A robust tissue laser platform for analysis of formalin-fixed paraffin-embedded biopsies

Abstract

Laser emission-based detection and imaging technology has attracted significant interest in biomedical research due to its high sensitivity, narrow linewidth, and superior spectral and spatial resolution. Recent advances have further revealed the potential to use laser emission to investigate chromatin dynamics, as well as to diagnose cancer tissues based on nuclear biomarkers. To move the laser emission based detection technology a step further towards practical use, in this work, we developed a highly robust tissue laser platform by microfabricating an SU8 spacer with a fixed height on the top mirror of the Fabry-Pérot (FP) cavity, which allows generation of reproducible and stable lasing results regardless of tissue thickness. Then we applied this platform to achieve lasing emission from formalin-fixed, paraffin-embedded (FFPE) lung tissues, which account for an overwhelming fraction of tissues collected for research and clinical use worldwide. We further showed that the cancer and normal FFPE lung tissues can be distinguished by their respective lasing thresholds. Two different tissue thicknesses (10 μm and 5 μm) commonly used in pathological labs were explored. Finally, we tested three additional types of tissues (colon, stomach, and breast) that were prepared independently by lab technicians in a pathology lab in China and shipped to the US in order to validate the general applicability and practicality of the laser emission-based technology as well as the corresponding sample preparation protocol and the tissue laser platform. Our work will not only vastly broaden the applications of laser emission-based detection/imaging technology but also help translate it from the laboratory to an automated system for clinical practice that may eventually benefit biomedicine and biological research.

Laser Recording of Subcellular Neuron Activities

“…The cavity length may also affect the lasing performance. Recently, we developed an FP cavity with SU-8 spacers of a fixed height microfabricated on the mirror, which ensures a consistent laser cavity length and highly repeatable lasing emission wavelength 44 .…”

Biological Lasers for Biomedical Applications

“…Finally, advancing to the tissue level, several tissue lasers have been demonstrated in recent two years, in which a thin flat tissue was sandwiched between the two mirrors (Figure f) . The tissue can be labeled with dyes that target specific sites inside the tissue (e.g., boron‐dipyrromethene (BODIPY) for adipose cells, YOPRO for nuclear acids, and antibody‐conjugated dyes for proteomic biomarkers).…”

“…Based on the different lasing thresholds between cancer and normal cells, the LEM enabled the identification and multiplexed detection of nuclear proteomic biomarkers, with high sensitivity for early‐stage cancer diagnosis. To date, LEM has been used to examine other types of cancer tissues, including stomach, colon, and breast, both frozen and formalin‐fixed paraffin‐embedded (FFPE) tissues . Similarly, the immuno‐laser that targets cancer biomarkers such as EGFR, p53, and Bcl‐2 has also been achieved on tissues by conjugating the corresponding antibodies to fluorophores …”

“…Biolasers have been employed in the detection of various bioactivities at the molecular, cellular, and tissue levels . Recently, their applications in cell tracking, labeling/probes, implantable devices, cell/tissue imaging start to emerge.…”

Lasing‐Encoded Microsensor Driven by Interfacial Cavity Resonance Energy Transfer

“…At present, most microsphere or droplet‐based WGM lasers are considered to be passive‐detection devices, as they require physical changes (e.g., refractive indexes) to induce a resonance spectral shift, and thus cannot provide detailed biochemical information . In contrast, active‐detection devices, which employ analytes as the gain medium, can provide more selective and sensitive information about the biospecies . Therefore, the ability to utilize a biological gain medium on the external surface of a microsphere cavity will allow us to amplify subtle changes in the gain medium and the resultant spectra, threshold, and lasing modes.…”