One of the hurdles in bioprinting bone is finding a suitable material that not only provides bone-like rigidity and porousness but also supports cell life throughout the fabrication process. Widely-used hydrogels, used for skin and liver tissues for example, lack stiffness. Materials that could provide substantial strength often require UV, harsh chemicals or high heat that would damage cells and therapeutic proteins.
Bioprinted constructs, before (left) and after (right) sintering.
Researchers at the Tissue Engineering Group at the University of Nottingham have announced progress in bioprinting bone tissue. In the journal Biofabrication, they reported news of bioprinting a microparticulate material at ambient temperature that “enables the incorporation of temperature-sensitive components such as cells and proteins in a spatially defined manner.” This material has properties that are similar to human cancellous bone, the spongy part of the bone that is typically filled with marrow and blood vessels.
The researchers combined poly lactic-co-glycolic acid (PLGA), an FDA-approved polymer, and polyethylene glycol (PEG), a compound used in medical and beauty products. “When mixed with aqueous carrier fluids at room temperature, these PLGA-based microparticles form extrudable pastes which can be formed to the desired scaffold shape,” says the researchers.
The initial use for this compound was for bone defect filler. Previous research had shown that proteins and cells maintain activity and viability in the mixing and extruding process. But this study looked at the feasibility of using this material in the Fab@Home printers, a platform of desk-top printers and programs which can produce functional 3D objects using open source software.
To optimize printing, the researchers adjusted the material in several ways including microparticulate size, carrier fluids and viscosity rates. The researchers then assessed compression rates, pore size and distribution, and cell viability.
“The work presented here has demonstrated the essential feasibility of using bioprinting and a thermo-responsive material to produce constructs which have mechanical properties comparable to cancellous bone,” they said. While quite promising, further work needs to be done in creating more sophisticated structures and optimizing cell seeding.
Kimberly Hatfield