Printed Carbon Nanotube Biosensor for Cardiac Health Monitoring
Authors: Cordeiro Milton Santos , Koehne Jessica E. 
Published: February 2020

Precise and accurate diagnosis of human-related diseases (i.e., genetic disorders, pathogen infection, etc.) is of paramount importance for health care. Early disease detection ensures the appropriate treatment response, leading to a better prognosis. Portable analytical devices hold great potential in minimizing the time between diagnosis and appropriate treatment whether in the doctor’s office or the field. Electrochemical biosensor devices are prime candidates for the development of cheap, disposable and sensitive diagnostic tests considering that they have low power requirements, linear output, can operate at room temperature and can be manufactured using high-throughput technologies (1). Inkjet printing is one of the promising manufacturing procedures for the development of reliable, low-cost, disposable electrochemical biosensor devices and allows mass production on inexpensive, flexible substrates such as paper and polymers (2). Here we present the first steps of the development of a print-on-demand carbon nanotube (CNT) electrochemical biosensor device for the detection of cardiac troponin T (cTnT). cTnT is one of the preferred biomarkers of cardiac infarction monitoring, being elevated up until 14 days after cardiac injury (3) and the infarct size can be estimated from the cTnT levels at 72 hours (4). Our cTnT device is comprised of a fully printed 3 electrode sensor. The first crucial step is to manufacture a suspended CNT ink by the generation of CNT defect sites and increased carboxylic acid functional groups. These functional groups aid in the dispersion of the CNT in water and improve the jetability of the CNTs. Inks are printed using a Dimatix piezo drop-on-demand printer. Upon CNT electrode printing, silver leads are printed, from a commercial silver nanoparticle ink, and insulated using dielectric material, such as SU-8. The surface of the CNTs were modified with antibody probes, anti-cTnT, using an EDC/NHS coupling reaction, to promote the specific detection of cTnT. The surface modification and the interaction between the antibody and cTnT were confirmed by an increase of the charge transfer resistance, measured via electrochemical impedance spectroscopy (EIS) (5) and by a decrease in the differential pulse voltammetry signal (DPV) (6). The immobilized antibodies mediate the specific capture of the target protein leading to the formation of a CNT-antibody-cTnT complex further increasing the charge transfer resistance (3,5) and decreasing the DPV signal. Initial results in device fabrication and cTnT will be presented.

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