Light-activated antimicrobial polymers for the prevention of catheter-associated infections

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Patients in hospital are often too ill to be given drugs by mouth or by injection and these have to be administered through a fine tube connected directly to a vein or artery. Also, they are often unable to urinate and so need a tube inserted directly into their bladder so that urine can drain through this into a collecting bag. Such tubes are known as catheters and are very widely used by hospitalised patients. One of the main problems with catheters is that microbes (usually from the patient's skin) inevitably stick to their surfaces where they grow to form a structure (known as a biofilm) consisting of millions of bacteria surrounded by a jelly-like material. Inside these biofilms, the microbes are protected from the body's defence systems as well as from antibiotics. Therefore, once biofilms have formed on a catheter they are very difficult to remove and they eventually cause an infection which can kill the patient. To prevent the patient dying from such an infection, the catheter often has to be removed and a new one inserted which is very unpleasant for the patient and time-consuming for medical staff. In this project we intend developing a new way of preventing such infections - this will be based on the use of light-activated antimicrobial agents (also known as photosensitisers). A photosensitiser is a chemical that has no effect on microbes in ordinary light but is 'activated' by light of a certain wavelength - this is usually provided by a small laser. The activated photosensitiser produces substances that can kill any microbes present. We intend adding a photosensitiser to the material used to make catheters and carrying out experiments to find out whether this material, when illuminated with laser light, can either stop microbes sticking to it or else actually kill them. Once we have found out the best concentration of photosensitiser to use and how much light is necessary, we will then carry out more complicated experiments in which we will use laboratory models of catheters. If our light-activated material can prevent microbes adhering or can kill them in laboratory models, then they are likely to be effective also in patients. The light source used to activate the photosensitiser would be a low-power laser similar to the laser pointers used by teachers and lecturers so making it convenient to use - it could easily be carried around by patients who are able to walk. Light from the laser would pass through optical fibres which would be connected to the catheter. We think that this approach using light-activated antimicrobial agents is an exciting, novel way of preventing infections associated with catheters and will be of great benefit to patients.