Taking the idea of nanoscale design for cell culture further, some cell biologists are investigating cellular responses to more complex three-dimensional structures.

Mathis Riehle: “With the E Beam you can be very specific.”

A collaboration in this field between cell biologists and electronic engineers at the University of Glasgow's Centre for Cell Engineering is proving fruitful.

The group has the advantage of a state-of-the-art electron-beam nanolithography system (E Beam) manufactured by Leica, which creates nanoscale features on a surface under the control of customized software (see also 'Down to the letter'). “We're quite unique in the United Kingdom in that we have access to such an incredible machine with which you can define structures so deliberately,” says Mathis Riehle, who directs research at the centre. “With the E Beam you can be very specific.”

The E Beam is used to define or “write” a pattern at nanometric resolution into an electron-sensing polymer. The pattern is developed and used as a template for etching or depositing material to form the desired nanotopographic features. This technique gives a greater degree of control than 'natural' lithography, which relies on self-assembly of colloidal particles in regular arrays to produce the pattern.

Riehle wants to explore the limits of the machine. “We've made tubes and we want to make more complicated three-dimensional structures — maybe structures that will look like cell 'car parks'. But to do that we would need something like origami, because at the moment the E Beam can only really write on a flat plane. We cannot write on a shaped, undulating surface.” The team will have to write its own software to create these complex structures.

As one of a consortium of institutions working on emerging nanopatterning methods, the Glasgow centre is also developing alternative methods of engineering 3D structures with nanoscale features for use as cell-culture substrates.

Kris Seunarine and Osian Meredith have fabricated a 'swiss roll' from e-poly-caprolactone, a biodegradable thermoplastic shaped by hot nano- and micro- embossing. This is the 'sponge' of the swiss roll, with the cells as the 'jam'.

Cell support: ridges on the surface of the 'swiss roll' will keep cells aligned, and pits provide anchorage. Credit: K. SEUNARINE & O. MEREDITH

Two levels of microfeatures are sculpted into the polymer (see photos). One aligns fibroblasts and smooth-muscle cells, keeping them from being squashed. The inward-facing surface is patterned at the nanoscale with a regular array of pits (100 nm diameter and 80 nm deep) spaced 300 nm apart, which define locations for endothelial cell adhesion. These cell scaffolds could be useful in developing methods for vascular and urogenital reconstruction.

H.M.B.