Biocompatibility

Cytotoxicity tests involve exposing cultured cells to substances extracted from your test material. Cell cultures are extremely sensitive to minute quantities of leachable chemicals and readily display characteristic signs of toxicity in the presence of potentially harmful leachables. In vitro cytotoxicity testing is also required to test the biocompatibility of medical devices. Typical testing programs will adhere the ISO test method to meet international regulatory requirements.

Agarose Overlay  – ISO 10993 Part 5

ISO Agarose Overlay Using L-929 Mouse Fibroblast Cells
L-929 mouse fibroblast cells are overlaid with a permeable agar film. A solid sample or liquid saturated disc is then placed in triplicate containers on the agar surface. Cells are examined at 24 hours for signs of toxicity.

USP Agarose Overlay Using L-929 Mouse Fibroblast Cells
L-929 mouse fibroblast cells are overlaid with a permeable agar film. A solid sample or liquid saturated disc is then placed in duplicate containers on the agar surface. Cells are examined at 24 hours for signs of toxicity.

MEM Elution (ASCA Accredited)

ISO MEM Elution Using L-929 Mouse Fibroblast Cells
Solid materials are extracted in cell culture medium, and the extracts are placed in triplicate containers of L-929 mouse fibroblast cells. Cells are examined up to 72 hours for signs of toxicity.

USP MEM Elution Using L-929 Mouse Fibroblast Cells
Solid materials are extracted in cell culture medium, and the extracts are placed in duplicate containers of L-929 mouse fibroblast cells. Cells are examined at 24 and 48 hours for signs of toxicity.

ISO MEM Endpoint Dilution Using L-929 Mouse Fibroblast Cells
If a material is suspected to have cytotoxic properties, performing the cytotoxicity test with dilutions can be useful. Solid materials are extracted in cell culture medium, and eight 2-fold dilutions are made to determine the toxic endpoint. Performance of the test will result in an estimate of the relative “strength” of the cytotoxic substance in the material.

Quantitative Assays

MTT Cytotoxicity Using L-929 Mouse Fibroblast Cells
Solid materials are extracted in cell culture medium. Multiple dilutions of the extract are prepared and added to triplicate wells. After incubation, MTT reagent {3-(4,5-Dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide} is added to each well. After a second incubation, the amount of formazan formed is determined. Results are calculated based on the formazan levels.

Neutral Red Uptake (NRU) Cytotoxicity
This assay is used to measure the viability of cells after exposure to a test material extract. Solid materials are extracted in cell culture medium. After extraction, cells are exposed to the extract in the presence of neutral red (NR), a supravital dye. Viability is measured based on the ability of the cells to incorporate and bind NR.

Colony Formation Cytotoxicity Using Chinese Hamster Lung Fibroblasts
Cytotoxicity screening of biomaterials or medical devices is based on colony formation by V79 cells. The V79 line has a stable growth curve and, as such, a high rate of colony formation; therefore, they are suitable for screening cytotoxicity tests. This assay utilizes the sensitivity of low cell density to evaluate the cytotoxicity of medical devices.

Sensitization tests estimate the potential for erythema, swelling, or delayed allergic response through the testing of appropriate materials or extracts.

ISO Guinea Pig Maximization Sensitization Test
Extracts of the device are prepared, and the skin surface of animals is exposed to the extract in the presence of an adjuvant. After a short waiting period, the animals are challenged with a lower dose of the same extract to estimate the potential for contact erythema, swelling, or delayed allergic response, or other edema responses through the testing of appropriate materials or extracts. Methods for both polymeric devices and liquid test articles available.

Buehler Dermal Sensitization Test
Extracts of the device are prepared, and the skin surface of animals is exposed to the extract in the absence of an adjuvant for at least 6 hours. After multiple such exposures, the animal is challenged with a sub-irritating dose of the extract, and contact erythema, swelling, or delayed allergic response, or other edema responses are measured.

Repeated Patch Derma Sensitization Test Here, animals are sensitized and challenged with the test article itself rather than with an extract from the test article.

Irritation tests assess the localized reaction of tissues to device materials or extracts. The selection of a test method is based on intended patient contact type.

ISO Intracutaneous Irritation Test
Test material solution or an extract of a device is injected under the top layer of skin to test the possible irritancy of the test article compounds.

USP Intracutaneous Irritation Test
Test material solution or an extract of a device injects under the skin to test the possible irritancy of the test article compounds.

ISO Mucosal Irritation Test
Materials that comes in direct or indirect contact with mucosal tissue receive repeated administration of a dose to observe possible irritation.

ISO Primary Skin Irritation Test
This test is performed to assess the potential topical irritation from acute exposure or device material.

ISO In Vitro Skin Irritation Test
This assay provides a quantitative method to screen materials for potential skin irritation potential.

The purpose of this test is to screen solutions or test article extracts for potential toxic effects as the result of systemic injection dosing. Toxicity tests estimate potential harmful systemic effects from a single exposure to polar or nonpolar extracts of device materials.

ISO Acute Systemic Toxicity Test– ISO 10993 Part 11
Test article solution or extract is injected to assess the potential toxicity compounds in the test article over a 72-hour period.

USP Acute Systemic Toxicity Test
Test article solution or extract is injected to assess the potential toxicity compounds in the test article over a 72-hour period.

Subacute toxicity is assessed after single or multiple exposures to extracts of device materials. The exposure period is longer than typical acute toxicity tests but not to exceed 10% of the animal’s lifespan.

Subchronic toxicity is assessed after repeated intravenous injections of the device material’s extract. These studies involve expanded evaluations and can include systemic changes, local irritation, body weight, blood values, and tissue changes as part of the protocol. The length of time for the test and the parameters evaluated depend on the end use of the device.

ISO Subacute Intraperitoneal Toxicity Study
Multiple extracts of a device and controls are prepared and injected for signs of toxicity through gross observation at the end of the study.

ISO Subchronic Intravenous Toxicity Study
Subchronic toxicity is assessed after repeated intravenous injections of a device material’s extract.

ISO Subchronic Toxicity – Dual Routes of Administration
Subchronic toxicity is assessed after repeated intravenous and intraperitoneal injections of a device material’s extract.

Genotoxicology (mutagenicity) tests evaluate the ability of a material to cause mutation or gross chromosomal damage. Any materials intended for implantation or long-term exposure must be evaluated for mutagenic properties. Unpolymerized materials, additives, trace monomers, or oligomers and biodegradative products can all be potential mutagens.

ISO Bacterial Mutagenicity Test (Ames Assay)
These tests are performed according to ISO 10993-3 using OECD test method 471. Growth of bacterial cells exposed to the test material’s extract is assessed on nutritionally deficient agar.

ISO In Vitro Chromosome Aberration Assay in Chinese Hamster Ovary (CHO) Cells
These tests are performed using OECD test method 473. Mammalian cells are exposed to the test material or extract in the presence and absence of metabolic activation and blocked in metaphase using a spindle poison.

ISO In Vitro Mouse Lymphoma Assay with Extended Treatment Using OECD Test Method 490
Mouse lymphoma cells are used to determine whether a test material has the capacity to induce either point mutations or clastogenic (chromosomal breakage) events in a cultured mammalian cell line.

ISO In Vivo Mouse Micronucleus Assay Using OECD Test Method 474
This assay is used to evaluate the potential of the test article to induce micronuclei formation in immature polychromatic erythrocytes.

Implantation tests assess the local effects of material or finished product in contact with living tissue. The implant site selection is based on the intended use of the device.

USP Intramuscular Implantation
The purpose of this study is to evaluate the potential for local effects of a test article implanted intramuscularly to assess the interaction of surrounding tissue.

ISO Intramuscular Implantation Test With Histopathology
The purpose of this study is to evaluate the potential for local effects of a test article implanted intramuscularly to assess the interaction of surrounding tissue. This study may be performed with or without Clinical Chemistry and Hematology.

ISO Subcutaneous Implantation Test With Histopathology
The purpose of this study is to evaluate the potential for local effects of a test article implanted subcutaneously to assess the interaction of surrounding tissue. This study may be performed with or without Clinical Chemistry and Hematology.

An important measure of hemocompatibility is the hemolysis test, which measures the ability of a material or material extract to cause red blood cells to rupture. Hemolysis testing should be performed on all materials directly contacting the bloodstream or on any materials used to form a conduit for fluids entering the circulatory system.

ASTM Hemolysis Assay
This test is intended for materials that directly contact the blood stream or compromised tissues and for materials through which fluid passes before entry into the body. This is performed through direct method, extract method, or both.

Complement Activation Assay
The activation of complement resulting from the use of a medical device has been associated with many adverse clinical findings. An enzyme immunoassay is used to screen for complement components in human sera that have been incubated with the test article. Elevated levels of complement components SC5b-9 and C3a indicate activation of the complement system. This test may be performed with a sponsor-supplied comparison product.

Partial Thromboplastin Time (PTT)
The PTT assay is a general screening test for the detection of coagulation abnormalities in the intrinsic coagulation pathway. The test determines the time it takes citrated human plasma to form a clot when it is exposed first to the test material, then to calcium chloride, and finally to partial thromboplastin. This test may be performed with a sponsor-supplied comparison product.

Platelet and Leukocyte Counts
Platelet and leukocyte counts are evaluated before and after exposure to the test material in human blood. Counts are evaluated for changes that may indicate activation, adhesion, aggregation, or lysis. This test may be performed with a sponsor-supplied comparison product.

Thromboresistance Evaluation (In Vivo)
This test assesses the thrombogenicity of the test material when compared to a sponsor-supplied material, preferably an approved medical device, when exposed to blood in an in vivo model.

Pyrogenicity tests determine the potential of materials, extracts, and/or a finished device to induce a pyrogenic (fever) response from sources other than endotoxin.

USP Rabbit Pyrogen Test
The test articles are injected to determine a significant increase in body temperature compared to the control article.

ISO Rabbit Pyrogen – Materials Mediated – ISO 10993 Part 11
The test articles are injected to determine a significant increase in body temperature compared to the control article.

USP Class Testing determines the biological response to elastomerics, plastics, and other polymeric materials. Six Plastic Classes are based on responses to a series of in vivotests relating to the intended end-use of the plastic articles. Test article extracts are taken in normal saline, alcohol solution, polyethylene gycol, and/or sesame oil. Testing may be conducted in either GLP or non-GLP conditions.

USP Class I
Acute Systemic, Intracutaneous Irritation

USP Class II
Acute Systemic, Intracutaneous Irritation

USP Class III
Acute Systemic, Intracutaneous Irritation

USP Class IV
Acute Systemic, Intracutaneous Irritation, 7 Day Intramuscular Implant

USP Class V
Acute Systemic, Intracutaneous Irritation

USP Class VI
Acute Systemic, Intracutaneous Irritation, 7 Day Intramuscular Implant