Printed biotin-functionalised polythiophene films as biorecognition layers in the development of paper-based biosensors

The integration of flexible electronic sensors in clinical diagnostics is visioned to significantly reduce the cost of many diagnostic tests and ultimately make healthcare more accessible. This study concentrates on the characterisation of inkjet-printed bio-functionalised polythiophene films on paper-based ultrathin gold film (UTGF) electrodes and their possible application as biorecognition layers. Physicochemical surface properties (topography, chemistry, and wetting) and electrochemical characteristics of water-soluble regioirregular tetraethylene-glycol polythiophene (TEGPT) and biotin-functionalised TEGPT (b-TEGPT) films were examined and compared. In addition, their specificity towards streptavidin protein was tested. The results show that stable supramolecular biorecognition layers of insulating b-TEGPT and streptavidin were successfully fabricated on a paper-based UTGF by inkjet-printing. Good adhesion of thiophene to UTGF can be attributed to covalent linkage between sulphur and gold, whereas the stability of the streptavidin layer is due to the high affinity between biotin and streptavidin. The device introduced can be utilised in the development of biosensors for clinically relevant analytes e.g. for detecting complementary DNA oligomers or antibody-antigen complexes.