Amperometric Biosensor Strip With Carbon Nanotube and Ketone Body 3-Hydroxybutyrate Dehydrogenase

We propose an amperometric biosensor strip for the detection of ketone body 3-hydroxybutyrate (3HB) in serum. The biosensor strip has a small volume (
$\approx 2 ~\mu \text{L}$
) capillary chamber. The working electrode consists of carbon nanotubes (CNTs) and 3HB dehydrogenase (3HBDH). The CNTs are dispersed in aqueous media with sodium cholate (SC) surfactant and mixed with HBDH solution. Ultraviolet–visible, electrochemical impedance spectroscopy (EIS), and atomic force microscopy (AFM) demonstrated that the CNTs were well dispersed in aqueous solution. Any type of CNT enhances the current owing to an enzymatic reaction without an electron transfer mediator. A small amount of HBDH/CNT solution is dipped into a small-area (1.5 mm2) electrode and sealed with a coversheet to make the reaction chamber. The sensor can detect 3HB in human serum within the range of 0.05–4.4 mM, which can cover physiological use. The response time is 15 s.