U.S. Food and Drug Administration

Catalog of Regulatory Science Tools to Help Assess New Medical Devices 

 

This regulatory science tool presents a lab method that helps determine the extractables profile of additive-manufactured orthopedic casts produced by fused filament fabrication method. Please see appendix.  

 

Technical Description

This tool describes the details on screening for extractables in additive-manufactured (AM) acrylonitrile butadiene styrene (ABS) pre- and post- processed materials and orthopedic cast as described in the peer-reviewed publication [1]. Filaments used included the United States Pharmacopeia (USP) Class VI ABS filaments, as well as consumer grade ABS filaments. Forearm casts (used as medical devices) were manufactured from USP Class VI (USPF) and consumer grade filaments (CGF) using fused filament fabrication (FFF) method. This tool provides a methodology for sample extraction and extract analyses by gas chromatography/mass spectrometry (GC/MS) and liquid chromatography/ mass spectrometry (LC/MS) techniques. Details of data processing including identification and semi-quantification information for the compounds identified in the extracts are also included to facilitate the ease of tool application.

Intended Purpose

This tool provides a method to determine the extractables profile of AM orthopedic casts produced by fused filament fabrication method.

Testing

Appendices A [2] and B [3] provide stepwise guidelines on how to execute the screening for extractables in medical device materials. The method has been tested with USP Class VI ABS filaments and consumer grade ABS filaments as well as orthopedic casts manufactured using the same filaments by fused fabrication method [1]. The method has been tested with USP Class VI ABS filaments and consumer grade ABS filaments as well as orthopedic casts manufactured using the same filaments by fused fabrication method. Sample preparation and analysis methods described in this tool have been adapted internally to conduct multiple research projects related to chemical characterization including an ISO 10993-12 round robin studyExternal Link Disclaimer.

Limitations

• Only tested with AM ABS materials generated by fused fabrication method. Different manufacturing and processing parameters along with other device materials would require optimization and validation.
• Tool does not include methodologies to screen for elemental impurities.
• Lack of available spectral database for extractables and leachables in medical device materials hinders the comprehensive identifications of the compounds extracted.

Supporting Documentation

1. The paper linked here describes the process of screening of extractables in medical devices using additive manufactured devices in alignment with ISO 10993-18 (2020) recommendations. https://doi.org/10.1016/j.talanta.2019.120464External Link Disclaimer
2. Appendix A: Protocol for sample extraction
3. Appendix B: Protocol for Chemical Analysis

Contact

• RST_CDRH@fda.hhs.gov

For more information:

• Catalog of Regulatory Science Tools to Help Assess New Medical Devices

Appendix A: Protocol for sample extraction

1. Label the empty vials (borosilicate) with the date of extraction, solvent & replicate number, and material information.
2. Cut¹ the medical device or medical device materials into representative samples
   1. Do not prerinse or preclean materials prior to use
   2. Cut the materials into representative samples with scissors and/or a cold chisel (1/2”, 12 mm)
   3. Clean scissors and/or chisel prior to use and between each material using water, acetone, and hexane (repeat 3 times) then dry with a Kimwipe
3. Weigh 200 mg of representative sample with an analytical balance capable of 0.1 mg measurement and then transfer to a clean, inert vials.
   1. Do not preclean vials or reuse vials
4. Prepare each representative sample in triplicate (e.g., 3 vials without material -blank, 3 vials with material-sample)
5. Add 1.0 mL of extraction solvent (e.g., LC/MS grade solvent) to each sample and blank vial using a calibrated pipette. Repeat for all 3 solvents (e.g., isopropanol, hexane, and water)² .
6. Seal the vials using the respective caps with an inert liner (e.g., PTFE). Record the pre-extract observation.
7. Place the sealed vials in a vial tray in the incubator shaker, close the cover and set the time and temperature to 24 hrs. and 50 °C, respectively. Agitate the vials at 60 rpm.
8. After 24 hrs., remove vials and allow to sit in the fridge for 1 hr. prior to transferring of the extract into a separate vial.
9. Check the sample vials for any swelling of the materials³ / precipitations⁴ / particulate formation⁵.
10. Remove the medical device material from the vials using clean tweezers and rinse the tweezers between each sample (Step 1c).
    1. Transfer the required amount of extract volume into LC/MS or GC/MS vials for analysis.
    2. Analyze the extracts within 24 hrs. Keep the extracts refrigerated until ready to use.

Appendix B: Protocol for Chemical Analysis

A. Protocol for volatile and semi volatile extractable analysis by GC/MS

1. Evaluate the GC/MS performance with vendor recommended standard operating procedures (tune evaluation with GC/MS tuning standard - perfluorotributylamine (PFTBA).
2. Prepare reference standard (as listed in table 1) calibration samples in isopropyl alcohol with the concentration range between 100 to 5000 μgL−1. Inject standard samples and determine the linear dynamic range for the samples. GC/MS parameters are listed on Table 1.
3. Bring the refrigerated extracts to room temperature (~30 min). Transfer 100 µL from each sample and blank extract to GC/MS vials and close the caps.
4. Pre inject few of the extracts to the GC/MS system to check if samples need to be diluted. A 10-50X dilutions may be required to bring the concentrations within the dynamic range.
5. Inject blank samples in between each extract sample runs.

Table 1: GC-MS instrument parameters

GC/MS data analysis

• Use Agilent Unknown Analysis software for the identification and semi-quantification of the compounds detected in GC/MS analysis of the sample extracts. Details on how to use the Unknown analysis software can be found on their website.
• Use NIST 1A v17 Mass Spectral Library (National Institute of Standards and Technology, Gaithersburg, MD) for the identification.
• Match factor of >80% can be used for the tentative identification. Expert judgment must be used in selecting the best match for the detected compounds.
• Only report the presence of a compound if it is identified in at least two of the 3 extract sample replicates.
• External calibration curves of the selected reference standards can be used for semi quantification. Select “average RF of the closest standard” for the semi-quantification of the identified compounds. (semi-quantitation will be performed using the calibration curve of the standard closest to the analyte. Other options can be selected based on the user preference and the experimental logistics).
• Use blank subtraction option to remove the background interferences from the quantifiable values.
• After all the samples have been processed, export the results as .CSV file for further evaluation/report generation.

B. Protocol for semi volatile and non-volatile extractable analysis by LC/MS

1. Tune and calibrate the LC/MS with vendor recommended standard operating procedures.
2. Prepare reference standard calibration samples (diethyl phthalate, stearic acid, and Irganox 1010) in isopropyl alcohol with the concentration range between 100 to 10000 μgL−1. Inject standard samples and determine the linear dynamic range for the samples. LC/MS parameters are listed on Table 2.
3. Bring the extracts to room temperature. Transfer 100 µL from each sample and blank extract to LC/MS vials and close the caps.
4. Pre inject a few of the extracts to the LC/MS system to check if samples need to be diluted. Dilute the samples with 1:1 hexane: Isopropyl alcohol mixture to appropriate concentration. 10-25X dilutions may be required to bring the concentrations within the dynamic range.
5. Inject blank samples in between each extract sample runs.

Table 2: LC-MS instrument parameters

LC/MS data analysis

• Use Agilent MassHunter Qualitative analysis software coupled with the Agilent Extractables and Leachables (E&L) Personal Compound Database and Library (PCDL) for the identification of the compounds detected in LC/MS analysis of the sample extracts. Details on how to use the Agilent MassHunter Qualitative Analysis softwareExternal Link Disclaimer can be found on their website.
• Setup mass accuracy for <10 ppm for the identification. Match factor of >80% can be used for the tentative identification. Expert judgment must be used in selecting the best match for the detected compounds.
• Only report the presence of a compound if it is identified in at least two of the 3 extract sample replicates.
• Use a five-point calibration curve per reference standard to perform semi- quantification. Use blank subtraction option to remove the background interferences from the quantifiable values. A: Protocol for sample extraction

 

1. Cut the samples only, if necessary, based on extraction logistics or provided sample dimensions. Analyzing the complete device without manipulation is preferred.
2. Follow the ISO 10993-12 recommendation to get the sample to extraction volume ratio.
3. Nondestructive swelling is acceptable if the extraction solvent is recoverable for the analysis.
4. If a precipitate is formed, a re-dissolution is recommended prior to sample analysis per ISO-10993-18 (2020) guidelines.
5. Particulates should be removed prior to extract analysis. Care should be taken to ensure that the particulate removal method will not alter the extractables profile of the device.