Upcycling Hospital Lab Polypropylene Waste into a Fully Integrated Additive Manufacturing Electroanalytical Sensing Platforms

Plastic waste is one of the largest contributors to landfill waste globally, with the healthcare industry contributing a large proportion of this. Recycling has been established as a key point of focus to reduce this waste, as addressed in The United Nations Sustainable Development Goals. To this end, this work demonstrates the upcycling of hospital lab waste poly-(propylene) (PP) into a new conductive filament for additive manufacturing, using a zero solvent methodology and incorporating 30 wt % carbon black as a conductive filler. The filament showed excellent low-temperature flexibility, high conductivity, and a low bulk resistance of 61 ± 7 Ω cm^-1. Moreover, the recycled conductive filament produced reproducible electrodes that were electrochemically characterized, showing a heterogeneous electron (charge) transfer rate constant (<i>k</i> ⁰ _obs) of (2.75 ± 0.12) × 10^-3 cm s^-1, improving that of conductive virgin polypropylene electrodes (2.05 ± 0.05) × 10^-3 cm s^-1. These electrodes were utilized in two electroanalytical setups developed for applications in clinical settings. First, the simultaneous electrochemical detection of acetaminophen (ACE) and phenylephrine (PHE) was investigated by using an external counter and reference electrode configuration. These analytes are commonly coformulated in over-the-counter cold and flu medications, highlighting the importance of their concurrent quantification for pharmaceutical quality control and clinical analysis. Second, the sensing of uric acid (UA) using printed electrodes for the working, counter, and reference electrodes, achieving a limit of detection of 0.03 μM and achieving a recovery of 97.6% in urine, sensing of uric acid in urine is important as it is a biomarker for illnesses, for example, gout. This work highlights how waste PP from high use sectors can be upcycled to added-value products, with excellent performance, while contributing toward a circular economy electrochemistry.