| || Detection of Ricin in Water Samples using Disposable Screen-Printed Electrodes
Author : Suresh, S.;Om Kumar;Kolhe, Pawan;Rao, V. Kameswara;Sekhar, K.
Source : Defence Science Journal ; Vol:57(6) ; 2007 ; pp 839-844
Subject : 60 Biotechnology;61 Medical Sciences
Keywords : Screen-printed electrode;Amperometric immunosensor;Ricin;Ppotentiostat;Plant toxin;ELISA
Abstract : Ricin is a highly toxic plant toxin, which is extracted from the beans of the castor plant, Ricinus communis. Ricin is thousand times more poisonous than cyanide and thirty times more potent than nerve gases. The toxin (ricin) could be used to contaminate food or water, causing panic. Attempts were made for the detection of ricin in water samples by utilising amperometric immunosensors. Single-use screen-printed electrodes were made using polystyrene and graphite. These electrodes were tested for their ability to detect 1-naphthol which is the product of the reaction between 1-naphthyl phosphate and the enzyme alkaline phosphatase conjugate. An indirect enzyme-linked immunosorbent assay (ELISA) system was used to detect ricin. First, ricin antigen was incubated on the screen-printed electrode. This was followed by blocking with BSA and incubation with antibody raised against ricin in rabbit. The last step wass the incubation with anti-antibody of rabbit conjugated to enzyme alkaline phosphatase. This electrode is inserted in an electrochemical cell containing diethanolamine buffer and a potential of 0.4 V wrt reference electrode (Ag/AgCl) was applied using a potentiostat. Various experiments were carried out for optimising the conditions like substrate concentration, amount of antibody raised against ricin, anti-antibody alkaline phosphatase conjugate, and blocking agents. It was found that the response of amperometric sensor is proportional to the logarithmic of ricin concentration from 100 ng/ml to 3200 ng/ml. Using traditional methods, it is possible to detect ricin concentration up to 300 ng/ml in 18 h, while with amperometric immunosensor, one can detect ricin as low as 40 ng/ml within 90 min. The details of making the screen-printed electrodes, characterisation, optimisation of various conditions for the highest sensitivity have been discussed.