Early Stage Researcher (PhD Year 1) Post-Doctoral Researcher/Senior Researcher/PI

Entry for the Engineers Ireland Biomedical Research Medal X Corresponding author has completed PhD and would

like to review BinI abstract submissionsPlease place an X in any appropriate categories

INTRODUCTION

Clean intermittent urinary self-catheterisation is the gold standard treatment for urinary retention. Users typically repeatedly catheterise, about 4 times per day, which can lead to urethral irritation, discomfort, bleeding, stricture, and reduced quality of life. Pre-lubricated intermittent catheters are coated with a hydrophilic coating to reduce the friction in the urethra. Despite their widespread use, there has been limited research into the effectiveness of these low friction coatings, particularly their effect on micro-trauma of the epithelium. Currently, the lubricity of the coatings is evaluated through a standard coefficient of friction (CoF) test. We aimed to create a more realistic CoF test by seeding a polydimethylsiloxane (PDMS) counter-surface with human urethral epithelial cells, which also permits investigation of epithelial micro-trauma in vitro. A 3D PDMS model of the urethra, based on a male cadaver, was created to investigate the role of catheter stiffness on friction. The PDMS model was seeded with epithelial cells to create a sensitive model to investigate the role of catheter eyelets on epithelial micro-trauma. Ex vivo porcine penis was also used as -a tissue model to investigate the role of the hydration fluids on the friction and epithelial micro-trauma.

MATERIALS AND METHODS

Three brands of intermittent urinary catheters were tested and compared across the different test methods (Cath A, B, and C). A custom-made PDMS cell culture dish was developed and seeded with human urethral epithelial cells. A bespoke CoF testing machine was also developed to accommodate the cell-seeded dish as a counter-surface, and this was compared to a typical rubber countersurface. A 3D model of the male urethra was isolated from the Visible Human Project dataset. This was used to form a 5 mm steel rod mandrel with the anatomical geometry of the urethra. PDMS was spin-coated onto the rotating mandrel to create thin-walled PDMS tubes with an accurate urethral geometry. The tubes were seeded with human urethral epithelial cells and catheterised with the eyelets facing either parallel or perpendicular to the sagittal plane.Porcine penises were collected from a local abattoir. Each penis was mounted into a test rig to replicate the tortuosity of the human male urethra The test rig consisted of a 3D-printed hand which gripped a catheter and inserted it into the urethra in a realistic manner, while measuring the friction force (Figure 1). The insertion friction force was compared to the extraction

friction force. The extraction friction force was measured after leaving the catheter in the urethra for either 2 or 10 minutes to replicate bladder drainage. Routine histology and scanning electron microscopy was performed on the urethral epithelium post-catheterisation.

RESULTS

Cath C experienced sticking to the rubber counter-surface but did not stick to the cell-seeded counter-surface, therefore provided a more realistic evaluation of lubricity. The 3D PDMS urethral model showed that stiffer catheters resulted in more friction, particularly when passing through the model sphincter, and the insertion friction was higher than the extraction friction. The porcine penis was characterised as a difficult catheterisation and therefore favoured stiffer catheters for insertion, in line with the experience of urology nurses. The extraction force was higher after 10 minutes in the urethra compared to 2 minutes for all catheters, the larger magnitude difference of Cath B suggests the hydration fluid may be drying in the urethra.

Figure 1 Image of catheter testing device. The device included a 3D-printed hand which gripped the catheter and allowed the measurement of both the insertion and extraction forces. The device catheterised either a PDMS urethral model (configuration shown) or porcine penis. Graph shows a higher extraction force after 10 minutes compared to 2 minutes

DISCUSSION

Our results suggest that manufacturers could develop catheters that do not dry out in the urethra; and, as stiffness can have an important effect on the friction, manufacturers could offer a range of stiffnesses for various user needs. These models can help manufacturers in the development of new catheter

Bioengineering in Ireland26, January 17-18, 2020

PHYSIOLOGICALLY REPRESENTATIVE URETHRAL MODELS FOR THE EVALUATION OF INTERMITTENT URINARY CATHETER LUBRICITY AND URETHRAL MICRO-TRAUMA

Humphreys, O.1,2, O’Cearbhaill, E.2, Flanagan, T.C.1,2

1 School of Medicine, University College Dublin, Dublin, Ireland.2 UCD Centre for Biomedical Engineering, University College Dublin, Dublin, Ireland.

Email: Owen.Humphreys@ucdconnect.ie

Early Stage Researcher (PhD Year 1) Post-Doctoral Researcher/Senior Researcher/PI

Entry for the Engineers Ireland Biomedical Research Medal X Corresponding author has completed PhD and would

like to review BinI abstract submissionsPlease place an X in any appropriate categories

designs, which can improve the quality of life of the users.

Bioengineering in Ireland26, January 17-18, 2020