Microneedle-Integrated Screen-Printed Electrode Modified with Gold Nanoparticle-Boron-Doped Diamond Nanoparticle Nanocomposites for Electrochemical Theophylline Detection

Theophylline is a drug with a narrow therapeutic index, with normal plasma levels ranging from 10 to 20 mg/L. Theophylline overdose can lead to several symptoms, including nausea, vomiting, headaches, pancreatitis, and death. Thus, it is important to monitor theophylline after its consumption. Microneedles (MNs) can be integrated with screen-printed electrodes (SPE) to enable the minimally invasive monitoring of theophylline. In this study, we developed a highly sensitive and accurate electrochemical sensor to detect theophylline based on a gold nanoparticle/boron-doped diamond nanoparticle nanocomposite-modified SPE (AuNP-BDDNP/SPE). In addition, this study aims to determine the feasibility of MN integration with AuNP-BDDNP/SPE for theophylline detection. UV-vis, TEM, and XPS confirmed the successful synthesis of AuNP-BDDNP, whereas FESEM images confirmed the successful modification of SPE. Theophylline detection was performed using differential pulse voltammetry (DPV) with concentrations ranging from 20 to 140 μM, producing an <i>R</i> ² value of 0.999, an LOD of 0.14 μM, and an LOQ of 0.48 μM. AuNP-BDDNP/SPE was also selective in the presence of interferents. AuNP-BDDNP/SPE can accurately detect theophylline in urine, coffee, and capsule samples. Moreover, AuNP-BDDNP/SPE was successfully integrated with MNs, maintaining the accuracy for detecting theophylline in urine, coffee, and capsule samples. AuNP-BDDNP/SPE demonstrated excellent performance in theophylline detection and can potentially be successfully integrated with MNs.