“Smart catheters” Sense the Start of an Infection

A novel catheter grapples with the problem of catheter-related blood and urinary tract infections by automatically releasing an antibacterial substance.

Researchers at the University of Michigan (Ann Arbor, MI, USA) have developed an electromodulated “smart catheter” that works by chemically sensing changes in the acid-base environment (pH) around the catheter. Certain pH changes signal the critical point when bacteria have formed a sticky biofilm on the catheter, and their numbers have increased to the point where a health-jeopardizing infection begins. At that point, the catheter releases nitrous oxide (NO), which disrupts the bacterial films and stops the forming infection. It then switches itself off, preserving its reserves of NO-generating material.


The method used to generate and modulate the release of NO is electrochemical generation by the reduction of nitrite ions by Cu(I) ions generated anodically at the surface of a copper electrode, and subsequent cleaning of the rapidly passivated electrode surface by applying a cathodic voltage pulse. The nitrite solution and the electrodes are separated from the external surroundings by the wall of a narrow bore silicone-rubber tube that keeps the internal solution inside, while allowing the NO gas to permeate.

Laboratory tests have shown that the NO releasing catheter tubing possesses antibiofilm formation properties for a period of two to seven days, and the researchers believe this can be extended to weeks. The study presenting the preliminary work, design, and tests of the “smart catheter” was presented at the 244th National Meeting & Exposition of the American Chemical Society (ACS), held during August 2012 in Philadelphia (PA, USA).

“About 1.5 million healthcare-associated infections are reported in the United States alone each year, resulting in 99,000 deaths and up to USD 45 billion in extra health care costs,” said lead author and study presenter Dipankar Koley, PhD. “Urinary tract infections, as one example, are the most common source of institutionally acquired infections in both acute care hospitals and long-term care facilities. Our smart catheter is being developed in response to that need.”

Nitric oxide is known to have several important physiological functions such as vasodilation, platelet adsorption, and activation inhibition, and as a mediator in antimicrobial activities. It is also a highly potent and natural bactericidal agent, and can be generated at physiologically relevant levels from inorganic sodium nitrite salt.

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