Bioactive paper platform for colorimetric phenols detection.

Polyphenols, as food antioxidants, are of great interest due to their health benefits as they decrease the risks of cancer and coronary cardiopathy (1). Moreover they influence the quality and organoleptic characteristics of foods (2). Lastly, some neurotransmitters are phenolic compounds. Hence the need to work out a sensitive, portable and inexpensive detection methods to monitor these compounds (3). We developed a disposable paper-based bioassay for the detection of phenolic compounds; the assay was successfully applied for the determination of polyphenols in a real matrix such as wine. The colorimetric quantification of the analyte is based on an enzymatic assay. The tyrosinase enzyme has been immobilized on a filter paper by simple over-spotting with 3-methyl-2-benzothiazolinone hydrazone (MBTH), that allows the detection of phenols by forming stable colored adducts with their enzymatic oxidation products. The color intensity of the adduct (developed after 5 min of reaction) was found to increase proportionally with the increase of the phenolic substrate concentrations. Analyte detection can be achieved by eye and quantification can be simply obtained by using a camera phone and an image analysis software. The response, characteristics of the sensor were determined using l-3,4-dihydroxyphenyl-alanine (l-DOPA), an archetype substrate of tyrosinase, as the analyte. This disposable paper-based biosensor relies on a rapid and simple method, without need of sophisticated instrumentation and trained personnel and could be extremely useful in remote locations or developing countries which does not have ready access to laboratory facilities and where simple, sensitive and low cost bioassays are essentials.