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

Bioinspired Multiple-Interaction Model Revealed in Adsorption of Low-Density Lipoprotein to Surface Containing Saccharide and Alkanesulfonate

A new “multiple-interaction model” for low-density lipoprotein (LDL) adsorption to a specific surface containing saccharide and alkanesulfonate ligands is proposed. The model suggests that there are interactions of the saccharide component beyond electrostatic interactions of the alkanesulfonate component that both influence the LDL adsorption process. This concept of multiple interactions between saccharide and LDL was inspired by the similarity in structures of LDL receptors (LDLR), heparin, and heparans used in LDL-apheresis. The model was confirmed by SPR analysis by the adsorption maxima on SAM surfaces with different compositions of saccharide and alkanesulfonate and additionally by CD detection of the conformation of LDL when in contact with saccharide

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

Both Hyaluronan and Collagen Type II Keep Proteoglycan 4 (Lubricin) at the Cartilage Surface in a Condition That Provides Low Friction during Boundary Lubrication

Wear resistant and ultralow friction in synovial joints is the outcome of a sophisticated synergy between the major macromolecules of the synovial fluid, e.g., hyaluronan (HA) and proteoglycan 4 (PRG4), with collagen type II fibrils and other non-collagenous macromolecules of the cartilage superficial zone (SZ). This study aimed at better understanding the mechanism of PRG4 localization at the cartilage surface. We show direct interactions between surface bound HA and freely floating PRG4 using the quartz crystal microbalance with dissipation (QCM-D). Freely floating PRG4 was also shown to bind with surface bound collagen type II fibrils. Albumin, the most abundant protein of the synovial fluid, effectively blocked the adsorption of PRG4 with HA, through interaction with C and N terminals on PRG4, but not that of PRG4 with collagen type II fibrils. The above results indicate that collagen type II fibrils strongly contribute in keeping PRG4 in the SZ during cartilage articulation <i>in situ</i>. Furthermore, PRG4 molecules adsorbed very well on mimicked SZ of absorbed HA molecules with entangled collagen type II fibrils and albumin was not able to block this interaction. In this last condition PRG4 adsorption resulted in a coefficient of friction (COF) of the same order of magnitude as the COF of natural cartilage, measured with an atomic force microscope in lateral mode