Biological Evaluation of Medical Plastic Devices: ISO 10993 Framework, Testing Samples, Items, and M

Biological evaluation of medical plastic devices is the systematic, risk-based assessment of potential adverse biological effects arising from contact between polymeric materials and patients, conducted in accordance with the ISO 10993 series of standards. This article explains the evaluation framework, the categorization of plastic device samples, core testing items such as cytotoxicity, sensitization, irritation, and hemocompatibility, and the analytical methods used by accredited third-party laboratories to support regulatory submissions worldwide.

Technical Overview

Medical plastic devices are among the most widely used products in modern healthcare, encompassing catheters, syringes, infusion sets, dialysis circuits, wound dressings, respiratory components, and implantable polymeric parts. Common materials include polyvinyl chloride (PVC), polypropylene, polyethylene, polycarbonate, polyurethane, silicone elastomers, and thermoplastic elastomers. During manufacturing, sterilization, storage, and clinical use, these materials may release additives, plasticizers, stabilizers, colorants, residual monomers, oligomers, degradation products, and sterilant residues that can produce cytotoxic, sensitizing, irritant, genotoxic, hemolytic, or thrombogenic effects.

Biological evaluation is the structured process of identifying, analyzing, and mitigating these biological risks. The internationally recognized framework is the ISO 10993 series, in which ISO 10993-1 defines the evaluation and testing strategy within a risk management process aligned with ISO 14971. The required biological endpoints are determined by the nature of body contact (surface-contacting, external communicating, or implant), the cumulative contact duration (limited, prolonged, or permanent), and the outcomes of material characterization. The process is documented through a biological evaluation plan (BEP) and concluded with a biological evaluation report (BER). In China, the equivalent standard series is GB/T 16886, which is adopted from ISO 10993, and testing is typically performed by accredited third-party laboratories operating under ISO/IEC 17025 or GLP quality systems.

• ISO 10993-1: Evaluation and testing within a risk management process
• ISO 10993-3: Tests for genotoxicity, carcinogenicity, and reproductive toxicity
• ISO 10993-4: Selection of tests for interactions with blood
• ISO 10993-5: Tests for in vitro cytotoxicity
• ISO 10993-6: Tests for local effects after implantation
• ISO 10993-10: Tests for skin sensitization
• ISO 10993-11: Tests for systemic toxicity
• ISO 10993-12: Sample preparation and reference materials
• ISO 10993-17: Toxicological risk assessment
• ISO 10993-18: Chemical characterization of medical device materials
• ISO 10993-23: Tests for irritation

Testing Samples

Test samples should represent the medical plastic device in its final finished form, including all processing, cleaning, and sterilization steps, because these steps can significantly alter the extractable chemical profile of the polymer.

Surface-Contacting Plastic Devices

These devices contact intact skin, mucosal membranes, or breached or broken surfaces, and typically require a reduced endpoint set focused on cytotoxicity, sensitization, and irritation or intracutaneous reactivity.

• Wound dressings, adhesive films, and transparent film dressings
• Surgical drapes, gowns, gloves, and face masks
• Ostomy bags and collection pouches
• Compression bandages and orthopedic casting tapes
• Electrode housings and temperature probe covers

External Communicating Plastic Devices

These devices are partially or indirectly connected to the body, either through an indirect blood path, circulating blood, or contact with tissue, bone, or dentin. They generally require the full baseline battery plus hemocompatibility or systemic toxicity endpoints.

• Intravenous catheters, central venous catheters, and extension tubing
• Syringes, needles hubs, infusion sets, and blood administration sets
• Extracorporeal circuits, dialyzers, and blood oxygenator housings
• Endotracheal tubes, breathing circuits, and anesthesia masks
• Urinary catheters and drainage bags
• Laparoscopic instrument shafts and insulation components

Implantable Plastic Devices

These devices are placed directly into tissue or bone for prolonged or permanent contact, requiring the most extensive evaluation, including implantation testing and long-term systemic endpoints.

• Absorbable fixation plates, screws, and sutures
• Polymer-based orthopedic spacers and drug-eluting depots
• Occlusion devices and embolic particles
• Intraocular lenses and glaucoma drainage implants
• Tissue expander shells and soft tissue implants

Materials, Components, and Packaging

In addition to finished devices, evaluation may cover polymer resins, masterbatches, colorants, adhesives, coatings, surface-modified layers, tubing and film subassemblies, and primary packaging that contacts the device, supporting supplier qualification and master-file documentation.

Testing Items

The specific test items are selected based on the ISO 10993-1 categorization matrix and a documented risk assessment, and typically include the following groups.

Core Screening Endpoints

• In vitro cytotoxicity (ISO 10993-5), evaluated using extract, direct contact, or indirect contact methods
• Skin sensitization (ISO 10993-10), using the guinea pig maximization test, Buehler test, or local lymph node assay
• Skin, ocular, or mucosal irritation and intracutaneous reactivity (ISO 10993-23)

Blood Contact Endpoints

• Hemocompatibility panel (ISO 10993-4): hemolysis, thrombosis, coagulation, platelet function, hematology, and complement activation
• Direct or indirect hemolysis rate determination
• Complement activation markers such as C3a and SC5b-9
• Coagulation assays including PT, APTT, and thrombin generation

Systemic and Long-Term Endpoints

• Genotoxicity battery (ISO 10993-3): bacterial reverse mutation test, in vitro chromosomal aberration or micronucleus test, and mouse lymphoma assay
• Acute, subacute, and subchronic systemic toxicity (ISO 10993-11)
• Material-mediated pyrogenicity (ISO 10993-11)
• Local effects after implantation (ISO 10993-6)
• Carcinogenicity and reproductive or developmental toxicity, only when triggered by the risk assessment

Chemical Characterization and Degradation

• Extractables and leachables screening and quantification (ISO 10993-18)
• Toxicological risk assessment against allowable limits and thresholds of toxicological concern (ISO 10993-17)
• Degradation product identification for absorbable and hydrolyzable polymers (ISO 10993-9 and ISO 10993-13)
• Volatile organic residue and sterilant residue analysis, for example ethylene oxide and ethylene chlorohydrin

Testing Methods

Sample Preparation and Extraction

Sample preparation follows ISO 10993-12. Test articles are cut or configured to a defined surface-area-to-volume ratio, commonly 3 cm² per milliliter for irregular solids thicker than 0.5 mm and 6 cm² per milliliter for thinner films. Both polar solvents (for example, sodium chloride injection or culture medium) and non-polar solvents (for example, vegetable oil) are used to cover the polarity range of potential extractables. Standard exaggerated extraction conditions include 37 ± 1 °C for 72 hours, 50 ± 2 °C for 72 hours, 70 ± 2 °C for 24 hours, or 121 ± 3 °C for 1 hour, with the extraction condition selected to be harsher than clinical use while avoiding polymer degradation or transformation of the extract.

In Vitro Test Methods

Cytotoxicity is most commonly performed as the MEM elution assay using L929 mouse fibroblast cells, with cell viability quantified by MTT, neutral red uptake, or similar colorimetric or fluorometric readouts; cell viability of at least 70 percent relative to the blank control is generally considered non-cytotoxic. Genotoxicity assays follow OECD test guidelines and include the bacterial reverse mutation test, in vitro micronucleus test, chromosomal aberration assay, and mouse lymphoma TK mutation assay. In vitro reconstructed human epidermis models are increasingly accepted for initial irritation screening, reducing animal use in line with ISO 10993-2 animal welfare principles.

In Vivo Test Methods

Sensitization is evaluated in guinea pigs using the maximization or Buehler protocol, or via the murine local lymph node assay, which measures lymphocyte proliferation. Intracutaneous reactivity involves intradermal injection of polar and non-polar extracts in rabbits followed by scoring of erythema and edema. Acute systemic toxicity assesses the physiological response to intravenous or intraperitoneal extract administration. Implantation testing places formed material specimens into muscle or bone for periods of one to twelve or more weeks, followed by histopathological scoring of the inflammatory and fibrotic response relative to control materials.

Analytical Chemistry Methods

Chemical characterization combines simulated-use extraction with exhaustive extraction, followed by targeted and non-targeted analysis using gas chromatography-mass spectrometry, liquid chromatography-tandem mass spectrometry, inductively coupled plasma-mass spectrometry for elemental impurities, total organic carbon analysis, and infrared spectroscopy for polymer identity. Results are reported against an analytical evaluation threshold derived from the toxicological threshold of concern, and identified compounds are subjected to toxicological risk assessment to determine whether specific biological tests can be waived or justified.

Applications

Biological evaluation data for medical plastic devices support a wide range of regulatory and quality objectives, and reports are accepted by major regulatory authorities when generated by accredited third-party laboratories.

• Market authorization submissions, including premarket notification and approval applications in the United States, CE technical documentation under the European Medical Device Regulation, and registration dossiers with the Chinese and Japanese authorities referencing GB/T 16886 and JIS standards
• Verification of design changes affecting materials, molding parameters, coatings, adhesives, or component geometry
• Qualification of new polymer suppliers, resin grades, colorants, or recycled-content claims
• Support for sterilization process selection and validation, including ethylene oxide, gamma, electron beam, and steam sterilization effects on extractables
• Construction of material master files that allow biological evaluation conclusions to be leveraged across a device family
• Periodic re-evaluation driven by new toxicological data, standard revisions, or post-market feedback

FAQ

How is the required test matrix for a plastic device determined?

The matrix is determined by the ISO 10993-1 categorization of body contact type and contact duration, combined with a documented risk assessment. For example, a limited-contact surface device may require only cytotoxicity, sensitization, and irritation, while a permanent blood-contacting catheter additionally requires hemocompatibility, genotoxicity, subchronic toxicity, and implantation data.

Can chemical characterization replace biological testing?

In many cases, yes. When ISO 10993-18 chemical characterization demonstrates that all extractables are below safety thresholds under the ISO 10993-17 toxicological risk assessment framework, certain biological endpoints can be scientifically justified as unnecessary. However, cytotoxicity, sensitization, and irritation are frequently still expected by regulators for final finished devices.

Must samples be tested in their final finished form?

Yes. ISO 10993-1 requires evaluation of the device in its final manufactured condition, because molding, machining, cleaning, and sterilization can introduce or transform extractable substances. Testing sterilized, packaged, and shelf-aged samples provides the most representative assessment of clinical exposure.

How long does a complete biological evaluation take?

Timelines vary by endpoint: in vitro cytotoxicity typically requires one to two weeks, irritation and acute toxicity several weeks, sensitization studies six to ten weeks, genotoxicity two to three months, and long-term implantation studies can extend from three months to more than a year depending on the intended contact duration.

Can a single report cover an entire family of similar plastic devices?

Yes, when a documented grouping and bracketing rationale demonstrates that the tested worst-case configuration shares identical materials, manufacturing processes, sterilization, and clinical use. This approach is widely accepted by regulatory authorities and significantly reduces redundant testing.