A multi-virus detectable microfluidic electrochemical immunosensor for simultaneous detection of H1N1, H5N1, and H7N9 virus using ZnO nanorods for sensitivity enhancement

This paper describes a multi-detectable and nano-flow immunosensor based on ZnO nanorods (NRs) grown on the inner surface of PDMS sensor region for sensing H1N1, H5N1, and H7N9 influenza viruses simultaneously using electrochemical method. Nanostructured ZnO NRs with a high isoelectric point (IEP ∼9.5) tend to interact electrostatically with proteins with lower IEP such as H1N1, H5N1, and H7N9 antibodies. ZnO NRs were hydrothermally grown on the upper inner surface of the nano-flow PDMS sensor region. The forementioned three influenza viruses were successfully detected from three separate sensing regions by measuring the oxidation current of 3,3′,5,5′-tetramethylbenzidine (TMB) by horseradish peroxidase (HRP) conjugated on capture antibody of those influenza viruses when proper potential was applied. The proposed immunosensors were evaluated using 1 pg/ml, 10 pg/ml, 100 pg/ml, 1 ng/ml, and 10 ng/ml of H1N1, H5N1, and H7N9 antigens by amperometry. These immunosensors showed high selectivity toward H1N1, H5N1, and H7N9, which was successfully confirmed by distinguishing the target virus individually from a mixture of three virus antigens. A low limit of detection was demonstrated by detecting as low as 1 pg/ml of each virus and it is believed that this was possible by enhancing the sensitivity with the ZnO NRs grown on the PDMS surface in the sensing region. The steady-state oxidation current output linearly increased with respect to the logarithm of the H1N1, H5N1, and H7N9 virus concentrations in the range of 1-10 ng/ml.