Study Outline for Cytotoxicity/MEM/Agar Overlay
Devices/materials are generally extracted in serum-supplemented mammalian cell culture media (MEM), but may be extracted in cell culture media without serum if requested by the sponsor. The devices/materials are extracted for 24 – 25 hours at 37 ± 1ºC generally with agitation. After extraction, the extracts are placed in contact with a monolayer of L-929 cells (mouse fibroblasts).
The cells are incubated at 37 ± 1ºC in 5 ± 1% CO2 for either 48 ± 3 hours or 72 ± 3 hours (or other incubation times as requested by the sponsor). The cells are then scored for cytopathic effect using a scale from 0 – 4 as listed in AAMI/ANSI/ISO 10993-5 and USP <87>. The device/material meets ISO and USP requirements if the cytotoxic response is not greater than grade 2 (mildly reactive).
Materials are generally tested by surface area using at least 100 mm2 of material per well. Weight may also be used for liquids, gels, or powders using at least 100 mg per well. The material is placed on a layer of agarose that is placed on top of a monolayer of L-929 cells and incubated for 24 – 26 hours at 37 ± 1ºC in 5 ± 1% CO2. After incubation, the zone of cell destruction is measured and scored based on a 0 – 4 scale listed in AAMI/ANSI/ISO 10993-5 and USP <87>. The material meets ISO and USP requirements if the cytotoxic response is not greater than grade 2 (mildly reactive).
Cytotoxicity Failure Program
A common failure source for medical devices is metal ions that can leach from metal implants, reusable instruments, and single-use polymers containing colorants. However, it is often difficult to determine if these failures are associated with the test article material or if they are caused by residual manufacturing solvents or cleaning fluids. In the past, if your product failed cytotoxicity testing, you would need to send new samples for additional testing to determine the cause of the failure. We have recently added a new service to help our customers potentially save time and money when conducting these evaluations. If you request the Nelson Labs Cytotoxicity Failure Program (CTX702) when submitting your samples to the lab, we will store an aliquot of the extraction fluid from your cytotoxicity test until you receive your test results. In the case of a failing result, we will connect you with one of our subject matter experts who will help you develop a plan for investigation. Because we have retained a sample extract from your original cytotoxicity test, we can quickly test the retained fluid for metals using inductively coupled plasma – mass spectrometry (ICP-MS). If the test detects cytotoxic metals in the extract, we will then contact you with details regarding initiating a toxicological risk assessment. Our toxicologists can assess the metals and determine if the concentration would be sufficient to lead to any patient safety issues.
Customer Benefits of Cytotoxicity Failure Programs
Preservation of the original sample extract will allow us to quickly conduct a failure investigation to help identify and eliminate any potential causes. No need to provide additional samples, which could increase costs and delay testing. Follow-up testing will not only identify if cytotoxic metals are present in the sample, but also provide a quantitative analysis of those metals. If requested, the toxicological risk assessment will evaluate if the concentration of metals found would be sufficient to lead to any patient safety issues.
Study Outline for Cytotoxicity Failure Program
The cytotoxicity test is a highly sensitive toxicity assay which is designed to determine if there are cytotoxic leachable substances or surface contaminants present in medical devices or raw materials. It is required testing for most medical devices and is used frequently as a routine screening test for raw materials and cleaning validations.
Occasionally, a device or material will exhibit a level of cytotoxic reactivity that is higher than what is allowed by the ANSl/AAMl/ISO 10993-5 standard and will result in a failed test. Although your product may have failed a cytotoxicity test, it does not necessarily mean that your device or material is unsafe for clinical use. It simply means that you are obligated to identify the source of the failure and assess any toxicological risks.
There are several possible causes for a failure, and Nelson Labs provides services to help you assess the failure and any toxicological risks.