INNOVATION ARTICLES THE IDEA SUBMISSION PORTAL FROM MEDTRONIC

Decreasing cost and better access to 3D printing is fuelling a research explosion into using the technique for medical applications. While the technology has created impressive external cosmetic replacements such as ears and noses, research into internal devices constructed through 3D printing for hips, knees, elbows and jaws is on-going. Perhaps even more exciting is the potential to construct products embedded with biological materials for regenerative purposes, a process known as bioprinting. Multiple applications of this process are being explored.

In June 2012, researchers in Belgium used 3D printing to create a replacement titanium lower jaw. An 83-year-old female patient had suffered from osteomyelitis, losing her original jaw to the infection. After an MRI scan, the image was fed through a 3D printing system using a precision laser with titanium powder particles to create a patient-specific implant replacement, layer-by-layer. Within four hours post-implantation, the woman was able to eat and talk. This contrasts with existing options: a standard off-the-shelf jaw prostheses in a limited size range or a moulded jaw, which is time consuming and often cost prohibitive.

Researchers believe the same technique could be applied to hip, knee, elbow and shoulder prostheses, and even large portions of the skull. Washington State University Professors Susmita Bose and Amit Bandyopadhyay report that the creation process is much swifter than casting moulds with the first design iteration available within hours of a patient scan, manufacturing then taking just five to six hours. The Washington State University team is exploring the use of tantalum and ceramics for 3D printed layered implants, with pores or textures to promote osseointegration. Bandyopadhyay anticipates that by 2020 custom 3D printed implants will be close to standard practice.

In cardiology, custom valves and stents are areas that lend themselves to 3D printing, but interesting work also is being done in heart wraps that have the potential to monitor and offer drug delivery. Current support heart sacs are one-size fits all, but each patient’s heart shape is unique. Professors Igor Efimov of Washington University and John Rodgers of the University of Illinois have designed 3D printed fabric mesh sacs embedded with electrode sensors to monitor pH, mechanical strain and temperature. Depending upon what sensors are used they could deliver electrical pulses or deliver medication as well. Physicians can position the electrodes by attaching the mesh wrap with sutures or adhesives. Designed to treat ventricle deformities and arrhythmias, researchers believe the mesh could find much wider use for bladder control, kidney diseases and nervous system disorders.

At Mount Sinai’s Airway Center in New York, Drs Robert Lebovics and Faiz Bhora are leading research into 3D bioprinting using biological gel tracheas embedded with stem cells for growth. The stem cells differentiate into cartilage after surgery. This could be transformative for young patients as the trachea implants will grow with the patients, eliminating the need for additional surgeries and replacements. Currently in animal testing, the team hopes to implant the first in-human 3D printed trachea in a few years.

One of the most interesting research areas focuses on a 3D bioprinted brain implant that could lead to a paradigm shift in treatment for mental illness. At the University of Wollongong in Australia, investigating Professors Xu-Feng Huang and Gordon Wallace are developing organic-based polymers that can conduct electricity. Using bioprinted 3D implants made from carbon, hydrogen and nitrogen, embedded with proteins, the investigators have proven that electrical signals can be transmitted to excitable cells such as nerve and muscle cells. Therefore, influencing the development and behaviour of those cells. Wallace said, “The polymers are organic and they’re unusual in that they conduct electricity. Those two things together lead us to believe that they may be very effective as electronic interfaces to biological systems.”

The hope is that by implanting this biologically active device in the specific problem area of the brain, the proteins will promote healthy cell development, improving connections between brain cells. This offers the promise of new treatment pathways for epilepsy and schizophrenia, among other potential areas. “The idea is to use an implant or a conduit to facilitate the natural regeneration process. Then having facilitated that regeneration process, the conduit will biodegrade and leave the body,” Wallace said.

Considering other parts of the body, Wallace reports that it is important to tune the implant not only to cope with any stress that may be placed upon the device, but also to what cells that may interact with the materials. “The mechanical properties can be tuned across a wide range,” he said. “The beauty of 3D biofabrication is that it can be customised, not just in terms of shape, but also in composition.” Wallace notes that while personalised medicine for pharmaceuticals is well known, we are on the cusp of highly personalised medical devices. He believes that for simpler structures like cartilage regeneration, products may be in a clinical setting in a few years. However he cautions, “The science and technology is progressing at a staggering rate. I think it’s going to be interesting to see how the regulatory authorities keep up.”