Theophylline (TPN) is a medication commonly used in treatment of chronic asthma disorder. However, it is associated with a number of known troublesome side effects, hence, the need to monitor its concentration levels in pharmaceutical formulations. In this work, a nanocomposite based on ZnONPs – MWCNTs – Cyt c (zinc oxide nanoparticles – multiwalled carbon nanotubes – Cytochrome c) were used in the modification of a highly sensitive electrochemical sensor for quantification of TPN in pharmaceutical formulations. The synthesized ZnONPs, ZnONPs-MWCNTs and ZnONPs-MWCNTs-Cyt c were characterized using Thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Transmission electron microscopy (TEM), surface area analysis by Brunauer–Emmett–Teller (BET) and electrochemical impedance spectroscopy (EIS). Cyclic voltammetry was employed to study electro-catalytic properties of ZnONPs-MWCNTs-Cyt c-GCE towards oxidation of TPN. The dependence of peak currents and potentials on scan rates and pH were also investigated and the working parameters were optimized. Remarkably, ZnONPs-MWCNTs-Cyt c-GCE exhibited improved anodic peak currents as compared to ZnONPs-MWCNTs-GCE, MWCNTs-GCE and bare GCE for 0.1 M TPN at 1.0 V vs. Ag/AgCl. The linear range of the established electrochemical biosensor was from 0.4 to 15 µM (R² = 0.9903) with detection limit of 0.0012 µM, thus making it a better candidate for the detection of TPN in pharmaceutical formulation.

茶碱（TPN）是常用于治疗慢性哮喘疾病的药物。然而，它与许多已知的麻烦的副作用有关，因此需要监测其在药物制剂中的浓度水平。在这项工作中，基于ZnONPs-MWCNTs-Cyt c（氧化锌纳米颗粒-多壁碳纳米管-Cytochrome c）的纳米复合材料被用于修饰高度敏感的电化学传感器，以定量药物制剂中的TPN。使用热重分析（TGA），傅立叶变换红外光谱（FT-IR），X射线衍射（XRD），透射电子显微镜（TEM），表面对合成的ZnONPs，ZnONPs-MWCNTs和ZnONPs-MWCNTs-Cyt c进行了表征Brunauer–Emmett–Teller（BET）和电化学阻抗谱（EIS）进行面积分析。采用循环伏安法研究了ZnONPs-MWCNTs-Cyt c-GCE对TPN氧化的电催化性能。还研究了峰值电流和电位对扫描速率和pH的依赖性，并优化了工作参数。值得注意的是，对于1.0 M TPN的ZnONPs-MWCNTs-GCE，MWCNTs-GCE和裸露的GCE，在1.0 V相对于Ag / AgCl的情况下，ZnONPs-MWCNTs-Cyt c-GCE表现出改善的阳极峰值电流。建立的电化学生物传感器的线性范围为0.4至15 µM（ZnONPs-MWCNTs-Cyt c-GCE在1.0 V vs.Ag/AgCl的条件下，与ZnONPs-MWCNTs-GCE，MWCNTs-GCE和裸GCE相比，在0.1 V TPN下表现出改善的阳极峰值电流。建立的电化学生物传感器的线性范围为0.4至15 µM（ZnONPs-MWCNTs-Cyt c-GCE在1.0 V vs.Ag/AgCl的条件下，与ZnONPs-MWCNTs-GCE，MWCNTs-GCE和裸GCE相比，在0.1 V TPN下表现出改善的阳极峰值电流。建立的电化学生物传感器的线性范围为0.4至15 µM（R ²  = 0.9903），检测限为0.0012 µM，因此使其更适合用于检测药物制剂中的TPN。