Immunosensors are biospecific recognition elements of immunoactive substances.
It is a type of biosensor and is based on the complex formation of the antigen and antibody.

Immunosensors produced by immobilizing antigens or antibodies to the sensor surface are generally classified according to the measurement principle.

Immunosensors can provide rapid and highly sensitive immunological responses. Therefore, it is a subject of great interest in the field of diagnosis.

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Indium tin oxide (ITO), one of the most widely utilized transparent conductive oxide thin film, is a promising material to develop different technologies such as biosensors, flat-panels and photovoltaics due to its two main properties; good electrical conductivity and optical transparency. ITO is an excellent material, which has been extensively utilized in biosensor studies owing to its unique properties such as good optic transparency, wide working window, high electrical conductivity, substrate adhesion, low capacitive current, and stable electrochemical and physical features. Owing to these unique features, it can be used in electrochemical researches. ITO sheet is relatively cheaper than other conventional electrodes such as gold, silver and platinum, so it is mostly preferred. 

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Electrochemical impedance spectroscopy (EIS) is an effectual and useful method to investigate complex electrical resistances, sensitivities of the surfaces, and quantitative changes in biosensing systems. It is often used in metal corrosion mechanisms, charge transfer through membranes, and characterization and optimization of membrane/solution interfaces. In recent years, this technique has been increasingly preferred in the investigation of both the preparation steps of biosensors and the specific interactions of biomolecules. The impedance spectroscopy techniques are useful and preferable to accomplish the surface characterization of the electrode and examine the interaction between the biorecognition material and bioanalyte. EIS is an important method for investigating surface morphology with imaging techniques due to these features. 

A lateral flow test (LFT) is an assay also known as a lateral flow device (LFD), lateral flow immunochromatographic assay, or rapid test. It is a simple device intended to detect the presence of a target substance in a liquid sample without the need for specialized and costly equipment. LFTs are widely used in medical diagnostics in the home, at the point of care, and in the laboratory. For instance, the home pregnancy test is an LFT that detects a specific hormone. These tests are simple and economical and generally show results in around five to thirty minutes. Many lab-based applications increase the sensitivity of simple LFTs by employing additional dedicated equipment.

Quartz tuning fork (QTF) sensors are piezoelectric transducers with a high-quality factor (above 10.000 at atmospheric pressure) that are used in various applications such as scanning near-field optical microscopy, and digital electronics. They have unique mechanical properties such as high stiffness (>103N/m) and small oscillation amplitude (<1 nm). The QTFs have been originally manufactured by the watch industry as a standard 32768 Hz clock oscillator. Also, QTF sensors have various applications such as AFM, quartz-enhanced photoacoustic spectroscopy-based trace gas sensors and as a time–frequency standard in watches. QTF sensors work by vibrating at a constant frequency when striking against any surface. The fork sensors are tuned at a particular frequency according to the type of industry and are generally factory calibrated. Some advantages of using quartz tuning fork sensors include their high sensitivity and stability. They are also highly resistant to temperature changes and have low power consumption. Therefore, they are potential electrodes for developing biosensors. By optimizing the biorecognition element, modifying the electrode surface, miniaturizing the biosensor, enabling multi-sensing, and integrating with microfluidic systems, QTF-based biosensors can be designed for a wide variety of applications in healthcare, environmental observation, and other fields.

A working electrode is placed in a stagnant solution containing a conductive material over time. When a linearly increasing potential program is applied, the current-potential curve appears as a peak.In this application, potential scanning is carried out in a certain direction in forward. If the potential is reversed to decrease linearly after reaching its value, this technique is called cyclic voltammetry.The CV method is used in many areas. Some of these are: quantitative analysis, surface modification, examination of the kinetics of electrode reactions, various finding physicochemical constants (D, n, i, K, E, α…), examining adsorption, examining the mechanisms of electrode reactions, determining complex structures, examining immobilization steps in biosensors.