β-Cyclodextrin Modified Paper-Based Electrodes Fabricated with Ti3C2Tx MXene/NiO Conductive Ink for Selective Non-Enzymatic Phenylalanine Detection

Abstract

Phenylalanine (Phe), an essential amino acid, plays a critical role in key biological processes, including protein biosynthesis and neurotransmitter production. It also serves as a biomarker in the diagnosis of diseases that may result in severe neurological damage, such as phenylketonuria. Therefore, the development of selective and sensitive sensing platforms for Phe detection is of great importance. In this study, a novel non-enzymatic electrochemical detection platform was developed based on a Ti3C2Tx MXene/NiO conductive ink integrated onto paper-based screen-printed electrodes (SPEs). The high surface area and adsorption capability of the MXene/NiO composite enabled the effective immobilization of beta-cyclodextrin (beta-CD) onto the electrode surface, promoting selective Phe recognition via host-guest interactions. Under optimized conditions, the sensor exhibited a wide linear range from 0.05 to 1000 mu M and a low detection limit of 0.0157 mu M for Phe determination. The platform also showed good selectivity against common interfering species. In artificial sample analysis, recovery% values ranged from 97.0% to 114.0%, with RSD% values between 2.68% and 3.50%, indicating acceptable accuracy and precision. Morphological, structural, and electrochemical characterizations were performed using environmental scanning electron microscopy (ESEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and Fourier-transform infrared spectroscopy (FT-IR). These results demonstrate that the proposed platform offers a promising, low-cost, and versatile strategy for the development of flexible and wearable electrochemical sensors for biomedical applications. Ti3C2Tx MXene and NiO were incorporated into conductive inks for Phe detection.beta-CD was dropped onto the paper SPEs prepared with the developed conductive ink.MXene/NiO/beta-CD/G/SPE enabled Phe detection through inclusion complex formation.MXene and NiO facilitated the Phe oxidation process by promoting adsorption.Flexible SPEs show high repeatability, low detection limit, and strong anti-interference performance.