The rapidly evolving landscape of medical technology is increasing the significance of coatings in medical devices. The relentless drive to enhance effectiveness, safety, and functionality fuels the medical device industry's exploration of novel coating solutions.1 This article discusses the application of advanced coating techniques to medical devices.
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Why Use Advanced Coating?
Advanced coating techniques like magnetron sputtering and plasma-enhanced chemical vapor deposition (PECVD) are becoming crucial for medical devices. These techniques offer many benefits, such as improved corrosion resistance, higher durability, and enhanced self-cleaning properties, compared to conventional coating methods like dip coating.
Medical devices often require specialized coatings to improve overall performance, reduce friction, and prevent bacterial growth. Coatings can also decrease the risk of rejection by the patient’s immune system and improve the biocompatibility of implants.
For instance, the application of advanced coating techniques substantially improves the lubricious nature of medical devices, such as catheters and stents. This facilitates their smoother navigation and insertion through neurovascular and peripheral systems, resulting in greater patient comfort and reduced risk of vessel trauma.1,6
Fundamentals of Advanced Coating Techniques
Atomic Layer Deposition
Implantable medical devices must endure the corrosive internal environment of the human body for long periods. Hermetic sealing, which protects devices from this corrosive environment, is crucial for ensuring their longevity.
In atomic layer deposition, the substrate that will be coated is sequentially exposed to precursor chemicals, which react with the substrate's reactive surface sites to form a chemically bonded adsorption layer. This film growth method enables extremely uniform and conformal coatings on all shapes of three-dimensional objects, making it suitable for hermetic sealing objects with complex shapes.
Atomic layer deposition is, therefore, advantageous over other methods for medical applications that require the use of sensitive substrate materials and have extreme requirements for chemical/temperature resistance and coating quality.
For example, studies have shown that conformal hermetic sealing of sub-millimeter-sized microelectronic chiplets using multilayered atomic layer deposition significantly prolonged the operational life of the wireless body implants by preventing electronic failure and degradation.3
PECVD
PECVD is a CVD technique that utilizes gas-phase precursors within an inert carrier gas to grow thin films, allowing low-temperature growth through capacitive coupling with plasma. For example, this technique has been used to deposit amorphous silicon carbide thin films for passivation in biomedical devices.
For passivation in biomedical devices, amorphous silicon carbide shines due to its wide band gap, excellent biocompatibility, and inherent robustness. Passivation with high biocompatibility and conformability, low stress, high resistance, and long lifetimes is crucial to developing next-generation biomedical devices.4
Magnetron Sputtering
Magnetron Sputtering is a common technique used for growing thin films, favored for its ability to fabricate a large amount of thin films with high purity at a low cost. This process involves ejecting material from a target/source onto a substrate, such as a silicon wafer.
Magnetron sputtering is utilized to tune the implant surface with higher chemical, mechanical, and thermal safety. Coatings deposited using this technique yield better corrosion and wear resistance than other methods.
Coating properties can be controlled by modifying the post-deposition annealing treatment, substrate temperature, deposition time, bias voltage, and discharge power. For example, the surface properties of metallic implants can be improved using magnetron sputtering.5
Enhancements in Device Performance, Biocompatibility, and Patient Safety
Companies like Hydromer and Endura Coatings offer advanced bio-approved medical device coating solutions, including anti-microbial and anti-corrosive coatings, for various applications, such as surgical disposable instrumentation devices, diagnostic probes, cannulas, and catheter manufacturing.
For instance, Endura 320M is a proprietary multi-layer fluoropolymer coating system possessing non-stick surface characteristics and extremely high-release properties. This coating reduces tissue adhesion on different surgical ablation tools, which ensures enhanced cutting accuracy.
Similarly, Endura 200TX is a proprietary nickel co-polymer coating system developed for surgical disposable anvils utilized in abdominal surgery. This coating offers enhanced lubrication, chemical corrosion protection, and low friction and surface energies.
The advantages of advanced coating solutions, including corrosion resistance and promised longevity, coupled with their ability to directly deliver therapeutic substances like antiseptics or antibiotics where required, ensure sterility and result in higher patient safety.6,7
Drug release from implant coatings has gained significant attention from the scientific community. The most common platforms for sustained drug release include polymer coatings, ceramic materials, or the drugs themselves. Controlled drug release can be achieved using coatings of enzymatically degradable, pH-responsive, and soluble polymers. This type of drug release maximizes bio-efficacy and improves the quality of life.8
Polymeric coatings, such as those made from hyaluronic acid, chitosan, and collagen, possess antibacterial and antifouling properties, which prevent implantable medical device-associated infections.9,10
Metal coatings deposited using magnetron sputtering or PECVD are often used in medical devices for improved corrosion protection, durability, and wear resistance. However, the potential toxicity and allergic reactions associated with metal coatings pose significant risks, necessitating regulatory oversight to ensure the safety of the medical device.11
Innovations in Diagnostic and Wearable Devices
Parylene, as a conformal coating, offers many advantages for wearable, diagnostic, and other medical devices, including biocompatibility and pinhole-free and uniform coatings. For instance, this coating minimizes the risk of adverse sensitivities or reactions when a wearable medical device is in direct contact with a user's skin.
The light and thin nature of this conformal coating not only reduces the weight and size of the device, enhancing functionality and user comfort, but also ensures consistent protection across the entire device surface.
Parylene's dielectric insulation properties safeguard electronic components from electrical malfunctions, while its chemical resistance and moisture barrier capabilities effectively protect the devices from environmental hazards during daily use. Its UV and temperature stability also offer all-weather protection.
Parylene conformal coatings also retain their protective integrity under chemical stress and over long periods, making them suitable for diagnostic and wearable medical devices.
Parylene coating is thus paving the way for advancing personalized medicine and enhancing patient care by improving the longevity, user-friendliness, and efficacy of wearable medical devices like fitness trackers, hearables, and epidermal sensors.12
The Future of Medical Device Coating
A study recently published in Nature Communications proposed a poly(carboxybetaine) microgel-reinforced poly(sulfobetaine) (pCBM/pSB) pure zwitterionic hydrogel coating with exceptional anti-swelling properties and mechanical robustness for blood-contacting biomedical devices. The pCBM/pSB hydrogel maintained favorable stability, even after 100 sandpaper abrasions, 1000 underwater bends, half an hour of strong water flushing, and 21 days of PBS shearing.
The pCBM/pSB hydrogel-coated PVC tubing also effectively mitigated the foreign body response and prevented thrombus formation ex vivo in rabbits' and rats' blood circulation without anticoagulants.13
Overall, advanced coating techniques like magnetron sputtering and PECVD offer significant advantages for medical devices by improving corrosion resistance, durability, and biocompatibility. These coatings enhance device performance and patient safety, with applications in implants, wearables, and diagnostic tools.
More from AZoM: Technical Ceramics in Medical Devices
References and Further Reading
1. Oscoff, G. (2024). The Critical Role of Advanced Coatings in Enhancing Medical Devices. [Online] Medium. Available at: https://grahamoscoff.medium.com/the-critical-role-of-advanced-coatings-in-enhancing-medical-devices-98e456d45271 (Accessed on 15 March 2024)
2. Manney, D. (2023). It Sounds Crazy, but Advanced Coatings Technologies are Here! [Online] CWF. Available at: https://cwfinishing.net/advanced-coatings-technologies/#:~:text=Advanced%20coatings%20technologies%20have%20become,protect%20and%20enhance%20different%20materials (Accessed on 15 March 2024)
3. Blomberg, T., Ritasalo, R., Matvejeff, M., Ylivaara, O., Kärkkäinen, A., Kivioja, J. (2019). Atomic Layer Deposition Coatings for Medical Devices. Electrochemical Society Meeting Abstracts. doi.org/10.1149/MA2019-02/24/1126
4. Greenhorn, S., Bano, E., Stambouli, V., Zekentes, K. (2023). Amorphous SiC Thin Films Deposited by Plasma-Enhanced Chemical Vapor Deposition for Passivation in Biomedical Devices. Materials. doi.org/10.3390/ma17051135
5. Akhtar, M., Uzair, S. A., Rizwan, M., Ur Rehman, MA. (2022). The Improvement in Surface Properties of Metallic Implant via Magnetron Sputtering: Recent Progress and Remaining Challenges. Frontiers in Materials. doi.org/10.3389/fmats.2021.747169
6. Endura. Medical Device Coatings. [Online] Endura. Available at: https://www.enduracoatings.com/medical.html (Accessed on 15 March 2024)
7. Hydromer. The Power of Advanced Coatings in Medical Device Safety. [Online] Hydromer. Available at https://hydromer.com/the-power-of-advanced-coatings-in-medical-device-safety/ (Accessed on 15 March 2024)
8. Zafar, MS., Fareed, MA., Riaz, S., Latif, M., Habib, SR., Khurshid, Z. (2020). Customized Therapeutic Surface Coatings for Dental Implants. Coatings. doi.org/10.3390/coatings10060568
9. Luis, J. (2023). Strategies to Enhance Biomedical Device Performance and Safety: A Comprehensive Review. Coatings. doi.org/10.3390/coatings13121981
10. Chu, X., Yang, F., Tang, H. (2022). Recent Advance in Polymer Coatings Combating Bacterial Adhesion and Biofilm Formation. Chinese Journal of Chemistry. doi.org/10.1002/cjoc.202200434
11. ProPlate. What are the regulatory considerations for medical devices with metal coatings in terms of patient safety? [Online] ProPlate. Available at https://www.proplate.com/what-are-the-regulatory-considerations-for-medical-devices-with-metal-coatings-in-terms-of-patient-safety/ (Accessed on 15 March 2024)
12. VSI PARYLENE. The Bright Future Of Parylene Coating For Wearable Medical Devices. [Online] VSI PARYLENE. Available at https://vsiparylene.com/resources/the-bright-future-of-parylene-coating-for-wearable-medical-devices/ (Accessed on 15 March 2024)
13. Yao, M., Wei, Z., Li, J., Guo, Z., Yan, Z., Sun, X., Yu, Q., Wu, X., Yu, C., Yao, F., Feng, S., Zhang, H., Li, J. (2022). Microgel-reinforced zwitterionic hydrogel coating for blood-contacting biomedical devices. Nature Communications. doi.org/10.1038/s41467-022-33081-7
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