Biosensors are now viewed as ideal prognostic tools not only for disease detection but also everyday wellness. Wearable and implantable biosensors are likely to emerge as the key enablers for device innovation and will be commercialized as prognostic tools
A typical biosensor system combines a biocatalyst with a physicochemical transducer to produce an electrical signal that is amplified, processed and displayed in a readout. Under this definition, most often an enzyme or another biological component is added to a transducer platform to detect and quantify analytes. The term is often erroneously used to refer to any sensor system that detects biological analytes, without using a biological agent for the actual detection; under this definition, a pulse oximeter or an ECG device would also qualify as a biosensor. Frost & Sullivan clearly distinguishes these two sensor types: the latter is a medical sensor; the former, using an active biological agent for detection and quantification, is a biosensor.
Within the crystallized definition of biosensors, segmentation is based on the system’s detection technique and the biological molecule that is used for detection. These classifications are illustrated in Exhibits 1 and 2.
Exhibit 1: Classification of Biosensors by Detection Technique
Based on the detection method, biosensors can be broadly classified as label-free or label-based. The label-based techniques are dependent on the specific properties of labels, such as fluorescence and chemiluminescence, for detecting a particular target. A challenge associated with these methods is the loss of samples during labeling and purification processes. This becomes critical when test sample quantity is limited. Label-based techniques can also affect the functionality and stability of molecules, such as proteins. Label-free biosensing includes mass spectrometry, surface plasmon resonance, acoustic wave, and surface stress-based techniques.
Exhibit 2: Classification of Biosensors by Detection Molecule
Biosensor adoption and use are limited by factors including sensitivity, readout time (speed), half-life of the biomolecule used (stability), cost and handling requirements. Enzyme sensors determine the concentration of a chemical substrate by measuring the potentiometric or amperometric response caused by the enzyme-catalyzed reaction between substrate and analyte. Enzyme sensors remain limited to chemistries that allow for a clear signal, such as a change in color, pH (hydrogen ion value) or oxidation state.
Market Demand from Some Unusual Suspects
Frost & Sullivan estimated the global biosensors market to be valued at $14.6 billion in 2016; it is poised to exceed $25 billion by 2020. Point-of-care diagnostic kits are currently the largest market segment, accounting for more than 43% of revenue, whereas home health monitoring kits, such as glucose monitors, are the fastest-growing segment—expected to account for 20% of the market by 2020.
Interestingly, the automotive industry, which is usually far-removed from health care technologies’ impact, is likely to emerge as an important application area for biosensors.
Canada-based Sensor Diagnostics, Inc. has designed Sober Steering, a biosensor-based steering system to monitor and control drunk driving. The steering wheel contains a sensor that can detect alcohol in the gases that emanate from the driver’s palms. If the alcohol level is above a preset value, the steering locks down, the vehicle is immobilized and an alert is sent to the driver’s contact. Other companies, including Freer Logic of Fletcher, N.C., and global automobile majors BMW and Ford, are experimenting with other biosensor platforms that can monitor driver alertness, emotional state and general wellness to ensure safety.
Skin-worn, often embedded, biosensors give the appearance of tattoos and enable continuous monitoring of the wearer’s physiological parameters. In 2016, researchers Shalini Prasad and Rujuta Munje at the University of Texas at Dallas demonstrated the capabilities of a biosensor they designed to reliably detect and quantify glucose in human sweat. The prototype was an inch-long, rod-shaped glucose sensor encased in a biocompatible polymer that could be implanted or embedded in the skin. If this sensor proves capable in clinical testing, it could be of great use for the diabetes community, eliminating the need for daily needle pricks. The same team had earlier demonstrated that the technology could detect cortisol in perspiration.
Sweden-based Biosensor Applications is the first company to develop a multi-application drug and explosive detector called BIOSENS. This biosensor combines state-of-the-art nanofluidics, biochemistry and electronics with advanced software algorithms that enable real-time detection and analysis. BIOSENS is based on immunoassay principles that detect 12 substance groups simultaneously.
The Road Ahead
Miniaturization and multi-sensing capabilities empower biosensors to continuously and non-intrusively monitor patients. Biosensors are now viewed as ideal prognostic tools not only for disease detection but also everyday wellness. Wearable and implantable biosensors are likely to emerge as the key enablers for device innovation and will be commercialized as prognostic tools. Due to large investments in research, scientists and engineers are developing rapid detection test instruments to deliver real-time results without compromising accuracy or sensitivity, or increasing cost.
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