Electrochemical Biosensors

Electrochemical Biosensors

1. Electrochemical biosensors combine the sensitivity of electroanalytical methods with the inherent bioselectivity of the biological component. The biological component in the sensor recognizes its analyte resulting in a catalytic or binding event that ultimately produces an electrical signal monitored by a transducer that is proportional to analyte concentration. After the analyte contacts a recognition element on the surface of the biosensor, physical or chemical changes yield a reaction that is transformed into an electrochemical signal. This information can be further processed to determine the concentration of the pathogen and changes in the composition of the analyte.

   • Characteristics
     • Converting the biological information to an easily processed electronic signal is challenging due to the complexity of connecting an electronic device directly to a biological environment. Electrochemical biosensors provide an attractive means to analyze the content of a biological sample due to the direct conversion of a biological event to an electronic signal.
       • Additional measurement techniques, which have been shown useful in combination with electrochemical detection, are also summarized, such as the electrochemical versions of surface plasmon resonance, optical waveguide lightmode spectroscopy, ellipsometry, quartz crystal microbalance, and scanning probe microscopy. The signal transduction and the general performance of electrochemical sensors are often determined by the surface architectures that connect the sensing element to the biological sample at the nanometer scale.
         • The most common surface modification techniques, the various electrochemical transduction mechanisms, and the choice of the recognition receptor molecules all influence the ultimate sensitivity of the sensor. New nanotechnology-based approaches, such as the use of engineered ion-channels in lipid bilayers, the encapsulation of enzymes into vesicles, polymersomes, or polyelectrolyte capsules provide additional possibilities for signal amplification.
   • Applications
     • Some of these sensor devices have reached the commercial stage and are routinely used in clinical, environmental, industrial, and agricultural applications.
       • One of electrochemical biosensors main uses is to directly monitor analytes or the biological activity related to the analyte (production or consumption). Through this, the biosensor can monitor the activities of living cells or enzymes.
         • Indirect monitoring can be done to analyze organic pesticides or inorganic substances that interfere with the biocatalytic properties of the sensor. This involves monitoring of heavy metals, fluoride, cyanide, and others that have high importance in industry and environment. However, these are often irreversible, and therefore often provide less exact analyte concentration measurements.
   • Advantages
     • Such as lacking the high complexity of the sensor setup and the high cost of other biosensors. electrochemical biosensors are associated with the cheap production of microelectronic circuits and a user-friendly interface with conventional electronic processing and results.
       • Electrochemical biosensors are also robust, easy to miniaturize, and offer broad detection limits even when only small volumes of analyte are present. Furthermore, electrochemical biosensors can be used to analyze biofluids with high turbidity and optically absorbing and fluorescing compounds.
   • Disadvantages
     • They do not have the type of surface architecture that would facilitate high sensitivity and unique recognition of the response to the selected biochemical event. This means that the pH and ionic strength of biofluids can vary greatly and thereby influence the behavior of vital biosensor classes, such as immunosensors.
       • Due to the above, nanotechnology has had increased applications in electrochemical biosensing by being used to minimize elements of electrochemical sensor into sizes that increase the signal-to-noise ratio. This is particularly important for processes that are intended to occur at the device’s interface and can be used to discover methods to use several enzymatic labels to increase the intensity of the event signal.
   • Types
     • The receptor can be selective for a biocatalytic event such as a reaction that is catalyzed by macromolecules, including enzymes, or for a specific bioaffinity, such as the interaction between an analyte and a macromolecule, independent of their biological environment.
     • The detection methods for electrochemical transducers are diverse. The methods include amperometry, which is based on measuring the electroactive species’ electrochemical oxidation or reduction current. The current relates directly to the concentration of the electroactive species.
     • Another method is conductometry, which relies on the conductometrics of enzyme reactions and biological membranes.
     • Potentiometry is a detection method that involves the potential difference of an indicator electrode and a reference electrode when no current flows between them. These are most commonly pH electrodes but can be ion-selective electrodes.
     • Electrochemical biosensors can measure analytes by the surface charge using field-effect transistors. These can determine ion concentrations by attaching an ion-selective membrane to a transistor, which becomes a biosensor when coupled with a biocatalytic or bioaffinity layer.
   • Nanomaterials
     • Carbon allotropes such as graphene and carbon nanotubes, have been incorporated in electrochemical biosensors for highly sensitive and selective detection of various analytes. The superior physical and electrical properties like high carrier mobility, ambipolar electric field effect, high surface area, flexibility and their compatibility with microfabrication techniques makes these carbon nanomaterials easy to integrate in field-effect transistor (FET)/chemiresistor type configuration which is suitable for portable and point-of-use/field-deployable sensors. This review covers the synthesis of carbon nanostructures (graphene and CNTs) and their integration into devices using various fabrication methods.

Bilder und Dateien der Mindmap