A miniaturized optical biosensor for the detection of Hg2+ based on acid phosphatase inhibition

In the present study, a simple low cost and portable optical biosensor has been fabricated for the detection of Hg2+ 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 measurement of transmitted light intensity through the yellow coloured solution of p-nitrophenol (λ405) liberated as a result of enzymatic reaction and was measured in terms of volts. The optical system was successfully employed for the detection of Hg2+ 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.