Eliminating Complex Matrices: A Minimalist Approach to Enzyme-Based Biosensors Using Screen-Printed Electrodes with a...

Enzyme-based biosensors commonly rely on complex immobilization matrices to ensure sensitivity and stability, increasing fabrication cost and limiting scalability. Here, we demonstrate a simple and straightforward packing strategy to allow using a minimalist lactate biosensor that eliminates these matrices by directly immobilizing lactate oxidase onto screen-printed electrodes. This matrix-free configuration achieved the highest sensitivity (4.22 μA dL mg^-1) and a low detection limit (3.1 mg dL^-1), outperforming electrodes incorporating nanomaterials or chemical stabilizers. Although crosslinking and polymeric additives slightly reduced sensitivity, they preserved concentration discrimination without offering clear performance advantages. When tested in human plasma samples containing potential interferents, the biosensor exhibited comparable behavior, achieving a sensitivity of 4.89 μA dL mg^-1. Long-term durability tests showed stable enzymatic activity and consistent current responses over six months when electrodes were stored using a simple aluminum packaging and desiccant strategy, demonstrating that appropriate post-fabrication preservation can replace complex immobilization approaches. In the absence of appropriate packaging, the biosensors exhibited significant performance degradation, leading to underestimation of lactate concentrations after two days of storage under ambient temperature and humidity conditions. The biosensor reliably detects lactate across clinically relevant concentrations and establishes that simplifying design can enhance performance, durability, and translational potential, supporting more accessible point-of-care lactate monitoring.