Developing of a versatile and compact paper-based microfluidic biosensors for detection of copper in food products

Abstract

In this contribution, a versatile, inexpensive and compact paper-based microfluidic biosensor was developed to detect heavy metals in food products. The underlying principle was based on sensing of ammonia (NH ) released during urease- 3 catalyzed hydrolysis of urea. At the presence of heavy metals, the amount of NH 3 produced diminished due to inhibition of urease enzyme. Therefore, the concentration of target heavy metals could be indirectly determined from NH , 3 qualitatively, semi-quantitatively or quantitatively. Hydrophobic barriers of functional areas the sensor were fabricated by paraffin-dipping method. Urease enzyme wa s physically immobilized onto the sensor and phenol red was used for qualitative and semi-quantitative detection of heavy metal via image analysis. The sensor was also integrated into an electrochemical system using simple screen- printed electrodes. In the current study, Cu was used as a model heavy metal ++ for testing performance of the sensor. Qualitative results showed that a strong contrast between safe and unsafe sample, which was critical for the practical applicability of the sensor. Relationship between color intensity and Cu ++ concentration was characterized by a R of 0.98 and the linear range covered Cu 2 ++ concentrations from 0.01 – 1 ppm. Detection limit was estimated to be 0.018 ppm which was well below standard limit established by WHO and EC for Cu . + + Quantitative tests were still at beginning stage and were worth further investigations. The findings from this study demonstrated that the proposed paper-based biosensor could be a promising platform to develop low-cost test kits for detection of heavy metals in foods. Keywords: Paper-based biosensor, wax-printing, screen-printing electrodes, SPEs, colorimetric test, amperometric test.