Biosensors are powerful tools aimed at providing selective identification of toxic chemical compounds at ultratrace levels in industrial products, chemical substances, environmental samples (e.g., air, soil, and water) or biological systems (e.g., bacteria, virus, or tissue components) for biomedical diagnosis. Combining the exquisite specificity of biological recognition probes and the excellent sensitivity of laser-based optical detection, biosensors are capable of detecting and differentiating big/chemical constituents of complex systems in order to provide unambiguous identification and accurate quantification. A new generation of biosensors discussed in this presentation uses antibody and DNA probes.

NanoSensors: Exploring the Sanctuary of Individual Living Cell

The combination of nanotechnology, biology, advanced materials and photonics opens the possibility of detecting and manipulating atoms and molecules using nano-devices, which have the potential for a wide variety of medical uses at the cellular level. We have recently reported the development of nano-biosensors and in situ intracellular measurements of single cells using antibody-based nanoprobes. The nano-scale size of this new class of sensors also allows for measurements in the smallest of environments. One such environment that has evoked a great deal of interest is that of individual cells. Using these nanosensors, it is possible to probe individual chemical species and molecular signaling processes in specific locations within a cell. We have shown that insertion of a nano-biosensor into a mammalian somatic cell not only appears to have no effect on the cell membrane, but also does not effect the cell's normal function. The possibilities to monitor in vivo processes within living cells could dramatically improve our understanding of cellular function, thereby revolutionizing cell biology.

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Real-time monitoring of molecular signaling processes in a live cell

This research is a significant challenge for the next phase of genomics and proteomics studies. Conventional methods for determining molecule interactions often employ in vitro approaches using fixed cells or cell lysates. These methods are often time-consuming or less sensitive and may not represent true physiological conditions of cells in vivo. Furthermore, they cannot provide us any dynamic information about molecular interactions during cell division or environmental changes. To bridge the gap created by the inability of these conventional techniques to produce in vivo measurements in living cells, we have recently developed a class of unique optical nanobiosensors that can be inserted into single living cells to monitor and measure biomolecules and biochemicals of biomedical interest without disrupting normal cellular processes. Optical nanobiosensors are integrated nanoscale devices consisting of a biological recognition molecule coupled to the optical transducing element such as an optical nanofiber interfaced to a photometric detection system. They are capable of providing specific quantitative, semi-quantitative or qualitative analytical information using biological recognition elements (e.g., DNA, protein) in direct spatial contact with a solid-state optical transducer element. This nanobiotechnology-based devices are being developed in our laboratory and could provide unprecedented insights into intact cell function, allowing, for the first time, studies of molecular functions (such as apoptosis, DNA-protein interactions, protein-protein interaction, functioning of nanomachines, etc.) in the context of the functional cell architecture in a systems biology approach. These devices will lead to novel and powerful tools for fundamental biological research, ultra-high throughput drug screening and medical diagnostics applications.

Antibody-based fluoroimmunosensors (FISs)

FISs have been developed for the carcinogen benzo[a]pyrene (BaP) and related adducts such as benzopyrene tetrol (BPT). Polyclonal or monoclonal antibodies produced are immobilized at the terminus of a fiber optics probe or contained in a micro-sensing cavity within the FIS for use both in in-vitro and in-vivo fluorescence assays. High sensitivity is provided by laser excitation and optical detection. The FIS device utilizes the back-scattering of light emitted at the remote sensor probe. A single fiber is used to transmit the excitation radiation into the sample and collect the fluorescence emission from the antigen. The laser radiation reaches the sensor probe and excites the BaP bound to the antibodies immobilized at the fiberoptics probe. The excellent sensitivity of this device illustrates that it has considerable potential to perform trace analyses of chemical and biological samples in complex matrices. Measurements are simple and rapid (~ 5 min), and the technique is applicable to other compounds provided appropriate antibodies are used.