Biocompatibility Tests

Biocompatibility Tests

Cytotoxicity

Cytotoxicity testing is a biological assessment performed in vitro to determine the potential harmful effects of a biomaterial or medical device on cells. This test examines whether the medical device or material damages the integrity of the cell membrane or adversely affects cellular metabolism. Generally, it is assessed whether the material causes cell death or suppresses cellular functions. Cell damage is detected by various qualitative and quantitative analyses on cell cultures. In these tests using cell lines such as L2929 (Mouse Fibroblast Cell), substances that damage the cell membrane, toxic compounds that can disrupt cellular energy metabolism or agents that drive cells to death can be identified.

Test Process: The sample is extracted into a suitable cell culture medium such as DMEM (Dulbecco’s Modified Eagle Medium). The extract obtained is contacted with the cells for a certain period of time. The survival rate of the cells is evaluated by spectrophotometric methods. Extraction processes are carried out in accordance with the conditions specified in TS EN ISO 10993-12 standard. Controls are carried out using polyethylene tubes and substances such as lanolin.

Standards and Procedures:

  • TS EN ISO 10993-5: Biological evaluation for medical devices – Part 10993: Cytotoxicity tests
  • TS EN ISO 10993-12: Sample preparation and reference materials for biological tests.

Irritation

The irritation test is performed to determine whether the biomaterial or medical device produces a potential inflammatory response on skin, eye or mucosal surfaces. It is assessed whether reactions such as localised inflammation and redness of the skin occur as a result of direct contact of the tested material with skin tissue. Skin irritation is measured by grading skin reactions such as swelling and redness. Each material sample is tested on animal models (rabbits) or alternative test systems.

Standards and Procedures:

  • TS EN ISO 10993-10: Biological evaluation for medical devices – Part 10: Irritation and sensitisation tests
  • During the evaluation of the material, the inflammatory responses observed in the tested area are carefully analysed and reported.

Sensitisation

The sensitisation test examines whether the material causes an allergic immune response. The test is performed to determine whether it causes Type IV delayed hypersensitivity reactions (allelgy). This experiment on guinea pigs measures the allergic responses that may occur as a result of applying the material to the skin. Typically, skin that is sensitised after the first exposure gives a stronger response on the second exposure. Sensitisation testing is an important safety assessment step, especially for medical devices intended for skin contact.

Standards and Procedures:

  • TS EN ISO 10993-10: Biological evaluation for medical devices – Part 10: Irritation and sensitization tests.

Genotoxicity

Genotoxicity testing assesses whether the material has potentially harmful effects on genetic material. This test is intended to detect agents that may cause gene mutations, chromosome aberrations or other DNA damage. Methods such as bacterial mutation tests (e.g. Ames test) and chromosome aberration tests in mammalian cells are used. The Ames test on bacteria (Salmonella typhimurium) is commonly used to determine whether chemical substances are mutagenic.

Test Process: The test can be performed both in vitro and in vivo. The Ames test detects whether genotoxic substances present in the sample cause genetic changes in bacterial DNA.

Standards and Procedures:

  • TS EN ISO 10993-3: Biological evaluation for medical devices – Part 10993: Genotoxicity, carcinogenicity and reproductive toxicity
  • OECD 471: Standard for bacterial mutation testing.

Systemic Toxicity

Systemic toxicity testing examines the potential harmful effects that biomaterials may cause in the body if they enter the systemic circulation. This test evaluates the toxic effects that the material may cause by oral, dermal or intravenous routes by being transported from the local application site to distant organs. Acute systemic toxicity tests analyse the possible side effects of the tested material within 72 hours of administration.

Testing Process: Experiments are usually carried out on rodents and various biochemical parameters are evaluated.

Standards and Procedures:

  • TS EN ISO 10993-11: Biological evaluation for medical devices – Part 11: Systemic toxicity.

Subchronic Toxicity

Subchronic toxicity testing is performed to assess whether medical devices or biomaterials have potentially harmful effects on organ systems as a result of prolonged or repeated exposure. This test is performed to examine the effects of applications lasting three months or more on organ functions and general health status.

Test Process: In experiments conducted on rodents, the effects of the material on different organs of the organism are determined by histopathological and biochemical analyses.

Standards and Procedures:

  • TS EN ISO 10993-11: Biological evaluation for medical devices — Part 11: Systemic toxicity.

Implantation

Implantation testing examines local tissue reactions caused by biomaterials or medical devices in living tissues. The material is implanted in a region suitable for clinical application (usually the rat gluteal muscle) and macroscopic and microscopic evaluations are performed on the tissue. Reactions such as fibrosis, inflammation or tissue repair that occur after implantation are carefully observed.

Standards and Procedures:

  • TS EN ISO 10993-6: Biological evaluation for medical devices — Part 6: Evaluation of local effects for materials in contact with tissue.

Hemocompatibility

The hemocompatibility test evaluates the interactions of biomaterials with blood and the adverse effects they may have on blood components. The hemolytic effect test determines whether the biomaterial causes erythrocyte damage and releases hemoglobin. Effects such as blood clotting, platelet activation or hemolysis are observed as a result of the interaction of the material with blood.

Standards and Procedures:

  • TS EN ISO 10993-4: Biological evaluation for medical devices — Part 4: Interaction tests for devices in contact with blood
  • ASTM F756-08: Standard for hemolytic tests.

Pyrogenicity

The pyrogenicity test determines whether the biomaterial contains pyrogenic agents that can cause fever in the body. A sterile extract of the material is injected intravenously into rabbits and then the animals’ body temperature is measured to observe possible fever reactions. Pyrogenicity can produce reactions similar to those that usually occur in the body, such as infection or inflammatory reactions.

Standards and Procedures:

  • TS EN ISO 10993-11: Biological evaluation for medical devices — Part 11: Systemic toxicity.
  • European Pharmacopoeia: Guide standards for pyrogenicity tests.