"Reverse" 3D printing used to produce bone-repairing scaffold implants
For some time now, we've been hearing about scaffolding-like implants that encourage bone tissue or cartilage to grow back into areas where it's missing. Now, scientists have developed a method for more quickly and easily 3D-printing such implants.
First of all, just how does so-called "microscaffolding" work? Well, if a patient is missing a section of bone (due to accident or disease), doctors start by producing an implant which gets surgically placed within the gap where the bone should be. That implant has a three-dimensional scaffolding-like microstructure, and is made of biocompatible, biodegradable materials. It may also contain compounds that nurture cell growth.
Because the implant's internal structure is similar to that of natural bone, cells from the patient's adjacent bone tissue gradually start migrating into it, "roosting" within its linked empty spaces. Those cells proceed to reproduce, displacing the scaffolding material as it harmlessly dissolves. Eventually, all that's left is pure, natural bone, filling the former gap.
3D-printing the implants can be tricky, though, due to the fact that the walls of the empty spaces are very thin and intricate – the print nozzles on most commonly used 3D printers simply aren't capable of that level of detail. That's where the new technique comes in.
Known as Negative Embodied Sacrificial Template 3D (NEST3D) printing, it was developed by scientists at Australia's RMIT University and St. Vincent’s Hospital Melbourne. The process begins by 3D printing a negative template of the scaffolding's empty spaces, in which they're represented by solid polyvinyl acetate (PVA) glue. A regular printer nozzle is fully capable of doing the job.
After that template is placed in a mold, a biocompatible/biodegradable liquid material such as a polymer is poured in, filling in the spaces not occupied by the template. Once the polymer has solidified, water is used to dissolve the soluble PVA glue. As a result, the template disappears, and all that's left behind is an intricate polymer "skeleton" that forms the scaffolding.
Along with its role in repairing bone deficits, the technology could conceivably also find use in applications such as growing replacement body parts in a lab.
"It’s extraordinary to create such complex shapes using a basic 'high school' grade 3D printer," says the lead scientist, RMIT's Dr. Cathal O’Connell. "That really lowers the bar for entry into the field, and brings us a significant step closer to making tissue engineering a medical reality."
The research is described in a paper that was recently published in the journal Advanced Materials Technologies.