Biocompatibility Testing Matrix for Long-Term Implantable Silicone Components

This page is a map for custom silicone components that will live in the body longer than a transient procedure. It is not a regulatory filing, not a 510(k), not a CE technical file, and not a biological evaluation report (BER). The legal manufacturer of the device owns ISO 10993-1 (biological evaluation of medical devices) aligned with ISO 14971. A molder can supply a platinum compound, a process window, and specimens. A molder cannot stamp a molded nipple “implant approved.”

Long-term / permanent contact in the 10993 language is the bin that used to be taught as greater than 30 days. ISO 10993-1:2025 keeps risk management central, counts contact days, and organizes effects by contact type rather than a single photocopied Annex A shopping list. Confirm the edition your notified body or FDA reviewer expects. Do not treat a 2018 matrix printout as automatic 2025 compliance.

Chemistry: long-term implant paths are platinum LSR or platinum HCR from a supplier healthcare policy that actually allows the implantation duration you need. Many “medical” gums are capped at limited implantation. Peroxide HCR needs a serious post-cure story. Tin-cure RTV is not an implant elastomer.

Start from contact and duration, not from a test catalog

ISO 10993-1 asks what the device touches and for how long, then which biological effects are relevant. Classic teaching used:

• Surface devices vs externally communicating vs implants
• Limited (≤ 24 h), prolonged (> 24 h to 30 d), permanent (> 30 d)

The 2025 revision emphasizes contact type (including intact skin, mucosa, breached/internal tissue, circulating blood) and contact-day counting. Implants are evaluated by the tissue they contact, not by the word “implant” as a magic class. Local effects after tissue contact replaced some “implantation effects” wording. Chemical characterization is upstream, not an optional appendix.

For a long-term implantable silicone component, the evaluation typically has to consider, as relevant:

• Cytotoxicity (10993-5)
• Sensitization and irritation / mucosal (10993-10; irritation also 10993-23 in current practice)
• Systemic toxicity (10993-11)
• Genotoxicity (10993-3)
• Implantation / local effects after tissue contact (10993-6)
• Hemocompatibility if blood contact (10993-4)
• Chemical characterization (10993-18) and toxicological risk assessment (10993-17)
• Degradation if the material or device can degrade (10993-9 / 13 as applicable)
• Pyrogenicity, carcinogenicity, reproductive endpoints only when the BEP says the risk is not otherwise controlled

That is a consideration list. It is not an order form for every animal test. 10993-1 plus 14971 plus 10993-18/17 can justify not repeating a test when chemistry is known and residual risk is acceptable. Blindly running “the full matrix” is neither required nor ethical.

USP Class VI (USP <88>) is an acute plastics screen. It is not a chronic implant study and not a junior 10993-1. FDA reviewers have long treated it as supporting material identity, not as the device file.

The test article is the finished, sterilized component

A natural 40A LSR plaque is not a barium-striped, pigmented, post-cured, EtO-sterilized catheter bumper. Endpoints attach to the article that sees the patient:

• Compound (platinum LSR/HCR, hardness, lot)
• Pigment, radiopacifier, self-lube fluid, antimicrobial, dissipative package
• Cure and post-cure
• Mold release that remains
• Secondary operations (bonding, coating, laser)
• Sterilization residuals (EtO per ISO 10993-7 if used; radiation effects on the network)

If you change any of those, the BEP is reopened. A molder’s “we used medical grade” sentence does not survive that change control.

Extractables and leachables (10993-18) are how you stop guessing. Silicone-specific issues: cyclic siloxanes, platinum traces, peroxide split products if that chemistry was used, pigment extractables, barium if radiopaque. Post-cure and vacuum bake are process controls that change the chromatogram. They belong in the described manufacturing process.

What a custom silicone manufacturer can and cannot own

Can:

• Hold a healthcare-policy compound with a stated implantation duration limit
• Document cure, post-cure, clean environment, lot traceability
• Provide supplier biological summaries on named specimens
• Mold geometry inside that window
• Mold and post-cure coupons for the OEM’s lab
• Refuse tin-cure, untested color, or a duration the gum’s policy forbids

Cannot:

• Issue ISO 10993 certification of the customer’s device
• Extend a 29-day policy gum to a five-year implant by extra baking
• Substitute Class VI for 10993-6 chronic implantation
• Hide a new additive inside an old report

ISO 13485 at the molder is quality-system evidence. It is not biocompatibility.

Animal implantation studies (10993-6) have durations that must match risk, not a folklore “30-day implant equals permanent.” Permanent implants often need longer local-effect evidence or a chemical/toxicological argument that replaces it. That decision is the BEP, written by people who own the device.

A specification block that keeps roles straight

“Component material: platinum [LSR or HCR], healthcare grade [code], supplier implantation policy ≥ [duration]. Pigments/additives: [listed]. Cure and post-cure: [T / t / thickness]. Supplier biological data attached for [specimen, endpoints, edition]. Device-level biological evaluation per ISO 10993-1 [edition] and ISO 14971 is the legal manufacturer’s, on finished, sterilized articles, including 10993-18 characterization as required. This purchase order is not a regulatory submission. Tin-cure RTV, peroxide grades without a qualified post-cure, and duration extensions beyond the gum policy are excluded.”

If the OEM asks the molder to “just run 10993,” the honest reply is: which part, which contact, which edition, which test article, and who writes the BEP. Then the molder can ship coupons.

FAQ

Does a blog checklist or a Class VI certificate make my silicone part implantable?

No. Implant use requires a device-level biological evaluation under ISO 10993-1 and the applicable device regulations. Class VI is an acute plastics screen. This article is orientation for a spec, not a filing.

Which ISO 10993 parts apply to a >30-day silicone implant?

The BEP decides. Long-term tissue or blood contact commonly forces you to *consider* cytotoxicity, sensitization, irritation/local effects, systemic toxicity, genotoxicity, implantation/local tissue effects, 10993-18 chemistry, and 10993-4 if blood-contacting. 2025-edition contact-day and contact-type tables may change how you document that. It is not a mandatory animal-test shopping cart.

Can the molder certify ISO 10993 on the molded SKU?

No. 10993 is not a product mark. The molder can certify the compound, the process, and that specimens were made as stated. The device manufacturer signs the BER.

Why isn’t USP Class VI enough for a pacemaker lead or a long-term port?

Class VI does not cover genotoxicity, chronic implantation, hemocompatibility, or chemical characterization of the sterilized, additive-containing article. It is the wrong duration and the wrong scope.

If ISO 10993-1:2025 de-emphasizes the old matrix, can I skip testing?

Only if chemical characterization and toxicological risk assessment, plus existing data, control the endpoints the new contact tables still require you to address. You skip *redundant animals*, not the evaluation. Record the edition you used.