Infrared optical immunosensor: application to the measurement of the herbicide atrazine

Simultaneous determination of paraquat and atrazine in water samples with a white light reflectance spectroscopy biosensor

An optical immunosensor based on White Light Reflectance Spectroscopy for the simultaneous determination of the herbicides atrazine and paraquat in drinking water samples is demonstrated. The biosensor allows for the label-free real-time monitoring of biomolecular interactions taking place onto a SiO₂/Si chip by transforming the shift in the reflected interference spectrum due to reaction to effective biomolecular layer thickness. Dual-analyte determination is accomplished by functionalizing spatially distinct areas of the chip with protein conjugates of the two herbicides and scanning the surface with an optical reflection probe. A competitive immunoassay format was adopted, followed by reaction with secondary antibodies for signal enhancement. The sensor was highly sensitive with detection limits of 40 and 50 pg/mL for paraquat and atrazine, respectively, and the assay duration was 12 min. Recovery values ranging from 90.0 to 110% were determined for the two pesticides in spiked bottled and tap water samples, demonstrating the sensor accuracy. In addition, the sensor could be regenerated and re-used at least 20 times without significant effect on the assay characteristics. Its excellent analytical performance and short analysis time combined with the small sensor size should be helpful for fast on-site determinations of these analytes.

Plastic antibody based surface plasmon resonance nanosensors for selective atrazine detection

This study reports a surface plasmon resonance (SPR) based affinity sensor system with the use of molecular imprinted nanoparticles (plastic antibodies) to enhance the pesticide detection. Molecular imprinting based affinity sensor is prepared by the attachment of atrazine (chosen as model pesticide) imprinted nanoparticles onto the gold surface of SPR chip. Recognition element of the affinity sensor is polymerizable form of aspartic acid. The imprinted nanoparticles were characterized via FTIR and zeta-sizer measurements. SPR sensors are characterized with atomic force microscopy (AFM), scanning electron microscopy (SEM), Fourier transform infrared spectrophotometry (FTIR) and contact angle measurements. The imprinted nanoparticles showed more sensitivity to atrazine than the non-imprinted ones. Different concentrations of atrazine solutions are applied to SPR system to determine the adsorption kinetics. Langmuir adsorption model is found as the most suitable model for this affinity nanosensor system. In order to show the selectivity of the atrazine-imprinted nanoparticles, competitive adsorption of atrazine, simazine and amitrole is investigated. The results showed that the imprinted nanosensor has high selectivity and sensitivity for atrazine.

Environmental applications of photoluminescence-based biosensors

For monitoring and treatment of soil and water, environmental scientists and engineers require measurements of the concentration of chemical contaminants. Although laboratory-based methods relying on gas or liquid chromatography can yield very accurate measurements, they are also complex, time consuming, expensive, and require sample pretreatment. Furthermore, they are not readily adapted for in situ measurements.Sensors are devices that can provide continuous, in situ measurements, ideally without the addition of reagents. A biosensor incorporates a biological component coupled to a transducer, which translates the interaction between the analyte and the biocomponent into a signal that can be processed and reported. A wide range of transducers have been employed in biosensors, the most common of which are electrochemical and optical. In this contribution, we focus on photoluminescence-based biosensors of potential use in the applications described above.Following a review of photoluminescence and a discussion of the optoelectronic hardware part of these biosensor systems, we provide explanations and examples of optical biosensors for specific chemical groups: hydrocarbons and alcohols, halogenated organics, nitro-, phospho-, sulfo-, and other substituted organics, and metals and other inorganics. We also describe approaches that have been taken to describe chemical mixtures as a whole (biological oxygen demand and toxicity) since most environmental samples contain mixtures of unknown (and changing) composition. Finally, we end with some thoughts on future research directions that are necessary to achieve the full potential of environmental biosensors.

Self-assembled monolayers (SAMs) of carboxylic acids: an overview

The field of self-assembled monolayers (SAMs) of organic compounds on different substrates is of importance because it provides a suitable and efficient method of surface modification. The formation of robust, stable monolayers from carboxylic acids on two and three dimensional surfaces of different substrates have been reported. Carboxylic acids are promising class of organic compounds for monolayer formations where traditional alkanethiols or alkoxysilanes show limitations.

Molecular simulation of protein-surface interactions: benefits, problems, solutions, and future directions

While the importance of protein adsorption to materials surfaces is widely recognized, little is understood at this time regarding how to design surfaces to control protein adsorption behavior. All-atom empirical force field molecular simulation methods have enormous potential to address this problem by providing an approach to directly investigate the adsorption behavior of peptides and proteins at the atomic level. As with any type of technology, however, these methods must be appropriately developed and applied if they are to provide realistic and useful results. Three issues that are particularly important for the accurate simulation of protein adsorption behavior are the selection of a valid force field to represent the atomic-level interactions involved, the accurate representation of solvation effects, and system sampling. In this article, each of these areas is addressed and future directions for continued development are presented.