Liquid Biopsy Technologies
Our Liquid Biopsy Technologies
With continuous support from NCI via U54, R21, R33, R01, P01, U01, and SBIR funding mechanisms, our research team has built a series of nanotechnology and microfluidics-enabled in vitro diagnostic technologies that are capable of processing liquid biopsy samples, i.e., circulating tumor cells (CTCs) and extracellular vesicles (EVs). More specifically, our nanomaterials-embedded diagnostic platforms, including NanoVelcro CTC Chips, NanoVilli EV Chips, and Click Chips, introduce powerful non-invasive diagnostic solutions for detection, isolation, and characterization of CTCs and EVs in peripheral blood. Over the past decade, our research endeavors have led to multiple generations of technologies, which have been used to explore the full potential of CTCs and EVs as cancer biomarkers for a variety of clinical applications, e.g., prognostic prediction, disease detection/staging, mutational analysis, and transcriptomic profiling. Our 2020 Advanced Materials review article summarizes our contribution in the field of liquid biopsy.
1st-Generation NanoVelcro – for capture and characterization of CTCs
The working mechanism of NanoVelcro lies in the use of silicon nanowire substrates (SiNWS), which allow for Velcro-like interactions between SiNWS and nanoscale cell-surface components. In combination with a microfluidic chaotic mixer (which ensures the cells touch the nanowire), and anti-EpCAM capture agent (grafted onto the nanowire substrate via biotin-streptavidin conjugation), NanoVelcro chips can capture CTCs and other circulating rare cells with high efficiency.
These 1st-Gen NanoVelcro Chips allow for visual characterization and enumeration of these rare cells. Our studies have focused on enumeration of CTCs in prostate cancer, hepatocellular carcinoma, as well as circulating fetal nucleated cells (CFNCs) from pregnant women.
2nd-Generation NanoVelcro – PLGA chips for laser capture microdissection
To allow for single cell and few cell analyses, we developed a set of nanovelcro chips made of PLGA polymer. These chips capture CTCs of epithelial origin, and can be viewed under a fluorescent microscope. The key innovation with these chips however, is their ability to be used with laser capture microdissection, where a laser is used to cut out a portion of the chip. LCM can be used to individually select cells of interest for downstream molecular analyses.
3rd-Generation NanoVelcro – ThermoResponsive-NanoVelcro chips for temperature-dependent capture and release
By grafting ThermoResponsive polymer brushes onto SiNWS, we developed a third generation of NanoVelcro chip with the ability to enrich rare cells from a sample. At 37°C, these brushes lie in a conformation that allows cells to be captured by the nanowires. When the temperature is dropped to 4°C, the nanowires undergo a change in conformation, causing the captured cells to be released.
5th-Generation Click Chips – for instant purification of rare targets
Click Chips use silicon nanowire substrates (SiNWS) similar to our earlier NanoVelcro chips, but instead of using traditional antibody-antigen capture to immobilize CTCs, they use a pair of highly reactive “Click Chemistry” motifs, Tz and TCO, to lock cells in place. Specifically captured cells can then be released using DTT to cleave the disulfide bond in the Clicked motifs that tethers the cells to the SiNWS.
Click Chips has been applied for instant purification of CTCs, paving the way for downstream molecular analysis with minimum background.
Click Chips has also been applied for instant purification of EVs, enabling early detection of hepatocellular carcinoma (HCC).