During cancer progression, tumors shed different biomarkers into the bloodstream, including circulating tumor cells (CTCs), extracellular vesicles (EVs), circulating cell-free DNA (cfDNA), and circulating tumor DNA (ctDNA). The analysis of these biomarkers in the blood, known as ‘liquid biopsy’ (LB), is a promising approach for early cancer detection and treatment monitoring, and more recently, as a means for cancer therapy. Previous reviews have discussed the role of CTCs and ctDNA in cancer progression; however, ctDNA and EVs are rapidly evolving with technological advancements and computational analysis and are the subject of enormous recent studies in cancer biomarkers. In this review, first, we introduce these cell-released cancer biomarkers and briefly discuss their clinical significance in cancer diagnosis and treatment monitoring. Second, we present conventional and novel approaches for the isolation, profiling, and characterization of these markers. We then investigate the mathematical and in silico models that are developed to investigate the function of ctDNA and EVs in cancer progression. We convey our views on what is needed to pave the way to translate the emerging technologies and models into the clinic and make the case that optimized next-generation techniques and models are needed to precisely evaluate the clinical relevance of these LB markers.
Spectroscopy in the sub-terahertz (sub-THz) range of frequencies has been utilized to study the picosecond dynamics and interaction of biomolecules. However, widely used free-space THz spectrometers are typically limited in their functionality due to low signal-to-noise ratio and complex setup. On-chip spectrometers can revolutionize THz spectroscopy allowing integration, compactness, and low-cost fabrication. In this paper, a low-loss silicon-based platform is proposed for on-chip sub-THz spectroscopy. Through functionalization of silicon chip and immobilization of bio-particles, we demonstrate the ability to characterize low-loss nano-scale biomolecules across the G-band (0.14–0.22 THz). We also introduce an electromagnetic thin-film model to account for the loading effect of the immobilized biomolecules, i.e. dehydrated streptavidin and immunoglobulin antibody, as two key molecules in the biosensing discipline. The proposed platform was fabricated using a single mask micro-fabrication process, and then measured by a vector network analyzer (VNA), which offers high dynamic range and high spectral resolution measurements. The proposed planar platform is general and paves the way towards low-loss, cost-effective and integrated sub-THz biosensors for the detection and characterization of biomolecules.
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