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

Abstract

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.

Polyelectrolyte multilayers of poly (l-lysine) and hyaluronic acid on nanostructured surfaces affect stem cell response

“…35,36 In previous studies we could show that LIL can be used to design defect-free structures of gold of different size and periodicity on silicon as model surface. 24 We could demonstrate further that spreading of human adipose-derived stem cells (hADSC) decreased with increasing feature dimensions, which had an effect on cell differentiation. 24 In another study we studied how polyelectrolyte multilayers (PEM) made of hyaluronic acid (HA) and poly-L-lysine (PLL), either as native or cross-linked system varying in elastic modulus, guide hADSC adhesion, growth, and differentiation.…”

“…24 We could demonstrate further that spreading of human adipose-derived stem cells (hADSC) decreased with increasing feature dimensions, which had an effect on cell differentiation. 24 In another study we studied how polyelectrolyte multilayers (PEM) made of hyaluronic acid (HA) and poly-L-lysine (PLL), either as native or cross-linked system varying in elastic modulus, guide hADSC adhesion, growth, and differentiation. 37 We found that hADSC spread and grew more on stiffer, highly cross-linked than on soft native PLL/HA multilayers.…”

“…Hexagonally arranged nanostructures were designed by threebeam LIL as previously described. 24 Briefly, silicon surfaces were cleaned with acetone (Roth) and isopropanol (Roth) before use and cut to (20 × 20) mm 2 . An adhesion promoter and, subsequently, a negative photo resist (All Resist, Germany) were spin-coated to the cleaned silicon samples and baked at different temperatures.…”

“…SAM were used to passivate and activate the nanostructured samples with varying surface chemistry as previously described. 24 Briefly, a long-chain organo-silane with 43 poly (ethylene glycol) (PEG) units was synthesized and linked to the silicon background. The nanostructured samples were immersed in a 0.25 mM solution of PEG-silane in dry 99.5% toluene (Roth) and 1 μL of triethylamine (Sigma-Aldrich, Germany) was added.…”

“…22 In a recent work we showed that the nanofeature dimensions obtained by NSL can be generated defect-free by interferometric lithography, but with improved long-range order. 24 This technique is called laser interference lithography (LIL) and its benefit is the cost-efficient and fast patterning of surfaces at nanoscale over large areas. 25,26 There, the interference of mutually coherent light beams leads to periodic and quasi-periodic interference patterns on a photosensitive material.…”