Cyanide is commonly used in metallurgy, electroplating, fishing, gold mining, and in the polymer industry. So it is often found as an environmental contaminant. Cyanide is a toxic anion with strong affinity for the heme unit of cytochrome oxidase and blocks the oxidative metabolism in humans, leading to death.
Literature indicates that a cyanide concentration of even 0.5 mg per kg of body weight is lethal. As per the WHO, a maximum of 1.9 µM is the acceptable limit of cyanide in drinking water.
There are optical, electrochemical, spectrometric, chromatographic and quartz crystal microbalance techniques to detect and quantify cyanide. But they require sophisticated instrumentation, skilled users and come at a cost.
Optical chemosensors to test for cyanide in water are less costly. The chemosensors have an electrophilic centre to detect the nucleophilic cyanide. However, such chemosensors entail complicated procedures and have poor detection limits. Moreover, the response time is also poor.
Kiran Gore and team from Mumbai University collaborated with Ganesh N. Nawale of Sweden to develop a cyanide sensor using a synthetic analogue of green fluorescent protein, a widely used marker. Their students, Lavanya Mittapelli and Abhishek Mirajkar in Mumbai University, have been working on fluorescent protein chromophores. The structural motif in green fluorescent protein, 4-arylidene-5-imidazolinone, is easily synthesizable for sensing applications.
The scientists modified the chromophore of the fluorescent protein with a tertiary butyldimethylsilyl group. This group has a Si-O bond which, when cleaved, increases the fluorescence 24 fold! The method is simple and cost effective.
Gore and team also filed a patent with the Indian patent office.
DST-INSPIRE funding has taken the research so far. There is an urgent need to translate these findings to develop a cost effective technology for water quality monitoring and for public health security
Ref: Sens Act B 265, 257-263 (2018); DOI: 10.1016/j.snb.2018.03.068
Report by: N Sekar, Institute of Chemical Technology, Matunga, Mumbai