In situ cancer diagnosis through online plasmonics.

Most cancer diagnoses rely on biomarkers detection. This could be improved if directly conducted in suspicious cancer spots, preventing the need for biopsy. Lung cancer remains a perfect study-case for such a development, as it is generally detected at advanced stage and is in the need for early diagnosis techniques. To this aim, we have designed a minimally invasive catheter-embedded biosensor. It combines a specific grating structure photo-imprinted in a telecommunication-grade optical fiber and an overlay made of a thin metal coating on which receptors are grafted, yielding plasmonic coupling. Our optrode targets a type of cytokeratins, overexpressed at the surface of cancer cells. It was assayed ex vivo in resected lung tissues collected from a dozen of patients. Biosensing responses were confirmed by immunohistochemistry, conducted on the same samples. In addition to accurate biosensing, our gratings inherently enable force-sensing features, which also allow a fine positioning of the probe in the tissue. Finally, the in vivo navigation of the bronchoscope-embedded sensor was validated into pig lungs. These achievements are a critical milestone towards the development of this micro/nano biosensor as a cost-effective and weakly invasive diagnostic tool for applications in areas of critical access such as brain, liver or prostate.