Electrodes: Foreign Body Response

Question 1

What are the three stages of foreign body response?

Answer 1

1. Onset
2. Progression
3. Resolution

Question 2

What happens during onset?

Answer 2

Absorption of blood and plasma proteins to the surface of the implant leads to second step.

Platelets and immune cells release pro-inflammatory cytokines, trigers inflammation

Question 3

What happens during progression?

Answer 3

Macrophages fuse into foreign body giant cells. Fibroblasts deposit collagen, form fibrous capsule around the electrode.

Question 4

What happens during resolution?

Answer 4

Fibrous capsule may thicken over time, leading to chronic inflammation and cause performance issues.

Question 5

What are three strategies to combat FBR?

Answer 5

i) Design and geometry of the device - surface roughness, electrode shape, size and flexibility
ii) Chemical composition of the coating - new organic and synthetic polymer substrates
iii) Interface-Microenvironment Interaction - control delivery of therapeutic molecules using biomimetic and biodegradable coatings

Question 6

What are zwitterions?

Answer 6

Zwitterions are net neutral ions.

Electrical charge can affect the response. Using ion-neutral is better.