1. How to Test for Biocompatibility
Follow the ISO 10993 Standard Series:
This is the gold standard for biocompatibility testing and what regulatory bodies like the FDA, EMA, and Health Canada expect.
Start With a Biological Evaluation Plan (BEP)
Includes:
- Intended use (implantable? contact with blood?)
- Duration of contact (transient, short-term, long-term)
- Material composition
Key Tests (Choose Based on Use Case):
| Test Type | Description | Relevant For |
|---|---|---|
| Cytotoxicity | Test if material kills or damages cells | All devices |
| Sensitization | Checks if material causes allergic reactions | Skin/mucosal contact |
| Irritation | Checks local irritation effects | Topical or mucosal devices |
| Systemic Toxicity | Evaluates toxic effects throughout the body | Implanted or injectable |
| Hemocompatibility | Tests effects on blood (e.g., clotting, hemolysis) | Blood-contact devices |
| Genotoxicity | Tests if the material damages DNA | Long-term or implantable |
| Implantation | Observes tissue response to an implanted sample | Long-term implants |
| Degradation Analysis | What does it break down into? Are byproducts toxic? | Resorbable/bioactive materials |
Tip: Many tests start in vitro, but in vivo animal models are often required for regulatory approval.
2. How to Choose the Right Material
Ask These Questions:
A. What is the contact type?
- Skin only? → Silicone, TPU, soft polyurethane
- Blood contact? → Heparin-coated PTFE, titanium, stainless steel
- Bone contact? → Hydroxyapatite, titanium, PEEK
- Mucosal or internal organ contact? → Soft silicone, medical TPU
B. How long is contact duration?
- Transient (<1 min) → Minimal requirements
- Short-term (up to 24h) → Basic cytotoxicity, irritation
- Long-term (>30 days) → Full ISO panel required
C. What mechanical properties are needed?
- Flexible? Durable? Absorbable?
| Material | Use Case | Properties |
|---|---|---|
| Silicone | Implants, tubing | Soft, inert, long-term biocompatible |
| Titanium | Implants (e.g., bone, dental) | Strong, osseointegration, non-toxic |
| PEEK | Spinal cages, joint implants | Strong, radiolucent, long-term stable |
| Hydrogels | Drug delivery, wound care | Moist, absorbent, good drug carriers |
| PLGA/PLA | Resorbable sutures, scaffolds | Biodegradable, tunable degradation |
3. Applying Biocompatibility to a Specific Project
Example: Say you’re designing a wearable patch with embedded electronics
Key Biocompatibility Considerations:
- Skin contact → Ensure outer layer is non-irritating (e.g., medical-grade silicone or TPU)
- Adhesive → Use skin-safe adhesives like 3M medical tapes
- Sensors/electronics → Encapsulate in waterproof, biocompatible barrier
- Duration of contact → If worn >24h, test for irritation and sensitization