Fabrication of a PVC Membrane Sensor Based on a HKUST-1 Metal-organic Framework for Direct Determination of Cysteamine in Pharmaceutical Formulation

Background: The most common use of cysteamine is the treatment of cystinosis. Excessive intake of cysteamine can lead to serious side effects and health complications. Therefore, the monitoring of cysteamine levels is highly significant. Objective: Several techniques have been developed to measure cysteamine accurately. Many of these methods are constrained by various limitations, including labor-intensive pre-treatment procedures, sophisticated equipment, skilled operators, and costly consumables. The present study aims to fabricate a cysteamine-selective potentiometric sensor based on HKUST-1 metal-organic framework exhibiting a wider linear range and more sensitive potentiometric responses compared to the ion pair-based cysteamine-selective sensor that was developed previously. Methods: A novel PVC membrane cysteamine-selective sensor was fabricated by coating the membrane cocktail consisting of poly(vinyl chloride), HKUST-1 metal-organic framework, plasticizer (o-nitrophenyloctylether), and ionic additive (potassium tetrakis (4-chlorophenyl) borate) onto the conductive solid contact surface. The potentiometric performance characteristics of the sensor were evaluated in detail. Results: The sensor exhibits a linear response to cysteamine concentration in the range of 1.0×10−6 M -1.0×10−2 M (R2=0.9958) with a slope of 51.5 mV/decade and a detection limit of 8.0×10-7 M. It operates effectively within a pH range of 3.9-5.7 and displays a rapid response time. Conclusion: Compared to the cysteamine-selective sensor available in the literature, the current sensor stands out with its wider linear operating range and lower detection limit. The sensor consistently yields reproducible and stable potentiometric responses towards cysteamine. The fabricated cysteamine-selective sensor effectively quantifies cysteamine content in pharmaceutical formulations. 2026, Bentham Science Publishers