Investigating the interplay of lateral and height dimensions influencing neuronal processes on nanogrooves

Abstract

In this work, nanogroove dimensions as a design input parameter for neuronal differentiation and neurite outgrowth in brain-on-a-chip (BOC) applications are investigated. Soft lithography in polydimethylsiloxane (PDMS) is used extensively in organ-on-a-chip applications to create environments for in vitro models. As such, here it is used to fabricate cell culture substrates with nanogrooved patterns. Using a newly developed analysis method, the effect of the nanogrooved, biomimetic PDMS substrates is compared with lateral and height variations within the nanometer range as measured by means of atomic force microscopy (AFM). PDMS culture substrates were replicated from a cyclic olefin copolymer template, which was fabricated either directly by thermal nanoimprinting from a jet and flash imprint lithography (J-FIL) resist pattern (process I) on a polished silicon wafer or via an intermediate reactive ion etched all-silicon mold (process II) that was fabricated by using the J-FIL resist pattern as in process I as a mask. To study the interplay between the lateral and height dimensions of nanogrooves on the differentiation process of SH-SY5Y cells, which are a well-established model for neuronal cells that form networks in culture, the authors first characterized the feature sizes of the PDMS substrates received from both processes by AFM. On average, nanogrooved patterns from process I had a 1.8 ± 1.1% decrease in pattern period, a 15.5 ± 12.2% increase in ridge width compared to the designed dimensions, and a height of 95.3 ± 10.6 nm. Nanogrooved patterns for process II had a 1.7 ± 1.7% decrease in pattern period, a 43.1 ± 33.2% increase in ridge width, and a height of 118.8 ± 13.6 nm. Subsequently, they demonstrated that neurite outgrowth alignment was particularly strong if the pattern period was 600 nm or 1000 nm with the additional constraint for these patterns that the ridge width is <0.4 times the pattern period. Increasing pattern height increased the fraction of differentiated cells within the cell culture and increased neurite length, but had no direct impact on outgrowth alignment. This study forms the basis for optimization in the bottom-up engineering of neuronal network architecture, for which specific patterns can be selected to assist in neuronal cell differentiation and direct neurite growth and alignment. Such organized neuronal networks can aid in the design of in vitro assay systems for BOC applications by improving biological response readouts and providing a better understanding of the relationship between form and function of a neuronal network.