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Understanding Interactions of Human Tissue with Medical Devices

Final Report Summary - UNITISS (Understanding Interactions of Human Tissue with Medical Devices)

The Scientific and technological vision of the UNITISS project was to meet the needs of today’s healthcare industry and social expectations in minimizing the invasiveness of catheter-based procedures, thus reducing clinical complications, patient discomfort and total healthcare costs. The main research objectives were to improve understanding of the mechanical interactions between catheters and blood vessels during minimally invasive catheterization procedures and how these interactions relate to the occurrence of clinical complications and patient trauma. Also, to develop catheter design strategies for improving the latter, and to develop in vitro test methods that avoid the need for in vivo animal testing. The UNITISS consortium comprised Philips as industrial partner, together with The University of Sheffield (UK) and The West Pomeranian University of Technology (Szczecin, PL).

Improved understanding of the mechanical interactions was achieved through a combination of tribological testing to induce damage, evaluating and applying various methods for assessing the tissue damage, mechanical testing, and modelling. In vitro test methods were developed that avoided in vivo human and animal testing. For most experiments, fresh ex vivo porcine aorta was used as the human tissue model for blood vessels and a test protocol was developed for damaging the blood vessel tissue in a controlled way using actual catheter tips. Methods were developed to assess the tissue damage using ATR-FTIR, second harmonic generation (SHG) imaging and two photon excitation fluorescence (TPEF), and histology. Good progress has also been made with the development of an artificially-diseased porcine tissue model [1].

Finite Element and Elasto-Hydrodynamic Lubrication models were developed to further understand the mechanical and tribological interaction between catheters and blood vessels, leading to valuable insights into optimum catheter tip design.
For experiments with skin friction, tissue-engineered skin based on human dermis, whilst showing a similar mechanical behaviour to human skin, was not found to provide the required tribological behaviour. Mild skin interactions were tested in vivo on human skin and a new synthetic artificial human skin model was developed that simulates the tribological and mechanical behavior of human skin in dry and moist environmental conditions [5].

The investigation of solution spaces for improving catheter design included concepts for controlling catheter stiffness, concepts for direction-sensitive pressure sensors to detect contact with, and pressure against, the vessel wall, and new hydrophilic catheter coatings incorporating both lubricity and anti-microbial functionality.

As of May 2016, nine papers from the UNITISS project have been published in scientific journals and further papers are currently under review. More than twenty-five oral and poster presentations have been given at various international conferences. Full up-to-date information is given on the UNITISS website:

The European Congress on Advanced Materials and Processes EUROMAT 2015 (Warsaw, Poland, 20-24 Sept. 2015, was used as a medium to present many of the UNITISS project results. Topic F3 within this congress, coordinated by UNITISS project fellows Steve Franklin and Jolanta Baranowska, comprised two symposia and included eighteen UNITISS-related oral and poster presentations. Three patent applications have been filed on catheter-related design improvements and a further three are currently pending.
Further information on the UNITISS project, consortium and dissemination can be found on the project website: Contact: Dr. Steve Franklin, Philips Research, High Tech Campus, 5656AE Eindhoven, The Netherlands.

[1] Christopher Noble, Nicole Smulders, Nicola H. Green, Roger Lewis, Matt J. Carre, Steve E. Franklin, Sheila MacNeil, Zeike A. Taylor “Creating a model of diseased artery damage and failure from healthy porcine aorta”, Journal of the Mechanical Behavior of Biomedical Materials 60 (2016) 378–393.
[2] Wojnowski J., Noble C., Mank A., Dellimore K., Franklin S.E. “Evaluation of porcine aorta damage using FTIR spectroscopy”, Poster presentation at European Congress on Advanced Materials and Processes EUROMAT 2015, Warsaw, Poland, 20-24 Sept. 2015.
[3] Maiti, R; Ling, Z; Gerhardt, L; Liu, X; Byers, R; Franklin, S.E.; Lewis, R; Matcher, S.J.; Carré, M.J. “Understanding the strain behaviour in the human finger-pad and forearm skin”, European Congress on Advanced Materials and Processes EUROMAT 2015, Warsaw, Poland, 20-24 Sept. 2015.
[4] X. Hu ; R. Maiti ; X. Liu ; L. C. Gerhardt ; Z. S. Lee ; R. Byers ; S. E. Franklin ; R. Lewis ; S. J. Matcher ; M. J. Carré “Skin surface and sub-surface strain and deformation imaging using optical coherence tomography and digital image correlation”, Proc. SPIE 9710, Optical Elastography and Tissue Biomechanics III, 971016 (March 9, 2016); doi:10.1117/12.2212361.
[5] Małgorzta Nachman; Steve Franklin “Artificial Skin Model simulating dry and moist in vivo human skin friction and deformation behaviour”, Tribology International, 97 (2016), 431–439, doi:10.1016/j.triboint.2016.01.043.
[6] Oliver Burke, Ferry van der Linde, Frank Hakkens, Steve Franklin “Feasibility Assessment of Concepts for a Controllable Stiffness Catheter”, European Congress on Advanced Materials and Processes EUROMAT 2015, Warsaw, Poland, 20-24 Sept. 2015.
[7] A. Niemczyk, M. El Fray, S.E. Franklin, "Friction Behaviour of Hydrophilic Lubricious Coatings for Medical Device Applications", Tribology International, DOI: 10.1016/j.triboint.2015.02.003.