1 Polyethylene glycol applied to latex urinary catheters Brett Mulawka, Darshan Patel, Benjamin Roedl, Patrick Schenk May 9, 2007 Abstract Urinary catheterization occurs widespread in the United States with one quarter of all hospital patients experiencing it. Catheter problems include blockage, leakage, and infections and are predominately caused by proteins that adhere to the catheter surface and quickly build up on each other forming a protein layer. Current strategies to avoid these problems include coating a catheter with silver alloy to reduce bacteria on the catheter surface. An alternative solution is presented involving coating latex, a common urinary catheter material, with a microlayer (5-100 microns) of polyethylene glycol. This hydrogel is applied using an interfacial photopolymerizatoin process with ethyl eosin as the photoinitiator. A 25 PPM concentration of ethyl eosin provided the strongest gel to surface adhesion and significantly lowered protein adhesion when compared to an uncoated latex substrate. Keywords: Hydrogel; Polyethylene glycol; Catheter; Urinary tract infection; Interfacial photopolymerization; Latex; Ethyl eosin 1. Introduction A urinary catheter is a medical device inserted into the body and used to collect urine from the bladder. Typically a urinary catheter is a tube made of a soft, flexible material such as silicon, latex, or Teflon. This tube removes the urine from an individual and is used under a variety of conditions. Catheters are most often used to help with urinary incontinence and retention [1]. Urinary catheterization occurs widespread in the United States with one quarter of all hospital patients experiencing it [2]. Currently, patients using catheters for multiple days often encounter problems involving catheter blockage, leakage, and infection. These problems are a direct result of protein and bacteria adhering to the surface of the catheter. Once on the catheter surface, the bacteria can cause infection and the protein crystallizes to form obstructions. The obstructions cause discomfort, and usually result in an ineffective catheter which needs replacement [3]. The problems of long term catheter use are common and affect a large amount of users, cause extra time and effort for hospitals, and require the frequent replacing of catheters. Blockage is prevalent in half of all long term catheter users [3]. Patients using obstructed catheters can experience pain and trauma which require extra attention in a medical setting. Every time a catheter leaks, becomes blocked, or causes an infection it has to be removed, discarded, and replaced. By limiting these problems, fewer catheters need to be purchased and money can be saved by both home users and medical facilities. The healthcare industry spends an extra 1.8 billion dollars a year due to urinary tract infections that are directly related to catheter use [4]. As many as 62,000 people die from catheter related urinary tract infections each year, costing another 6.25 billion dollars [4]. The catheter that can solve these issues has the potential to help patients and reduce healthcare costs. The aforementioned problems of leakage, blockage, and infection are caused by proteins that adhere to the catheter surface and quickly build up on each other forming a protein layer called a biofilm [5]. Bacteria from the urine and surrounding tissue can then easily colonize on2 the biofilm along with other particles and microorganisms that exist in the urinary tract. As the layers build up they can crystallize, providing the major source of blockage and leakage. A non-magnified view of a catheter that has become encrusted by a crystallized biofilm can be seen in Figure 1 [3]. Fig. 1. A catheter that has undergone encrustation. Once an initial layer of abundant adsorbed proteins forms on an implant the Vroman Effect follows. This phenomenon explains that subsequent layers of proteins replace other proteins while at the same time increasing the layers. This is an affinity and concentration dependent process in which the protein present in the largest amount has a greater affinity to adsorb than proteins with smaller concentrations [5]. The different proteins that adsorb onto implantable devices vary based on what proteins and phagocytes are present, along with the properties of the implantable device. Texture, charge, and material composition all contribute to which molecules adsorb and influences the interactions between the subsequent protein and bacteria that builds up on a surface [6]. Once the bacteria start to multiply, preventative measures, such as removing the catheter or washing out the area, are necessary to prevent infections. Figure 2 shows an example of a urinary catheter under a high powered microscope with common minerals struvite and calcium phosphate crystallized on its surface [3]. Fig. 2. Electron micrograph of calcium phosphate and struvite crystallized on the surface of a catheter. Because of the widespread problems associated with catheter use, several procedures and products have been created in an attempt to limit the negative effects. Doctors try to identify patients who are prone to catheter problems and develop a strategy of avoidance [3]. Catheter3 maintenance is often performed by cleaning the catheter with a wash out fluid [3]. This is done when frequent recatheterization is causing discomfort or getting too expensive, but the acidic fluid can irritate the lining of the bladder [3]. Physical modification of urinary catheters has also taken place in the form of a silver coating. Silver-coated urinary catheters showed a 57% percent decrease in urinary tract infections over non coated catheters [2]. However, silver alloy coatings can lead to increased silver resistance for bacteria. Because silver is already used as an antibacterial agent in many places in a hospital, it is even more possible that resistance can develop [2]. Coating catheters with a microlayer of PEG hydrogel could reduce catheter problems without irritating the patient, or requiring the high costs of silver coatings. The problems of obstruction, leakage, discomfort, infection, and replacement can be reduced by limiting the protein that adsorbs to the surface of a catheter. Doing this will decrease the probability of a biofilm and protein crystallization. Removing this bacteria prone environment could decrease infections. Additionally, if an
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