Biocompatibility evaluation of materials

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Information about Biocompatibility evaluation of materials

Published on February 28, 2008

Author: muralicv


Medical Polymers : Biological Evaluation :  Medical Polymers : Biological Evaluation Muraleedharan CV Division of Artificial Organs, Biomedical Technology Wing Sree Chitra Tirunal Institute for Medical Sciences & Technology Thiruvananthapuram – 695012, INDIA Agenda:  Agenda Polymers in medical devices Biocompatibility & Biomaterials Material Responses Test Methods Standards - ISO 10993 Selection of tests Indian Scenario SCTIMST Testing services How to approach Biocompatibility:  Biocompatibility The ability of a material to perform with an appropriate hoist response in a specific situation Host response : The local and systemic response, other than the intended therapeutic response, of living systems to the material Material response : The response of the material to living system Biomaterials:  Biomaterials A nonviable material used in a medical device, intended to interact with the biological system. Metals and alloys Ceramics Polymers Composites Classes of Biomaterials:  Classes of Biomaterials Inert Biomaterials: Implantable materials that elicit little or no host response Interactive Biomaterials : Implantable materials designed to elicit specific, beneficial responses, such as tissue in growth, adhesion etc Viable Biomaterials : Implantable materials, incorporating or attracting live cells at implantation, that are treated by the host as normal tissue matrices and are actively resorbed or remodeled Replant Biomaterials : Implantable materials consisting of native tissue, cultured in vitro from cells obtained previously from specific patient. Polymers as Biomaterials:  Polymers as Biomaterials Polymers are attractive in medical applications because of their Wide range in properties Ease of manufacturing Low cost Polymers used in medical applications falls into the category of interactive biomaterials Both host response as well as material response need to be taken into consideration while selecting a polymer material for a specific application Material Responses:  Material Responses Swelling and leaching Corrosion and dissolution Friction and wear Deformation and failure Effect of surface morphology Effect of degradation products ISO 10993 - Philosophy:  ISO 10993 - Philosophy Testing shall be performed on the final product / material The selection of tests shall take the end use into consideration If extracts are used for testing, the extraction vehicle should be appropriate to the nature of exposure Positive and negative controls shall be used where ever applicable ISO 10993 – Selection of tests:  ISO 10993 – Selection of tests The choice of the test procedure shall take into account The nature, degree, duration, frequency and conditions of exposure to the device The chemical and physical nature of the final product The toxicological activity of the chemical elements / compounds in the formulation of the final product The relationship of the device surface area to the recipient's body size Existing information based on the literature / experience ISO 10993 – Evaluation Decision:  ISO 10993 – Evaluation Decision Host Response:  Host Response Short term Acute toxicity Irritation (to the eye, skin, mucosal surfaces) Sensitization Hemolysis Thrombogenicity Long term Subchronic and chronic toxicity Genotoxicity Carcinogenicity Effects on reproduction, including teratogenicity Cytotoxicity:  Cytotoxicity With the use of cell culture techniques, these tests determine lysis of cells (cell death), inhibition of cell growth, other effects on cells caused by the device, material or its extracts. In vitro method Mandatory for all biomaterials Sensitization:  Sensitization These tests estimate the potential for contact sensitization of medical devices, materials and / or their extracts using suitable animal models These tests are appropriate because exposure or contact to even minute quantities of potential leachables can result in allergic or sensitization reactions Mandatory for all biomaterials Irritation:  Irritation These tests estimate the irritation potential of medical devices, materials or their extracts, using appropriate sites for implant tissue such as Skin Eye Mucous membrane in a suitable animal model. These tests are performed using appropriate route (skin, eye or mucosa) and duration of exposure or contact to determine irritant effects of materials or potential leachables Intrcutaneous Reactivity:  Intrcutaneous Reactivity Assesses the localized reaction of tissue to medical device / material extracts. These tests are carried out in such devices, where determination of irritation by dermal or mucosal tests are not appropriate Eg : Devices having access to the blood path OR where material extractables are hydrophobic Systemic Toxicity (Acute Toxicity):  Systemic Toxicity (Acute Toxicity) Estimates the potential harmful effects of either single or multiple exposures, during the period of less than 24 hours, to medical devices, materials or their extracts in suitable animal model Pyrogenicity tests carried out to detect material mediated pyrogenic reactions of extracts of medical devices or materials Note : Pyrogenicity tests are also conducted to ensure the safe level of endotoxins in the finished / sterlized product Subchronic Toxicity (Subacute Toxicity):  Subchronic Toxicity (Subacute Toxicity) Estimates the potential harmful effects of either single or multiple exposures, during the period of NOT less than 24 hours to a period not greater than 10% of the life span of the animal model, to medical devices, materials or their extracts in suitable animal model Note : These tests may be waived for materials which has chronic toxicity data Genotoxicity:  Genotoxicity These tests apply mammalian or non-mammalian cell culture techniques to determine gene mutations changes in chromosomal structure and number other DNA or gene toxicities caused by the device, material or their extracts Implantation:  Implantation Assesses the local pathological effects on the living tissue, at both the gross level and microscopic levels Sample of the material or the device is surgically implanted in an appropriate site (muscle, dentin or bone) based on the intended application Note : For a material, these tests are equivalent to sub chronic toxicity tests, if systemic effects are also investigated Haemocompatibility:  Haemocompatibility Evaluates the effects on blood or blood components by blood contacting devices or materials Specific haemocompatibility tests may have to be designed to simulate the Geometry contact conditions flow dynamics of the final application Haemolysis tests determine the degree of blood cell lysis and release of hemoglobin caused by device / material samples Chronic Toxicity:  Chronic Toxicity Estimates the effects of either single or multiple exposures, during the period of at least 10% of the life span of the animal model, to medical devices, materials or their extracts in suitable animal model Carcinogenicity:  Carcinogenicity These tests determine the tumorigenic potential of medical devices, materials or their extracts The test duration shall cover a period over the major portion of the life span of the animal model Can be carried out along with chronic toxicity studies Note : Required to be conducted only if there are suggestive data from other sources Reproductive & Developmental Toxicity:  Reproductive & Developmental Toxicity Studies the potential effects on reproductive function embryonic development (teratogenicity) prenatal and early post natal development Note : Need to be conducted only if the device has potential impact on the reproductive potential of the subject Biodegradation:  Biodegradation Where the potential for resorption / degradation exists, these tests determine the process of degradation biotransformation elimination of degradation products Note : ISO 10993 is not very specific on the norms for selection of biodegradation studies; only the method is described Basis for Selection of Tests :  Basis for Selection of Tests Categorization based on the nature of contact with human body Non contact devices Surface contacting devices External communicating devices Implant devices Categorization based on the duration of contact Limited exposure devices (< 24 hours) Prolonged exposure devices (multiple or long term exposure up to 30 days) Permanent contact devices (contact exceeds 30 days) Non contact devices:  Non contact devices Packaging materials Medical instruments that does not come in contact with either the patient or the operator (Eg. Electrical components in a medical instrument) No specific biological qualification is required except ensuring that these materials does not introduce leachants into the contacting products that could become harmful. Surface contacting devices:  Surface contacting devices Skin : Devices that contact intact skin surfaces only Electrodes, fixation tapes, compression bandages and various monitors Mucosal membranes : Devices that contact intact mucosal membranes only Endo tracheal tubes, contact lenses, bronchoscopes, intra uterine devices Breached or compromised surfaces : Devices that contact breached or otherwise compromised body surfaces Wound dressings, occlusive patches for ulcers, burns etc External communicating devices:  External communicating devices Blood path, indirect : Devices that contact the blood path at one points and serve as entry to the vascular system IV sets, transfer sets, syringes, BT sets Tissue / bone / dentin : Devices that contact any of these tissues Laprascopes, dental cements, skin staples Circulating blood : Devices that contact circulating blood Intravascular catheters, oxygenators, dialyzer accessories, CPB tubings etc Implant Devices:  Implant Devices Bone : Devices that principally contact bone Examples : Orthopedic pins, plates, bone cements Tissue : Devices that contact tissue or tissue fluids Pacemakers, neuromuscular stimulators, ligation clips Blood : Devices that contact circulating blood Artificial heart valves, vascular grafts, drug delivery catheters Evaluation Framework : Surface Contacting Devices:  Evaluation Framework : Surface Contacting Devices A .. Limited contact (<24h) B .. Prolonged contact (< 30d) C .. Permanent contact Evaluation Framework : External Communicating Devices:  Evaluation Framework : External Communicating Devices A .. Limited contact (<24h) B .. Prolonged contact (< 30d) C .. Permanent contact Evaluation Framework : Implant Devices:  Evaluation Framework : Implant Devices A .. Limited contact (<24h) B .. Prolonged contact (< 30d) C .. Permanent contact

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