Increasing sensitivity and selectivity for electrochemical sensing of uric acid and theophylline in real blood serum through multinary nanocomposites

The sensing of theophylline (TP) and uric acid (UA) is important for the diagnosis and treatment of diseases in the early stages. While the first proofs show the potential of electrochemical sensors, the simultaneous detection of TP and UA is still not satisfactory. Herein we present an electrochemical sensor showing high sensitivity and selectivity for the detection of the two purine derivatives, TP and UA in blood serum. Key for this is a multinary nanocomposite which was specially designed for the sensing purpose and is based on titania nanoparticles, copper oxide, and boron-doped reduced graphene oxide, Au nanoparticles as also the modification of the supporting carbon electrode with 2-amino-5-mercapto-1,3,4-thiadiazole through electropolymerization. The study showed that the multinary nanocomposite improves the electrochemically active surface area and the electron transfer rate of the sensor, which together boosts the current response for the sensing strongly. It could be shown that the electrochemical sensor provides an excellent linear relationship between 0.5 nM and 10.0 µM for UA and for TP between 1.0 nM and 10.0 µM. Detection limits of 0.18 nM and 0.36 nM results for UA and TP, respectively. The sensitivity is 1.27 μA µM−1 cm−2 for UA and 1.06 μA µM−1 cm−2 for TP. Additionally, the method was used for the simultaneous measurements of UA and TP in real blood serum, which demonstrated the excellent applicability of the device.