Fiber optic profenofos sensor based on surface plasmon resonance technique and molecular imprinting Anand M. Shrivastav, Sruthi P. Usha, Banshi D. Gupta n Physics Department, Indian Institute of Technology Delhi, New Delhi 110016, India article info Article history: Received 27 July 2015 Received in revised form 15 November 2015 Accepted 30 November 2015 Available online 2 December 2015 Keywords: Optical fiber Sensor Pesticides Surface plasmon resonance Molecular imprinting Profenofos abstract A successful approach for the fabrication and characterization of an optical fiber sensor for the detection of profenofos based on surface plasmon resonance (SPR) and molecular imprinting is introduced. Mo- lecular imprinting technology is used for the creation of three dimensional binding sites having com- plementary shape and size of the specific template molecule over a polymer for the recognition of the same. Binding of template molecule with molecularly imprinted polymer (MIP) layer results in the change in the dielectric nature of the sensing surface (polymer) and is identified by SPR technique. Spectral interrogation method is used for the characterization of the sensing probe. The operating profenofos concentration range of the sensor is from 10 À4 to 10 À1 mg/L. A red shift of 18.7 nm in re- sonance wavelength is recorded for this profenofos concentration range. The maximum sensitivity of the sensor is 12.7 nm/log (mg/L) at 10 À4 mg/L profenofos concentration. Limit of detection (LOD) of the sensor is found to be 2.5 Â 10 À6 mg/L. Selectivity measurements predict the probe highly selective for the pro- fenofos molecule. Besides high sensitivity due to SPR technique and selectivity due to molecular im- printing, proposed sensor has numerous other advantages like immunity to electromagnetic inter- ference, fast response, low cost and capability of online monitoring and remote sensing of analyte due to the fabrication of the probe on optical fiber. & 2015 Elsevier B.V. All rights reserved. 1. Introduction Pesticides are the broad range of chemicals which are mainly used to kill or repel the pests on crops. These are widely used on vegetables, ornaments, fruits, grains, etc. and are characterized on the basis of functional groups present in their molecular structure (inorganic, organophosphorus, organochlorine, etc.) and on the basis of their biological activity on target species (herbicides, fungicides, insecticide, etc.) (Hoff and Zoonen, 1999; Hajslovaè et al., 1999). Organophosphorus pesticides (OPPs) are specifically used for controlling the large range of pests on the cotton, vege- tables, rice, sugarcane, etc. Further, OPPs are responsible for the inhibition of the activity of nervous system enzyme acet- ylcholinesterase (AChE) which regulates the acetylcholine. AChE is an enzyme which digests the neurotransmitter acetylcholine by hydrolyzing it. Due to the very high catalytic activity of AChE, it hydrolyzes around 25,000 molecules of acetylcholine (ACh) per second once ACh comes in its domain. The hydrolytic process results in the recycling of the byproduct-choline produced to synthesize ACh again (Quinn, 1987). Thus, OPPs can cause injurious effects to the nervous system of humans even at low concentrations. Due to this, OPPs are also known as neurotoxins (Cremisini et al., 1995; Guerrieri et al., 2002). In addition, these are also eco-toxic to birds, aquatic organisms and bees (Laschi et al., 2007). Profenofos, o-(4-bromo 2-chlorophenyl)-o-ethyl-s-propyl phosphorothioate, is a type of OPP which is extensively used nowadays and therefore a rapid, highly sensitive and selective method is required for its detection. Numerous methods for pro- fenofos detection have been reported in the literature. These methods are mainly based on chromatography, immunology etc. In the case of chromatography various sub-methods like gas chromatography–mass spectroscopy (GC–MS) (Chu et al., 2005; Frenich et al., 2007; Qu et al., 2010), gas chromatography-flame potentiometric detector (GC-FPD) (Li et al., 2007), gas chromato- graphy-nitrogen phosphorus detector (GC-NPD) (Solé et al., 2000), high performance liquid chromatography (HPLC) (Cappielo et al., 2002) and high performance liquid chromatography–mass spec- troscopy (HPLC–MS) (Kruve et al., 2008) are in use. However, above methods are quite sensitive and accurate but are time consuming, require expert handling and use expensive instru- ments. In the immunological methods one of the methods used is enzyme-linked immunosorbent assay (ELISA) (Nunes et al., 1998). Although this shows high sensitivity, selectivity and suitability for the analysis of a large number of samples within a very short time Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/bios Biosensors and Bioelectronics http://dx.doi.org/10.1016/j.bios.2015.11.095 0956-5663/& 2015 Elsevier B.V. All rights reserved. n Corresponding author. E-mail address: bdgupta@physics.iitd.ernet.in (B.D. Gupta). Biosensors and Bioelectronics 79 (2016) 150–157