Direct Plasmonic Detection of Circulating RAS Mutated DNA in Colorectal Cancer Patients

By exploiting a liquid biopsy approach, we developed an ultrasensitive nanoparticle-enhanced plasmonic method for detecting RAS single nucleotide variants (SNVs) in the plasma of CRC patients. The PCR-free method we developed is based on an imaging platform and allows the direct detection of ~1 attomolar RAS sequences in plasma with a sandwich hybridization assay using peptide nucleic acids probes. The assay involves a simple pre-analytical procedure that does not require the extraction of tumor DNA from plasma and detects it in volumes as low as 40 uL of plasma, which is at least an order of magnitude smaller than that required by state of the art liquid biopsy technologies. The most prevalent RAS SNVs are detected in DNA from tumor tissue with 100% sensitivity and 83.33% specificity. Spike-in experiments in human plasma further encouraged assay application on clinical specimens. Assay performances were then proven in plasma from CRC patients and healthy donors, demonstrating its promising avenue for cancer monitoring.