The growing importance of surface coatings engineering in today’s world of medical devices cannot be denied. A medical device’s surface has a significant impact on its safety, patient comfort, performance, and the long-term clinical success of the device. Catheters and stents illustrate this very clearly, since both of these medical devices come in direct contact with sensitive tissues, blood vessels, and body fluids. Both hydrophilic and hydrophobic coatings are used for catheters and stents by most medical device OEMs. Findings from many studies highlight that the use of hydrophilic coatings for catheters and stents are the best choice.
Hydrophilic coatings create a water-loving, lubricious surface. This provides a dramatic reduction in surface friction. This low-friction, lubricious surface helps reduce trauma to the patient, increasing patient comfort. It also provides an increase in performance of the device, allowing for easier insertion and navigation through tortuous pathways.
A hydrophobic coating, on the other hand, is designed to resist (repel) water. This type of coating is best used as a means to provide an external layer of protection against moisture. Hydrophobic coatings are not designed to meet the functional and biological needs of catheter and stent applications.
This article provides a data-backed explanation of why hydrophilic coatings are the better fit vs hydrophobic coatings for catheters and stents.
8 Reasons Why Hydrophilic Coatings Are a Better Choice For Catheters and Stents (vs Hydrophobic)
Choosing the right type of surface coating for catheters and stents is critical to patient safety and product success. These devices need to navigate sensitive and tortuous pathways in the body. Examples include the urinary tract or the vascular system. They need a biocompatible coating that minimizes friction.
Hydrophilic and hydrophobic coatings are the two most common coatings for catheters and stents.
Hydrophobic coatings create water-repelling surfaces. They do offer some friction reduction, but not close to that of hydrophilic coatings. In turn, they often need lubricants.
Hydrophilic coatings are water-loving. They form a slippery, biocompatible surface when in contact with bodily fluids. As a result, they offer several advantages over hydrophobic coatings.
Below we provide 8 reasons why hydrophilic coatings are a better choice for catheters and stents.
1. Superior Lubricity for Easily Insertion and Navigation
Catheters and stents need to pass through delicate and narrow pathways. Such pathways include the urethra, vascular system, biliary duct system, and neurovascular channels. The key benefit of hydrophilic coatings is that they attract and retain moisture by forming a hydrated, gel-like layer around the device. These lubricious coatings drastically reduces device friction when inserting and removing catheters and/or stents.1
Why This Matters:
- Less Pain: Easier insertion means less pain and discomfort.
- Safer for Tissues / Reduced Trauma: Reduces the risk of tiny injuries, bleeding, and swelling.
- Better Control: Helps doctors guide the tools more easily, even in complex pathways.
Compared to Hydrophobic Coatings:
On the other hand, hydrophobic coatings, even if they are polished or silicon-based, cannot offer the same level of lubricity as hydrophilic coatings. This is because they do not employ the same hydration mechanism to develop a low-friction interface. In turn, these coatings may repel moisture; however, they do not produce a lubrication layer mediated by water.
2. Reduced Tissue Trauma and Complication Rates
When placing a catheter or stent, the friction created can affect the risk of complications. A hydrophilic coating, which attracts water, forms a low friction, biocompatible layer that helps protect tissues from damage.1,2
Benefits of hydrophilic coatings:
- Less tearing of tissue during urinary catheterization
- Lower risk of damage to blood vessels
- Reduced chance of blood vessel spasms during stent or catheter placement
- Lower pain scores as reported by patients.
These benefits are particularly important for long or difficult procedures, repeated catheterizations, and complex placements like those in the brain or heart.
Compared to Hydrophobic Coatings:
Alternatively, hydrophobic coatings may increase surface drag on catheter devices and stent devices under real physiologic conditions. This is especially true where the fluid composition is not constant (blood, lymph, urine, contrast). Increasing surface drag increases the force required to advance the device. This can result in increased trauma and increased risk for subsequent complications.
3. Enhanced Biocompatibility and Hemocompatibility
Hydrophilic coated surfaces are advantageous for devices that contact body fluids. These surfaces produce a hydrated layer when in contact with bodily fluids. This layer decreases both protein absorption and the likelihood of platelet activation. This helps to reduce thrombogenic and inflammatory responses.3,4
Benefits of hydrophilic coatings:
- Less protein buildup, which means less friction and better long-term performance of the devices.
- Fewer platelets sticking to surfaces reduces the risk of blood clots during procedures like inserting catheters.
- Lower risk of inflammation, which is important for devices like stents and permanent catheters.
Compared to Hydrophobic Coatings:
Unlike hydrophilic surfaces, hydrophobic surfaces do not have a biologically “invisible” hydrated layer that separates cells from the surface. In turn, they tend to attract proteins to their surface and develop Biofilms quickly. This increases the risk of complications, such as thrombosis, encrustation, infection, etc.
4. Better Performance in Wet, Dynamic Environments
Catheters and stents are used in the presence of biological fluids, such as blood and urine. Hydrophilic coatings are “slippery-when-wet”, which makes them a great fit for these these environments.4,5
In other words, hydrophilic coatings work better in these conditions. They become slippery and swell when exposed to fluids, making them ideal for catheters and stents.
Compared to Hydrophobic Coatings:
On the other hand, hydrophobic coatings have disadvantages in wet, dynamic environments. These include:
- Lose slipperiness in water.
- Require extra lubricants that wash away quickly.
- Their water-repellent nature can make them unstable in flowing fluids.
- Attract proteins and fats, which can reduce their effectiveness in these applications.
5. Improved Patient Comfort and Experience
Comfort isn’t just an advantage; it’s a sign of a good clinical outcome.1,4
Catheters with a hydrophilic coating often improve patient comfort and experience.
Benefits of hydrophilic coatings:
- Less pain when inserting and removing
- Reduced burning and/or irritation
- Less anxiety for patients needing frequent catheter use
- Lower risk of injury to the urethra, etc.
Compared to Hydrophobic Coatings:
There is evidence from both patient surveys and clinical assessments in this area. Studies demonstrate that patients catheterized with hydrophilic catheters experienced greater comfort than those catheterized with a hydrophobic coating. This has led to increased patient compliance, decreased emergency department visits, and better overall quality of life.
In addition, hydrophobic-coated catheters usually require an external lubricant applied. However, this lubricant can wear out at an unequal rate. This can create additional discomfort and trauma for the patient. It can also increase their risk of injury due to friction against their skin.
6. Reduced Risk of Infection and Encrustation
Hydrophilic coatings make surfaces slippery and reduces stickiness by attracting water and forming a hydration layer.6 This helps prevent the buildup of:
- Biofilms
- Mineral deposits
- Crystalline layers
- Protein or mucus
- Other fouling
This is especially useful for urinary and vascular catheters. This is because it helps stop infections and failures.
Hydrophilic coatings can also be formulated to serve as antimicrobial coatings and/or have antimicrobial properties.
Compared to Hydrophobic Coatings:
On the other hand, hydrophobic coatings repel water. They can accidentally trap biological materials, which might lead to bacteria sticking or blood clots.
7. Predictable and Controlled Deployment of Stents
Stents need to be placed very precisely. Hydrophilic coatings help with the deployment of stents by:
- Making it easier to crimp and expand balloon stents
- Reducing friction between the stent and the catheter
- Ensuring the stent comes out of the sheath smoothly
- Lowering the risk of the stent bending, moving, or getting stuck
Compared to Hydrophobic Coatings:
On the other hand, hydrophobic coatings can cause uneven release. This is because they lack a water-based lubrication layer. This can affect how accurately stents are placed, especially in complex heart or artery areas.
8. Compatibility with Modern Polymer Substrates 7,8
Most catheters and stent delivery systems use thermoplastics. These include:
- Nylon
- PEBAX
- Polyurethane
- Polyethylene
- Silicone-based blends
Hydrophilic coatings stick really well to surfaces using special primers or chemical bonds.
Compared to Hydrophobic Coatings:
On the other hand, hydrophobic coatings, like those with fluorine or silicone, can have trouble sticking and might come off when stressed.
Hydromer®: A Proven Leader in Hydrophilic Coating Solutions
Hydromer®, Inc is one of the longest-standing hydrophilic coatings manufacturers. We have 40+ years of experience in the fields of coatings formulation and polymeric chemistry. Our company offers a full-line of ultra-low-friction, biocompatible, and durability-enhanced hydrophilic coatings specifically developed for catheters, guidewires, introducers, and stent delivery systems.
Hydromer’s advanced hydrophilic medical coatings deliver:
- High degree of long-lasting hydration
- Strong substrate adhesion
- Exceptional wear resistance to flexing, bending, folding, and deployment
Hydromer’s team of coating, R&D, and application experts has the capabilities to aid Catheter and Stent OEMs in developing their next generation of medical devices.8,9
Conclusion: Hydrophilic Coatings Are A Clear Choice for Catheters and Stents
Hydrophilic coatings consistently outperform hydrophobic coatings for catheters and stents. This is especially true when it comes to mechanical, biological, and patient-centered dimensions. They provide unmatched lubricity, biocompatibility, hydration-driven performance, and predictable deployment characteristics. As a result, they align perfectly with the needs of modern medical devices, including catheters and stents.
Hydrophobic coatings remain a useful solution for outer-barrier functions or as protective layers. However, they simply cannot match the clinical performance demands of intraluminal devices.
Hydromer, Inc., a leader in hydrophilic medical coatings, provides advanced, customizable hydrophilic coatings as well as a range of coating services. As a result, device manufacturers have access to the technology and expertise need to deliver safer, more comfortable, and more reliable catheter and stent systems.
Contact the Hydromer coating experts today with questions or to start your coatings project.
References:
Click to see references for this article:
1. Plata M, Santander J, Zuluaga L, et al. Hydrophilic versus non-hydrophilic catheters for clean intermittent catheterization: a meta-analysis to determine their capacity in reducing urinary tract infections. World Journal of Urology. 2023/02/01 2023;41(2):491-499. doi:10.1007/s00345-022-04235-5
2. Burns J, Pollard D, Ali A, McCoy CP, Carson L, Wylie MP. Comparing an Integrated Amphiphilic Surfactant to Traditional Hydrophilic Coatings for the Reduction of Catheter-Associated Urethral Microtrauma. ACS Omega. 2024/05/21 2024;9(20):22410-22422. doi:10.1021/acsomega.4c02109
3. Obiweluozor FO, Tiwari AP, Lee JH, et al. Thromboresistant semi-IPN hydrogel coating: towards improvement of the hemocompatibility/biocompatibility of metallic stent implants. Materials Science and Engineering: C. 2019;99:1274-1288.
4. Ali S, Khan OS, Youssef AM, Saba I, Alfedaih D. Hydrophilic catheters for intermittent catheterization and occurrence of urinary tract infections. A retrospective comparative study in patients with spinal cord Injury. BMC urology. 2024/06/12 2024;24(1):122. doi:10.1186/s12894-024-01510-y
5. Li K, Tang H, Peng J, et al. Smart lubricant coating with urease‐responsive antibacterial functions for ureteral stents to inhibit infectious encrustation. Advanced Functional Materials. 2024;34(2):2307760.
6. Barken KB, Vaabengaard R. A scoping review on the impact of hydrophilic versus non-hydrophilic intermittent catheters on UTI, QoL, satisfaction, preference, and other outcomes in neurogenic and non-neurogenic patients suffering from urinary retention. BMC urology. Sep 19 2022;22(1):153. doi:10.1186/s12894-022-01102-8
7. Hydromer. Hydrophilic Coatings: What They Are and Common Uses. https://hydromer.com/hydrophilic-coatings-comprehensive-guide/
8. Hydromer. Hydrophilic Coatings For Medical Device Substrates. https://hydromer.com/hydrophilic-coatings-for-medical-device-substrates/
9. Hydromer. Breakthroughs in Hydrophilic Coating Technology. https://hydromer.com/sb/breakthroughs-in-hydrophilic-coating-technology/
