Rapid Prototyping of Polymeric Nanopillars by 3D Direct Laser Writing for Controlling Cell Behavior

Abstract

Mammalian cells have been widely shown to respond to nano- and microtopography that mimics the extracellular matrix. Synthetic nano- and micron-sized structures are therefore of great interest in the field of tissue engineering, where polymers are particularly attractive due to excellent biocompatibility and versatile fabrication methods. Ordered arrays of polymeric pillars provide a controlled topographical environment to study and manipulate cells, but processing methods are typically either optimized for the nano- or microscale. Here, we demonstrate polymeric nanopillar (NP) fabrication using 3D direct laser writing (3D DLW), which offers a rapid prototyping across both size regimes. The NPs are interfaced with NIH3T3 cells and the effect of tuning geometrical parameters of the NP array is investigated. Cells are found to adhere on a wide range of geometries, but the interface depends on NP density and length. The Cell Interface with Nanostructure Arrays (CINA) model is successfully extended to predict the type of interface formed on different NP geometries, which is found to correlate with the efficiency of cell alignment along the NPs. The combination of the CINA model with the highly versatile 3D DLW fabrication thus holds the promise of improved design of polymeric NP arrays for controlling cell growth.

High‐Aspect‐Ratio Nanostructured Surfaces as Biological Metamaterials

“…The model also suggests that membrane wrapping around the nanowire is not normally energetically favorable and requires external force. They were able to verify their model against literature and experimental data, also observing an intermediate settling between the fully deformed and on‐top regimes.…”

“…The result of Xie et al highlighting the lack of spontaneous penetration provided an assumption (exploited in later models) that to effectively understand cell behavior, the balance of free energy of the membrane (rather than gravitational force) should be considered. Martinez and co‐workers have extensively studied geometry‐dependent cell response both experimentally and theoretically . Their model considers the cell as a soft‐shelled droplet, and defines the free energy of the cell–substrate interaction as the sum of the cell–substrate adhesion, the change in surface tension caused by an increase in cell surface area, and the change in elastic energy caused by bending the membrane .…”

“…The high photon density in the focal point results in upconverted photons with UV energies, resulting in a smaller patterning region and enhanced resolution. This approach has been used by different groups to directly pattern cell‐interfacing polymer nano‐ and microneedles with tip diameters in the 500 µm regime …”

The Fabrication of Micro/Nano Structures by Laser Machining

“…In 2017, N. Mnson et al demonstrated the fabrication of polymer nanopillars (NP) using 3D direct laser writing (3D DLW). It have been shown that polymer NPs generally provided a biocompatible environment for cell adhesion and sustained cell growth, therefore, synthetic nano-and micro-sized structures were of great importance in the field of tissue engineering [152]. Scanning electron microscopy (SEM) images of an array of 3 µm long NPs of all pitches tested in the cell studies described were shown in Figure 17b-g.…”

Electron beam lithography fabrication of SU-8 polymer structures for cell studies

“…Micro-and nanostructured surfaces can be fabricated using various lithographic techniques. Fabrication approaches such as mask-based photolithography 22 and mask-less photolithography 23,24 are frequently applied, but structure resolution are for both techniques limited by the optical diffraction limit. Other approaches such as dip pen lithography, 25 nano-sphere lithography, 26 block-copolymer lithography 27 and other similar approaches 28 are able to perform structuring with sub-100 nm resolution, but have a limited throughput.…”