A copper oxide-ionic liquid/reduced graphene oxide composite sensor enabled by digital dispensing: Non-enzymatic paper-based microfluidic determination of creatinine in human blood serum

Highlights: • A CuO/IL/ERGO modified paper-based screen printed electrode was constructed and used as a non-enzymatic creatinine sensor. • An HP D300 dispenser was used to enable efficient electrode modification, leading to improved sensitivity and reproducibility. • The sensitivity was sufficient for detecting clinically relevant creatinine levels in acute kidney injury diagnosis. -- Abstract: A paper-based analytical device (PAD) with an integrated composite electrode for non-enzymatic creatinine sensing was developed. The electrode was produced and optimization was efficiently accomplished using a rapid digital dispensing approach. The electrochemical sensor was fabricated using an HP D300 digital dispenser to deliver a copper oxide and ionic liquid composite onto an electrochemically reduced graphene modified screen-printed carbon electrode (CuO/IL/ERGO/SPCE) on a PAD. The modified electrode was characterized using electrochemical and microscopic techniques. Electrochemical detection of creatinine was performed on the SPCE using amperometry at a constant potential. Under optimized conditions, the paper-based sensor exhibited a linear range of 0.01–2.0 mM (R² = 0.99) and the limit of detection was 0.22 μM (S/N = 3, IUPAC definition) for creatinine. The simple fabrication process, low cost, and clinically appropriate creatinine sensitivity make this device applicable for point-of-care use.