Georgia-Paraskevi Nikoleli

Construction of a simple optical sensor based on air stable lipid film with incorporated urease for the rapid detection of urea in milk.

This work describes the construction of a simple optical sensor for the rapid, selective and sensitive detection of urea in milk using air stable lipid films with incorporated urease. The lipid film is stabilized on a glass 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. Urease is incorporated within this mixture prior to the polymerization. The presence of the enzyme in these films quenched this fluorescence and the colour became similar to that of the filters without the lipid films. A drop of aqueous solution of urea provided a switching on of the fluorescence which allows the rapid detection of this compound at the levels of 10(-8) M concentrations. The investigation of the effect of potent interferences included a wide range of compounds usually found in foods and also of proteins and lipids. These lipid membranes were used for the rapid detection of urea in milk.

Preparation of a selective receptor for carbofuran for the development of a simple optical spot test for its rapid detection using stabilized in air lipid films with incorporated receptor

The present technique describes the preparation of a selective receptor for carbofuran and the development of a simple sensitive spot optical test for the rapid one-shot detection of carbofuran using stabilized lipid films supported on a methacrylate polymer on a glass fiber filter with incorporated artificial receptor. The selective receptor was synthesized by a chemical reaction using a resorcin[4]arene receptor by transforming all the -OH groups into phosphoryl groups. The lipid films without this receptor provided fluorescence under a UV lamp. The use of the receptor in these films quenched this fluorescence and the colour became similar to that of the filters without the lipid films. A drop of aqueous solution of carbofuran provided a switching on of the fluorescence which allows the rapid detection of this insecticide at the levels of 10(-9)M concentrations. The effect of potent interferences included a wide range of compounds. The results showed no interferences from these compounds in concentration levels usually found in real samples. The effect of interference of proteins and lipids was also examined. The reproducibility of the method was checked in about 100 samples and all of them were found to provide similar results. The device was tested/evaluated in real samples of fruits, vegetables and dairy products. Note that the colours of the filters remain stable for periods of more than 2 months.

Development of an electrochemical chemosensor for the rapid detection of zinc based on air stable lipid films with incorporated calix4arene phosphoryl receptor

This work describes the preparation of a selective receptor for the rapid, selective, and sensitive electrochemical flow injection analysis of zinc using air stable lipid films supported on a methacrylate polymer on a glass fibre filter with incorporated artificial receptor. The selective receptor was synthesised by transformation of the –OH groups of resorcin4arene receptor into phosphoryl groups. These lipid films were supported on a methylacrylate polymer (i.e. methacrylic acid was the functional monomer for the polymerisation, ethylene glycol dimethacrylate was used as the crosslinker and 2,2′-azobis-2-methylpropionitrile as an initiator). A minisensor device was constructed for the electrochemical flow injection analysis of zinc based on air stabilised lipid films supported on a polymer. The device can sense the analyte in a drop (75 µL) of sample. Zinc was injected into flowing streams of a carrier electrolyte solution. A complex formation between the calix4arene phosphoryl receptor and zinc takes place. This enhances the pre-concentration of zinc at the lipid membrane surface which in turn causes dynamic alterations of the electrostatic fields and phase structure of membranes; as a result ion current transients were obtained and the magnitude of these signals was correlated to the substrate concentration. The response times were ca 5 s and zinc was determined at concentration levels of nanomolar. The analytical curve was linear in the concentration range 1.00 × 10−7 − 1.20 × 10−6 M with detection limit of 5.00 × 10−8 M and a relative standard deviation lower than 4%. The effect of potent interferences included a wide range of other metals. As an analytical demonstration, trace concentrations of Zn(II) were successfully detected in real samples of waters without any laborious and time-consuming treatment.

Portable Biosensing of Food Toxicants and Environmental Pollutants

Portable biosensing of food toxicants and environmental pollutants , Portable biosensing of food toxicants and environmental pollutants , کتابخانه دیجیتالی دانشگاه علوم پزشکی و خدمات درمانی شهید بهشتی

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

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.

Prototype Biosensing Devices

Abstract Nanotechnology is playing an increasingly important role in the development of biosensors. Use of nanomaterials in biosensors allows the use of many new signal transduction technologies in their manufacture. Because of their submicron size, nanosensors, nanoprobes, and other nanosystems are revolutionizing the fields of chemical and biological analysis, to enable rapid analysis of multiple substances in food and environmental samples. Recent progress in nanotechnology has resulted in producing affordable, mass-produced devices and in integrating these into components and systems (including portable ones) for mass market applications for food toxicants monitoring. Sensing includes chemical and microbiological food toxicants, such as toxins, insecticides, pesticides, herbicides, microorganisms, bacteria, viruses, and other microorganisms, phenolic compounds, allergens, genetically modified foods, hormones, and dioxins. The sensitivity and performance of biosensors is being improved by using nanomaterials for their construction. The use of these nanomaterials has allowed the introduction of many new signal transduction technologies in biosensors. Because of their submicron dimensions, nanosensors, nanoprobes, and other nanosystems have allowed simple and rapid analyses in vivo. Portable instruments capable of analyzing multiple components are becoming available. This chapter reviews the status of the various nanostructure-based biosensors and investigates prototype biosensing devices: design and microfabrication based on nanotechnological tools yield devices suitable for the rapid in the field detection of food toxicants and environmental pollutants.