Animal bone implants that resemble natural bone

Jul 15 2004

A team of researchers at the Institute of Bioengineering and Nanotechnology (IBN) has moved one step closer to developing an ideal bone scaffold for reconstructive surgery.

Using animal bone and a US-patented tissue processing technique, the IBN team – lead scientist Dr Pei-Lin Mao, Ms Shona Pek, Ms Lihong Liu and Mr Michael Yu – has prepared an implantable anorganic scaffold that has the original chemical and physical properties of natural bone.

Tests have shown that it maintains the natural 3-dimensional conformation and chemical components with non-homogeneous distribution of trace/essential elements and can be shaped easily for specific treatments.

Currently, orthopedic patients receive bone grafts from several sources. One method is to obtain bone from a different part of the patient’s body (autograft). Although autografts are highly recommended for patients with serious bone defects, they require additional surgery and may result in further infection at the donor site. Other procedures involve the harvesting of bone from another person (allograft) or animal (xenograft). Allografts are restricted by the limited donor bone supply and patients run the risk of viral infection.

The challenge with using acquired human or animal bone also lies with the bone graft preparation process, where the bone needs to be cleaned and purified before implantation. These bone tissues may lose their original physical and chemical properties during this preparation process, and patients still run the risk of contracting transmitted diseases with the processed bone.

Most of the immune rejection is from the proteins within the bone tissue, as well as other components like cell debris. To remove these elements, stringent solvents and extremely high temperature must be applied. Those solvents that are currently available are highly toxic in nature, and are not easily removed through rinsing because of the high porosity of bone tissue.

In addition, the high temperature will lead to a change in the original chemical components of the bone as well as its conformational structure. Hence, the processing of solvent-treated bone tissue can be a complex and expensive exercise. Nevertheless, the use of animal bone presents several practical advantages, such as its low cost and wide availability. Hence, to address the current problems associated with animal bone implants, Dr Mao and her team have designed a bioprocessed tissue preparation that eliminates the use of toxic chemicals and enzymes.

The technique involves the use of natural treatments and a mild solvent on organic porcine (pig) bone. A repeated boiling process successfully disrupts the extracellular matrix (ECM) and cells without changing the physical properties of the bone scaffold. The ECM and bone marrow cells can be easily removed by further ultrasound treatment, leaving the scaffold that has almost the same properties as natural human bone. The resulting bioprocessed anorganic porcine bone (APB) retains its original architecture and components, and is hence, biocompatible and can be implanted safely without the risk of viral infection or immunological response. It is highly osteoconductive, serving as a scaffold on which bone cells can attach and grow. It is also highly osteoinductive, stimulating immature bone cells to grow and mature, thus forming healthy bone tissue. Most importantly, IBN’s bone bioprocessing method is a simple procedure and can be performed at a very low cost.

The bioprocessed bone can be stored under airtight conditions before implantation. Bone scaffolds of different sizes may either be seeded with the patient’s own cells or directly implanted into the patient’s body. “In the near term, our technology is available immediately for use in in vitro cell culture for tissue engineering. Most significantly, the bioprocessed bone represents the natural bone scaffold and it will provide a model to elucidate the natural mechanism of bone remodeling in vitro,” said Dr Mao, a Principal Research Scientist at IBN. “In the long-term, our bone material has the potential to replace all existing bone scaffold materials, as our scaffold maintains the original architecture and components that are most suitable for bone repair.”

http://www.ibn.a-star.edu.sg