Researchers are developing ways to repair skull fractures – or reconstruct faces damaged in accidents - by using live cells in 3D-printed implants.
3D printing promises to change the way we think about production. Instead of factories making millions of shoes in a dozen sizes and shipping them around the world, local stores could make bespoke shoes just by scanning your feet.
Sometimes called additive manufacturing, 3D printing typically involves adding layer after layer of materials until the final product takes shape.
The same principle holds true for medicine. Dentists can already print customised replacement teeth in their own mini-labs, while orthopaedic surgeons can order tailor-made titanium hip and knee implants.
These processes rely on putting powdered metal, plastic or ceramic into a 3D printer, but researchers are now working on 3D-printed implants that use living cells to replace damaged body parts.
This would open the door to producing fragments of bone to repair fractures suffered by victims of accidents like car crashes.
One of the main challenges is to make a scaffold – a tailor-made frame which is the exact shape of the missing bone and grows with the body. Then stem cells, which are derived from bone marrow, are planted into the scaffold by printing and can survive and turn into more specialised cells, a process called cell differentiation. Finally, the implants would be replaced by the regenerated bone.
‘Our dream is to insert an implant that will be replaced by the body’s own cells.’
Professor Werner E. G. Müller, the coordinator of BIO-SCAFFOLDS
‘Our dream is to insert an implant that will be replaced by the body’s own cells,’ said Professor Werner E. G. Müller, coordinator of the EU-funded BIO-SCAFFOLDS project. To create the scaffold, the project will use 3D printing techniques such as selective laser sintering, where a laser is used to fuse the material into the required shape.
Finding the right material for a scaffold is a challenge in itself, but Prof. Müller, based at the University Medical Center of the Johannes Gutenberg University Mainz, Germany, has drawn inspiration from nature. ‘In our search for an inorganic, absorbable and biocompatible polymer we studied the biosilica skeleton of marine sponges,’ he said.
Using the genetic blueprint from these marine sponges, the group hopes to have made a usable scaffold by the time the project finishes in 2016.
‘The next step will be to put cells into the scaffold that we print and then make bone. Nobody has succeeded in doing this yet,’ Prof. Müller said. The process is technically challenging as the cells must be kept alive during the process.
While Prof. Müller’s group is working on a biosilica scaffold, Dr David Eglin, who coordinates the EU-funded RAPIDOS project, is attempting to solve the same problem using a printed scaffold made of molecules that can be broken down by the human body, a process known as being ‘resorbed’.
Professor Werner E. G. Müller, coordinator of the EU-funded BIO-SCAFFOLDS project.‘We will load this polymer with calcium phosphate ceramic. Our main interest in this material is that the surface will slowly erode, exposing the bone-conductive ceramic. As the scaffold is slowly resorbed, we hope a new matrix will be formed by the cells so we can recreate new bone,’ he said.
The RAPIDOS project is a European-Chinese collaboration which also plans to use a Chinese medicine extract, Icaritin, known to enhance bone healing. If it works, the implant could even become a drug-delivery system, according to Dr Eglin, who is principal scientist at the AO Research Institute in Davos, Switzerland.
The team wants to be able to rapidly generate a patient-specific scaffold for people with large orbital floor fractures – severe injury to the bone around the eye socket.
‘We are taking real images from patients, recreating a shape which can be printed into a 3D scaffold, and would then place cells into this porous structure creating a biological implant,’ Dr Eglin said. 'My guess is that four to five years would be necessary to develop a product based on our printed patient-specific implant.'
The work is of particular interest to developing countries. ‘In China, addressing orbital floor fractures is really relevant as car accidents are a big burden,’ he said.
Many replacement hips and knees currently implanted in Europe are made of strong but light titanium alloys. Surgeons order the model which is the best fit for their patient, who then adjusts to the implant as they recover from surgery.
However, 3D printing technology is making it easier and quicker to produce personalised artificial joints. Taking a scan of a patient’s knee joint and building a tailor-made replacement promises shorter surgery times, and faster recovery for patients because the implant is a perfect fit.
It is all thanks to improvements in advanced manufacturing that allow scientists to add fine titanium alloy powder to a 3D printer which then effectively welds tiny layers of liquid metal according to instructions received from computer aided design (CAD) software.
‘Research on 3D printing has intensified over the past decade and it has really exploded in the last two years,’ says Sozon Tsopanos of the TWI Technology Centre, in the UK. He worked on the EU-funded IMPALA project, which has helped to advance key aspects of 3D printing for medical devices by fine-turning systems for transferring data from a patient scan to computer design software and then to production of the implant.
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