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More Efficient Growth Factor Delivery Technique Devised

Todd McDevitt

Todd McDevitt (Georgia Institute of Technology)

29 May 2014. Biologists and engineers at Georgia Institute of Technology in Atlanta developed a new process that delivers tissue-building proteins used in regenerative medicine known as growth factors in much higher concentrations than current methods. The team led by Georgia Tech bioengineering professor Todd McDevitt published its findings online yesterday in the journal Biomaterials (paid subscription required).

Growth factors are protein molecules in the body that regulate cell division and survival, by binding to receptors on the surface of cells and activating the proliferation or differentiation of those cells. Some growth factors operate on a range of cell types, while others work within a narrow range or even with single types of cells. Harnessing growth factors for regenerative medicine is a challenge, however, because of the difficulty in targeting their delivery to sites in the body where needed. As a result, growth factor therapies can be expensive and wasteful.

McDevitt and colleagues focused on bone morphogenetic protein 2, or BMP-2, a growth factor that stimulates bone and cartilage tissue. Current methods for administering BMP-2 use a collagen sponge-like mechanism that delivers a large and imprecise first dose, much of which is scattered and diffuse, requiring much more BMP-2 in the dose than is needed.

The Georgia Tech team developed a solution adapting the drug heparin that prevents blood clots from occurring in surgery, dialysis, or transfusions. Heparin, however, also has chemical properties that bind it to BMP-2 and other growth factors. For this technique, the researchers generated microparticles of pure heparin from a heparin methacrylamide compound.

The team found that BMP-2 can bind to the heparin microparticles, and at a much higher capacity than previously reported. The results showed their process made it possible to bind BMP-2 at a rate 1,000 times higher than other heparin-containing biomaterials, such as gelatin.

Not only could the researchers vastly increase the concentrations of BMP-2 with this process, the BMP-2 stayed bound to the heparin for much longer periods. The results show after 28 days, only a quarter of the BMP-2 was released from the heparin microparticles. “The net result,” says McDevitt in a university statement, “is more efficient and spatially controlled delivery of this very potent and very valuable protein.”

The researchers tested the process on the ability to generate bioactivity in precursor skeletal tissue cells in lab cultures with BMP-2 using the heparin-binding method versus current techniques. The team reports the more efficient heparin-binding technique to deliver BMP-2 generated comparable levels of bioactivity as current methods.

Further research will extend the process to tests of the process with lab animals. “If we can get a more robust response by actually using less growth factor,” adds McDevitt,  “then I think we’re on to something that can be a more efficient delivery system.”

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