br Methods br Results and discussion br Conclusion A very

Methods
Results and discussion
Conclusion A very sensitive generic mAb (2G8) against both 3–5 ring unsubstituted and methylated PAHs has been developed through a three-step hybridoma screening procedure. 2G8 has been successfully applied on the KinExA Inline Biosensor for quantifying total 3–5 ring PAH concentrations in a variety of aqueous environmental samples including sediment pore water. The high sensitivity and small sample volumes (1–5mls) required by the biosensor allows convenient analysis of difficult to obtain environmental samples such as sediment pore waters. Total 3–5 ring PAH quantification compared favorably with GC–MS and the method can also be applied as a screening tool for sample prioritization for further GC–MS analysis when imatinib mesylate specific analysis is required. The method is low cost on a per sample basis, is rapid when compared with conventional chromatographic methods and shows great promise for rapid monitoring of PAH pollution. The following are the supplementary data related to this article.
Author contributions
Acknowledgments We thank Stephen L. Kaattari for his supervision and guidance throughout this study. He is fondly remembered and missed. We thank the anonymous reviewers for their helpful comments to improve this manuscript. This research was supported by the NIEHS-SRP grant 1RO1ES020949-3. This paper is Contribution No. 3532 of the Virginia Institute of Marine Science, College of William & Mary.
Introduction Detection of live bacteria is required for many applications in a wide range of different concentrations, from less than 1CFU/mL in food and drinking water control to hundreds of CFU/mL in waste water treatment processes [1]. Current standard analytical methods are based on an enrichment phase in a selective media followed by detection of colonies or individual cells. Detection has been traditionally based on time-consuming visual examination, either with naked eye or under microscope [2, 3]. More recently developed methods like automated flow cytometry or most probable number (MPN) approaches rely on optical detection using fluorescence [4]. Impedance based detection is also becoming popular because of its low-cost, versatility and easy implementation in multi-channel systems [5, 6]. The impedance across two electrodes immersed in a solution can be altered in many different ways by the presence of bacteria. For example, the metabolic activity of bacteria can be monitored through changes in the culture media conductivity [7]. Several systems based on this principle are currently available in the market. The presence of cells on the surface of electrodes has also been detected by changes in the interface impedance [8–10]. When no electroactive species are present in the solution, the interface impedance is basically composed of the double layer capacitance in series with the impedance of any material attached to the electrodes. Cells captured at the surface of the electrodes will slightly alter the interface impedance by blocking low frequency currents at the area of contact. Using interdigitated electrodes (IDEs) and impedance spectroscopy techniques also enable measuring the electrical properties of the volume of solution close to the surface [11]. By fitting the impedance spectra of the IDEs to an electrical equivalent circuit (EEC), the resistance and capacitance of the solution between the electrodes can be obtained [12]. The presence of bacteria at the surface alters the value of these EEC components. In this context, selective detection of live E. coli cells was demonstrated by measurement of changes in the solution capacitance of antibody-functionalized polysilicon IDEs [13]. However, bacteria cells complex structure do not fit well to an EEC [14], and hence, the use of EEC fitting can easily lead to false interpretation of results in the presence of other interfering phenomena like conductivity changes or unspecific adsorption of other components of the solution to the electrode surface [15].