Comparative study of osteogenic activity of multilayers made of synthetic and biogenic polyelectrolytes

Polyelectrolyte multilayer (PEM) coatings on biomaterials are applied to tailor adhesion, growth, and function of cells on biomedical implants. Here, biogenic and synthetic polyelectrolytes (PEL) are used for layer-by-layer assembly to study the osteogenic activity of PEM with human osteosarcoma MG-63 cells in a comparative manner. Formation of PEM is achieved with biogenic PEL fibrinogen (FBG) and poly-l-lysine (PLL) as well as biotinylated chondroitin sulfate (BCS) and avidin (AVI), while poly(allylamine hydrochloride) (PAH) and polystyrene sulfonate (PSS) represent a fully synthetic PEM used as a reference system here. Surface plasmon resonance measurements show highest layer mass for FBG/PLL and similar for PSS/PAH and BCS/AVI systems, while water contact angle and zeta potential measurements indicate larger differences for PSS/PAH and FBG/PLL but not for BCS/AVI multilayers. All PEM systems support cell adhesion and growth and promote osteogenic differentiation as well. However, FBG/PLL layers are superior regarding MG-63 cell adhesion during short-term culture, while the BCS/AVI system increases alkaline phosphatase activity in long-term culture. Particularly, a multilayer system based on affinity interaction like BCS/AVI may be useful for controlled presentation of biotinylated growth factors to promote growth and differentiation of cells for biomedical applications

Effect of Polyelectrolyte Multilayers Assembled on Ordered Nanostructures on Adhesion of Human Fibroblasts

Nanosphere lithography (NSL) and the layer-by-layer (LbL) technique are combined here for the first time to design a flexible system to achieve nanotopographical control of cell adhesion. NSL is used-to generate regular patterns of tetrahedral gold nanodots of different size and distance. Besides the change in topography, LbL is used to generate a polyelectrolyte multilayer (PEM) system consisting of heparin (HEP) and poly(ethylene imine) (PEI) on top of the gold dots. The localized formation of PEM on gold dots is achieved by prior passivation of the surrounding silicon or glass surface. Properties of PEM are changed by adjusting the pH value of HEP solution to either acidic or alkaline values. Studies with human dermal fibroblasts (HDF) reveal that cells spread to a higher extent on PEM formed at pH 5.0 in dependence on the structure dimension. Further, filopodia formation is highly increased in cells on nanostructures exhibiting HEP as a terminal layer. The new system offers a great potential to guide stem cell differentiation in the future owing to its high degree of chemical and topographical heterogeneity

Effect of Polyelectrolyte Multilayers Assembled on Ordered Nanostructures on Adhesion of Human Fibroblasts

Nanosphere lithography (NSL) and the layer-by-layer (LbL) technique are combined here for the first time to design a flexible system to achieve nanotopographical control of cell adhesion. NSL is used to generate regular patterns of tetrahedral gold nanodots of different size and distance. Besides the change in topography, LbL is used to generate a polyelectrolyte multilayer (PEM) system consisting of heparin (HEP) and poly­(ethylene imine) (PEI) on top of the gold dots. The localized formation of PEM on gold dots is achieved by prior passivation of the surrounding silicon or glass surface. Properties of PEM are changed by adjusting the pH value of HEP solution to either acidic or alkaline values. Studies with human dermal fibroblasts (HDF) reveal that cells spread to a higher extent on PEM formed at pH 5.0 in dependence on the structure dimension. Further, filopodia formation is highly increased in cells on nanostructures exhibiting HEP as a terminal layer. The new system offers a great potential to guide stem cell differentiation in the future owing to its high degree of chemical and topographical heterogeneity

Nanoscaled Surface Patterns Influence Adhesion and Growth of Human Dermal Fibroblasts

In general, there is a need for passivation of nanopatterned biomaterial surfaces if cells are intended to interact only with a feature of interest. For this reason self-assembled monolayers (SAM), varying in chain length, are used; they are highly effective in preventing protein adsorption or cell adhesion. In addition, a simple and cost-effective technique to design nanopatterns of various sizes and distances, the so-called nanosphere lithography (NSL), is discussed, which allows the control of cell adhesion and growth depending on the feature dimensions. Combining both techniques results in highly selective nanostructured surfaces, showing that single proteins selectively adsorb on activated nanopatterns. Additionally, adhesion and growth of normal human dermal fibroblasts (NHDF) is strongly affected by the nanostructure dimensions, and it is proven that fibronectin (FN) matrix formation of these cells is influenced, too. Moreover, the FN fibrils are linked to the hexagonally close-packed nanopatterns. As a result, the system presented here can be applied in tissue engineering and implant design due to the fact that the nanopattern dimensions give rise to further modifications and allow the introduction of chemical heterogeneity to guide stem cell differentiation in the future

Introduction of Laser Interference Lithography to Make Nanopatterned Surfaces for Fundamental Studies on Stem Cell Response

The extracellular matrix (ECM) is a nanostructured environment that provides chemical, mechanical, and topographical stimuli for various cellular functions. Here, we introduce the application of laser interference lithography (LIL) to generate hexagonally arranged gold nanostructures of three different dimensions on silicon to study the effect of feature dimensions on human adipose-derived stem cells (hADSC) in terms of adhesion, growth, and differentiation. Self-assembled monolayers (SAM) were used to passivate the background silicon surface with a long-chain polyethylene glycol (PEG), whereas the gold nanostructures were activated with mercaptoundecanoic acid (MUDA) to direct protein adsorption and cell adhesive structures to them, only. It was possible to show that the size and distance of the nanostructures affected the spreading of hADSC with a decrease of cell size with the increase of feature dimensions, which corresponded also to the expression of focal adhesions and presence of the small GTPase RhoA. Effects of these early events, related to outside-in signal transduction, were visible by an enhanced cell growth on smaller feature dimensions and distinct effects on cell differentiation. Because of the precise control of chemical and topographical cues, the presented system offers great potential to study effects of material topography on stem cell behavior, which may pave the way for applications in tailoring surfaces of implants and tissue engineering scaffolds