Professor develops new bone-repair material

A sturdy form of plastic is a more effective material for bone repair than pins and plates, Masdar Institute professor says.

Dr Raed Hashaikeh says his system maximises molecular strength, bonding and elasticity. Sammy Dallal / The National

Bone cells are smart. When they break, they can be reluctant to attach themselves to the various foreign materials used by doctors to bridge a gap - which can make repairs, especially of major fractures, extremely difficult.

Screws, pins and plates have long been a solution for bone repair, offering sturdy support. But none of these materials is naturally found in the body, making immune reactions a problem. So, too, is their permanence - a pin in your bone isn't going anywhere unless you take it out. On top of that, pins tend to be solid, which causes problems for circulation of blood and other materials, and for regrowth.

So the challenge in recent years has been to use more natural materials such as stem cells or bone grafts.

These have their own problems, though.

Not only can they too trigger adverse immune reactions unless introduced carefully, it is hard to make them strong enough to support a patient's weight.

Now a UAE-based scientist believes he has found a better material for tricking the cells into growing new bone around it: nanocrystalline cellulose, a hybrid substance that mimics the structure and chemistry of bone.

Its strength and sponge-like structure provide the right environment for cells to grow new sections where there is major damage or where the bone is completely lost - and that could eliminate the need for bone grafting or stem cells for complex surgeries such as spine fusion, hip reconstruction, dental implants or to repair localised bone loss caused by cancer.

It would also reduce the risks associated with bone donations, such as disease transmission or inability to fuse the bones correctly.

Dr Raed Hashaikeh, an assistant professor in materials science and engineering at the Masdar Institute, is developing a sturdy, compostable plastic that mimics bones' chemical composition and is porous enough to allow blood to circulate and provide nutrients to bone cells so that they can regenerate tissue.

It is a strong candidate for use in bone-like scaffolding currently being developed by Dr Hala Zreiqat from the University of Sydney's biomedical engineering department. Researchers there have been using a similar, ceramic-based material, but they believe Dr Hashaikeh's could be even stronger and might dissolve faster.

It will, Dr Hashaikeh believes, be hundreds of times stronger than those currently available. A major component in developing the material involves tiny crystalline particles extracted from long chains of cellulose, which gives wood its remarkable strength.

A common extraction process requires the cellulose to be fed into heated screws, where it is mixed and melded with polymer and fillers. But Dr Hashaikeh is developing a new system that simultaneously combines extraction and mixing, which he says will improve the molecules' bonding, strength and elasticity.

The result is a nanocrystalline cellulose that contains calcium, phosphorous, magnesium, strontium, zinc and other ions, mimicking the composition of bone.

At Dr Zreiqat's lab, where the scaffolds are prepared, the chemicals are mixed in a lab into a milky paste, which is poured over a foam mould cut to the shape needed. The foam is then melted away in a 1,200C furnace, leaving a hollow structure that can be fitted onto the bone.

Once set in place in the patient, the material hosts new bone cells, which have access to nutrients carried in blood flowing freely through the porous material.

"This is a three-dimensional structure that not only acts as a support structure to mechanically hold loads of weight applied, but it is able to mimic native bone well enough that new bone and cells will actually grow on it," said Dr Zreiquat. "This is something that no one in the world has done before."

The new bone begins to grow within a month. After three months, the scaffolding will be almost entirely dissolved, leaving new bone in its place.

There is also evidence that blood vessels could form around the material as well.

"With very large defects, the bone will not heal on its own, but we found that these materials are highly effective and bone regenerates very quickly," she said, adding that the results are "not evident in anything commercially available at the moment."

So far, the substance has been tested on large bone defects in animals. The researchers expect to be able to begin clinical trials in two or three years.

Dr Hashaikeh's material is also intended for other applications. Because the compostable plastic is incredibly light, it lends itself well to environmentally friendly packaging.

By mixing tiny fibres of polylactic acid - derived from corn - with cellulose and exposing it to high voltages, the solvent evaporates, leaving a thin, biodegradable plastic film.

If used for packaging products, the material could break down in landfills in an enzymatic process that would take two to 10 years. In a controlled composting environment, microbes would digest the material into fertiliser.

"We believe that for much of the world's packaging, we can replace non-biodegradable with degradable," he said. "This could be the key to waste management and environmental problems."