December 1, 2013
Modified Sea Coral Material For Better Bone Grafts
Ranjini Raghunath for redOrbit.com - Your Universe Online
Changes to artificial bone grafts made from sea coral material make them more easy-to-dissolve while retaining their bone-healing properties, according to new research from Swansea University in the UK.
Artificial calcium-based bone grafts, on the other hand, are strong, closely resemble human bone and have a porous structure that provides a scaffold for new bone cells to grow on.
There is one caveat: bone fractures may take up to five years to heal, and these artificial bone grafts need to dissolve within that time frame to make way for naturally reconstructed bone.
One such material is Coralline hydroxyapatite (CHA), made from calcium carbonate found in sea coral shells. CHA has successfully been used to make artificial bone grafts since the 1970s. CHA-based bone grafts, however, have mostly been limited to temporary scaffolds, as they do not dissolve completely in the human body.
"When biomaterials do not biodegrade and remain in skeletal tissue, they may continuously cause problems in the host. In extreme conditions, it is possible that the different mechanical properties of the artificial bone graft may cause a re-fracture or become a source for bacterium growth in infection,” said Zhidao Xia, Swansea University researcher, in a statement.
A partially converted form of CHA, however, can degrade completely within 1-2 years and has shown promising results in lab mice as well as initial clinical trials, according to the paper published in Biomedical Materials.
The incompletely-converted form called CHACC (CHA/calcium carbonate) also retained CHA’s original porous structure as well as its compatibility with the human body.
The researchers made CHACC from sea coral harvested in South China.
In initial tests, CHACC was mixed with mesenchymal stem cells – precursors to bone cells – and implanted in lab mice. In 10 weeks, new bone cells were found to form on the CHACC’s surface.
Next, the researchers surgically implanted CHACC in 16 patients suffering from various bone defects and tested the growth of bone cells and CHACC’s durability. In four months, the bones started healing and within 2 years, most of the CHACC had dissolved.
"Our methods have considerably improved the outcome of bone grafts by using the partial conversion technique, in which the biodegradable composition from natural coral is reserved,” Xia stated.
While CHACC bone grafts provide a strong-yet-soluble scaffold for new bones to grow, they still do not have the autografts’ innate ability to trigger bone growth on their own. Once this disadvantage is overcome, CHACC could provide a permanent bone graft alternative for the several million people worldwide who need transplants each year, according to the paper.
“Our future work is to combine controlled growth factor delivery and stem cell technology in order to develop an even better solution for bone graft materials." Xia stated.