immunosensor

An immunosensor is a type of biosensor that detects target molecules through antigen–antibody interactions. It combines a biorecognition element, typically an antibody or, less commonly, an antigen or aptamer, with a transducer that converts the binding event into a measurable signal. Immunosensors are designed to detect proteins, pathogens, hormones, or other biomarkers at low concentrations in complex samples.

Principle and transduction: Upon target binding, the interaction changes a physicochemical property that the transducer converts into an electronic, optical, or acoustic signal. Common transduction modalities include electrochemical (amperometric, voltammetric, impedance), optical (fluorescence, chemiluminescence, surface plasmon resonance), and mass/velocity-based methods (piezoelectric, quartz crystal microbalance).

Configurations: Immunosensors may be label-free, detecting binding directly by impedance or mass, or labeled, using secondary signal tags to amplify the output (for example, enzyme labels or fluorescent tags). Formats include sandwich assays, or competitive assays for small targets.

Applications and performance: Immunosensors are used in clinical diagnostics, infectious disease testing, allergy screening, cancer biomarker monitoring, environmental monitoring, and food safety. They aim for high sensitivity and specificity, wide dynamic range, low limit of detection, fast response, and suitability for point-of-care use. Challenges include non-specific binding, stability of biological components, reproducibility, and matrix effects in real samples. Advances focus on nanomaterials, microfluidics, multiplexing, and integrated readouts to improve robustness and reduce cost.