An Ultrasensitive Four-Response Ratiometric Electrochemical Homogeneous Biosensor Based on a Positive MOF Biomaterial for Direct Diagnosis of Breast Cancer Types in Human Serum

Continued development of high-performance, low-cost, in vitro diagnostic tools is critical for cancer diagnosis and therapeutic prognosis. Herein, we propose a four-response ratiometric electrochemical homogeneous biosensor based on positive MOF biomaterial for detection of the estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor-2 (HER2), and cell proliferation index (Ki67) protein biomarkers, and for simultaneous diagnosis of 10 types of breast cancer directly in human serum using a single electrode within one system. The principle of this specific four-response ratiometric electrochemical biosensor relied on neutral red (NR), tolonium blue (TB), tetramethylbenzidine (TMB), and malachite green (MG) loaded on the surface of UiO-66-NH₂. These electrically active organic molecules with positive charges can be driven by negative voltage-induced diffusion to concentrate on the surface of an ITO electrode via electrostatic interactions. However, if the target bioprotein molecule shows a positive charge when the pH value of the PBS buffer solution is below its isoelectric point, it will change the diffusion path of the electroactive organic molecule due to the charge repulsion, thereby affecting the diffusion rate. The biosensor has a short detection time of 60 min; however, the current clinical tissue testing time takes about 1 week. Additionally, the biosensor selectively detects HER2, ER, Ki67, and PR in a range of 0.0134/0.0331/0.0194/0.0250-35 pg/mL with detection limits of 0.0134, 0.0331, 0.0194, and 0.0250 pg/mL, respectively. Notably, compared with traditional gene chip and immunohistochemistry technology, the test object achieves the transformation from tissue to body fluid analysis by electrochemical sensing technology.