A compact automated magnetic digital microfluidic chemiluminescence immunoassay system for rapid and sensitive detection of protein biomarkers

The rapid and sensitive detection of specific protein biomarkers is essential for early diagnosis and monitoring of diseases. Magnetic digital microfluidics (MDMF), capable of integrating and miniaturizing chemiluminescence immunoassay (CLIA), offers significant advantages for biomarker detection, including high flexibility, high efficiency, and low sample consumption. Magnetic bead manipulation, as a key component of MDMF, plays a critical role in improving detection sensitivity and accuracy within a short analysis time. In this study, we proposed an automated MDMF-based CLIA system and developed a compact analyzer, enabling faster and more sensitive biomarker detection through optimized magnetic bead manipulation. The system employs a film-sandwiched microfluidic chip, along with a specially designed spliced magnet to generate a stronger and more concentrated magnetic force, significantly enhancing the control over the motion of magnetic beads. By using the magnet to drive magnetic beads through water-in-oil droplets, the system automates the entire CLIA workflow. Through theoretical analysis, simulations, and experiments, we validate the system's advantages in magnetic bead aggregation and transfer, achieving a high magnetic bead collection rate of 97.07% with excellent cleaning effect after three cleaning rounds. The detection of cardiac troponin I (cTnI) can be completed within 10 min, with a limit of detection (LOD) of 2.09 pg mL^-1, a detection range of 0.01 to 20 ng mL^-1, and a strong linear correlation with conventional CLIA (R² = 0.9961). This system achieves rapid, sensitive, and automated CLIA, making it a promising platform for clinical diagnostics.