Key driving forces for new or next generation products include (1) critical need, (2) broad, global usage and (3) sufficient volume requirements to justify R&D expenditures. Glucose sensing/monitoring meets these criteria and more. In the United States alone, the American Diabetes Association (ADA) says over 133 million Americans have diabetes or prediabetes [1]. According to the US Centers for Disease Control and Prevention, more than 37 million US adults have diabetes and 1 in 5 do not know they have it [2]. From a critical need standpoint, diabetes is the seventh leading cause of death in the United States and the No. 1 cause of kidney failure, lower-limb amputations and adult blindness.
Globally, the World Health Organization (WHO) notes that the number of people with diabetes is increasing rapidly based on cases rising from 108 million in 1980 to 422 million in 2014 [3].
Historically, self-monitoring of blood glucose (SMBG) involved enzyme-coated test strips manufactured with a precise amount of specific enzymes that reacted to a single blood sample [4]. Since, diabetic patients must do this at least three times a day and 7 days a week, the need for an updated approach to biosensing was solved in the 1990s with continuous glucose monitors (CGMs).
Instead of a test strip, a CGM uses a filament coated in glucose sensing enzymes to detect glucose in the (interstitial) fluid between the user’s cells. As a wearable sensor, a CGM automatically detects and measures glucose levels 24 hours a day but still requires insertion into the test site [4]. Typical sensor mounting locations include the stomach, hip and upper arm. Another limitation is a limited time before requiring sensor replacement – from as little as several days to a few weeks
The global CGM devices market is valued at USD 5.13 billion in 2021 and is projected to reach USD 13.24 billion by 2028 with a compound annual growth rate (CAGR) of 10.8% during the forecast period of 2022–2028 [5]. Dexcom’s G6 and Abbott Laboratories’ FreeStyle Libre are two CGMs that have been certified for usage in hospitals.
CGM systems typically consist of three components: (1) a glucose oxidase (GOD)-based glucose sensor and (2) a transmitter attached to the sensor to transfer the data to (3) a receiver/smartphone for displaying the results [6]. Image Source: De Gruyter.
The ultimate glucose sensor for glucose-level monitoring would be a noninvasive technique that could be miniaturized and connected to a mobile device such as a smartphone. In pursuit of this goal, a variety of optical methods have been investigated for non-invasive blood glucose detection [7]. These include:
- Infrared Spectroscopy using both the absorption and scattering phenomenon of light
- Raman Spectroscopy using the scattering phenomenon of the light
- Fluorescent Spectroscopy using the fluorescence produced from the sample tissue
- Thermal Spectroscopy using the emission of infrared light as compared to the glucose absorption
- Optical Coherence Tomography (OCT) using super luminescent light
- Ocular Spectroscopy using specially designed hydrogel-based eye contact lenses that change color depending up on the glucose concentrations
Researchers could be getting very close to having a manufacturable product. For example, Quantum Operation uses core technologies that include the novel spectrometer materials, one designed to emit an optimal spectrum with LED illumination and another highly responsive material to target spectra. In addition, proprietary firmware efficiently extracts targeted data by canceling noise to achieve noninvasive 24/7 glucose monitoring [8]. The company’s Noninvasive Glucometer Wristband technology was demonstrated at CES 2022.
Using laser-based analysis instead of LEDs, Rockley Photonics is also working toward noninvasive 24/7 monitoring [9]. Using a Spectrophotometer-on-a-Chip approach, itsVitalSpex sensor modules generate a large number of discrete laser outputs from a single silicon chip covering a broad optical band. The company’s biomarker sensing capabilities are in various stages of development with the VitalSpex Pro Module having the highest capabilities. Incorporating an advanced suite of sensors, the VitalSpex Pro enables the measurement of several biomarkers that are helpful for monitoring more complex health conditions including a glucose indicator as well as blood alcohol content (BAC) and blood lactate (BL).
References
[4] How Does a Glucose Sensor Work? (agamatrix.com)
[6] Basics and use of continuous glucose monitoring (CGM) in diabetes therapy (degruyter.com)
