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SPOTLIGHTS
Biosensors: A million senses
Here is a look at the global biosensors market and how the next generation of biosensors could transform the management and delivery of healthcare

What are they?

The term “biosensor” is short for biological sensor, because it combines a biological component with a physicochemical detector. Biosensors are analytical instruments used to quantify the presence and concentration of different analytes. The device comprises mainly of a biological element and a physicochemical transducer.

Biological elements or bioreceptors may be tissues, enzymes, antibodies, nucleic acids etc., and are biologically derived materials that interact, bind, or recognise with the analyte under study. 1

Through the interaction of the analyte with the biological element, it produces a measurable effect (e.g. pH change, heat, light, mass change). The transducer works in a physicochemical way: optical, piezoelectric, electrochemical, electrochemiluminescence etc., so the measurable signal obtained will be transformed into a measurable electrical parameter – usually a current or voltage. 1 The final signal is then read on a display device.

Early applications

Biosensors can measure a wide spectrum of analytes including organic compounds, gases, ions and bacteria. They are cost-effective, easy to use, rapid, sensitive and accurate for various research and commercial applications.

In the early 1960s, Clark and Lyons (1962) reported the possibility of measuring glucose by means of a platinum electrode to detect oxygen in the sample. In the late 1960s, Updike and Hicks (1967) used Clark’s idea and trapped the enzyme, glucose oxidase (GOD) in a polyacrylamide gel. The enzyme activity would be modified according to the surrounding oxygen concentration. Acting as a catalyst, GOD catalyses the oxidation of glucose, producing gluconic acid and hydrogen peroxide. 1

The sensor then detects the reduction in oxygen partial pressure, which indirectly detects the glucose concentration in the sample. The higher the glucose content, the more oxygen is consumed.

The enzymatic oxidation of glucose catalysed by glucose oxidase is one of the earliest forms in biosensor development. 4 Its function in blood glucose monitoring is useful for diabetes management as it provides a quick response to manage high or low blood sugar levels, indicating a change in diet, exercise or insulin. For non-diabetics, it can also reveal changes in blood glucose over time.

Applications in the connected world

In the medical sector, glucose, pregnancy and urea sensors are used for general healthcare diagnosis and monitoring. In the food industry, biosensors are used for quality control such as measuring carbohydrate, alcohol and acid levels or for microbiology functions like detecting pathogens in foods. In industrial applications, biosensors play a role in pollution and safety by monitoring air and water quality (e.g. concentration of pesticides in ground water). 3

The medical sector dominates the overall biosensors market, 6 contributed by the increased use of diagnostic kits such as blood glucose monitoring, cholesterol testing, pregnancy testing, drug discovery and infectious diseases. They play an essential role in the detection and monitoring of a range of medical conditions from acute to chronic diseases.

With the advent of technology advances, research in biosensors and its applications are being further explored. Professor Richard Luxton, director of the Institute of Bio-sensing Technology at the University of the West of England says the number of papers published over the past 15 years in biosensor research has increased. He says there is great interest in wearable technology and point-of-care (POC) applications in terms of diagnostic and monitoring devices.

In a report by MarketsandMarkets, the development of accurate and rapid testing kits for POC applications accounted for the largest share of the overall biosensors market in 2016. 6 Mr Tan Eng Tong, vice president of strategic management at SilTerra, a Malaysia-based semiconductor company says, “Traditionally, medical testing is confined to a medical laboratory where specimens have to travel from the point of care. Now, POC is defined as medical diagnostic testing at or near the point of care, which is the time and place of the patient.” According to Professor Luxton, POC devices are quick and simple to use at the primary care level, potentially improving the management of various diseases, especially in remote settings with no laboratory infrastructure. In developing countries where access to healthcare and timely medical care is challenging, POC technologies can help in screening malaria, detecting circulating tumour cells in oncology, etc. without the wait for lengthy lab results. Aim to shorten hospital stays and establish outpatient care models have increased demand for home-based POC devices in developed countries.

“Smart wearable technologies" or “wearable devices" describe seamlessly embedded portable computer and advanced electronics that allow interaction between users and a smart environment at any time and from anywhere. 5 Professor Luxton says wristwear devices for fitness and wellness such as smart watches and wrist bands are already available in the market and gaining popularity. Among wearable biosensors, these wristwear biosensors accounted for the largest size of the biosensors market in 2016. 6 The factors driving this market include easy-to-use user interface, real-time health monitoring, and cost effectiveness. He says many researchers are putting their efforts into wearable healthtech (e.g. measuring heart rate) to serve not just a single measurement, but multiple measurements. Because of the diverse uses of wearables, they are useful and potentially disruptive for the healthcare industry. But he warned that security issues, especially cyberattacks on connected IoT (Internet of Things) healthcare devices will have to be studied and prevented.

State of sensors

In the same report by MarketsandMarkets, the biosensors market was valued at US$15.96 billion in 2016, and is expected to reach US$27.06 billion by 2022, with a CAGR of 8.84 percent. 6

Among the different applications of biosensors, optical biosensors are expected to contribute the highest growth in the market. These sensors can determine affinity and kinetics of a wide variety of molecular interactions in real time, without a molecular tag or label, making them commonly used to analyse biomolecular interactions. They are currently being studied for life sciences applications in drug discovery including target identification and assay development. Optical biosensors are classified into direct and reagent-mediated. Direct biosensors are where the analyte contains optical properties such as luminescence or absorbance. In reagent-mediated biosensors, the analyte has no optical properties, which is generally the most common case. 1 The response time depends on the rate of molecular interactions, and not the rate of signal transduction. The advantages in optical biosensors over other signal transduction methods includes no direct electrical connection to the transduction system, making them immune to noise (interfering electrochemical effects). The optical biosensor is only as good as the recognition element it uses, and new types of recognition molecules like DNA and peptide aptamers are being developed, to replace traditional antibodies in applications where most antibodies are incompatible. 1

By geographical regions, North America held the largest share of the overall biosensors market (45 percent) in 2017, largely owing to higher healthcare expenditures. POC diagnostics devices mostly contributed to the growth. Some likely reasons for this include the increase in addressable patient population base, and the increase in waiver of Clinical Laboratory Improvement Amendments (CLIA) for certain POC diagnostic devices such as coagulation, glucose monitoring, and hematology devices. 6 According to Mr Tan, Asia-Pacific is expected to exhibit the fastest growth over the next few years. “The biggest growth is in Asia, specifically China. Its life sciences and engineering sectors already have the resources and talent. Due to its huge population, there is demand for medical needs pertaining to certain diseases including cancer, diabetes, and infectious diseases. There is a constant need to improve healthcare expenditure in China, which impacts the region too,” he says.

In-vitro to in-vivo

In medical applications, biosensors are emerging as powerful tools in research and diagnostic testing as they are selective, sensitive and rapid. They can be broadly categorised into in-vitro and in-vivo.

An in-vitro biosensor conducts its measurement outside a living organism (e.g. in a test tube). The enzyme biosensor for blood glucose monitoring is one such example. Today, in-vitro biosensors are mainly used in diagnostics applications. Dr Paru Deshpande, vice president of the department of life sciences technologies at imec, a Belgium-based research hub in nanoelectronics and digital technologies says, “There is a real push towards POC diagnostics so that patients can get their results quickly in any environment, even at home.This is democratisation of healthcare, everybody should have access to the same healthcare.” Dr Deshpande also believes that in-vitro biosensors hold potential in regenerative medicine and bone regeneration.

On the other hand, an in-vivo biosensor is implanted and operates inside the body. There is a plethora of challenges when creating in-vivo biosensors for the biocompatibility factor. It must be non-invasive, safe for the individual, no harmful interactions, and failure of the device must be avoided. 7 A potential application for in-vivo biosensor includes the ability to monitor insulin within the body.

Dr Deshpande shares, “One challenge now is in developing a non-invasive blood glucose monitoring device, such as a wearable device on the skin. The skin is the largest organ in the body and is full of complex tissues coupled with detecting something that is very low in concentration, a device that can help the 300 million diabetes patients in the world avoid taking blood samples and invasive sensing approach will be highly valued.”

Due to the challenges associated with meeting all the requirements, there are relatively few studies on in-vivo research and even lesser in the market. The interface between the semiconductor material and biological material must be bridged, which means having the right material to trigger the right signal. With the growth in implantable type of technologies, there is more emphasis on biocompatible packaging, plastics, resins and encapsulation materials. The challenge is in not having the body attacks the device and vice versa. Dr Deshpande explains, “The right material for the application may not be the right material for the manufacturing environment (semiconductor fab). It has to be both biocompatible and fab compatible.” He says the human body is corrosive in nature and any material in a device for human use must be treated first.

All medical devices, whether in-vitro or in-vivo, must receive approval from the respective regulatory bodies (e.g. FDA, CE marking). Before these devices are released into the market, they will go through clinical trials with human patients. An exception is a device solely for research purposes. Devices that do not go through approvals tend to be lifestyle-related products (e.g. sleep monitor, steps tracker).

There are applications for gold in the medical sector such as gold teeth, so if you have wondered if gold is a likely material for biosensors, Dr Deshpande says, “Sometimes, gold material is used in the medical field because it is biocompatible. But gold is not compatible for the semiconductor fab. When we are doing high volume manufacturing, gold is typically not an option.”

Both Mr Tan and Dr Deshpande advised the life sciences and semiconductor industries to adapt and develop mutual understanding. Only then can they develop solutions for the people suffering. “Our current healthcare system is managing sickness, not health. Sensors need to be powerful, cost-effective and easy to use/deploy. This can help our healthcare system to better manage health,” Dr Deshpande says.

The future of biosensors is promising

Professor Luxton predicts that biosensors in the future of the connected world "will be POCT or wearables, used for the targeting of infectious agents and cancer through DNA detection (molecular diagnostics).”

The emergence of microfluidics which is the processing of small quantities of fluids through tiny channels, will transform biosensor designs and provide advantages such as the use of very low sample volumes, miniaturisation and open doors to new applications.

New technology like lab-on-a-chip conducts detection of analytes in a miniaturised system, with a portable or handheld device. The benefits of operating on this scale are reducing response time (rapid reactions), detecting simultaneous analytes, reduced cost and being disposable.

There is also emerging interest in low cost, accurate, non-corrosive compatible materials for biosensors. Potential applications for in-vivo biosensors include general health monitoring especially in age-related illnesses, pre-natal screening, diagnostics in oncology and infectious diseases where there is high mortality and morbidity.

One thing is for sure; there will not be a gold biosensor in the near future.

References:

  1. Valentinuzzi, M. (2017). Further Understanding of the Human Machine. Singapore: World Scientific Publishing.
  2. Robertson, S. (2018). What are Biosensors [online] News-Medical.net. Available at: https://www.news-medical.net/health/What-are-Biosensors.aspx [Accessed 21 Sep. 2018].
  3. Mandal, A. (2018). Biosensor Applications. [online] News-Medical.net. Available at: https://www.news-medical.net/health/Biosensor-Applications.aspx [Accessed 21 Sep. 2018].
  4. Blum, L. (1997). Bio- and chemi-luminescent sensors. Singapore: World Scientific.
  5. Dehghani, M. and Kim, K. (2018). Past and Present Research on Wearable Technologies: Bibliometric and Cluster Analyses of Published Research From 2000 to 2016. International Journal of Innovation and Technology Management, [online] 16(1). Available at: https://www.worldscientific.com/doi/abs/10.1142/S021987701950007X.
  6. marketsandmarkets (2017). Biosensors Market by Application (POC, Home Diagnostics, Research Labs, Biodefense, Environmental Monitoring, Food & Beverages Industry), Technology, Product (Wearable and Non-Wearable), and Geography - Global Forecast to 2022. [online] marketsandmarkets. Available at: https://www.marketsandmarkets.com/Market-Reports/biosensors-market-798.html# [Accessed 24 Sep. 2018].
  7. Koschwanez, H. E., & Reichert, W. M. (2007). In Vitro, In Vivo and Post Explantation Testing of Glucose-Detecting Biosensors: Current Methods and Recommendations. Biomaterials, 28(25), 3687–3703. http://doi.org/10.1016/j.biomaterials.2007.03.034

This article is derived from the Semiconductors in Life Sciences Symposium (18 September 2018) held in Penang, Malaysia. Organised by SilTerra, supported by imec.

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EDITORS' CHOICE  
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APBN Editorial Calendar 2018
January:
Obesity / Outlook for 2018
February:
Searching for the fountain of youth
March:
Women in Science - Making a difference
April:
Digestive health in the 21st century - Trust your guts
May:
Dental health - The root to good health
June:
Cancer - Therapies and strategies for better patient outcomes
July:
Water management - Technologies for biotech and pharmaceutical industries
August:
Regenerative technology - Meat of the future
September:
Doctor Robot - The digital healthcare revolution
October:
Bones / Breast cancer
November:
Liver health / Top science research nations & institutions
December:
AIDS / Breakthrough of the year/Emerging trends
Editorial calendar is subjected to changes.
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