Perspective on Optical Biosensors and Integrated Sensor Systems

Abstract

Optical biosensors have begun to move from the laboratory to the point of use. This trend will be accelerated by new concepts for molecular recognition, integration of microfluidics and optics, simplified fabrication technologies, improved approaches to biosensor system integration, and dramatically increased awareness of the applicability of sensor technology to improve public health and environmental monitoring. Examples of innovations are identified that will lead to smaller, faster, cheaper optical biosensor systems with capacity to provide effective and actionable information. Keywords optical biosensors; microfluidics; optofluidics; polymer optics; nanotechnology; point of useIn the 1980's, only a limited number of groups were publishing data on optical sensors with integrated biological recognition molecules. 1-5 The possibility of moving a biosensor off an optical bench was still a long-term goal primarily because of the bulky optics available at the time. Moreover, reagent manipulations were all performed manually. The primary challenges being addressed were maintaining the activity of the recognition molecules after immobilization or entrapment, collecting the relatively weak fluorescent or absorbance signals, and discriminating a recognition event from nonspecific adsorption. Only after these problems were well understood and the manner in which they needed to be addressed was better appreciated could the next level of challenges be undertaken: consideration of binding kinetics at surfaces; operation under flow as opposed to static equilibrium conditions; utilization of new solid-state optical devices, recognition molecules, enzymes for signal amplification, and near-IR and long-lifetime fluorophores; multiplexed analyses; system automation; and constraints for utility at the point-of-use. Both as a result of this foundational work and advances in other fields, a number of new devices and techniques evolved including a wide variety of solid state optical elements, immobilization chemistries, genetically engineered recognition molecules, microarrays of capture molecules, and fluidics for continuous monitoring. The result has been a variety of relatively expensive but commercially available optical biosensors for specific application areas including medical diagnostics, environmental testing, and food safety. 6Twenty years from now, will we have the Star Trek Tricorder that tells us at a distance the identity of a target of interest, be it chemical, biological or mineral? Current users of optical biosensors clearly want a device usable anywhere by anyone that tests for everything of interest, in real-time, and at trivial expense. While it is unlikely that this goal will be accomplished, optical biosensors will be constructed to meet the needs of operators in various fields of use in cost-effective packages. For example, in ten years, biosensors with capacity to test for all common food pathogens in vegetable or carcass washes, beverages, or homogenized food samples could be in place. Point-of-ca...

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