Corrositex Assay Step-by-Step
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Qualification of Test Material
Each test material is added to a vial containing the Chemical Detection System (CDS) to determine if the test material will qualify for testing. The CDS is a pH neutral solution that contains two pH indicator dyes. A color change can be detected when the pH of the CDS drops below 4.5 or rises above 8.5. Test materials must cause a color change in the CDS to be tested in this assay.
Once qualified, the test material is categorized to determine the appropriate timetable for Packing Group Assignment. The test material is added to two tubes. The resulting color change in each tube is compared to the color chart provided by In Vitro International. A category 1 test material will be evaluated for up to 4 hours; while a category 2 test material will be evaluated for up to 1 hour.
After a test material has qualified for the Corrositex assay, biobarrier membranes are prepared. To prepare the biobarrier membranes, the biobarrier matrix powder is completely solubilized. The solubilized collagen matrix, composed of water and dissolved proteins, is then added to a membrane disc containing a porous cell membrane. Once prepared, the biobarrier membranes are refrigerated and used within seven days.
Biobarrier Qualification with the Positive Control
A biobarrier membrane is placed on top of a vial containing CDS. The positive control is then added onto the biobarrier membrane disc. The vial is continuously monitored until a color change (i.e. break through) has occurred. The break through time is then compared to the IIVS positive control historical data range. Following the acceptance of the positive control, the test materials can then be dosed.
Dosing of the Test Material
Each test material is tested in four replicate biobarrier membranes. The biobarrier membrane is placed onto a vial of CDS. The test material is added onto the biobarrier membrane disc. The vial is continuously monitored for the first ten minutes. If no color change occurs, this process is repeated an additional three times until the remaining biobarrier membranes are treated with the test material. The vials are observed until a color change (i.e. break through) occurs. When a color change occurs in each vial, the break through times are recorded. Category 1 test materials are observed for a break through for up to four hours. Category 2 test materials are observed for up to one hour.
Determination of Packing Group
To determine the appropriate packing group for a test material, a mean break through time is calculated from the four replicates. Each test material is evaluated using the appropriate category on U.N. Packing Group Assignment Table. When a break through does not occur in the time alloted, the Packing Group of the test material is designated as non corrosive according the Corrositex protocol.
|U.N. Packing Group Table|
|Category||Time Required for CDS Change|
|Category 1||0 to 3 minutes||>3 to 60 minutes||>60 to 240 minutes||>240 minutes|
|Category 2||0 to 3 minutes||>3 to 30 minutes||>30 to 60 minutes||>60 minutes|
|Packing Group I||Packing Group II||Packing Group III||Non-Corrosive|