Carbon based nanomaterials for biosensing applications

Abstract

There is an unmet need of fast, reliable and highly sensitive determination of different biomarkers in untreated physiological samples in the Point-of-Care setting. Among many types of biosensors, electrochemical and electronic transducers seem to fulfill many requirements for future diagnostic devices such as label-free and real-time analyte determination, as well as a potential for mass-manufacturability. A recent advancement of nanomaterials, with particular focus on carbon nanomaterials, triggered a foundation of a new branch of biosensors to explore. In this work, two carbon nanomaterials - graphene and carbon nanotubes, were used to construct both electronic and electrochemical biosensors – able to work in physiological environment and with a potential for further development into the Point-of-Care environment. The two types of transduction were assessed - 1) electronic (i.e. field-effect transistor (FET) based), based on analyte determination by its charge, and 2) electrochemical (i.e. amperometric), based on analyte determination by the redox reactions that occur at the electrode. Firstly, for the construction of carbon nanotube network based field-effect transistor biosensor, novel and stable receptor molecules were employed - nanobodies, and studied in a label-free system with green fluorescent protein as a model analyte. The biosensor exhibited a wide dynamic range with low detection limit and triggered the next, more applicable study. Secondly, a graphene-based field-effect transistor (GFET) was employed as a transducer for construction of thyroid-stimulating hormone (TSH) specific biosensor. This solution resulted in coverage (and also going far beyond) of TSH reference values in physiological samples. Finally, for the electrochemical based detection, using the setup from GFET study, graphene was used as a working electrode and in combination with the enzyme - flavin adenine dinucleotide dependent glucose dehydrogenase (FAD-GDH), resulted in an electrochemical glucose biosensor. Direct electron transfer from the enzyme to the graphene electrode was additionally observed. The results of this work shed light and contribute to the development of multimodal detection of analytes in physiological samples for further application in Point-of-Care setting.