Hydrophilic medical device coatings help improve patient comfort and make devices more effective. They also help ensure that medical devices are safe to use in the body. Their main function is to absorb water and create a lubricious, low-friction surface, but custom hydrophilic coatings can be formulated to do a lot more. These coatings are not one size fits all. As a result, creating these coatings involves a lot of complex engineering. Hydrophilic coatings need to be specifically designed for different types of medical devices, such as flexible catheters, delicate neurovascular systems, long-lasting implants, and precision surgical tools. Each type of device has unique material, performance, and safety requirements that the coatings must meet.
This article explores how hydrophilic coatings can be custom formulated to meet the specific requirements of different medical devices. These include performance and regulatory requirements. At the end, we also explore new advancements that are shaping the future of medical technology. If you are a biomedical engineer or otherwise involved in developing medical devices you will not want to miss this article.
Related: Learn more about Hydrophilic Coatings for Medical Devices: Benefits & Uses.
1. Catheters and Guidewires: High Lubricity and Wear Resistance
What they are & how they are used
Catheters, guidewires, and introducers are essential tools used in multiple, minimally invasive procedures. They are widely used in medical fields like urology, cardiology, and interventional radiology. These devices need to move smoothly through a complex network of blood vessels or body structures with very little resistance.
Catheters and Guidewires Performance Requirements
- Enhanced lubricity to reduce insertion force and friction
- Abrasion resistance during repeated movement in body passages
- Biocompatibility to prevent adverse tissue reactions inside the body
- Durability for prolonged procedures and repeated use
Hydrophilic Coating Formulation Strategies for Catheters and Guidewires
Hydrophilic catheter coatings can be custom formulated to meet the requirements of the catheters. These coatings are typically applied via dip, spray, or in some cases meniscus coating. After coating, they are cured to ensure that the coating is properly adhered. Common materials used to formulate these coatings include crosslinked polymers like polyvinylpyrrolidone (PVP) or polyacrylamide. These polymers are great at holding water and have strong adhesion. Sometimes, multi-layer coating systems are employed, where a primer ensures bonding to the catheter substrate (often polyurethane, nylon, or Pebax), and the hydrophilic topcoat delivers surface lubricity and other properties. 1-3
Regulatory and Innovation Trends Around Catheters and Guidewires
Regulators like the FDA increasingly expect validated durability testing (e.g., lubricity after simulated use). Companies like Hydromer®, Inc. have responded by developing fast curing, highly durable, UV-curable hydrophilic coatings. These UV-cured coatings offer robust adhesion, rapid curing, and custom-tuned thickness for improved wear resistance without compromising flexibility. 4,5 Thermal cure systems are available as well.
2. Neurovascular Devices: Precision Meets Biocompatibility
What they are & how they are used
Neurovascular devices, such as microcatheters and embolization systems need to work in very sensitive environments. These devices operate in very delicate situations where both their size and performance need to be optimized.
Neurovascular Devices Performance Requirements
- Ultra-thin coatings for small vessels, arteries, or micro-lumen compatibility
- Precise control of lubricity to enable navigation in small, delicate vessels
- Minimal particulate generation to prevent embolic risks
- Excellent hemocompatibility to reduce thrombus formation
Hydrophilic Coating Formulation Strategies for Neurovascular Devices
Hydrophilic coatings for neurovascular devices require extremely thin and uniform layers. These coatings are often applied using precision spray techniques. To reduce thrombotic risk, anti-thrombogenic agents may be integrated into the coating. Hydromer’s anti-thrombogenic, hydrophilic coatings provide both surface lubrication and reduced platelet adhesion. This is critical to ensure biocompatibility and avoid clot formation. 6-8
Regulatory Considerations for Neurovascular Devices
Neurovascular devices are considered high-risk. They are classified as Class III in most regulations. Because of this, they must undergo and pass strict testing. This includes testing that checks for shedding of tiny particles during simulated use. This is to make sure that the coatings are strong and safe. Tests include those such as accelerated aging and simulated flow tests.
3. Implantable Devices: Long-Term Hydration and Biostability
What they are & how they are used
Implants like stents, orthopedic pins, and pacemaker leads need specialized hydrophilic coatings. These coatings must keep the implants moist and be able to last in the body for months or even years.
Implantable Devices Performance Requirements
- Long-term biostability without degradation or delamination
- Controlled drug elution, where applicable
- Resistance to immune response
Hydrophilic Coating Formulation Strategies for Implantable Devices
Hydrophilic implant coatings may use permanently hydrophilic polymers. Such coatings are sometimes combined with bioresorbable layers or drug reservoirs. These coatings are often applied using plasma treatments or grafting techniques to ensure chemical bonding to metal or polymer surfaces. For instance, a promising strategy to prevent restenosis is to introduce drug-eluting hydrophilic coatings. These advanced medical device coatings are applied to stents and balloons during coronary interventional procedures. This may reduce protein adhesion and smooth endothelialization. 9,10
In orthopedic devices, sustained hydration can prevent biofilm formation. This helps to aid in infection control. Surface modifications that combine hydrophilic properties with antimicrobial properties are a growing area of interest.11,12 Learn more about hydrophilic, antimicrobial coatings.
Regulatory Considerations For Implant Device Coatings
Implantable coatings must demonstrate exceptional long-term safety, including:
- Biostability data over the years.
- ISO 10993 biocompatibility panels.
- Sub-chronic and chronic toxicity assessments.
Hydromer’s expertise in hydrophilic chemistry has enabled the development of implant-safe coatings. They remain stable and functional over time without introducing harmful degradation products. Hydromer also offers antimicrobial coating solutions to safeguard from infections.12
4. Minimally Invasive Surgical Instruments: Balancing Grip, Safety, and Reusability
What they are & how they are used
Hydrophilic coatings have helped to significantly improve minimally invasive surgeries. These coatings help make surgical instruments work better, safer, and last longer. How? These coatings reduce friction. This helps lessen damage to tissues and leads to more precise surgeries and better outcomes for patients.
Performance Requirements for Minimally Invasive Surgical Equipment
- Low-friction interface between the body’s tissue and metal
- Enhanced visibility and functionality
- Compatibility with repeated sterilization cycles for durability and longevity
Hydrophilic Coating Formulation Strategies for Minimally Invasive Surgical Tools
For surgical instruments, hydrophilic coatings must resist degradation from autoclaving or chemical sterilization.
Some coatings can be designed to be hydrophilic only upon wetting. This helps to maintain instrument grip during dry handling while activating lubrication during use (when intended). 13,14
Hydromer’s custom formulated hydrophilic coatings address these dual demands by enabling multi-use applications with retained functionality. This is particularly valuable for cost-sensitive healthcare systems. Additionally, their thromboresistant and antimicrobial solutions make them brand leaders when it comes to safe and biocompatible coating solutions. 5,15,16
Utilize our contract R&D services in order to develop a custom formulation designed and tested to the specific requirements of your product.
The Role of Different Substrates in Custom Surface Treatments
Regardless of device class, the effectiveness of a hydrophilic coating depends on its interaction with the underlying substrate. Metals like stainless steel and nitinol require different primers or plasma treatments compared to polymers like polyimide or PTFE. Surface activation techniques such as corona discharge, plasma treatment, or silane coupling agents are frequently used to improve coating adhesion.17
Hydromer formulates substrate-specific coating systems that ensure consistent adhesion and performance across a wide range of materials. This allows manufacturers to scale coating processes across multiple product lines.15 Our custom formulated hydrophilic coatings range from one-step coatings to multi-step systems.
Future Directions and Material Innovations
Medical devices are becoming more advanced, smarter, smaller, and more integrated with digital health systems. As these innovations are happening hydrophilic coatings also need to advance in order to support them. Innovative, smart coatings are being developed with advanced, multi-functionality, such as:
- Stimuli-responsive coatings that change behavior with things such as pH or temperature
- Bioactive hydrophilic layers that deliver antibiotics, growth factors, or anti-inflammatory agents
- Combination coatings that merge hydrophilic and hydrophobic domains for tunable surface behavior
- And more.
Coating manufacturers, such as Hydromer, are developing custom formulated hydrophilic coatings to meet these ever-changing, complex requirements.
Conclusion
Hydrophilic coatings are important for medical devices like catheters, neurovascular tools, implants, surgical instruments, and more. They do more than just coat the surface. They help these devices work better, keep patients safe, and ensure successful treatments and better patient outcomes.
There are no shortage of coatings in the industry. But each type of device needs a customized approach to how the coating is made, applied, and tested. Each coating needs to be custom formulated to meet the specific requirements of the device.
Companies such as Hydromer are meeting these needs by providing custom coating solutions. These coatings are designed to meet the strict regulations and healthcare performance requirements. As devices become more complex and regulations become stricter hydrophilic coatings will also need to advance. This means creating interfaces that are smarter, safer, and more adaptable for use in different parts of the body. Hydromer is here to help you meet your project and regulatory requirements.
Contact our coating experts now with questions or to start your project.
References
Click to view references for this article.
1. La Porte RJ. Hydrophilic polymer coatings in the development and manufacture of medical devices. University of Massachusetts Lowell; 1996.
2. Jang H, Choi H, Jeong H, et al. Thermally crosslinked biocompatible hydrophilic polyvinylpyrrolidone coatings on polypropylene with enhanced mechanical and adhesion properties. Macromolecular Research. 2018;26(2):151-156.
3. Chang PP, Hansen NA, Phoenix RD, Schneid TR. The effects of primers and surface bonding characteristics on the adhesion of polyurethane to two commonly used silicone elastomers. Journal of Prosthodontics: Implant, Esthetic and Reconstructive Dentistry. 2009;18(1):23-31.
4. Hydromer. UV Curing for Medical Devices: Role of PEG, PVP, Chitosan. Hydromer. https://hydromer.com/uv-curing-for-medical-devices-role-of-peg-pvp-chitosan/#:~:text=Materials%20like%20PEG%2C%20PVP%2C%20and,%2C%20and%20drug%2Dreleasing%20stents.
5. Hydromer. HydrUV™: Revolutionizing UV Medical Device Coatings. https://hydromer.com/hydruv-revolutionizing-uv-medical-device-coatings/
6. Zoppo CT, Mocco J, Manning NW, Bogdanov AA, Gounis MJ. Surface modification of neurovascular stents: from bench to patient. Journal of NeuroInterventional Surgery. 2024;16(9):908-913.
7. Henkes H, Bhogal P, Aguilar Pérez M, et al. Anti-thrombogenic coatings for devices in neurointerventional surgery: case report and review of the literature. Interventional Neuroradiology. 2019;25(6):619-627.
8. Hydromer. Hydromer Announces Launch of HydroThrombX Medical Device Coating Technology. https://hydromer.com/hydromer-announces-launch-of-hydrothrombx-medical-device-coating-technology/
9. Meng S, Liu Z, Shen L, et al. The effect of a layer-by-layer chitosan–heparin coating on the endothelialization and coagulation properties of a coronary stent system. Biomaterials. 2009;30(12):2276-2283.
10. Zhang K, Liu T, Li JA, Chen JY, Wang J, Huang N. Surface modification of implanted cardiovascular metal stents: from antithrombosis and antirestenosis to endothelialization. Journal of Biomedical Materials Research Part A: An Official Journal of The Society for Biomaterials, The Japanese Society for Biomaterials, and The Australian Society for Biomaterials and the Korean Society for Biomaterials. 2014;102(2):588-609.
11. Rodríguez-Merchán EC, Davidson DJ, Liddle AD. Recent strategies to combat infections from biofilm-forming bacteria on orthopaedic implants. International journal of molecular sciences. 2021;22(19):10243.
12. Hydromer. Candida A Study For CarvaTech® Antimicrobial Formulation. https://hydromer.com/wp-content/uploads/2023/07/Candida-A-Research-Study-OL.pdf
13. Kumar S, Bhushan P, Bhattacharya S. Coatings on Surgical Tools and How to Promote Adhesion of Bio‐Friendly Coatings on Their Surfaces. Adhesion in Pharmaceutical, Biomedical and Dental Fields. 2017:207-233.
14. Pokki J, Parmar J, Ergeneman O, et al. Mobility-enhancing coatings for vitreoretinal surgical devices: hydrophilic and enzymatic coatings investigated by microrheology. ACS applied materials & interfaces. 2015;7(39):22018-22028.
15. Hydromer. Medical Device Coatings. Hydromer. https://hydromer.com/medical-device-coatings/
16. Hydromer. Breakthroughs in Hydrophilic Coating Technology. https://hydromer.com/sb/breakthroughs-in-hydrophilic-coating-technology/#:~:text=Hydrophilic%20coating%20is%20a%20technology,reduced%20friction%2C%20and%20enhanced%20efficiency.
17. Hydromer. Hydrophilic Coatings For Medical Device Substrates. https://hydromer.com/hydrophilic-coatings-for-medical-device-substrates/
