A rosette for surgical structures

Artificial implants need to perform as well as natural joints, with the body’s tissues accepting the foreign material. One of the key innovations of nanotechnology - inducing synthetic molecules to organise themselves into ordered structures - is proving to be useful in this field, as shown with a new discovery from Purdue University in Indiana, US, and Canada’s National Institute of Nanotechnology (NIC) at the University of Alberta. Ai Lin Chin and Thomas Webster, from Purdue, and Jesus Morales and Hicham Fenniri of the NIC have made nano-scaled titanium structures to which bone-producing cells, known as osteoblasts, can anchor and grow.

The nanostructures themselves were developed by Fenniri, using a trick borrowed from DNA. He used guanine and cytosine, two of the DNA bases, which linked together in groups of six to form a rosette-shaped ring. Because of the self-assembly properties of DNA, these rosettes then formed rod-like nanotubes, about 3.5nm across.

Webster, meanwhile, had been working on osteoblast attachment. Generally, Ti used in implants has surface features on the micron scale which the body can recognise as foreign. He had found that osteoblasts attach faster and firmer to nano-scale features on the Ti surface. The NIC research interested him, because the rosettes had a similar shape to the structure of collagen fibres in bone. ’[Fenniri] had these nice nanotubes, and I had this work that showed nice bone synthesis and other tissue regeneration on nanomaterials, so we said, "Wouldn’t it be great to actually combine these two and see if his material can promote new bone growth with these nanotubes?"’ says Webster.

The teams pooled their resources and made samples of Ti coated with the nanoscale rosettes. They immersed these in a suspension of osteoblasts which had been stained with a fluorescent dye, then counted the attached osteoblasts. Out of 2500 cells in the original suspension, 2300-2400 had adhered to the nanostructures, compared with about 1500 on a non-coated Ti sample.

The attached osteoblasts were more active than cells attached to the control sample, and small concentrations of the nanotubes worked just as well as higher concentrations. ’It’s cheap,’ Webster says. ’You don’t need a lot of it to get the effect you want.’

Moreover, he adds, the organic nature of the rosettes could make it possible to tailor the coating.

Stuart Nathan