In biosensor development, materials are often selected from suppliers that describe them as “biocompatible.” Datasheets may reference cytotoxicity studies, published literature or previous medical applications. At first glance, this appears to remove a major regulatory hurdle.
Yet many development teams eventually discover that biological testing must be repeated regardless.
This situation is common across diagnostic and sensing technologies, and it can significantly extend development timelines. The reason lies in how biological safety is evaluated under ISO 10993 and how evidence must be interpreted within the specific context of a device.
Understanding why repeat testing occurs helps biosensor developers avoid unexpected delays and make more informed material decisions earlier in the design process.
Biocompatibility can be treated as a property of a material. In practice, regulators assess it as a risk-based evaluation of a finished device and its intended clinical exposure.
ISO 10993-1 establishes that biological safety must be evaluated in the context of:
Because of this, evidence supporting one application cannot automatically be transferred to another.
For example, a polymer previously tested for short-term skin contact may still require additional evaluation if used in a device exposed to mucosal tissue, blood or long-term wear. Similarly, testing performed on a research-grade material may not be representative of the commercial manufacturing state used in a regulated product.
As a result, materials that are described as biocompatible can still require substantial additional evidence before they are considered suitable for a specific diagnostic platform.
Repeat testing rarely occurs because previous studies are incorrect. More often, it happens because the available evidence does not match the biological evaluation required for the final device. Several common gaps in supplier documentation can trigger this situation.
Biological tests are selected based on how a device interacts with the body. A wearable sensor, an oral diagnostic device and a blood-contacting biosensor all require different biological endpoints. If the supplier’s testing programme was conducted for a different contact scenario, regulators may consider the evidence insufficient.
Manufacturing processes can significantly alter a material’s biological profile. Sterilisation methods such as gamma irradiation, ethylene oxide or autoclaving may change surface chemistry or introduce residual compounds. Likewise, device fabrication steps such as coatings, printing processes or adhesive integration can modify the material environment.
If biological testing was performed before these steps were introduced, the data may not fully represent the final device.
Regulatory submissions require traceable, well-documented evidence. Academic literature or exploratory research data can be valuable during early R&D, but studies performed outside Good Laboratory Practice (GLP) environments may not satisfy regulatory expectations. Without detailed documentation of extraction conditions, manufacturing state or test protocols, regulators may request new studies to confirm biological safety.
These gaps can create a cascade of additional work during development.
If biological evidence cannot be directly incorporated into the device’s Biological Evaluation Report (BER), developers must commission new studies. This may involve cytotoxicity, irritation, sensitisation, systemic toxicity or extractables and leachables analysis depending on the device architecture.
Each study introduces new timelines for laboratory testing, toxicological interpretation and regulatory documentation. For biosensor teams working under tight commercial timelines, this can delay critical milestones such as:
In some cases, repeated testing cycles also increase development costs and introduce uncertainty if unexpected biological responses appear late in the process.
Whilst every device must ultimately be evaluated in its final configuration, strong material-level biological data can significantly reduce the likelihood of repeat testing. When materials are supported by comprehensive, ISO-aligned testing programmes, developers gain several advantages:
This does not eliminate device-level evaluation, but it reduces the foundational testing burden and allows developers to focus on application-specific questions rather than starting biological evaluation from scratch.
For advanced sensing technologies, material choice increasingly influences both device performance and regulatory complexity.
Materials engineered with biological safety in mind from the outset provide a different development experience compared to those supported only by limited or indirect evidence. When the biological profile of a sensing material has already been investigated across multiple ISO 10993 endpoints, biosensor teams can move forward with greater confidence that foundational safety questions have already been addressed.
This approach reflects the philosophy behind Gii, the carbon nanomaterial platform developed by iGii.
Alongside its electrical performance and scalability for electrochemical sensing, Gii has undergone an extensive ISO-aligned biological evaluation programme carried out at accredited laboratories under OECD Good Laboratory Practice. The programme spans multiple biological endpoints, including cytotoxicity, irritation and sensitisation, systemic toxicity, implantation studies and extractables and leachables analysis.
Because this evidence already exists, it can form part of the biological safety foundation used when developers prepare their device-level evaluations. To find out more about Gii’s capabilities for biosensing and other applications, download our guide below.