A highly sensitive label-free aptamer sensor for timely detection of human serum albumin

The trace-level detection of proteins in the human body holds significant importance for health monitoring and disease prevention. To conduct real-time monitoring of the human body's health status, both wearable and implantable devices require label-free sensing. However, the signals of a considerable number of label-free electrochemical sensors originate from the signal capture medium. These signals are weak and are prone to being lost or masked by other signals. We report a Prussian blue (PB)-based self-redox aptamer sensor was developed, enabling real-time human serum albumin (HSA) detection without external redox mediators. The designed sensing interface successfully achieved the quantitative detection of HSA in PBS with a sensitivity of 124 fg mL^-1. In addition, to validate universality, the sensor was tested with retinol-binding protein (RBP4), showing comparable performance. This label-free electrochemical sensor can achieve one-step detection without additional reagents. This system has application potential in on-site detection, as well as wearable sensing.