Subnanomolar Cyanide Detection at Polyphenol Oxidase/Clay Biosensors

Abstract

A novel, inexpensive, and simple amperometric biosensor based on immobilization of polyphenol oxidase (PPO) into Zn-Al layered double hydroxides, also called anionic clays, is applied for determination of cyanide. The detection of cyanide was performed via its inhibiting action on the PPO electrode. Measurement was carried out with 3,4-dihydroxyphenylacetic acid as enzyme substrate, the enzymatically generated quinoid products being electroreduced at -0.2 V. An extremely sensitive detection limit (0.1 nM) was obtained for cyanide. Enzyme immobilization into an anionic exchanger clay seems to cause an increase in cyanide inhibition effects because of anion accumulation in the clay matrix.

Efficient Immobilization of Tyrosinase Enzyme on Layered Double Hydroxide Hybrid Nanomaterials for Electrochemical Detection of Polyphenols

“…These biosensor features correspond to averages, since obtained with a mixture of polyphenols extracted from green tea. Indeed, biosensor efficiency should vary with the nature of polyphenols, as described in literature [17]- [19], [22], [23], [30], [40], [58], [63]- [65]. However, it is possible to determine a mean molecular mass of polyphenols at 415 g.mol −1 , by taking into account the molar mass of each compound present in the mixture and its relative percentage determined from previous analyses [44].…”

“…At this potential value, two mechanisms can coexist: already mentioned oxido-reduction processes involving cobalt, and electrochemical reduction of products enzymatically formed by tyrosinase [26], [58]- [60], the global current intensity including the two processes. At both potential values (+0.13V and −0.25V), the saturation is observed at polyphenol concentration above 1000 ng.mL −1 (data not shown).…”

Electrochemical Sensors

“…145 The authors used synthetic Zn-Al layered double hydroxides (LDHs) as matrix to entrap the enzymes. The charge density of layers in LDHs is higher than that of other cationic clays, which makes them a good transducer for the detection of decreased amperometric response due to enzyme inhibition.…”

Cyanide Determination With a Modified Ninhydrin Reagent Using N-Acetyl Cysteine in the Presence of Heavy Metal Ions

“…6 PPO/ clay biosensors have the lowest detection limit (0.1 nM) for cyanide. 7 In environmental wastes, free cyanide can be determined after using time consuming techniques like solvent extraction, gas dialysis, microdiffusion, pervaporation. 8 Without using these techniques, any of above mentioned methods aren't usable in the presence of heavy metals.…”