As diagnostic technologies move closer to the patient (onto the skin, into the mouth, or even implants), the materials that enable these sensors must meet a fundamental requirement of being safe for use.
This is where biocompatibility comes in, but it can often be treated as a regulatory checkbox. Yet, for biosensor developers it is far more vital to get right. A material’s interaction with cells, tissues and biofluids determines everything from regulatory burden to long-term device reliability. Understanding biocompatibility at the material level can reduce risk in downstream development and accelerates the path from concept to clinical deployment.
A strong grasp of core material biocompatibility principles enables engineers to select and validate diagnostic materials that enhance reliability, reduce failure risk and streamline regulatory approval across device programmes.
In wearable and implantable biosensing, materials come into contact with biological environments in three primary ways:
In each case, “biocompatible” does not necessarily mean that it is simply non-toxic. Rather, it means that the material does not provoke adverse biological responses and remains chemically and physically stable in the environment it’s designed for.
ISO 10993-1 (the global standard for biological evaluation of medical devices) breaks these requirements into multiple domains. Four of these are particularly important for biosensor materials.
Cytotoxicity assesses whether a material harms or disrupts cellular function. For sensor materials, this is the most foundational safety test. If the extract of a material kills or degrades cells in vitro, it will not progress to any form of body-contacting application.
Typical assessments (e.g., ISO 10993-5) expose L-929 fibroblasts to saline and solvent extracts from the material. A biocompatible material demonstrates:
This is the first indicator that a sensor substrate is not releasing harmful chemicals or residual contaminants. These are both critical risks in carbon nanomaterials produced through chemical methods. Materials manufactured cleanly and without catalysts avoid many of these pitfalls from the outset.
Wearable and point-of-care sensors are increasingly used on delicate or reactive tissues. Cutaneous and mucosal irritation tests (ISO 10993-10) determine whether the material causes redness, swelling or local inflammation following direct exposure. A non-irritant material demonstrates:
Materials with a Primary Irritation Index of 0.00 indicate full compatibility with dermal applications. This matters for wearable diagnostics designed for repeated or prolonged skin contact where irritation can compromise both comfort and device adherence.
A material may be non-irritating yet still capable of inducing allergic sensitisation after repeated exposure. For diagnostic materials (particularly those used in chronic health monitoring) this is an essential endpoint. A biocompatible sensor substrate should demonstrate:
Sensors intended for mucosal, subcutaneous or blood-contacting applications must demonstrate that their materials do not introduce systemic toxicity. Two forms of systemic evaluation are typically required:
Biocompatibility also extends to chemical factors when it comes to diagnostics materials. Extractables and leachables (E&L) testing determines whether a material releases volatiles, semi-volatiles, non-volatiles or elemental impurities when exposed to biofluids. For sensor materials, extractables can:
Every medical device must ultimately undergo biological evaluation in its final form. Material-level testing does not remove this regulatory requirement. However, preclinical biocompatibility data at the material stage provides three major advantages.
Biocompatibility in diagnostic materials is built by evidence. Demonstrating that a substrate is non-cytotoxic, non-irritant, non-sensitising, systemically safe and chemically stable across biofluids is what gives developers confidence that a device can move forward without hidden biological risks.
This is the rationale behind Gii, developed by iGii as a high-performance carbon nanomaterial engineered for clinical environments. Through extensive ISO 10993 testing, Gii has already demonstrated the biological safety profile that diagnostic teams typically need to establish themselves. This runs parallel to the impressive performance and scalability profile of the material, making Gii a perfect fit for future biosensing applications.
To find out more about Gii and how it can support your next-generation diagnostic platform, download the guide below.