Highly Efficient Photoelectrochemical Detection of Cystatin C Based on a Core-Shell MOF Nanocomposite with Biomimetic-Catalysis Amplification

Cystatin C (CysC) has been proven to be used to diagnose acute kidney injury (AKI) rapidly and sensitively early. Therefore, it is urgent to develop a sensitive, novel, and rapid method for detecting CysC. In this work, a novel photoelectrochemical (PEC) biosensor was designed for ultrasensitive CysC detection. Ti-MOF@DM-LZU1@Au as a photosensitive material was first modified on the ITO electrode surface. Then, Ab₁ and CysC were assembled on the electrode via the specific immunoresponse of an antigen and antibody. Lastly, the conjugate Ab₂/l-Cys bilayer/l-Cys-hemin/G-quadruplex with self-catalytic Enzyme performance, as a signal amplification approach, could further react with CysC and Ab₁, which resulted in a stronger photocurrent. As expected, the constructed PEC sensor realized the ultrasensitive detection of CysC, with a detection range of 10 pg/mL to 16 μg/mL and a lower limit of 8.023 pg/mL. The biosensor had excellent repeatability, selectivity, and stability. Moreover, it can provide a new method for the sensitive and rapid detection of other protein molecules in clinical practice.