MOF composites functionalized portable electrochemical sensor for sensitive detection of cysteine in food

Due to cysteine’s role as a common food additive and flavor enhancer, monitoring its levels in various food industries is crucial to prevent excessive intake and ensure consumer health protection. An electrochemical sensor was developed using a screen-printed carbon electrode (SPE) modified with a nanocomposite of metal-organic framework (MOF, PCN-222(Fe)), cobalt phthalocyanine (CoPc) and multi-walled carbon nanotubes (MWCNTs) (PCN-222(Fe)/CoPc/ MWCNT) for sensitive detection of cysteine (Cys) in food samples. The PCN-222(Fe)/CoPc/MWCNT nanocomposite was synthesized via a hydrothermal method combined with ultrasonic dispersion, and then deposited onto the surface of SPE using an electrochemical method. The designed sensor was highly sensitive and specific, owing to the favorable catalytic properties of CoPc, the porous structure and stability of PCN-222(Fe), and the excellent electron transport capacity of MWCNTs. The results demonstrated that the PCN-222(Fe)/CoPc/CNT sensor was capable of real-time detection of Cys from 1 μM to 1 mM with a low detection limit of 0.11 μM (S/N=3) and excellent selectivity and stability. Moreover, the developed electrodes were used to detect Cys in yogurt and juice samples, achieving a recovery rate of 96.20-102.70%. This work provides reliable technical support for the practical application of food analysis and detection.