MOF-based tri electrode aptasensor platform for effective detection of sepsis markers with minimal cross-interference

In recent years, several multiplexed point-of-care platforms have been developed as diagnostic tools for sepsis. However, the current versions suffer from poor electrode consistency, analyte interference, and complicated production challenges. Here, we report a polymethyl methacrylate (PMMA)-based trimodal multiplex sensor for the concurrent detection of three sepsis biomarkers: procalcitonin (PCT), C-reactive protein (CRP), and interleukin-6 (IL-6). The device has three active sensing areas. Each area contains a conductive paste comprising trypan blue (TB)-functionalized metal-organic framework (MOF). The MOF paste acts as a transduction layer and is modified with aptamers specific to each analyte. The design includes barriers, optimized channel geometries, and capillary stops to keep electrolytes separate, preventing cross-contamination and off-target binding. The TB-MOF material, with its extended π-conjugation, allows direct electron transfer, which is amplified by surface modification with 3-phosphonopropionic acid (3-PPA). This enhanced electron transfer reduces charge transfer resistance (R_ct), lowers redox potential, and increases peak currents by ∼5-10-fold compared to the unmodified MOF paste. The increased density and orientation of aptamers, caused by the phosphonic acid groups of 3-PPA, also increase the number of binding sites, leading to significant changes in electrochemical reversibility following immobilization. With such arrangements, the subsequent aptasensors achieved detection limits of approximately 0.204 pg mL^-1 (PCT), 0.02 mg mL^-1 (CRP), and 0.315 pg mL^-1 (IL-6), with cross-reactivity below 5%. Overall, this single-formulation platform is graphene-free, shows reproducible baseline stability, and provides a cost-effective approach for producing disposable diagnostic cartridges for sepsis with high specificity.