Clay nanotubes as growth factor delivery vehicle for bone tissue formation

A wide variety of natural and synthetic materials (and combinations) have been used to bioengineer bone tissue. Growth factors have been supplied to progenitor cells in various forms to trigger a series of metabolic pathways leading to cellular proliferation, differentiation and functionality. The challenge is to supply these proteins, in the range of nano or even picograms, and in a sustained fashion over a period of time. Such a delivery system has yet to be developed. Alginate hydrogels are widely used to as a drug delivery system. We used halloysite nanotubes (HNTs) as carriers for the delivery of BMPs 2, 4 and 6, singly and in combination. Growth factors were vacuum loaded into HNTs and doped HNTs added to osteoblast-seeded alginate hydrogels. Cell proliferation, functionality and mineralization were observed over a 21-day period. Controls had unloaded HNTs dispersed within the alginate hydrogel. Halloysite nanoparticles showed a sustained release of all BMPs over a 21-day period with the dosage in picograms per milliliter. Increased collagen deposition, bone protein expression and formation of a mineralized matrix were observed that increased over the 21-day period. There was an increase in hydrogel material properties. Osteoblast proliferation, bone protein expression and mineralization in control cultures were reduced in comparison to experimental cultures. The data supports the potential use of a hydrogel-growth-factor doped HNT system as part of a novel osteogenic system that can deliver growth factors to the injured site (fracture, bone loss) and assist in bone repair. David K. Mills et al., J Nanomed Nanotechnol 2013, 4:6 http://dx.doi.org/10.4172/2157-7439.S1.013