Construction of a Simple Portable Optical Sensor Based on Air Stable Lipid Film with Incorporated Acetylcholinesterase for the Rapid Detection of Carbofuran in Foods

Abstract

This work describes the construction of a simple portable optical biosensor for the rapid, selective, and sensitive detection of carbofuran in foods using air stable lipid films with incorporated acetylcholinesterase. The stabilized substance supported on a polymer lipid film on a glass fiber filter was formed on the filter by polymerization using UV (ultra-violet) radiation prior its use. Methacrylic acid was the functional monomer, ethylene glycol dimethacrylate was the crosslinker, and 2,2′-azobis-(2-methylpropionitrile) was the initiator. Acetylcholinesterase was incorporated within this mixture prior to the polymerization. The polymerization process took place by using UV irradiation. The polymerized lipid films without this enzyme provided fluorescence under a UV lamp. The presence of the enzyme in these films quenched this fluorescence. A drop of aqueous solution of acetylcholine provided a “switching on” of the fluorescence, which allowed the rapid detection of this compound at the levels of 10⁻⁸ M concentrations. These lipid membranes were used for the rapid detection of pesticides. Carbofuran was chosen as a typical pesticide. A drop of carbofuran in the filters quenched again the fluorescence. Carbofuran could be determined at concentration levels of 10⁻⁷ to 10⁻⁹ M. The investigation of the effect of potent interferences included a wide range of compounds usually found in foods and also of proteins and lipids. The technique was applied in real samples of fruits, vegetables, and dairy products. This allowed the rapid detection of the pesticide in markets and in the field.

Keywords:

• Acetylcholine
• Acetylcholinesterase
• Carbofuran
• Optical portable biosensor
• Stabilized lipid films

Acknowledgments

This work was carried out in the framework of the “Receptronics” EC project (NMP4-CT-2005-017114) with the financial contribution of the European Commission (Contract no. 70/3/8307). The authors acknowledge the financial help of the Greek Ministry of Development, General Secretariat of Research and Technology (Contract 70/3/8268) and Special Account for Research Grants of the National & Kapodistrian University of Athens (Contract 70/4/5730). T. Hianik is grateful to the Agency for Promotion and Development (contract No. APVV-0362-07) for financial support. This article is dedicated to the memory of Prof. G. G. Guilbault who first taught us biosensor and enzyme electrode technology. Jery Guilbault was a person with a noble and kind heart who was always there to help us. The authors hope that his memory will always remain with us who were his collaborators and friends for almost 40 years.

Notes

n.d.: amount of carbofuran is below the detection limit. The % recovery in the last column was calculated as follows: known amounts of standard solution of carbofuran were added to the sample after its preparation and was determined by our method. The % recovery represents the ratio of the found/added × 100.