Selecting Circulating Tumor Cells from Blood as a Diagnostic for Cancer
The fundamental entities primarily responsible for spawning metastatic disease in many epithelial-based cancers (breast, colon, stomach, prostate, pancreatic, ovarian, lung, etc.) are circulating tumor cells (CTCs), which can be produced during early stages of tumorigenesis. Elucidating the quantity of CTCs in peripheral blood can serve as an indicator for the clinical management of several cancer-related diseases by providing information on the success/failure of therapeutic intervention and disease stage forecasting.
We have generated a novel microfluidic device that can selectively and specifically isolate exceedingly small numbers of CTCs from blood using a monoclonal antibody (mAB) mediated process by sampling large input volumes (≥1 mL) of whole blood directly in short time periods (>37 min). The CTCs can be concentrated into small volumes (190 nL) and the number of cells captured read without labeling using an integrated conductivity sensor following release from the capture surface. The microfluidic device contains a series (51) of high-aspect ratio microchannels (35 µm width x 150 µm depth) replicated in poly(methyl methacrylate), PMMA, from a metal mold master. The microchannel walls were covalently decorated with mABs directed against CTCs over-expressing the epithelial cell adhesion molecule (EpCAM).
Building Nanofluidic Systems for DNA Sequencing
While the cost of DNA sequencing has dropped significantly over the last few years ($3 billion in 2003 to ~$1 million in 2008 for sequencing a human genome) due to the evolution of next-generation sequencing instruments, there still exists the need to produce new technology that can significantly reduce sequencing cost and time and improve the level of automation to realize the ability of transitioning DNA sequencing into such areas as the clinic for in vitro diagnostics. The goal of this project is to generate a novel DNA sequencing platform that can substantially reduce the cost, labor and time associated with acquiring DNA sequencing information using a fully automated platform. The strategy uses nano-scale sensors that read the identity of mononucleotide bases from their characteristic retention time through a nano-chromatography column (10 nm in width and depth; >15 µm in length) fabricated in a thermoplastic, such as Plexiglas, via low-cost replication-based techniques.
The mononucleotide bases are generated from an intact DNA fragment (~50,000 bp) using a processive exonuclease, which is covalently anchored to a nanopillar contained within a bioreactor that feeds the mononucleotides into the nano-column. The retention time is transduced using 2 pairs of nanoelectrodes poised at each end of the nano-column with the signal resulting from perturbations in the tunneling current or conductivity induced by the mononucleotide. The retention time is carefully selected by tailoring the surface chemistry of the 2D nanochannel using unique polymeric material or grafting highly ordered monolayers to the nanochannel surface, which also controls the physical dimensions (width and depth) of the nanochannel. These nanosensors are produced on a plastic module that can be integrated via novel interconnect technologies to other DNA processing modules to provide complete automation of the DNA sample processing pipeline.