Mats of LbL nanotubes for bacterial encapsulation

Details

Supervisors

Jonas, Alain M. ; Demoustier-Champagne, Sophie

Faculty

Ecole polytechnique de Louvain

Degree label

Master [120] : ingénieur civil biomédical

Abstract

A lack or a too low concentration of S. epidermidis in the biome allows colonization of the skin by pathogens and decreases the efficiency of the host for fighting back the inflammation and keeping the skin healthy. In this context, mats of membrane templated Layer-by-Layer nanotubes for bacteria encapsulation have been developed. Nanotubes were built by the successive deposition of PAH and PSS on the wall of a porous membrane of PC. The PC was dissolved to release the tubes, and the mat was obtained by the filtration of the suspension on a PET porous membrane. The patches developed combine three nanopaper layers, first and last ones made of nanotubes only, while the layer in the middle contains in addition fluorescent latex particles, modeling the bacteria. The first step of this master thesis was to optimize the nanotubes production process. The aim was to accelerate their build-up. Two parameters have been adjusted: the dipping time (5-10-15 min) and the number of polyelectrolytes bilayers (3-6-9). SEM observations have shown a flattening and a fusion of the tubes of three and six bilayers, while the nine bilayers tubes were well-shaped and separated. The dipping time did not have a significant influence on the morphology of the tubes. The conclusion was thus to reduce the time in solution to ten minutes while keeping nine bilayers, allowing to save 1h30 of the 6h30 initially needed for the fabrication of nanotubes. Then, the mechanical properties of the three-layered nanopapers have been evaluated. As the mat is kept on its PET filtration membrane in a saline solution, UV-visible spectroscopy combined with fluorescence microscopy have allowed to observe that the system was decomposing, by the releasing of big chunks, while the particles were well entrapped in the network. Therefore, two methods have been suggested to consolidate the structure. The adhesion of the mat on the PET membrane was increased by coating the PET with PEI, or PEI/PSS and the cohesion of the paper was improved thanks to a (PAH/PSS)_6 post-coating and a PAH/PSS complexation on the three-layered nanopaper. The analyses have shown that PEI/PSS deposition enabled a better adhesion of the paper on PET than only PEI, and that the gel was the best consolidator. Tests at 37°C have revealed that the improved mat decomposes neither with the temperature. The confirmation that the fluorescent latex particles were entrapped in the middle of the patch has been obtained by optical microscopy of thin transversal cuts of the paper, and confocal microscopy of the whole system. Finally, a transposition to biobased polyelectrolytes has been investigated. PAH/PSS complexation has been replaced by an ALG/gCHT complexation, showing no alteration of the mechanical properties. ALG/gCHT LbL on a flat substrate has also been built to characterize the growth by ellipsometry and the roughness by AFM. An exponential growth, expected as the polymers are naturals, has been obtained. Although further explorations, as the construction of ALG/gCHT nanotubes, and the replacement of the particles by bacteria are needed to completely develop the studied system, this work has already given keys for the design of such medical patches.