Electrochemical ratiometry: A new route towards bioaffinity-based in vitro diagnostics

In vitro diagnostics (IVD) is aimed at ensuring human welfare and life security. Electrochemical sensors have been utilized in different applications, such as environmental contaminant detection and food safety, especially in the field of IVD, due to their excellent properties such as high sensitivity, simple to use, and cost-effectiveness. However, reluctant reproducibility and accuracy are among the most insurmountable hindrances for electrochemical IVD sensors, especially bioaffinity-based ones essential in disease biomarker detection and infection prognoses. In recent years, inspired by the ratiometric strategy from fluorometry, electrochemically ratiometric biosensors have been increasingly developing. This review highlights recent advances in bioaffinity based electrochemically ratiometric sensors (BERS) for IVD applications. Their signal generation strategies and analysis applications, especially for potential applications in the real world, are introduced. Finally, we enlighted several thoughts and insights into the design and application of BERS in IVD and provided the challenges and perspectives in this domain.