make CS biocompatible. They created the electrode by adding titanium dioxide nanoparticles in CS solution and spreading a thin film on indium-tin-oxide (ITO).
To test the electrode, they spread a solution of rabbit antibodies on its surface. Ochratoxin-A (OTA), a toxin released by the fungus Aspergillus ochraceus, was added to the electrolyte. Titanium dioxide bonded with CS and degraded it into oligosaccharide. The oligosaccharide facilitated the reaction between rabbit antibodies and OTA.
It is well known that toxic chemicals target our immune system. "Hence, our main interest was to study the interrelation between OTA and the rabbit antibodies," says lead researcher Marshal Dhayal from the Liquid Crystal and Self Assembled Monolayer Section of National Physical Laboratory, New Delhi. The unbounded sites (with no rabbit antibodies) on the CS/TiO2 matrix were blocked using a protein called bovine serum alubumin. "This was done to eliminate any possibility of direct interaction of OTA with the matrix," says Dhayal.
The sensitivity of bioactive electrode increased with an increase in TiO2 concentration and the electrode showed promise as immunosensor. "TiO2 added CS sensitivity was four times higher than only CS," he says.
- Khan, R. et al. Nanocrystalline bioactive TiO2–chitosan impedimetric immunosensor for ochratoxin-A. Electrochem. Commun. 10, 492-495 (2008)