Biofouling and Foreign Body Response

The Body's Defense Mechanism

The Foreign Body Response (FBR) is the primary physiological limiter of CGM lifespan and accuracy.

The Timeline of FBR

Immediate Response (First Hours)

Upon insertion, the sensor is immediately coated in proteins (biofouling), followed by an attack from neutrophils and macrophages.

Early Phase (First 24 Hours)

This creates a local environment of high metabolic consumption, leading to:

• "Run-in" instability
• Potential low-glucose artifacts

Chronic Phase (Days to Weeks)

Over days, the body walls off the sensor with a dense, avascular fibrous capsule. This capsule:

• Acts as a barrier to glucose diffusion
• Causes signal drift
• Reduces sensitivity
• Increases lag time

Manufacturer Mitigation Strategies

Wired Enzyme Technology

Modern sensors reduce reliance on local oxygen (which is depleted by inflammation).

Biocompatible Outer Membranes

• Zwitterionic polymers
• Hydrogels
• These minimize protein adsorption and delay the immune attack