Title: Bioactive interfaces between synthetic surfaces and biological fluids Author: Andrés de los Santos Pereira Institute: Institute of Macromolecular Chemistry, Czech Academy of Sciences Supervisor of the doctoral thesis: RNDr. Eduard Brynda, CSc., Institute of Macromolecular Chemistry, Czech Academy of Sciences Abstract: The application in medicine of label-free affinity biosensors, advanced implants, and blood-contacting devices requires that their surfaces resist non-specific protein adsorption (fouling) and associated complications in blood-derived fluids while displaying immobilized bioreceptors that provide specific biofunctionality. The aim of this thesis was to explore the strategies for the preparation of these antifouling bioactive surfaces. Various types of recently developed antifouling polymer brushes were synthesized and evaluated in terms of their ability to prevent fouling from blood plasma (obtained from various commercial sources and individual donors) as well as thrombus formation when contacted with whole blood. Moreover, single-cell force spectroscopy was utilized to characterize the bacterial adhesion force and energy on these polymer brushes, which were significantly reduced in comparison to various reference substrates. The immobilization of bioreceptors was tackled by means of a...

Current strategies for designing biomaterials involve creating materials and interfaces that interact with biomolecules, cells and tissues.  This thesis aims to investigate several bioactive surfaces, such as nanocrystalline diamond (NCD), hydroxyapatite (HA) and single crystalline titanium dioxide, in terms of material synthesis, surface functionalization and characterization. Although cochlear implants (CIs) have been proven to be clinically successful, the efficiency of these implants still needs to be improved. A CI typically only has 12-20 electrodes while the ear has approximately 3400 inner hair cells. A type of micro-textured NCD surface that consists of micrometre-sized nail-head-shaped pillars was fabricated. Auditory neurons showed a strong affinity for the surface of the NCD pillars, and the technique could be used for neural guidance and to increase the number of stimulation points, leading to CIs with improved performance. Typical transparent ceramics are fabricated using pressure-assisted sintering techniques. However, the development of a simple energy-efficient production method remains a challenge. A simple approach to fabricating translucent nano-ceramics was developed by controlling the morphology of the starting ceramic particles. Translucent nano-ceramics, including HA and strontium substituted HA, could be produced via a simple filtration process followed by pressure-less sintering. Furthermore, the application of such materials as a window material was investigated. The results show that MC3T3 cells could be observed through the translucent HA ceramic for up to 7 days. The living fluorescent staining confirmed that the MC3T3 cells were visible throughout the culture period. Single crystalline rutile possesses in vitro bioactivity, and the crystalline direction affects HA formation. The HA growth on (001), (100) and (110) faces was investigated in a simulated body fluid in the presence of fibronectin (FN) via two different processes. The HA layers on each face were analysed using different characterization techniques, revealing that the interfacial energies could be altered by the pre-adsorbed FN, which influenced HA formation. In summary, micro textured NCD, and translucent HA and FN functionalized single crystalline rutile, and their interactions with cells and biomimetic HA were studied. The results showed that controlled surface properties are important for enhancing a material’s biological performance.

Actuellement, il est largement reconnu que la décision des cellules souches de maintenir leur caractère souche ou se différencier vers une lignée spécialisée dépend particulièrement de la nature de leur microenvironnement, appelé niche cellulaire. Une des composantes essentielles de cette niche cellulaire est la matrice extracellulaire (MEC), qui au-delà de sa fonction de support cellulaire, détermine le devenir des cellules souches en fonction de sa composition biochimique, sa structure et sa localisation. D’un point de vue rationnel, un biomatériau destiné à remplacer la fonction d’un tissu endommagé doit non seulement jouer le rôle d’échafaudage cellulaire mais également mimer les propriétés de la MEC dans son ensemble. Malheureusement, il est extrêmement difficile de concevoir des biomatériaux mimétiques de la MEC naturelle tenant compte de sa complexité structurelle et fonctionnelle. Pour pallier à cette problématique, il semble nécessaire d’effectuer un travail en amont de déconstruction/reconstruction de la complexité de la MEC en étudiant l’effet individuel puis combiné de ses propriétés sur la différenciation des cellules souches. Ce projet de doctorat rentre dans le cadre de ce travail et vise à déterminer le rôle spécifique ou concomitant de différentes propriétés inhérentes à la MEC sur la différenciation ostéoblastique des cellules souches mésenchymateuses humaines (hCSMs). En effet, nous avons évalué l’effet de la composition biochimique de la MEC et la distribution spatiale des ligands sur la différenciation des hCSMs, en fonctionnalisant la surface d’un matériau modèle avec les peptides RGD et/ou BMP-2, distribués d’une manière aléatoire ou structurée. / Actually, it is well-established that maintaining the stemness character of stem cells or eliciting their lineage-specific differentiation is closely related to the nature of their microenvironment, known as stem cell niche. The extracellular matrix (ECM), a key component of stem cell niche, not only provides a support function for stem cells but also dictates their fate decision. From a rational point of view, a biomaterial intended to replace a damaged tissue should mimic the natural ECM in all its aspects, including its biochemistry, 3D structure, topography, porosity, rigidity…. etc. Unfortunately, the design of biomaterials that fully mimic the natural ECM is still a big challenge, due to its high structural and functional complexity. Towards the development of finely-tuned biomaterials, it seems important to start by deconstructing and then reconstructing the complexity of the ECM. In this context, the thesis project, herein, seeks to evaluate both the individual and the synergistic effect of different properties inherent to the natural ECM on human mesenchymal stem cells (hMSCs) osteogenic differentiation. Indeed, we investigated whether the biochemical composition of the ECM and the spatial distribution of its components modulate hMSCs osteogenesis. This was achieved by creating different artificial ECMs, in vitro, containing RGD and/or BMP-2 mimetic peptides, distributed randomly or as specific micropatterns on the surface of a model material.