Balsam for the bones: Chemists develop a nanopaste for the repair of bone defects

Following accidents or cancer surgery surgeons often have to transplant healthy bone tissue or synthetic material to repair the resulting bone defects. Unfortunately, these procedures do not always have the desired effect.

Now a professor for inorganic chemistry, Matthias Epple was attracted to the interface between biology and medical science. "We have been investigating the impact of mineral tissue such as teeth, bone and sea shells for many years and are now using the knowledge we have gained to produce new biomaterials." To achieve this he has collaborated closely with medical scientists and his current project – carried out with three of his doctoral students – was no exception.

"The repair of bone defects presents a real challenge for surgeons," he relates. "When possible they collect the patient's own bone from various locations, such as the iliac crest, and implant it where needed to fill defects." The researcher explained that since there is only a limited amount of surplus bone material in the body, synthetic materials are now being used. "Calcium phosphate is a natural choice here since it is an inorganic mineral found in bones in the form of nanocrystals. It is a material familiar to the body, which makes it a suitable carrier." He added that the calcium and phosphate ions lead to improved new bone formation.

However, the use of synthetic materials creates a host of new problems: the bones heal more slowly, the risk of infection is greater and the mechanical stability is not ideal. Epple's team has now created a bone repair paste by coating synthetic nanocrystals of calcium phosphate with nucleic acids – in other words, with DNA. The professor explains what happens when this paste is injected into a bone defect: "The nanoparticles are taken up by cells. The calcium phosphate dissolves and the DNA that is released stimulates the formation of two proteins important for healing: BMP-7, which stimulates bone formation, and VEGF-A, which is responsible for the creation of new blood vessels. As a result, the new bone is supplied with valuable nutrients."

The UDE researchers expect that the paste will have a long-lasting effect since the nanoparticles are released successively and thus continuously stimulate the surrounding cells. They have demonstrated that the paste works in three different cell types. Further tests now have to be conducted. Epple and his co-researchers hope that "our development will be used several years from now in the field of traumatology and in the treatment of osteoporosis."