Nano-aptamer Based Quantitative Detection of Chloramphenicol
Chloramphenicol (CAP) is a broad-spectrum antibiotic, chronic use of which leads to aplastic anaemia and bone marrow suppression. Most countries, including India, have banned CAP from animal food production. However, it has still been detected in milk, ho
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1 Introduction Chloramphenicol is a highly-effective antibiotic used widely in the treatment of animals. However, prolonged intake of CAP is associated with aplastic anaemia (AA) and bone marrow suppression in humans with percent mortality of 40–50 % (Shukla et al. 2011). Most countries, including India, have prohibited usage of CAP in production of animal food (Food Safety and Standards Regulations 2011) while maximal permissible levels is 0.3 parts per billion (ppb) in milk (Vora and Raikwar 2013). However, in recent years traces of it have been detected in milk, honey, shrimp and other aquaculture products raising serious concerns about health of consumers and the export of antibiotic-containing honey from India (Shukla et al. 2011; Islam et al. 2014). Most available assays are based on antibodies employing conjugated enzymes. These assays, though sensitive, suffer from issues such as adjuvant addition, high cost, cumbersome and time-consuming primary and secondary antibody generation (Samsonova et al. 2012). Thus, need exists for quick, simple and cost-effective yet sensitive detection of CAP. The proposed assay is based on salt-induced aggregation of gold nanocolloids that leads to red-to-blue colour change. Gold nanocolloids (5–100 nm) show R. Sharma K.V. Ragavan K.S.M.S.Raghavarao (&) Academy of Scientific and Innovative Research (AcSIR), CSIR-Central Food Technological Research Institute (CSIR-CFTRI), Mysore, India e-mail: [email protected] R. Sharma K.V. Ragavan K.S.M.S.Raghavarao Department of Food Engineering, CSIR-Central Food Technological Research Institute (CSIR-CFTRI), Mysore, India M.S. Thakur (&) Materials Science Centre, University of Mysore, Mysore, India e-mail: [email protected] © Springer Science+Business Media Singapore 2016 Prasanna B.D. et al. (eds.), Biotechnology and Biochemical Engineering, DOI 10.1007/978-981-10-1920-3_21
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Fig. 1 a Principle of gold nanocolloid and aptamer-based colorimetric determination of CAP. b Dispersed and aggregated nanocolloids
remarkable size-dependent optical properties. They are being widely used in detection systems, a major portion of which constitutes of colorimetric aggregation based bioassays (Katiyar et al. 2013; Sharma et al. 2015b). In this technique dispersed gold nanocolloids (usually red in colour) are protected by a biorecognition element from salt-induced aggregation, the absence of which leads to the formation of larger particles changing the colour to bluish purple. When added, analyte binds and engages the biorecognition element that can no more protect the nanocolloids. The salt ions interfere with the electrostatic repulsive forces between nanoparticles, leading to formation of bigger clumps. The resulting colour change is observed visually and measured spectrophotometrically. Aptamers are highly specific biorecognition elements that change conformation on analyte binding (Sharma et al. 2015b). The present method involves protection of nanocolloids by a DNA aptamer that has a strong affinity for CAP
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