Free-flowing urine through “non-blocking” urinary catheters

The main aim of this thesis was to develop a standardised methodology for growth of struvite crystals, commonly present in CAUTIs, to facilitate further investigation of the molecular mechanism, and potential inhibition, of crystal nucleation. The quantification of the anisotropic kinetics of struvite crystallisation over a broad range of conditions was performed. Subsequently, the molecular mechanism of crystal growth was resolved, showing that layers on crystal surfaces advance from either screw dislocations or 2-dimensional generation and spreading of islands, demonstrating a classical pathway of growth.Additionally, the crystal modifying and antimicrobial effects of weak organic acids were assessed against struviteand the common uropathogens Proteus mirabilis and Staphylococcus aureus, respectively.

Adipic acid, citric acid and hydroxycitric acid displayed the most promising crystal growth modifying effects, thus their antimicrobial activities were investigated. All acids exhibited inhibitory and biocidal activities against both bacteria, therefore they could be used for the development of catheter hydrogel coatings, which would be resistant to infections, as well as would exhibit crystal growth modifying properties.Furthermore, the antibiofouling properties of oxygen plasma treatment on silicone rubber, a common material used in the manufacture of urinary catheters, was studied at three different times of treatment (60, 90 and 120 seconds).

However, the treatment conditions employed were not an efficient strategy for preventing bacterial adherence and encrustation.The final strand of work was focused on the development of a novel infection-detection system for CAUTIs at an early-stage. The system investigated herein, was based on the generation of hydrogen peroxide by xanthine oxidase. Elevated xanthine oxidase levels have been reported in presence of bacteria in the urinary tract.

Three colorimertric assays, Amplex Red hydrogen peroxide/horseradish peroxidase, p-Nitrophenylboronic acid and ferrous oxidation-xylenol orange, were investigated for their potential to be incorporated into the infection-detection system. The application of these methods was concluded to not be suitable, hence an alternative colorimetric method should be investigated in the future.<br><i><br>Thesis is embargoed until 31 December 2029.</i>