Optik 127 (2016) 8807–8811 Contents lists available at ScienceDirect Optik journal homepage: www.elsevier.de/ijleo Original research article A miniaturized optical biosensor for the detection of Hg 2+ based on acid phosphatase inhibition Chandrakant K. Tagad a,b , Atul Kulkarni c , R.C. Aiyer b , Dewyani Patil b , Sushma G. Sabharwal a,b,∗ a Biochemistry Division, Department of Chemistry, Savitribai Phule Pune University, Pune 411007, India b Centre for Sensor Studies, Department of Electronic Science, Savitribai Phule Pune University, Pune 411007, India c Nanoparticle Technology Lab, Sungkyunkwan University, Suwon 440746, South Korea a r t i c l e i n f o Article history: Received 3 May 2016 Accepted 29 June 2016 Keywords: Optical biosensor Acid phosphatase Inhibition based Portable device a b s t r a c t In the present study, a simple low cost and portable optical biosensor has been fab- ricated for the detection of Hg 2+ based on inhibition of acid phosphatase activity. Poly-dimethoxysiloxane (PDMS) sensor chip module containing reaction and detection wells was fabricated. Acid phosphatase from the seeds of Macrotyloma uniflorum was immobilized at the bottom of reaction well to carry out the enzymatic reaction using p-nitrophenyl phosphate as a synthetic substrate. The detection was based on the measure- ment of transmitted light intensity through the yellow coloured solution of p-nitrophenol ( 405 ) liberated as a result of enzymatic reaction and was measured in terms of volts. The optical system was successfully employed for the detection of Hg 2+ based on inhibition of enzyme activity. Response of the sensor was found to be linear in the range of 0.01–10 mM. The biosensor was stable up to 20 days of storage at 4 ◦ C without any appreciable loss in activity. © 2016 Elsevier GmbH. All rights reserved. 1. Introduction Heavy metals, even in small concentrations, are one of the most serious environmental pollutants worldwide because of their non bio-degradable nature that can lead to severe health hazards [1]. Numerous uses of metals in metal plating factories, mining industries, tanning, dye and chemical manufacturing industries, etc., are major sources of environmental pollution [2]. Mercury, lead, chromium, cadmium, copper and zinc are amongst the most frequently occurring metal contaminants and mercury is known to be the highest threat for the environment as well as for human health. Mercury occurs in elemental, inorganic and organic form. Elemental Hg, liquid at room temperature volatizes readily and is rapidly distributed in body through vapours, but is poorly absorbed. Exposure to inorganic mercury can result in dermal toxicity whereas, organic mercury, being lipid soluble, gets absorbed via gastrointestinal track, lungs, skin and can cross placenta and into breast milk [3]. Consequently, environmental awareness is growing among consumers and industrialists while legal constraints on emissions, both at national and international levels, are becoming increasingly strict [4]. In this context, reliable, efficient and cost-effective wastewater treatment technologies are needed for monitoring of heavy metal pollutants that adversely affect human health. Various sophisticated analytical techniques like inductively ∗ Corresponding author at: Biochemistry Division, Department of Chemistry, Savitribai Phule Pune University, Pune 411007, India. E-mail address: ssab@chem.unipune.ac.in (S.G. Sabharwal). http://dx.doi.org/10.1016/j.ijleo.2016.06.123 0030-4026/© 2016 Elsevier GmbH. All rights reserved.