Electrochemical Biosensing of Exosomes. From Separation Strategies to Clinical Diagnostics
Exosomes are nano-sized extracellular vesicles secreted by cells and they have emerged as promising biomarkers for non-invasive clinical diagnostics. However, their small size (30–200 nm) and low abundance in biofluids pose significant challenges for isolation and detection. This review highlights recent advances in electrochemical biosensors for exosome detection, with particular emphasis on immunomagnetic separation (IMS) strategies and electrochemical platforms developed for clinical diagnostics. Within this context, this review discusses a coherent series of exosome biosensing platforms developed within our research group, contextualized with representative contributions from other teams in the field. The reviewed platforms rely on immunological, enzymatic, and nucleic acid–based recognition strategies, and integrate selective exosome capture, typically assisted by magnetic separation, with electrochemical or related readouts for sensitive detection in complex biological matrices. These approaches integrate selective exosome capture, typically assisted by magnetic separation with electrochemical transduction, enabling sensitive detection in complex biological matrices. Methodologically, the platforms exploit different exosomal features, including surface-associated proteins, intrinsic enzymatic activity, and nucleic acid cargo, illustrating the versatility of electrochemical biosensing for exosome analysis. Reported limits of detection range from approximately 10⁵ down to 10² exosomes μL⁻¹, with demonstrated capability to discriminate clinically relevant samples (e.g., cancer versus healthy controls, Alzheimer’s disease versus controls). The integration of magnetic separation with electrochemical readout in portable formats supports sensitive, specific, and rapid analysis, highlighting the potential of these approaches for POC applications and resource-limited settings. In this regard, this article pays tribute to Prof. Kubota’s legacy in biosensing by reflecting his long-standing emphasis on transforming innovative analytical concepts into solutions suited for real diagnostic settings.