Sensor Chemistry and Enzymatic Reactions

How CGM Sensors Work

CGM sensor technology relies on amperometric electrochemical detection, primarily utilizing the enzyme Glucose Oxidase (GOx) to convert interstitial glucose into an electrical signal.

Sensor Generations

First Generation Sensors

Early sensors detected hydrogen peroxide produced by the GOx reaction. These were oxygen-dependent, making them susceptible to errors during tissue compression when local oxygen levels dropped.

Second Generation ("Wired Enzyme") Sensors

Modern sensors used by Dexcom and Abbott utilize "wired enzyme" technology:

• Employ synthetic redox mediators (such as Osmium complexes)
• Shuttle electrons directly from the enzyme to the electrode
• Operate at lower electrical potentials
• Drastically reduce interference from substances like acetaminophen
• Function independently of local oxygen fluctuations

Protective Membranes

The sensor filament is encased in flux-limiting membranes that:

• Control glucose diffusion to ensure signal linearity
• Protect the electrode from bio-fouling
• Shield against immune system encapsulation