Current diagnostic tumor biopsies are invasive and can disrupt and spread the tumor. Liquid biopsies are inadequate for early-stage detection, resulting in lower survival rates and poorer prognoses. Raman spectroscopy can detect many cancers by identifying subtle cancer-associated metabolites in circulating biofluids. This study investigates preanalytical variables affecting Raman biofluid measurements in head and neck cancer patients, namely spatially correlated changes caused by Marangoni and capillary flow, aiming to streamline testing by reducing sample acquisition time and human intervention. This method is fully automated, providing a high-throughput assay for large-scale screening, paving the way for widely available, sensitive cancer detection.
Breath biopsy holds great potential for noninvasive and early-stage cancer detection and diagnosis. Volatile organic compounds (VOCs) are low molecular weight metabolites released in breath and biofluids as the result of pathophysiological changes such as cancer. Hundreds of VOCs are expired per breath, providing an information-rich resource of diagnostic potential. To pare down the complexity of the breath volatilome and detect low concentration (ppmV to pptV) cancer-associated VOCs from ubiquitous VOCs, we have engineered a combinatorial nanoplasmonic sensor array for multiplexed adsorption of VOCs. This dual-stage platform features (1) an engineered array of selectively sorbent core-shell nanostructures consisting of plasmonic nanoparticle cores encapsulated by tunable metal-organic frameworks (MOFs) for more specific VOC capture, followed by (2) ultrasensitive readout via surface-enhanced Raman spectroscopy (SERS), i.e., a “SERS-MOF” nanomaterial sensing array. This work focuses on the nanoscale materials synthesis efforts towards lead SERS-MOFs based on ZIF-8 MOF / gold nanourchin particles and preliminary testing of the platform on relevant VOC analytical standards.
Extracellular vesicles (EVs) carry molecular cargo that includes nucleic acids, lipids, proteins, and various other biomarkers. Raman and SERS spectroscopy are label-free spectroscopy techniques based on inelastic scattering of laser light interacting with molecular vibrations. In our study, we employed Raman and SERS spectroscopy for the detection of amyloid beta protein in the molecular cargo of small EVs and bulk chemical analysis of EVs. We observed considerable variation as a reflection of the biochemical content of EVs related to the Aβ peptide incorporated in EVs extracted from the AD cell culture model. Next, we developed a new CMOS-based sensing platform for trapping, imaging, and chemical characterization of EVs via SERS (CMOS TrICC) with the experimental enhancement factor 5.0 × 104. We employed this platform for parallel trapping and sensitive biochemical analysis of the 100 nm nanospheres and EVs.
Sensitive and specific detection of biomaterials packaged in exosomes and related extracellular vesicles (EVs) has the potential to revolutionize cancer diagnosis and monitoring. Yet current methods cannot readily distinguish tumor-associated EVs. Surface-enhanced Raman spectroscopy (SERS) represents a promising tool to address current limitations, but are challenging to implement in whole biofluids. Here we outline a simple SERS assay combining nanoparticles with biofluids purified to various extent. We measure variation between clinical samples of head and neck cancer and demonstrate that there is a trade-off between useful molecular information from purified EVs versus the time, cost, and difficulty of isolation procedures.
KEYWORDS: Raman spectroscopy, Proteins, Cancer, Chemical analysis, Biomedical optics, Laser spectroscopy, Principal component analysis, Industrial chemicals, Spectroscopy, Medical research
Exosomes are small (~100nm) membrane bound vesicles excreted by cells as part of their normal biological processes. These extracellular vesicles are currently an area of intense research, since they were recently found to carry functional mRNA that allows transfer of proteins and other cellular instructions between cells. Exosomes have been implicated in a wide range of diseases, including cancer. Cancer cells are known to have increased exosome production, and may use those exosomes to prepare remote environments for metastasis. Therefore, there is a strong need to develop characterization methods to help understand the structure and function of these vesicles. However, current techniques, such as proteomics and genomics technologies, rely on aggregating a large amount of exosome material and reporting on chemical content that is averaged over many millions of exosomes. Here we report on the use of laser-tweezers Raman spectroscopy (LTRS) to probe individual vesicles, discovering distinct heterogeneity among exosomes both within a cell line, as well as between different cell lines. Through principal components analysis followed by hierarchical clustering, we have identified four “subpopulations” of exosomes shared across seven cell lines. The key chemical differences between these subpopulations, as determined by spectral analysis of the principal component loadings, are primarily related to membrane composition. Specifically, the differences can be ascribed to cholesterol content, cholesterol to phospholipid ratio, and surface protein expression. Thus, we have shown LTRS to be a powerful method to probe the chemical content of single extracellular vesicles.
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