http://www.mdpi.com/journal/sensors/special_issues/toxin_sensors/ As defined for this special issue, toxins are a subset of poisonous materials – bio-organic compounds of biological origin that have a deleterious effect on humans and other higher animals. Although infectious agents can be detected and identified based on their nucleic acid sequences, the presence of an active toxin cannot necessarily be determined based entirely on the presence of its gene sequence. Furthermore, the short timeframe from exposure to clinical manifestation (minutes to hours) requires a rapid turnaround for mitigation and treatment of the toxic effects. Thus, rapid and sensitive sensors are needed to test not only for the presence of toxin, but also its concentration and activity. This special issue is devoted to describing the latest research in development and application of sensors for detection/identification of toxins as well as for diagnosis of intoxication. Specific topics of interest include: basic, proof-of-concept studies of new methods, materials, and systems for toxin detection/identification; use of toxin sensors in new environments or matrices; automation of state-of-the-art toxin sensors; use of sensors to diagnose intoxication, and blind testing of extant toxin sensors with unknown samples. Reviews of systems with demonstrated efficacy for toxin detection are also welcome. Submission Sensors (http://www.mdpi.org/sensors/) is a highly rated journal with a 1.870 impact factor in 2008. Sensors is indexed and abstracted very quickly by Chemical Abstracts, Analytical Abstracts, Science Citation Index Expanded, Chemistry Citation Index, Scopus and Google Scholar. All papers should be submitted to sensors@mdpi.org with copy to the guest editors. To be published continuously until the deadline and papers will be listed together at the special websites. Please visit the instructions for authors at http://www.mdpi.org/sensors/publguid.htm before submitting a paper. Open Access publication fees are 1050 CHF per paper. English correction fees (250 CHF) will be added in certain cases (1300 CHF per paper for those papers that require extensive additional formatting and/or English corrections.). http://www.mdpi.com/1424-8220/9/4/2976/ Biomagnetic nano and microparticles platforms have attracted considerable interest in the field of biological sensors due to their interesting physico-chemical properties, high specific surface area, good mechanical stability and opportunities for generating magneto-switchable devices. This review discusses recent advances in the development and characterization of active biomagnetic nanoassemblies, their interaction with biological molecules and their use in bioanalytical sensors. http://www.mdpi.com/1424-8220/9/4/2976/ Thu, 23 Apr 2009 00:00:00 CEST Sensors 2009-04-23 9 4 Review 2976 2999 1424-8220 Magnetic Particle-Based Hybrid Platforms for Bioanalytical Sensors 2009-04-23 doi: 10.3390/s90402976 Lia Stanciu Yu-Ho Won Mallikarjunarao Ganesana Silvana Andreescu http://www.mdpi.com/1424-8220/9/3/2117/ Harnessing the potential of cells as complex biosensors promises the potential to create sensitive and selective detectors for discrimination of biodefense agents. Here we present toxin detection and suggest discrimination using cells in a multianalyte microphysiometer (MMP) that is capable of simultaneously measuring flux changes in four extracellular analytes (acidification rate, glucose uptake, oxygen uptake, and lactate production) in real-time. Differential short-term cellular responses were observed between botulinum neurotoxin A and ricin toxin with neuroblastoma cells, alamethicin and anthrax protective antigen with RAW macrophages, and cholera toxin, muscarine, 2,4-dinitro-phenol, and NaF with CHO cells. These results and the post exposure dynamics and metabolic recovery observed in each case suggest the usefulness of cell-based detectors to discriminate between specific analytes and classes of compounds in a complex matrix, and furthermore to make metabolic inferences on the cellular effects of the agents. This may be particularly valuable for classifying unknown toxins. http://www.mdpi.com/1424-8220/9/3/2117/ Mon, 23 Mar 2009 00:00:00 CET Sensors 2009-03-23 9 3 Article 2117 2133 1424-8220 Metabolic Discrimination of Select List Agents by Monitoring Cellular Responses in a Multianalyte Microphysiometer 2009-03-23 doi: 10.3390/s90302117 Sven E. Eklund Roy G. Thompson Rachel M. Snider Clare K. Carney David W. Wright John Wikswo David E. Cliffel http://www.mdpi.com/1424-8220/9/3/1339/ Significant efforts have been invested in the past years for the development of analytical methods for fast toxin detection in food and water. Immunochemical methods like ELISA, spectroscopy and chromatography are the most used in toxin detection. Different methods have been linked, e.g. liquid chromatography and mass spectrometry (LC-MS), in order to detect as low concentrations as possible. Surface plasmon resonance (SPR) is one of the new biophysical methods which enables rapid toxin detection. Moreover, this method was already included in portable sensors for on-site determinations. In this paper we describe some of the most common methods for toxin detection, with an emphasis on SPR. http://www.mdpi.com/1424-8220/9/3/1339/ Thu, 26 Feb 2009 00:00:00 CET Sensors 2009-02-26 9 3 Review 1339 1354 1424-8220 Toxin Detection by Surface Plasmon Resonance 2009-02-26 doi: 10.3390/s9031339 Vesna Hodnik Gregor Anderluh http://www.mdpi.com/1424-8220/9/1/645/ Three PEG molecules (PEG-methacrylate, -diacrylate and -dimethacrylate) were incorporated into galactose-based polyacrylate hydrogels and their relative abilities to reduce non-specific protein adsorption in immunoassays were determined. Highly crosslinked hydrogels containing amine-terminated functionalities were formed and used to covalently attach antibodies specific for staphylococcal enterotoxin B (SEB). Patterned arrays of immobilized antibodies in the PEG-modified hydrogels were created with a PDMS template containing micro-channels for use in sandwich immunoassays to detect SEB. Different concentrations of the toxin were applied to the hydrogel arrays, followed with a Cy3-labeled tracer antibody specific for the two toxins. Fluorescence laser scanning confocal microscopy of the tracer molecules provided both qualitative and quantitative measurements on the detection sensitivity and the reduction in non-specific binding as a result of PEG incorporation. Results showed the PEG-modified hydrogel significantly reduced non-specific protein binding with a detection limit for SEB of 1 ng/mL. Fluorescence signals showed a 10-fold decrease in the non-specific binding and a 6-fold increase in specific binding of SEB. http://www.mdpi.com/1424-8220/9/1/645/ Fri, 23 Jan 2009 00:00:00 CET Sensors 2009-01-23 9 1 Article 645 655 1424-8220 Reduction of Non-Specific Protein Adsorption Using Poly(ethylene) Glycol (PEG) Modified Polyacrylate Hydrogels In Immunoassays for Staphylococcal Enterotoxin B Detection 2009-01-23 doi: 10.3390/s90100645 Paul T. Charles Veronte R. Stubbs Carissa M. Soto Brett D. Martin Brandy J. White Chris R. Taitt http://www.mdpi.com/1424-8220/9/1/542/ Phage-displayed single domain antibodies (sdAb) were compared to monomeric solubly expressed sdAb and llama polyclonal antibodies for the detection of ricin. SdAb are comprised of the variable domain derived from camelid heavy chain only antibodies (HcAb). Although HcAb lack variable light chains, they as well as their derivative sdAb are able to bind antigens with high affinity. The small size of sdAb (~16 kDa), while advantageous in many respects, limits the number of labels that can be incorporated. The ability to incorporate multiple labels is a beneficial attribute for reporter elements. Opportunely, sdAb are often selected using phage display methodology. Using sdAb displayed on bacteriophage M13 as the reporter element gives the potential for incorporating a very high number of labels. We have demonstrated the use of both sdAb and phage- displayed sdAb for the detection of ricin using both enzyme linked immunosorbent assays (ELISAs) and Luminex fluid array assays. The phage-displayed sdAb led to five to ten fold better detection of ricin in both the ELISA and Luminex assays, resulting in limits of detection of 1 ng/mL and 64 pg/mL respectively. The phage-displayed sdAb were also dramatically more effective for the visualization of binding to target in nitrocellulose dot blot assays, a method frequently used for epitope mapping. http://www.mdpi.com/1424-8220/9/1/542/ Mon, 19 Jan 2009 00:00:00 CET Sensors 2009-01-19 9 1 Article 542 555 1424-8220 Ricin Detection Using Phage Displayed Single Domain Antibodies 2009-01-19 doi: 10.3390/s90100542 Ellen R. Goldman Jinny L. Liu Rachael D. Bernstein Marla D. Swain Stanley Q. Mitchell George P. Anderson http://www.mdpi.com/1424-8220/8/12/8361/ The following review focuses on progress made in the last five years with the NRL Array Biosensor, a portable instrument for rapid and simultaneous detection of multiple targets. Since 2003, the Array Biosensor has been automated and miniaturized for operation at the point-of-use. The Array Biosensor has also been used to demonstrate (1) quantitative immunoassays against an expanded number of toxins and toxin indicators in food and clinical fluids, and (2) the efficacy of semi-selective molecules as alternative recognition moieties. Blind trials, with unknown samples in a variety of matrices, have demonstrated the versatility, sensitivity, and reliability of the automated system. http://www.mdpi.com/1424-8220/8/12/8361/ Mon, 15 Dec 2008 00:00:00 CET Sensors 2008-12-15 8 12 Review 8361 8377 1424-8220 Array Biosensor for Toxin Detection: Continued Advances 2008-12-15 doi: 10.3390/s8128361 Chris Rowe Taitt Lisa C. Shriver-Lake Miriam M. Ngundi Frances S. Ligler http://www.mdpi.com/1424-8220/8/12/8321/ This paper gives an overview of the literature data concerning specific and non specific inhibitors of Na+,K+-ATPase receptor. The immobilization approaches developed to improve the rather low time and temperature stability of Na+,K+-ATPase, as well to preserve the enzyme properties were overviewed. The functional immobilization of Na+,K+-ATPase receptor as the target, with preservation of the full functional protein activity and access of various substances to an optimum number of binding sites under controlled conditions in the combination with high sensitive technology for the detection of enzyme activity is the basis for application of this enzyme in medical, pharmaceutical and environmental research. http://www.mdpi.com/1424-8220/8/12/8321/ Mon, 15 Dec 2008 00:00:00 CET Sensors 2008-12-15 8 12 Review 8321 8360 1424-8220 Na+,K+-ATPase as the Target Enzyme for Organic and Inorganic Compounds 2008-12-15 doi: 10.3390/s8128321 Vesna Vasić Tatjana Momić Marijana Petković Danijela Krstić http://www.mdpi.com/1424-8220/8/12/8262/ An aflatoxin B1 (AFB1) electrochemical immunosensor was developed by the immobilisation of aflatoxin B1-bovine serum albumin (AFB1-BSA) conjugate on a polythionine (PTH)/gold nanoparticles (AuNP)-modified glassy carbon electrode (GCE). The surface of the AFB1-BSA conjugate was covered with horseradish peroxidase (HRP), in order to prevent non-specific binding of the immunosensors with ions in the test solution. The AFB1 immunosensor exhibited a quasi-reversible electrochemistry as indicated by a cyclic voltammetric (CV) peak separation (ΔEp) value of 62 mV. The experimental procedure for the detection of AFB1 involved the setting up of a competition between free AFB1 and the immobilised AFB1-BSA conjugate for the binding sites of free anti-aflatoxin B1 (anti-AFB1) antibody. The immunosensor’s differential pulse voltammetry (DPV) responses (peak currents) decreased as the concentration of free AFB1 increased within a dynamic linear range (DLR) of 0.6 - 2.4 ng/mL AFB1 and a limit of detection (LOD) of 0.07 ng/mL AFB1. This immunosensing procedure eliminates the need for enzyme-labeled secondary antibodies normally used in conventional ELISA–based immunosensors. http://www.mdpi.com/1424-8220/8/12/8262/ Mon, 15 Dec 2008 00:00:00 CET Sensors 2008-12-15 8 12 Article 8262 8274 1424-8220 Electrochemical Immunosensor Based on Polythionine/Gold Nanoparticles for the Determination of Aflatoxin B1 2008-12-15 doi: 10.3390/s8128262 Joseph H.O. Owino Omotayo A. Arotiba Nicolette Hendricks Everlyne A. Songa Nazeem Jahed Tesfaye T. Waryo Rachel F. Ngece Priscilla G .L. Baker Emmanuel I. Iwuoha http://www.mdpi.com/1424-8220/8/10/6433/ Baker’s yeast, Saccharomyces cerevisiae, is the simplest and most well-known representative of eukaryotic cells and thus a convenient model organism for evaluating toxic effects in human cells and tissues. Yeast cell sensors are easy to maintain with short generation times, which makes the analytical method of assessing antifungal toxicity cheap and less-time consuming. In this work, the toxicity of test compounds was assessed in bioassays based on bioluminescence inhibition and on traditional growth inhibition on agar plates. The model organism in both tests was a modified S. cerevisiae sensor strain that produces light when provided with D-luciferin in an insect luciferase reporter gene activity assay. The bioluminescence assay showed toxic effects for yeast cell sensor of 5,6-benzo-flavone, rapamycin, nystatin and cycloheximide at concentrations of nM to µM. In addition, arsenic compounds, cadmium chloride, copper sulfate and lead acetate were shown to be potent non-specific inhibitors of the reporter organism described here. The results from a yeast agar diffusion assay correlated with the bioluminescence assay results. http://www.mdpi.com/1424-8220/8/10/6433/ Thu, 16 Oct 2008 00:00:00 CEST Sensors 2008-10-16 8 10 Article 6433 6447 1424-8220 Real-time Monitoring of Non-specific Toxicity Using a Saccharomyces cerevisiae Reporter System 2008-10-16 doi: 10.3390/s8106433 Anna-Liisa Välimaa Anniina Kivistö Marko Virta Matti Karp http://www.mdpi.com/1424-8220/8/9/6045/ The following review of sensors and biosensors focuses on the determination of commonly studied small molecule biological toxins, including mycotoxins and small molecule neurotoxins. Because of the high toxicity of small molecule toxins, an effective analysis technique for determining their toxicity is indispensable. Sensors and biosensors have emerged as sensitive and rapid techniques for toxicity analysis in the past decade. Several different sensors for the determination of mycotoxins and other small molecule neurotoxins have been reported in the literature, and many of these sensors such as tissue biosensors, enzyme sensors, optical immunosensors, electrochemical sensors, quartz crystal sensors, and surface plasmon resonance biosensors are reviewed in this paper. Sensors are a practical and convenient monitoring tool in the area of routine analysis, and their specificity, sensitivity, reproducibility and analysis stability should all be improved in future work. In addition, accuracy field portable sensing devices and multiplexing analysis devices will be important requirement for the future. http://www.mdpi.com/1424-8220/8/9/6045/ Fri, 26 Sep 2008 00:00:00 CEST Sensors 2008-09-26 8 9 Review 6045 6054 1424-8220 Sensors and Biosensors for the Determination of Small Molecule Biological Toxins 2008-09-26 doi: 10.3390/s8096045 Xiang-Hong Wang Shuo Wang