Immunosensors

Immunosensors are analytical devices that integrate a biorecognition element, typically an antibody or antigen, with a transducer to convert antigen-antibody binding into a measurable signal. The specific binding between an antigen and its antibody provides selectivity, while the transducer outputs an electronic, optical, or acoustic signal that can be quantified. Immunosensors can be designed with various transduction modalities, most commonly electrochemical, optical, or mass-sensitive readouts.

In an immunosensor, the biorecognition element is immobilized on a sensing surface and exposed to a sample. Upon target binding, the transducer detects changes in current, impedance, voltage, fluorescence, refractive index, or mass, which are processed to produce a readout. Electrochemical immunosensors include amperometric, potentiometric, and impedimetric formats; optical immunosensors use surface plasmon resonance, fluorescence, chemiluminescence, or absorbance; mass-sensitive types include quartz crystal microbalance and acoustic wave devices.

Applications are widespread in clinical diagnostics (for pathogens, hormones, tumor markers), environmental monitoring (pesticides, toxins, heavy metals), and food safety (allergens, pathogens, adulterants). Advantages of immunosensors include rapid analysis, potential for miniaturization and point-of-care use, and high specificity. Limitations involve stability and reproducibility of the biological element, cross-reactivity, matrix effects, and the need for careful calibration and surface design.

Developments focus on label-free and multiplexed sensors, nanomaterial-enhanced transducers, aptamer-based recognition, and integrated microfluidics to enable truly portable diagnostic platforms.