Vapor Sensing of Colorectal Cancer Biomarkers in Isolation by Bare and Functionalized Nanoelectromechanical Sensors

Small dimensions and high resonance frequencies render nanoelectromechanical systems (NEMS) sensitive mass detectors. Mass detection capability can be used to sense chemicals in the gas phase by functionalizing the device, usually with a polymeric film. The performance of NEMS-based gas detectors in breath analysis applications depends crucially on the selectivity between selected functionalization layers and targeted biomarkers. Here, we report the detection of four colorectal cancer biomarkers at parts-per-million concentration levels, when introduced in isolation to the sensor system within a dry nitrogen stream. The biomarkers, 3-methylpentane, cyclohexane, nonanal, and decanal, were then discriminated from each other by using the combined response of three NEMS devices: one bare device, and two devices coated with either poly(ethyleneoxide) or poly(caprolactone). Our results indicate that bare NEMS are more responsive to high molar mass biomarkers, whereas functionalized sensors are more responsive toward more volatile biomarkers. Considering the inherently fast response times and minuscule limits of detection of NEMS devices, the combined response of differentially coated sensors can be used as the main sensing element to identify and distinguish cancer biomarkers in human breath.