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You might think that glass has no business acting as a replacement for bone, but it turns out the two materials have many similarities. For a new study in ACS Nano, researchers developed a 3D printable bio-active glass that served as an effective bone replacement material. In rabbits, it sustained bone cell growth better than regular glass and a commercially available bone substitute.

Both bone and glass can bear weight better than they can withstand being stretched because of the crystalline structures of the molecules and minerals forming them. But unlike bone, the main ingredient in glass—silica—can exist in a liquid form and can be 3D printed into any desired shape, such as a perfect match to a missing section of bone. However, most 3D-printable glass requires toxic plasticizing agents, or the glass needs to be fused at temperatures higher than 2,000°F (1,100°C).

So, Jianru Xiao, Tao Chen, Huanan Wang and colleagues wanted to develop a 3D-printable glass that didn't require plasticizers or extremely high temperatures to serve as a scaffold for bone-forming cells.

The researchers combined oppositely charged silica particles as well as calcium and phosphate ions—both known to induce bone cell formation—to form a printable, bio-active glass gel. After the glass was shaped with a 3D printer, it was hardened into its final shape in a furnace at a relatively cool 1,300°F (700°C). Next, they tested the new bio-glass against a 3D printed plain silica glass gel and a commercially available dental bone substitute by repairing skull damage in living rabbits.

Although the commercial product grew bone faster, the bio-glass sustained growth longer; after eight weeks, most bone cells present had grown on the bio-glass scaffold. The plain glass had barely any bone cell growth. The researchers say that this work demonstrates an easy, low-cost way to 3D print a bio-glass bone substitute, which could have wide-ranging applications across medicine and engineering.