Enhancing ELISA Sensitivity: From Surface Engineering to Synthetic Biology.

Accurate and sensitive detection of protein biomarkers is critical for advancing in vitro diagnostics (IVD), yet conventional enzyme-linked immunosorbent assays (ELISA) often fall short in terms of sensitivity compared to nucleic acid-based tests. Bridging this sensitivity gap is essential for improving diagnostic accuracy, particularly in diseases where protein levels better reflect disease progression than nucleic acid biomarkers. In this review, we present strategies developed to enhance the sensitivity of ELISA, structured according to the sequential steps of the assay workflow. Beginning with surface modifications, we then discuss the methodologies to improve mixing and washing efficiency, followed by a summary of recent advances in signal generation and amplification techniques. In particular, we highlight the emerging role of cell-free synthetic biology in augmenting ELISA sensitivity. Recent developments such as expression immunoassays, CRISPR-linked immunoassays (CLISA), and T7 RNA polymerase-linked immunosensing assays (TLISA) demonstrate how programmable nucleic acid and protein synthesis systems can be integrated into ELISA workflows to surpass the present sensitivity, affordability, and accessibility. By combining synthetic biology-driven amplification and signal generation mechanisms with traditional immunoassay formats, ELISA is poised to evolve into a highly modular and adaptable diagnostic platform, representing a significant step toward the next generation of highly sensitive and programmable immunoassays.