Urinary catheters can be inserted intermittently to drain urine from the bladder when required or, alternatively, remain in place for up to three months. Especially when used intermittently, it is important to ensure good lubricity of the surface as repeated catheterization with poorly lubricated catheters can cause urethral bleeding, trauma, pain, and inflammation as a result of high frictional forces between the biomaterial surface and interfacing tissue.
History of the urinary catheters and hydrophilic coatings
The history of urinary catheter dates as far back as to the 5th century BC. Back then, the bronze catheters were used. Although not known at the time, bronze is antimicrobial which probably helped to make the procedure somewhat possible. It is unclear though if any lubricant was used although it is suspected that some oil must have been applied to help the procedure. Application of a lubricant, most typically a hydrophilic hydrogel such as hydroxyethylcellulose, is now a common practice. However, more modern urinary catheters have hydrophilic coatings applied on them to minimize the need of handling the catheter prior insertion which reduces the risk of infections.
Requirements for hydrophilic coatings
The requirements for the coatings are somewhat different depending on the application. For devices used in-vivo the regulatory pathways are strict which has a tendency to limit the selection of coating materials to well-tried and understood polymers with known biocompatibility.
One important requirement for the hydrophilic coating used is that the coating should stay lubricious throughout the procedure to ensure smooth transition through the urinary tract. In addition to increased lubricity, the coating can provide antimicrobial properties to prevent the urinary tract infections commonly associated with catheter use.
If you would like to read more about how to evaluate the hydrophilic coatings with contact angle measurements, please download a case study through the link below.
Wyman, P., "Hydrophilic coatings for biomedical applications in and ex vivo" in Coatings for Biomedical applications, Woodhead Publishing limited (2012) 3 - 42.