| Summary: |
More than 30 million urinary catheters are inserted per year in the US and over 1.5 million ureteral stents are inserted worldwide. Urinary tract infection is one of the most common
hospital-acquired infections in the US (more than 560000 cases yearly and 13000 attributable deaths) and 75% of cases are catheter-associated urinary tract infections with a cost
of $451 million per year. About 80% of ureteral stents suffer from failure, causing severe pain and many require surgical intervention.
Urinary catheters and stents suffer from two distinct problems: Biofilm formation and encrustation. Escherichia coli is the most common pathogen infecting these devices, while
Proteus mirabilis is responsible for encrustation. Biofilm formation in catheters and stents is difficult to manage with antibiotics because the biofilm environment protects bacterial
cells from chemical treatment. One of the most promising strategies to improve catheter and stent performance is to develop coatings that prevent bacterial adhesion or have a
contact-killing mechanism, as release systems may contribute to the development of antimicrobial resistance.
Carbon nanotubes (CNTs) have been used to reduce bacterial adhesion and biofilm formation in industrial and environmental applications, but their perceived toxicity has prevented
their widespread use in biomedical devices. It has been shown that functionalization of CNTs decreases their cytotoxicity and incorporation into polymeric matrices further decreases
toxicity in both human and animal cells. We have previously shown that using small amounts (0.1% loading) of pristine CNTs in PDMS composites can reduce E. coli adhesion in the
hydrodynamic conditions found in urinary catheters. On that paper, we have also shown that CNTs were not exposed at the surface of the composite, which may contribute to
reduced cytotoxicity. However, biofilm formation studies were not performed at the time.
This project will test several CNT functionaliz  |
Summary
More than 30 million urinary catheters are inserted per year in the US and over 1.5 million ureteral stents are inserted worldwide. Urinary tract infection is one of the most common
hospital-acquired infections in the US (more than 560000 cases yearly and 13000 attributable deaths) and 75% of cases are catheter-associated urinary tract infections with a cost
of $451 million per year. About 80% of ureteral stents suffer from failure, causing severe pain and many require surgical intervention.
Urinary catheters and stents suffer from two distinct problems: Biofilm formation and encrustation. Escherichia coli is the most common pathogen infecting these devices, while
Proteus mirabilis is responsible for encrustation. Biofilm formation in catheters and stents is difficult to manage with antibiotics because the biofilm environment protects bacterial
cells from chemical treatment. One of the most promising strategies to improve catheter and stent performance is to develop coatings that prevent bacterial adhesion or have a
contact-killing mechanism, as release systems may contribute to the development of antimicrobial resistance.
Carbon nanotubes (CNTs) have been used to reduce bacterial adhesion and biofilm formation in industrial and environmental applications, but their perceived toxicity has prevented
their widespread use in biomedical devices. It has been shown that functionalization of CNTs decreases their cytotoxicity and incorporation into polymeric matrices further decreases
toxicity in both human and animal cells. We have previously shown that using small amounts (0.1% loading) of pristine CNTs in PDMS composites can reduce E. coli adhesion in the
hydrodynamic conditions found in urinary catheters. On that paper, we have also shown that CNTs were not exposed at the surface of the composite, which may contribute to
reduced cytotoxicity. However, biofilm formation studies were not performed at the time.
This project will test several CNT functionalizations, including acid oxidation, nitrogen doping, and metal impregnation. The functional groups responsible for the strongest
antimicrobial activity will be identified by performing thermal treatments that selectively eliminate some of the groups introduced during functionalization. This information will
enable the creation of multifunctional composites with the most active groups that will be tested in biofilm assays using a clinical isolate of E. coli in flow systems validated by
Computational Fluid Dynamics to mimic the hydrodynamics found in urinary catheters and stents. This is crucial since most of the published work concerning the antimicrobial
activity of CNTs has been made using cells and CNTs in suspension or biofilm testing of CNT coated surfaces in static conditions. It has been demonstrated that suspension assays do
not mimic the antimicrobial activity necessary to eradicate a biofilm and we have shown that the effect of surface properties is modulated by shear stress indicating that results
obtained in static conditions may not be applicable to devices operating under fluid flow such as catheters and stents. After an exhaustive characterization of the functionalized CNTs
and the composites with the highest antibiofilm activity, the composites will be tested during biofilm formation with single and dual-species biofilms of E. coli and P. mirabilis. Biofilm
cells will be probed for CNT induced functional changes (like membrane integrity and polarization changes, metabolic alterations and production of reactive oxygen species) so that
the mechanism of action of the CNTs with different functional groups can be unraveled using also the information obtained from the surface analysis. The best performing composites
will be tested for cytotoxicity, and at the end of the project, the best composites will be identified for in vivo testing.
The success of this project relies on the complementary skills of the research team. The PI and Co-PI of the project, Filipe Mergulhão and Luciana Gomes (respectively) from LEPABE,
are experts in bacterial adhesion and biofilms, particularly in the areas of surface development and testing under controlled hydrodynamics. Fernando Pereira and Olívia Soares from
LSRE/LCM are experts in carbon materials, particularly in CNTs and their chemical modification. Dr. Federico Soria is a medical doctor, researcher and inventor of ureteral stents. He will provide consultancy to the project advising the team towards the selection of the most promising candidates for in vivo testing that can be performed under his guidance at a later stage. Given his expertise in this area, he will also help the team to find industrial partners for the commercial exploitation of the results from this project. |
| Results: |
Dados os resultados modestos que form obtidos com a oxidação dos CNTs com ácido nítrico e sulfúrico, foi elaborado um plano de contingência para que diferentes abordagens pudessem ser testadas de forma independente e combinadas com a incorporação de CNTs na matriz polimérica em uma etapa posterior. Entre essas estratégias, a combinação de compósitos MWCNT/PDMS com probióticos ou quitosano demonstrou resultados promissores na inibição da formação de biofilmes de uropatogênicos. As restantes funcionalizações pevistas estão a ser implementadas.
Foram obtidas as seguintes publicações:
• Sousa-Cardoso, F.; Teixeira-Santos, R.; Campos, A.F.; Lima, M.; Gomes, L.C.; Soares, O.S.G.P.; Mergulhão, F.J. Graphene-Based Coating to Mitigate Biofilm Development in Marine Environments. Nanomaterials, 13, 381, 2023, doi:10.3390/nano13030381
• Gomes, M.; Gomes, L. C.; Teixeira-Santos, L.; Pereira, M. F. R.; Soares, O. S. G. P.; Mergulhão, F. J., Carbon nanotube-based surfaces: Effect on the inhibition of single- and dual-species biofilms of Escherichia coli and Enterococcus faecalis. Results in Surfaces and Interfaces, 9, 100090, 2022, doi: 10.1016/j.rsurfi.2022.100090
• Romeu, M. J.; Gomes, L. C.; Sousa-Cardoso, F.; Morais, J.; Vasconcelos, V.; Whitehead, K. A.; Pereira, M. F. R.; Soares, O. S. G. P.; Mergulhão, F. J., How do Graphene Composite Surfaces Affect the Development and Structure of Marine Cyanobacterial Biofilms? Coatings, 12 (11), 1775, 2022, doi: 10.3390/coatings12111775
• Romeu, M. J.; Lima, M.; Gomes, L. C.; Jong, E. D. D.; Morais, J.; Vasconcelos, V.; Pereira, M. F. R.; Soares, O. S. G. P.; Sjollema, J.; Mergulhão, F. J., The Use of 3D Optical Coherence Tomography to Analyze the Architecture of Cyanobacterial Biofilms Formed on a Carbon Nanotube Composite. Polymers, 14 (20), 4410, 2022, doi: 10.3390/polym14204410
• Sousa-Cardoso, F.; Teixeira-Santos, R.; Mergulhão, F. J. M., Antifouling Performance of Carbon-Based Coatings for Marine Applications: A Systematic Review. Antibiotics, 11 (8), 1102, 2022, doi: 10.3390/antibiotics11081102
• Teixeira-Santos, R.; Gomes, L. C.; Mergulhão, F. J. M., Recent advances in antimicrobial surfaces for urinary catheters. Curr. Opin. Biomed. Eng., 22, 100394, 2022, doi: 10.1016/j.cobme.2022.100394 |