Portable colorimetric sensor array technology

Humans as a species are generally audio-visual creatures and do not take full advantage of the olfactory sense. Nonetheless, even humans can recognize and differentiate among thousands of different odorants under challenging conditions. Molecular recognition by the olfactory system derives its specifity from a complex pattern of responses generated by cross-reactive olfactory receptors. These receptors are encoded by approximately one thousand genes, which represents roughly 3% of the entire human genome. As a concept, the use of multiple cross-reactive chemical sensors is broadly applicable to any situation in which the sensors can be simultaneously exposed to each of a set of multiple target analytes; such an "artificial nose" has significant potential in all areas of chemical sensor technology. The chemical sensor arrays discussed in this work are based upon cross-reactive colorimetric response: each of many sensor elements in an array is a mixture of dyes or other compounds that changes color upon exposure to an analyte. These arrays typically use strong, poorly-reversible chemical reactions involving a diverse set of color-changing dyes or chromogens; such colorimetric sensor arrays have evolved to be fast, sensitive, portable, and inexpensive. Importantly, the analyte scope of the developed arrays has been shown to be capable of tailoring based on their intended applications, and can be made to be either broad or narrow as desired: in previous works, they have proven to be capable of discriminating among a broad range of analytes including both gaseous and aqueous analytes involving many different types of chemical reactivity, including Lewis and Brønsted acidity/basicity, molecular polarity, redox properties, and chelation. Of particular interest is the study of chemicals which are hazardous to human life, by either directly interacting with the human body or indirectly causing a physical effect. This work discusses development of colorimetric sensor arrays for two such cases: aqueous toxins and explosives materials. Both types of analytes are particularly challenging due to their relative lack of chemical reactivity: aqueous toxins derive their toxicity from interaction with specific proteins within the human body, while explosives have high potential energy but are kinetically inert. Targeting these analytes while still maintaining high sensitivity, low noise, and the ability to discriminate among them was the primary focus of these two projects. Further, inexpensive portable technology for the quantitative analysis of these arrays is vitally necessary for their intended use outside of the laboratory. This work discusses development of an automated, truly portable device that fits into a pocket and improves upon previous instrumentation in scan speed, sensitivity, and noise. Since colorimetric sensor arrays are monitored by optical transduction, development of portable scanners involves investigating inexpensive, compact, low-noise optical imagers. Previous works focused on flatbed scanners, which have since shown to have limitations in portability (flatbed scanners will certainly not fit in someone's pocket), scan speed (~15-45 seconds per scan), noise (largely induced by the scanner's moving parts), and processing ability (processed manually). To improve upon this, an optical line imager known as a contact image sensor was used to act as the optical transducer; chemical sensor arrays were printed linearly so as to maintain compatibility with the line imager. The final device included disposable sensor array cartridges, a flow control system, control software, and analysis software for pattern matching

Nuevas estrategias para el desarrollo de biosensores ópticos aplicados al análisis de micotoxinas y hongos toxigénicos en alimentos

Tesis inédita de la Universidad Complutense de Madrid, Facultad de Ciencias Químicas, Departamento de Química Analítica, leída el 15-07-2019Mycotoxins are a diverse group of low molecular weight compounds produced as secondary metabolites by numerous species of filamentous fungi. This assemblage is chemically and toxigenically rather heterogeneous, but generally these toxins are known to cause disease and death in human and other vertebrates even at low concentrations. Mycotoxigenic fungi grow on a wide range of conditions and they can produce mycotoxins into the matrices on which they grow, often food intended for human consumption or animal feed. As a result of the ubiquitous nature of mycotoxigenic fungi, particularly in temperate and tropical regions of the world, mycotoxin contamination is often inevitable, and some calculations have estimated that approximately 25–50% of world crops are contaminated with these toxins. Although the awareness related to the hazards of mycotoxins as food and feed contaminants is growing, there are no absolute measures available for eliminating mycotoxins from agricultural products. While mycotoxin occurrence in the field can be decreased by good agronomic practices and planting resistant varieties, in the end, analytical methods capable of detecting mycotoxins and toxigenic fungi even at low concentration are of key importance for ensuring food safety...Las micotoxinas son metabolitos secundarios tóxicos producidos por algunas cepas de hongos que contaminan alimentos, especialmente cereales y hortalizas. Estos compuestos de bajo peso molecular son químicamente y toxigénicamente heterogéneos; sin embargo, muchas de estas toxinas pueden originar enfermedades, y en ocasiones la muerte, tanto en humanos como en otros vertebrados. Los hongos toxigénicos crecen en muchas condiciones muy diversas, lo que puede dar lugar a la aparición de micotoxinas en los alimentos destinados tanto al consumo humano como al animal. Los hongos toxigénicos están ampliamente distribuidos por todo el mundo, particularmente en las regiones templadas y tropicales, por lo que la contaminación natural por micotoxinas es casi inevitable. De hecho, se estima que aproximadamente el 25–50% de los cultivos mundiales están contaminados por estas toxinas, y la preocupación sobre los peligros asociados a su presencia en alimentos es cada día mayor. Actualmente, no existen alternativas viables para su eliminación en los productos agrícolas; aunque el empleo de buenas prácticas agrícolas o la plantación de variedades resistentes a los hongos, pueden ayudar a mejorar este problema. En cualquier caso, se requieren métodos analíticos sensibles y selectivos para la detección de micotoxinas y hongos toxigénicos, a bajas concentraciones, afin de garantizar la seguridad alimentaria...Depto. de Química AnalíticaFac. de Ciencias QuímicasTRUEunpu

Life Sciences Program Tasks and Bibliography for FY 1997

This document includes information on all peer reviewed projects funded by the Office of Life and Microgravity Sciences and Applications, Life Sciences Division during fiscal year 1997. This document will be published annually and made available to scientists in the space life sciences field both as a hard copy and as an interactive internet web page