Starts off with Definitions:
An accelerated extraction is a condition that measures leachables using conditions that shorten the duration but does not result in a chemical changes of those substances being extracted.
A blank is the extract fluid without test article in it, using a vessel identical to the vessels containing test article. The purpose of this is defined to eliminate effects stemming from the vessel, vehicles or process.
A certified reference material is accompanied with a certificate establishing traceability to specific values.
An exaggerated extraction is one that intentionally produces more chemical entities being released than would be under simulated use conditions.
An exhaustive extraction is a series of extractions where the final extraction yields less than 10% by weight of that seen in the original extraction.
Experimental Controls are used to validate a procedure or demonstrate the test system can produce results reliably.
An extract is the liquid that is the product of extracting a test material or control.
Extractables are entities that can be drawn out using extraction vehicles and or procedures that are at least as aggressive as clinical use conditions.
Homogeneous is a uniform structure or composition and yields predictable responses.
Leachables are entities that can come out of a medical device or material during clinical use.
A negative control yields a non reactive result. Now specifies blanks, vehicles, and reference materials.
A positive control yields a reactive result.
A reference material are well characterized materials that are used for calibration of apparatus or demonstrates the suitability of the test system to produce predictable responses both negative or positive.
A simulated use extraction uses conditions that mimic product use scenarios for the purpose of evaluating potential hazard to the end user under routine use. But the definition implies that this infact is not and extraction but a leaching.
Stability is the ability of a material to maintain a specific biological response when stored under specified conditions for a specified period of time.
A test sample is the extract of the subdivided sample or the subdivided sample itself.
Experimental controls shall be used in biological evaluations to validate a test procedure and to compare results between materials. Then can be negative and or positive controls.
Test Material: Should be the final product or representative samples from final product or materials processed in the same manner as the final product.
Test samples and reference materials shall be handled in a manner to prevent contamination. Manufacturing residues are considered integral to the final product. If the sample is sterile and the test requires sterility they should be handled aseptically. If sterilization is part of the use of the sample it should be sterilized by the manufacturer prior to testing. If cleaning is part of the sterilizing process then the cleaning procedure should be considered. When cutting a sample, consideration should be given to exposing previously unexposed surfaces. Tools shall be clean to prevent contamination.
When a whole device cannot be extracted, each individual material shall be proportionally represented in the test sample.
Coated products should be tested with the coating on the substrate. Even if the substrate has no intentional patient contact. If connections, joints or seals are present in the final form they should be included in the test sample.
Differing materials in one device could have synergies or interactions and this should be considered in choosing the test sample. The test sample should be selected to maximize the exposure to those materials that have a potential for a biological reaction.
Preparation of extracts:
The containers to be inert and of a size to minimize headspace and precautions taken to prevent contamination. Borosilicate tubes with caps with inert liners such as PTFE.
An accelerated extraction is a condition that measures leachables using conditions that shorten the duration but does not result in a chemical changes of those substances being extracted.
A blank is the extract fluid without test article in it, using a vessel identical to the vessels containing test article. The purpose of this is defined to eliminate effects stemming from the vessel, vehicles or process.
A certified reference material is accompanied with a certificate establishing traceability to specific values.
An exaggerated extraction is one that intentionally produces more chemical entities being released than would be under simulated use conditions.
An exhaustive extraction is a series of extractions where the final extraction yields less than 10% by weight of that seen in the original extraction.
Experimental Controls are used to validate a procedure or demonstrate the test system can produce results reliably.
An extract is the liquid that is the product of extracting a test material or control.
Extractables are entities that can be drawn out using extraction vehicles and or procedures that are at least as aggressive as clinical use conditions.
Homogeneous is a uniform structure or composition and yields predictable responses.
Leachables are entities that can come out of a medical device or material during clinical use.
A negative control yields a non reactive result. Now specifies blanks, vehicles, and reference materials.
A positive control yields a reactive result.
A reference material are well characterized materials that are used for calibration of apparatus or demonstrates the suitability of the test system to produce predictable responses both negative or positive.
A simulated use extraction uses conditions that mimic product use scenarios for the purpose of evaluating potential hazard to the end user under routine use. But the definition implies that this infact is not and extraction but a leaching.
Stability is the ability of a material to maintain a specific biological response when stored under specified conditions for a specified period of time.
A test sample is the extract of the subdivided sample or the subdivided sample itself.
Experimental controls shall be used in biological evaluations to validate a test procedure and to compare results between materials. Then can be negative and or positive controls.
Test Material: Should be the final product or representative samples from final product or materials processed in the same manner as the final product.
Test samples and reference materials shall be handled in a manner to prevent contamination. Manufacturing residues are considered integral to the final product. If the sample is sterile and the test requires sterility they should be handled aseptically. If sterilization is part of the use of the sample it should be sterilized by the manufacturer prior to testing. If cleaning is part of the sterilizing process then the cleaning procedure should be considered. When cutting a sample, consideration should be given to exposing previously unexposed surfaces. Tools shall be clean to prevent contamination.
When a whole device cannot be extracted, each individual material shall be proportionally represented in the test sample.
Coated products should be tested with the coating on the substrate. Even if the substrate has no intentional patient contact. If connections, joints or seals are present in the final form they should be included in the test sample.
Differing materials in one device could have synergies or interactions and this should be considered in choosing the test sample. The test sample should be selected to maximize the exposure to those materials that have a potential for a biological reaction.
Preparation of extracts:
The containers to be inert and of a size to minimize headspace and precautions taken to prevent contamination. Borosilicate tubes with caps with inert liners such as PTFE.
Temperature and times:
37oC +/- 1oC for 72 hours +/- 2 hours
50oC +/- 2oC for 72 hours +/- 2 hours
70oC +/- 2oC for 24 hours +/- 2 hours
121oC +/- 2oC for 1 hour +/- 0.1 hour
With a small text note that 37oC +/- 1oC for 24 hours +/- 2 hours in tissue culture medium is acceptable for cytotoxicity testing. There is a discussion that a lesser time point but no less than for 4 hours could be acceptable for limited exposure intact or mucosal surface contacting products and then refers to ISO 10993-5. Also, temperatures above 37oC +/- 1oC can alter the serum or other constituents in tissue culture media.
A statement that extract conditions above are intended to for risk estimation and that simulated clinical conditions need to be described and justified.
Materials that may dissolve or resorb under conditions of use still should be extracted, but complete dissolution may be acceptable.
Standard surface area can be used to determine volume of extract. The area is both sides but excludes indeterminate surface irregularities. When surface area cannot be determined then a mass to volume ratio shall be used.
Materials should be cut to enhance submersion in the extract liquid. Sizes of 10 mm x 50 mm or 5 mm x 25 mm are suggested. But, laminates, coated substrates and elastomers should be extracted intact.
Extract ratios
For a thickness less than half a millimeter a 6 cm2 per 1 ml with a 10% tolerance should be used. For a thickness of a half to 1 millimeter a 3 cm2 per 1 ml with a 10% tolerance should be used. Examples of materials for these ratios are tubing walls, sheets, film slabs and small molded items.
For a thickness greater than 1 mm a ratio of 3 cm2 per 1 with a 10% tolerance should be used on larger molded items. For a thickness greater than 1 mm a ratio of 1.25 cm2 per 1 with a 10% tolerance should be used for elastomeric closures. Irregularly shaped solid devices can use a 0.2 gram per 1 ml ratio for powders, pellets, foam and non-absorbent materials. Low density irregularly shaped products such as membranes should use a 0.1 gram per 1 ml ratio.
A description of how to extract absorbent materials is outlined. The absorbent capacity should be determined per gram and extracted at 0.1 gram or 1.0 cm2 per 1 ml beyond the absorptive capacity of the sample.
Elastomers, coated materials, composites and laminates should be tested intact whenever possible because of the exposure of unintended surfaces.
Extracts using both polar and nonpolar vehicles have to be performed.
Polar vehicle examples are water, physiologic saline, cell culture media without serum.
Non polar vehicle examples are vegetable oils such as cottonseed oil, sesame oil or oleum naturale
Alternate vehicle examples 5% ethanol in saline or water, polyethylene glycol 400 diluted to physiological osmotic pressure, dimethylsulfoxide and cell culture media with serum.
The extracts shall be performed under agitation. Extracts should be used within 24 hours, otherwise stability data is required.
The pH of the extract should not be adjusted.
The extract should not by standard practice be centrifuged, filtered or have suspended particulates removed. If these are performed then they should be reported.
Hazard Identification: Exhaustive extraction conditions should be considered. Solvents should not cause more than slight softening of a polymer. The extraction conditions should be based upon the physicochemical properties of the material or the chemicals expected to be extracted.
For materials or devices not expected to dissolve or resorb the extraction process shall not cause dissolution or the polymer formulation. No more than slight softening of the material is acceptable. The solvent then needs to be removed prior to a bioassay. Manufacturing processes and residues should be considered.
For soluble materials or solutions extraction procedures may not be appropriate. Consideration must be given to the compatibility with the test system and dose routes for a direct application of the test article or test article in solution.
Aqueous fluids shall be tested directly and not extracted.
Devices that circulate fluids can be extracted by creating a continuous loop but at least one condition, such as speed, temperature, volume or duration need to be exaggerated beyond clinical use conditions.
Test samples that cure in situ the extract shall be performed at the point at which the product is placed in situ. For test methods that are direct in nature the test should be conducted as if under clinical use.
37oC +/- 1oC for 72 hours +/- 2 hours
50oC +/- 2oC for 72 hours +/- 2 hours
70oC +/- 2oC for 24 hours +/- 2 hours
121oC +/- 2oC for 1 hour +/- 0.1 hour
With a small text note that 37oC +/- 1oC for 24 hours +/- 2 hours in tissue culture medium is acceptable for cytotoxicity testing. There is a discussion that a lesser time point but no less than for 4 hours could be acceptable for limited exposure intact or mucosal surface contacting products and then refers to ISO 10993-5. Also, temperatures above 37oC +/- 1oC can alter the serum or other constituents in tissue culture media.
A statement that extract conditions above are intended to for risk estimation and that simulated clinical conditions need to be described and justified.
Materials that may dissolve or resorb under conditions of use still should be extracted, but complete dissolution may be acceptable.
Standard surface area can be used to determine volume of extract. The area is both sides but excludes indeterminate surface irregularities. When surface area cannot be determined then a mass to volume ratio shall be used.
Materials should be cut to enhance submersion in the extract liquid. Sizes of 10 mm x 50 mm or 5 mm x 25 mm are suggested. But, laminates, coated substrates and elastomers should be extracted intact.
Extract ratios
For a thickness less than half a millimeter a 6 cm2 per 1 ml with a 10% tolerance should be used. For a thickness of a half to 1 millimeter a 3 cm2 per 1 ml with a 10% tolerance should be used. Examples of materials for these ratios are tubing walls, sheets, film slabs and small molded items.
For a thickness greater than 1 mm a ratio of 3 cm2 per 1 with a 10% tolerance should be used on larger molded items. For a thickness greater than 1 mm a ratio of 1.25 cm2 per 1 with a 10% tolerance should be used for elastomeric closures. Irregularly shaped solid devices can use a 0.2 gram per 1 ml ratio for powders, pellets, foam and non-absorbent materials. Low density irregularly shaped products such as membranes should use a 0.1 gram per 1 ml ratio.
A description of how to extract absorbent materials is outlined. The absorbent capacity should be determined per gram and extracted at 0.1 gram or 1.0 cm2 per 1 ml beyond the absorptive capacity of the sample.
Elastomers, coated materials, composites and laminates should be tested intact whenever possible because of the exposure of unintended surfaces.
Extracts using both polar and nonpolar vehicles have to be performed.
Polar vehicle examples are water, physiologic saline, cell culture media without serum.
Non polar vehicle examples are vegetable oils such as cottonseed oil, sesame oil or oleum naturale
Alternate vehicle examples 5% ethanol in saline or water, polyethylene glycol 400 diluted to physiological osmotic pressure, dimethylsulfoxide and cell culture media with serum.
The extracts shall be performed under agitation. Extracts should be used within 24 hours, otherwise stability data is required.
The pH of the extract should not be adjusted.
The extract should not by standard practice be centrifuged, filtered or have suspended particulates removed. If these are performed then they should be reported.
Hazard Identification: Exhaustive extraction conditions should be considered. Solvents should not cause more than slight softening of a polymer. The extraction conditions should be based upon the physicochemical properties of the material or the chemicals expected to be extracted.
For materials or devices not expected to dissolve or resorb the extraction process shall not cause dissolution or the polymer formulation. No more than slight softening of the material is acceptable. The solvent then needs to be removed prior to a bioassay. Manufacturing processes and residues should be considered.
For soluble materials or solutions extraction procedures may not be appropriate. Consideration must be given to the compatibility with the test system and dose routes for a direct application of the test article or test article in solution.
Aqueous fluids shall be tested directly and not extracted.
Devices that circulate fluids can be extracted by creating a continuous loop but at least one condition, such as speed, temperature, volume or duration need to be exaggerated beyond clinical use conditions.
Test samples that cure in situ the extract shall be performed at the point at which the product is placed in situ. For test methods that are direct in nature the test should be conducted as if under clinical use.
