A Potentiometric Formaldehyde Biosensor Based on Immobilization of Alcohol Oxidase on Acryloxysuccinimide-modified Acrylic Microspheres

Yew Pei Ling,Lee Yook Heng

doi:10.3390/s101109963

Abstract

A new alcohol oxidase (AOX) enzyme-based formaldehyde biosensor based on acrylic microspheres has been developed. Hydrophobic poly(n-butyl acrylate-N-acryloxy-succinimide) [poly(nBA-NAS)] microspheres, an enzyme immobilization matrix, was synthesized using photopolymerization in an emulsion form. AOX-poly(nBA-NAS) microspheres were deposited on a pH transducer made from a layer of photocured and self-plasticized polyacrylate membrane with an entrapped pH ionophore coated on a Ag/AgCl screen printed electrode (SPE). Oxidation of formaldehyde by the immobilized AOX resulted in the production of protons, which can be determined via the pH transducer. Effects of buffer concentrations, pH and different amount of immobilization matrix towards the biosensor’s analytical performance were investigated. The formaldehyde biosensor exhibited a dynamic linear response range to formaldehyde from 0.3–316.2 mM and a sensitivity of 59.41 ± 0.66 mV/decade (R2 = 0.9776, n = 3). The lower detection limit of the biosensor was 0.3 mM, while reproducibility and repeatability were 3.16% RSD (relative standard deviation) and 1.11% RSD, respectively (n = 3). The use of acrylic microspheres in the potentiometric formaldehyde biosensor improved the biosensor’s performance in terms of response time, linear response range and long term stability when compared with thick film immobilization methods.

Highlights

Formaldehyde (H2CO) is the simplest aldehyde compound
Photopolymerization caused the droplets of monomers to form poly(nBA-NAS) microspheres at room temperature and this method of polymerization can be terminated by removing the light source [49,50]
This work has shown that the use of hydrophobic acrylic microspheres for immobilization of enzyme, e.g., alcohol oxidase (AOX) can lead to an overall improvement in the analytical performance of the resulting biosensor

Summary

Introduction

Formaldehyde (H2CO) is the simplest aldehyde compound. It is commonly used as a disinfectant and biocide [1] and as a preservative in the food industry [2]. Formaldehyde is naturally present in living organisms, fruits, vegetables and biological compounds [3,4]. High concentration of formaldehyde can be found in seafood and crustaceans, due to the enzymatic dissociation of trimethylamine-oxide (TMAO) [5]. TMAO is often found in fish as a natural compound that exists in their muscles [6]. A high content of accumulated formaldehyde in food poses a threat to human health [5], as formaldehyde is toxic, allergenic and carcinogenic and can cause symptoms like headaches, burning sensation in the throat and difficulty in breathing [1] and it has been declared a potential carcinogen and mutagen [2]

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