Biocompatibility of 3D Printed Materials – Their Comparison, Legislation, and Practice

Material and Testing Procedure

The research team led by Dr. Nicole Senderovich from the Albert Einstein College of Medicine in New York tested five different 3D printing materials in a hospital environment. These included Formlabs and NextDent surgical resins, VisiJet M3-X photopolymer, VisiJet ENT elastomer, and DSM Arnitel thermoplastic elastomer fiber. As a comparative sample, a conventional Shiley  tracheostomy tube made of PVC for post-laryngectomy patients was used.

From each material, 3 disks in the shape of a C with a height of 15 mm, a diameter of 20 mm, and a thickness of 3 mm were printed. The comparative PVC tube had the same dimensions. All samples were sterilized and then inoculated with cultures of Staphylococcus aureus of the same concentration and incubated overnight at 37 °C. The grown biofilm was released from the disks using an ultrasonic bath and analyzed using microbiological culture techniques.

Study Results

Biofilm production was detected in all used materials. The Formlabs resin showed the most significant susceptibility to S. aureus growth, with a median colony-forming units (CFU) of 640 and an interquartile range (IQR) of 356–920, compared to the conventional Shiley  tube (CFU: 320; IQR 140–520). The thermoplastic elastomer fiber also seemed more prone to microfilm formation (CFU: 478; IQR 271–630), though there was no statistically significant difference compared to the conventional tracheostomy tube (p = 0.09).

In contrast, NextDent resin, VisiJet M3-X photopolymer, and VisiJet ENT elastomer did not show a significant difference in S. aureus colony growth compared to the Shiley  control tube. Therefore, according to the study's authors, these three materials appear promising for the production of personalized tracheostomy tubes.

Conclusion

The cited study from last year demonstrated that only FormLabs resin is significantly susceptible to the growth of S. aureus bacterial microfilm. The result was comparable to the conventionally produced tube for other materials.

An additional study from 2021, which evaluated the growth of Escherichia coli and Pseudomonas aeruginosa bacteria on 3D printed polylactic acid polymers (polylactide, PLA), found that bacterial biofilm growth on 3D printed polymers depends on surface structure, hydrophobicity, and potential antibacterial additives in the material.

According to the Chairman of the Czech Society for 3D Printing in Medicine ČLS JEP, Assoc. Prof. Ing. Lukáš Čapek, Ph.D., it is also essential to emphasize that susceptibility to the presence of S. aureus-type bacteria is not only a problem of 3D printing but of all materials and implants with surface modification.

Practice and Legislation in the Czech Republic

From the legislative perspective in the EU and the Czech Republic, Act No. 375/2022 Coll., on Medical Devices and in vitro Diagnostic Medical Devices, applies, where 3D printing falls mainly under the provisions related to custom-made medical devices, which are also addressed by Article 103 of the European Parliament Council Regulation EU 2017/745. From the biocompatibility perspective of materials, the ISO 10993 standard is significant, dividing materials according to the level of risk when in contact with a patient.

Suppliers are mainly responsible for the production and testing of materials, which must also come with a conformity record. For newly introduced materials, according to Assoc. Prof. Čapek, it is possible to conduct one's own tests according to ISO 10993 and sterility tests, for example, according to the Czech Pharmacopoeia at an accredited laboratory.

In the Czech Republic, the Czech Society for 3D Printing in Medicine ČLS JEP has been addressing the introduction of 3D printing in healthcare facilities since mid-2023. Its goal is to set up a system that is uniform, controllable, and primarily safe for the patient in accordance with current legislation.

(jko)

Sources:
1. Senderovich N., Shah S., Ow T. J. et al. Assessment of Staphylococcus Aureus growth on biocompatible 3D printed materials. 3D Print Med 2023; 9 (1): 30, doi: 10.1186/s41205-023-00195-7.
2. Hall D. C. jr., Palmer P., Ji H-F. et al. Bacterial biofilm growth on 3D-printed materials. Front Microbiol 2021; 12: 646303, doi: 10.3389/fmicb.2021.646303.
3. Czech Society for 3D Printing in Medicine 2023 ČLS JEP. 3D medicalprint, 2023. Available at: www.3dmedicalprint.cz