Nanostructured coatings for controlling bacterial biofilms and antibiotic resistance
- Autores: Kristina Dimitrova Ivanova
- Directores de la Tesis: Tzanko Tzankov (dir. tes.)
- Lectura: En la Universitat Politècnica de Catalunya (UPC) ( España ) en 2017
- Idioma: español
- Tribunal Calificador de la Tesis: Pere Garriga Solé (presid.), Guillermo Rocasalbas Lozano (secret.), Carlos Díaz Blanco (voc.)
- Materias:
- Enlaces
- Tesis en acceso abierto en: TDX
- Resumen
The accelerated emergence of drug resistant bacteria is one of the most serious problems in healthcare and the difficulties in finding new antibiotics make it even more challenging. To overcome the action of antibiotics bacteria develop effective resistance mechanisms including the formation of biofilms. Biofilms are bacterial communities of cells embedded in a self-produced polymeric matrix commonly found on medical devices such as indwelling catheters. When pathogens adopt this mode of growth on the surface, they effectively circumvent host immune defences and antibiotic therapy, causing severe and life threatening infections.
This thesis focuses on the development of advanced nanoscale materials and coatings for controlling bacterial biofilms and the emergence of drug resistance. To this end, acylase and amylase enzymes degrading essential for the biofilm growth components, were innovatively combined into hybrid nanocoatings to impart antibiofilm functionalities onto indwelling medical devices. Alternatively, ultrasound-assisted nanotransformation of antimicrobials was used as a tool for enhancing their antibacterial efficacy and overcoming the intrinsic drug resistant mechanisms in Gram-negative bacteria. These strategies offer new perspectives for prevention and treatment of biofilm infections, limiting the selection and spread of antibiotic resistance.
The first part of the thesis describes the building of enzyme multilayer coatings able to interfere with bacterial quorum sensing (QS) and prevent biofilm establishment on silicone urinary catheters. This was achieved by alternate deposition of negatively charged acylase and oppositely charged polyethylenimine in a Layer-by-Layer (LbL) fashion. The acylase-coated catheters degraded bacterial signalling molecules and inhibited the QS process of Gram-negative bacteria. These coatings also significantly reduced the biofilm growth on urinary catheters under conditions mimicking the real situation in catheterised patients, without affecting the human cells viability.
Acylase was further combined with the matrix degrading amylase enzyme into hybrid multilayer coatings able to interfere simultaneously with bacterial QS signals and biofilm integrity. The LbL assembly of both enzymes into hybrid nanocoatings resulted in stronger biofilm inhibition as a function of acylase or amylase location in the multi-layer coating. Hybrid nanocoatings with the QS inhibiting acylase as outermost layer reduced the occurrence of single and multi-species biofilms on silicone catheters in vitro and in an in vivo animal model.
The thesis also reports on the efficacy of nanomaterials for prevention and eradication of antibiotic resistant biofilms. Multilayer assemblies that contain in their structure and release on demand antibacterial polycationic nanospheres (NSs) were engineered on silicone surfaces. A polycationic aminocellulose (AC) conjugate was first transformed into NSs with enhanced bactericidal activity and then combined with hyaluronic acid to build bacteria-responsive layers on silicone material. When challenged with bacteria these multilayers disassembled gradually inhibiting both planktonic and biofilm modes of bacterial growth.
The same AC NSs were also covalently immobilised on silicone material using epoxy-amine conjugation chemistry. The intact NSs on the silicone material were able to inhibit bacterial biofilm growth, suggesting the potential of epoxy-amine curing reaction for generation of stable non-leaching coatings on silicone-based medical devices. Finally, ultrasound-assisted nanotransformation of penicillin G was used as a strategy to boost its activity towards bacteria. The efficient penetration of the NSs within a biomimetic membranes sustained the theory that they may reach the periplasmic space in Gram-negative bacteria and exert their bactericidal activity ¿unrecognised¿ as a threat by bacteria for selection of resistance.
