Systematically varied arrangements and geometries of SiO2 nanopillars serving as static and dynamic platforms for studying cell responses

Abstract

This present work focuses on the fabrication of various static and dynamic substrate systems based on the quasi-hexagonally ordered SiO2 nanopillar arrays, for the study of cell-surface interaction responses of human multipotent mesenchymal stromal cells (hMSC) and osteoblasts (hOB). Generation of the uniform nanopillar arrays is established by cyclic combination of block copolymer micellar lithography (BCML), photochemical growth and reactive ion etching (RIE) techniques. With a newly introduced combined method, the obstacle of achievable pillar heights in RIE due to the mask erosion is overcome. As a result, using the Au NPs which are generated by BCML technique with a starting diameter of 12 ± 1.5 nm, arrays of silica nanopillars with heights up to 680 nm and aspect ratios of 10:1 are fabricated.

Proof of principle investigations of adhesion, proliferation, osteogenic differentiation are accomplished for all pillar geometries below 150 nm. Osteogenic differentiation of hMSCs is increased with pillar height alteration from 20 nm to 50 nm (one donor).

Fabrications of well-defined gradient (non-uniform) nanopillar arrays are successfully established for pillar diameter, pillar-to-pillar distance and height separately and combined as multiparametric gradients with all dimensions again below 150 nm. For that purpose BCML, photochemical growth and RIE techniques are individually modified with additional shutter and mask systems.

In order to understand the mechanical stimulus which is exerted to hOBs in vivo, a dynamic environment which resembles the body conditions in vitro is established by fabrication of SiO2 nanopillar arrays on ultra-thin Si3N4 membranes and through an in-house built pressure-deflection setup. Initial cell-surface interaction studies reveal viable hOBs before and after mechanical stimulation with changed expression of mechanotransduction pathway genes.