Label-free electrochemical immunosensors: A practical guide

Label-free electrochemical immunosensors (ELFIs) are becoming increasingly indispensable tools in life science, medicine, chemistry, and biotechnology. They combine the rapidity and high sensitivity of label-free approaches, without additional assay reagents and tedious procedures, with the high-affinity bio-detection characteristic of antigen-antibody interactions, often integrated into miniaturised lab-on-a-chip electrochemical devices. This review delves into innovative technologies and emerging trends in ELFIs, covering transduction principles, device fabrication, and application. With it, we want to aid researchers, especially those venturing into ELFIs for the first time, by guiding them through the challenges associated with their development. Additionally, this work intends to provide knowledgeable users and curious readers a glimpse into the realm of electrochemical label-free strategies, demonstrating the method's dependability, practical applicability (i.e., environmental, clinical and food safety fields) and inherent limitations. [Display omitted] •The current output is proportional to the immunocomplex formed on the electrode.•Strategies for immobilization, amplification, and sensing of label-free electrochemical immunosensors are summarized.•Layer-by-layer electrochemical characterization enhances surface loading and reduces nonspecific binding.•Label-free electrochemical immunosensors offer sensitive, portable, and streamlined analysis for clinical, environmental, and food safety.•Challenges and future prospects of label-free electrochemical immunosensors are discussed.