[Show abstract][Hide abstract] ABSTRACT: We demonstrate detection of whole viruses and viral proteins with a new label-free platform based on spectral reflectance imaging. The Interferometric Reflectance Imaging Sensor (IRIS) has been shown to be capable of sensitive protein and DNA detection in a real time and high-throughput format. Vesicular stomatitis virus (VSV) was used as the target for detection as it is well-characterized for protein composition and can be modified to express viral coat proteins from other dangerous, highly pathogenic agents for surrogate detection while remaining a biosafety level 2 agent. We demonstrate specific detection of intact VSV virions achieved with surface-immobilized antibodies acting as capture probes which is confirmed using fluorescence imaging. The limit of detection is confirmed down to 3.5 × 10(5)plaque-forming units/mL (PFUs/mL). To increase specificity in a clinical scenario, both the external glycoprotein and internal viral proteins were simultaneously detected with the same antibody arrays with detergent-disrupted purified VSV and infected cell lysate solutions. Our results show sensitive and specific virus detection with a simple surface chemistry and minimal sample preparation on a quantitative label-free interferometric platform.
[Show abstract][Hide abstract] ABSTRACT: Label-free optical biosensors have been established as proven tools for monitoring specific biomolecular interactions. However, compact and robust embodiments of such instruments have yet to be introduced in order to provide sensitive, quantitative, and high-throughput biosensing for low-cost research and clinical applications. Here we present the Interferometric Reflectance Imaging Sensor (IRIS) using an inexpensive and durable multi-color LED illumination source to monitor protein-protein and DNA-DNA interactions. We demonstrate the capability of this system to dynamically monitor antigen-antibody interactions with a noise floor of 5.2 pg/mm(2) and DNA single mismatch detection under denaturing conditions in an array format. Our experiments show that this platform has comparable sensitivity to high-end label-free biosensors at a much lower cost with the capability to be translated to field-deployable applications.
[Show abstract][Hide abstract] ABSTRACT: Optical interference is a powerful technique for monitoring surface topography or refractive index changes in a thin film layer. Reflectance spectroscopy provides label-free biosensing capability by monitoring small variations in interference signature resulting from optical path length changes from surface-adsorbed biomolecules. Spectral reflectance data can be acquired either by broad wavelength illumination and spectroscopy at a single point, thus necessitating scanning, or by varying the wavelength of illumination and imaging the reflected intensity allowing for acquisition of a spectral image of a large field of view simultaneously. In imaging modalities, intensity fluctuations of the illuminating light source couple into the detected signal, increasing the noise in measured surface profiles. This article introduces a simple technique for eliminating the effects of illumination light power fluctuations by fabricating on-substrate self-reference regions to measure and normalize for the incident intensity, simplifying the overall platform for reflection or transmission-based imaging biosensors. Experimental results demonstrate that the sensitivity performance using self-referencing is equivalent or better than an optimized system with an external reference.
Journal of Modern Optics 09/2010; 57(16):1564-1569. · 1.16 Impact Factor