8 May 2014 Retroreflective imaging systems for enhanced optical biosensing
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Abstract
Biosensing is important for detection and characterization of microorganisms. When the detection and characterization of targeted microorganisms require micron-scale resolutions, optical biosensing techniques are especially beneficial. Optical biosensing can be applied through direct or indirect optical sensing techniques. The latter have demonstrated especially high sensitivities for the detection of targeted microorganisms with labeling. Unfortunately, such systems rely on high-resolution microscopy with microscopic sampling areas to image the labeled target microorganisms. This leads to long characterization times for applications such as pathogen detection in water quality monitoring where users must scan the micron-scale sampling areas across millimeter- or even centimeter-scale samples. This work introduces retroreflector labels for the detection and characterization of microorganisms for macroscopic sample sizes. The demonstrated retroreflective imaging system uses a laser source to illuminate the sample, in lieu of the fluorescent excitation source, and micron-scale retroreflector labels, in lieu of fluorescent stains/proteins. Antibodies are used to bind retroreflectors to targeted microorganisms. The presence of these microscopic retroreflector-microorganism pairs is monitored in a retroreflected image that is captured by a distant image sensor which shows a well-localized retroreflected beamspot for each pair. Characteristics of an appropriately-designed retroreflective imaging system which provide a quantifiable record of microorganism-coupled retroreflectors across macroscopic sample sizes are presented. Retroreflection directionality, collimation, and contrast are investigated for both corner-cube retroreflectors and spherical retroreflectors (of varying refractive indices). It is ultimately found that such a system is an effective tool for the detection and characterization of microorganism targets, down to a single-target detection limit.
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Mark H. Bergen, Mark H. Bergen, Jacqueline Nichols, Jacqueline Nichols, Christopher M. Collier, Christopher M. Collier, Xian Jin, Xian Jin, Jonathan F. Holzman, Jonathan F. Holzman, } "Retroreflective imaging systems for enhanced optical biosensing", Proc. SPIE 9129, Biophotonics: Photonic Solutions for Better Health Care IV, 912914 (8 May 2014); doi: 10.1117/12.2052523; https://doi.org/10.1117/12.2052523
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