Interactions of human primary immune cells with nanoparticles, two-dimensional micropatterns, hydrogels and three-dimensional nanofibres
The response of immune cells to any biomaterial determines its biocompatibility. This study aimed to identify the immunomodulatory properties of biomaterials from four different fields exhibiting various chemical, geometrical and morphological properties: nanoparticles, two-dimensional micropatterned structures, hydrogel with functional endgroups and three-dimensional nanofibers. It was shown in how far chemical, topographical and morphological properties of biomaterials affect the immune response. In the first part of this thesis, the uptake capacities of gold nanoparticles by the most important human primary leukocyte populations have been studied using a nanoparticle library encompassing both spherical and rod shaped gold nanoparticles. These studies were published (Bartneck et al. 2010a). The particles exhibited diameters between 15 and 50 nm as well as a variety of surface chemistries. Cetyl-trimethylammoniumbromide and citrate-stabilized nanoparticles were internalized rapidly within 15 minutes and in huge amounts by macrophages and monocytes. Interestingly, the uptake of CTAB-stabilized nanorods was more efficient than that of nanospheres. Blocking experiments and electron microscopic studies revealed macropinocytosis to be the underlying mechanism of this uptake. In addition to the studies on the intracellular uptake, a novel mechanism that results in the extracellular trapping of nanoparticles has been discovered and published (Bartneck et al. 2010b). It was shown that human neutrophils, monocytes and macrophages release extracellular traps which act as physical barriers for nanoparticles. The amount of particles which is trapped in the cell-gold networks strongly depends on the surface chemistry of the particles. Even PEG-coated nanoparticles are trapped to a significant extent by these extracellular structures. In the second part of this thesis, the impact of two-dimensional microtopographies on the inflammatory response of macrophages has been studied using four different microstructures generated from the novel non-degradable homo-polymer perfluoropolyether (PFPE). This study has been published in Acta Biomaterialia (Bartneck et al. 2010c). It was observed that each micropattern induced a specific morphology, phenotype, gene expression and cytokine release of macrophages. A microstructure of regular grooves induced a pro-inflammatory macrophage phenotype that did not secrete pro-inflammatory mediators. Large cylindrical posts induced an anti-inflammatory phenotype (M2) with a remarkable down-regulation of CXCL10. Smaller posts with a closer distance exhibited a stronger pro-inflammatory response than those with a larger distance, both on the level of phenotype and mediator release. It was demonstrated that the geometrical parameters of the microstructures, specifically the size and period of structures, play an important role in macrophage response. The influence of surface coating with hydrogels has been studied using star shaped poly(ethylene glycol-stat-propylene glycol), abbreviated Star PEG, in the third part of this thesis. Additionally, the effects of the functional peptide endgroups, RGD and GLF as well as six-armed glycidol on the attachment and response of macrophages were investigated. It was found that Star PEG led to the formation of macrophage cell clusters for up to three days of culture. After this period, the cells formed a dense monolayer. Noticeable, culture of macrophages on Star PEG strongly enhanced the number of alternatively activated macrophages. In contrast to this enhanced number of anti-inflammatory macrophages, Star PEG induced the release of pro-inflammatory mediators such as interleukin (IL)1beta, IL6, CCL2 and TNFalpha. Modifications of Star PEG with functional endgroups had no effects on cell attachment and little effects on the activation stage, compared to unmodified Star PEG. In the fourth part of this thesis, the interactions of macrophages with three-dimensional nanofibers were investigated. It was found that the degradation of nanofibers strongly depends on the material. Poly(lactide-co-glycolide) (PLGA)-based fibers were degraded more rapidly by macrophages compared to PLGA-Star PEG based scaffolds. Different densities of fibers resulted in specific effects on the response of macrophages and altered the expression of function-associated surface markers and cytokine release. Three-dimensional fibers inhibited the release of pro-inflammatory cytokines. This study provides novel insights into the reactions of macrophages to three-dimensional scaffolds compared to standard single layers. It could be shown that an optimization of nanoparticles, microstructures and three-dimensional nanofibers may enable to control the immune response and to avoid inflammatory adverse reactions.
info:eu-repo/classification/ddc/570, Entzündung, Biomaterial, Nanotechnologie, Differentielle Genexpression, Cytometrie, Biowissenschaften, Biologie, inflammation, nanotechnology, differential gene expression, cytometry
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