An advanced hyper-spectral imaging (HSI) system has been developed having obvious applications for cancer detection. This HSI system is based on state-of-the-art liquid crystal tunable filter technology coupled to an endoscope. The goal of this unique HSI technology being developed is to obtain spatially resolved images of the slight differences in luminescent properties of malignant versus non-malignant tissues. In this report, the development of the instrument is discussed and the capability of the instrument is demonstrated by observing mouse carcinomas in-vivo. It is shown that the instrument successfully distinguishes between normal and malignant mouse skin. It is hoped that the results of this study will lead to advances in the optical diagnosis of cancer in humans.

We demonstrate for the first time, the application and utility of a unique optical sensor having a nanoprobe for monitoring the onset of the mitochondrial pathway of apoptosis in a single living cell by detecting enzymatic activities of caspase-9. Minimally invasive analysis of single live MCF-7 cells for caspase-9 activity is demonstrated using the optical sensor which employs a modification of an immunochemical assay format for the immobilization of nonfluorescent enzyme substrate, Leucine-GlutamicAcid-Histidine-AsparticAcid-7-amino-4-methylcoumarin (LEHD-AMC). LEHD-AMC covalently attached on the nanoprobe tip of an optical sensor is cleaved during apoptosis by caspase-9 generating free AMC. An evanescent field is used to excite cleaved AMC and the resulting fluorescence signal is detected. By quantitatively monitoring the changes in fluorescence signals, caspase-9 activity within a single living MCF-7 cell was detected. By comparing of the fluorescence signals from apoptotic cells induced by photodynamic treatment and nonapoptotic cells, we successfully detected caspase-9 activity, which indicates the onset of apoptosis in the cells.

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In this work, the intracellular measurement of cytochrome c using an optical nanobiosensor is demonstrated. The nanobiosensor is a unique fiberoptics-based tool which allows the minimally invasive analysis of intracellular components. Cytochrome c is a very important protein to the process which produces cellular energy. In addition, cytochrome c is well-known as the protein involved in apoptosis, or programmed cell death. delta-Aminolevulinic acid (5-ALA) was used to induce apoptosis in MCF-7 human breast carcinoma cells. 5-ALA, a photodynamic therapy (PDT) drug in cells was activated by a HeNe laser beam. After the PDT photoactivation, the release of cytochrome c from the mitochondria to the cytoplasm in a MCF-7 cell was monitored by the optical nanobiosensor inserted inside the single cell and followed by an enzyme-linked immunosorbent assay (ELISA) outside the cell. The combination of the nanobiosensor with the ELISA immunoassay improved the detection sensitivity of the nanobiosensor due to enzymatic amplification. Our results lead to the investigation of an apoptotic pathway at the single cell level.

This article is an overview of the fabrication, operating principles, and applications of fiber-optic nanobiosensors with the capability of in-vivo analysis at the single-cell level. Recently, the cross-disciplinary integration of nanotechnology, biology, and photonics has been revolutionizing important areas in molecular biology, especially diagnostics and therapy at the molecular and cellular level. Fiber-optic nanobiosensors are a unique class of biosensor that enable analytical measurements in individual living cells and the probing of individual chemical species in specific locations within a cell. This article provides a review of the research performed in our laboratory and discusses the usefulness and potential of this nanotechnology-based biosensor system in biological research and its applications to biomonitoring of individual cells.