Contribution from our customer DTU
|Figure 1. Photo of a Chemotaxis 3D microfludic chip from the German company ibidi being loaded into the Nanoscribe system for in-channel writing of cellular micro-mazes. (Photo: N. Larsen / DTU)
(Niels Bent Larsen) The specific aim was to produce a polymer chip suitable for analyzing the directed cell migration of human dendritic cells, a type of immune cell central to initiate combat of infections and cancer cells in the body. The Nanoscribe system was found to be ideally suited for this challenging task by enabling free-form shaping at the required sub-cellular length scale.
Two-photon polymerization offers high spatial resolution but relatively low volumetric throughput. Thus, the researchers picked the best from two worlds of length scales by performing the writing process inside a commercially available microfluidic chip system from the German company ibidi.
Figure 1 shows the microfluidic chip platform being loaded into the Photonic Professional system on a custom-made sample holder. The outcome is a closed chip system in standard microscope slide format with micro-mazes for cell migration studies printed inside shallow 70 µm high microchannels in the chip. Figure 2 show examples of the micro-maze structures as well as a snapshot of how the dendritic cells seek their way through the maze by “sniffing” for the chemical attractant loaded into the opposite side of the chip.
More complex structures calling for spiralling motion of the dendritic cells to pass were also manufactured, with dendritic cells successfully finding their way by means of the attractant
Additionally, the research groups headed by Niels B. Larsen at DTU Nano-tech and Inge Marie Svane at Herlev University Hospital have recently extended their concept by exploiting the extremely high spatial resolution of the Nanoscribe system to introduce nanoscale perforations in the walls of closed microchannels during writing. Such nanoslits facilitates attractant diffusion while preventing cells from leaving the closed channels, thereby significantly improving the quality of the cell analysis.
Figure 2. (A) The cell micro-maze is written within the microfluidic channel bounded by the white dashed lines, between macroscopic reservoirs with (green) or without (red) cell attractant. (B) The simplest micro-mazes are woodpile constructs with pore diameter from 8 µm to 15 µm with a total height of 70 µm matching the microchannel height. (C) Phase contrast micrograph showing how three dendritic cells (hightlighted in green) try to find their way from right to left with cells 1 and 2 probing the best path by stretching long cellular protrusions into neighboring channels.
 Olsen, M.O., Hjortø, G.M., Hansen, M., Met, Ö., Svane, I.M., Larsen, N.B. “In-chip fabrication of free-form 3D constructs for directed cell migration analysis” (2013) Lab Chip 13(24) 4800-4890.
 Hjortø, G.M., Olsen, M.H., Svane, I.M., Larsen, N.B. “Confinement dependent chemotaxis in two-photon polymerized linear migration constructs with highly definable concentration gradients” Biomed. Microdev. (2015) in press.