Real-Time Monitoring of Trastuzumab Monoclonal Antibodies Using Electrochemical Aptamer-Based Sensors

The real-time monitoring of trastuzumab (Tmab), a monoclonal antibody used for cancer treatment, is critical for personalized, response-guided dosing and improved biomanufacturing quality control. Currently, Tmab concentrations are quantified using immunoassays and mass spectrometry, but these platforms provide only discrete measurements and require extensive sample preparation. Surface-tethered electrochemical aptamer-based (E-AB) sensors provide a unique alternative because they operate without free-floating reagents, enable continuous measurements, and can be engineered to achieve high sensitivity and specificity. However, using E-AB sensors to detect macromolecules such as antibodies, rather than small molecules, requires careful consideration of surface-induced steric hindrance effects. In this work, we present a surface-functionalized Tmab-targeting E-AB sensor with optimized surface density and square-wave voltammetry frequency. The Tmab E-AB sensor employs a linked displacement strand construct and achieves K D = 70.8 nM and LoD = 0.66 nM at an estimated surface density of 15 molecules/mm 2 × 10 −9 . We further study the use of active and passive refresh techniques to enable continuous and quasi-continuous monitoring and demonstrate direct sensing in human serum and cell culture media.