Biomechanical research has led to better designs for astronauts.Credit: Dima Zel/Shutterstock
Critical to the success of space travel is maintaining the health of astronauts as they endure extreme physical conditions. Shizhen Zhong, a clinical anatomist at Southern Medical University (SMU) in Guangzhou, China, leads a team that has been striving for two decades to understand and mitigate the risk of injuries sustained during launch and landing.
Along with Professor Wenhua Huang — leader of SMU’s national key discipline of Human Anatomy and director of the Guangdong Provincial Key Laboratory of Medical Biomechanics — he has led SMU to become one of China’s foremost hubs for biomedical engineering, bringing together a lot of laboratories and research centres to focus mechanics, digital medicine and 3D bioprinting.
After China’s first manned spaceflight in 2003, a major question was how to enable better cushioning and other physical support for astronauts in future missions, explains Zhong, who is also a member of the Chinese Academy of Engineering.
As part of a national team, Zhong and his colleague Lei Tang were invited to engineer better designs for spaceflight, following feedback from the pioneering taikonaut, Liwei Yang. He experienced extreme conditions during the 2003 launch and landing, including extreme g-forces, intense vibrations to his organs, and impacts on the cervical and lumbar vertebrae of his spine.
Biomechanic potential
Zhong led a team to run tests on the effect of impacts on astronauts under conditions of various heights, pressures, speeds and landing environments, and made a detailed analysis of the forces put on an astronaut’s spine, as well as the need for shock absorption. This work led to novel seat designs to ensure safety and comfort during launch, spaceflight and landing.
With Zhong’s expertise in biomechanics, the university has established a large-scale automobile crash experiment and research base in Guangdong Province, working to design cockpits and develop protective equipment for drivers and passengers.
Apart from the successful seat design, Zhong’s investigations on digital models of human anatomy has also greatly aided the research on surgery and even drug design.
In 2001, Zhong led the Chinese Digital Human Project to image and digitize the anatomy of the human body. In 2003, his team created the first digital image dataset of a female body with more than 8,000 cross sections in China. Later, the team imaged a male body at a higher resolution, with more than 9,000 image slices. The models provided invaluable data to create a 3D atlas of the body and a database of morphology and physiology.
With these tools, surgeons can simulate an operation based on a patient’s precise anatomical details and learn how to improve the accuracy of real procedures. The models have also been useful in disease diagnosis and drug development.
Medical 3D printing
Following Zhong’s digital work on human anatomy, Huang set out to combine digital medicine with clinical applications. His research on three-dimensional (3D) printing, for instance, has resulted in a series of innovations such as novel prosthetic and orthopaedic devices.
A model of the vasculature within the lungs, created via 3D printing.Credit: Southern Medical University
The industry has since grown so rapidly “that we have seen the acceleration of 3D printing” for medical applications, he explains.
Sacral fractures of the pelvis are often under-diagnosed and associated with neurological problems, he says. To ensure a painless and long-lasting functional joint, Huang’s team has employed 3D printing technology in minimally invasive surgery to repair the sacral fractures. Based on the 3D images of injured pelvises, the team create 3D models of sacral fractures, which allow for simulations of surgery before it takes place, and adjustment of steel plates to perfectly fit the individual shapes of a patient’s bones. The simulation and pre-adjustment of implants help improve significantly the quality of fracture resetting in a minimally invasive procedure, causing little damage to surrounding tissues.
The same technique has been adopted in the design of the world’s first minimally invasive keyhole surgery for fractures in the ball and socket of the hip joint. Traditionally, surgical treatment of ‘acetabular’ fractures, requires a large incision which can lead to considerable blood loss and a potentially lengthy recovery. But now, based on CT images, Huang’s team create 3D-printed model of the hip socket and fracture. A simulated surgery is then performed on a model, and later a steel plate of the precisely required size and shape is inserted via the abdomen, rather than the outside of the hip, minimizing blood loss and recovery time.
Smart biofabrication
Huang says that 3D bioprinting technology has offered new possibilities for regenerative medicine to repair damaged tissues and organs, and may one day provide synthetic bioprinted organs that remove the need for donor organs to save lives.
To achieve the goal of alternative transplantable organs, Yaobin Wu in Huang’s SMU team has created biomimetic 3D models, from which bone and muscle tissue can be fabricated using engineered biomaterials known as bioinks, a mixture of materials and live cells. In the models, 3D scaffolds can be printed, providing a structural support for cells, stimulating the growth and formation of desired tissues. The team has made great progress in formulating types of bioinks using microspheres of hydrogel — a polymer that mimics the extracellular matrix of tissues.
The initials of Southern Medical University are 3D printed in gel.Credit: Southern Medical University
A current treatment for injured cartilage involves injecting chondrocytes — cells responsible for cartilage formation — into joints to encourage repair, but the low retention and survival of the injected cells means uses are limited.
To overcome these limitations, Huang’s team have trialled the use of hydrogel microspheres to carry chondrocytes into the body. In a 2020 publication, the team reported the methodology results in more viable cells. “Cell-laden microspheres were injectable and the cell viability was still high after injection. And the microspheres can self-assemble into a 3D cartilage-like scaffold, showing potential in cartilage tissue engineering,” says Huang.
The team has also synthesized a bioink from microspheres and hydrogel, which can release growth factors to maintain the survival of nerve cells. The bioink can be used alongside 3D bioprinted composite scaffolds for peripheral nerve tissue regeneration.
Hydrogels are also used for patients who have to undergo abdominal surgery. Bands of scar tissue following surgery, known as adhesions, can result in intestinal blockages, infertility or chronic pain. To help prevent this, Huang worked with Professor Guoxin Li, in the Department of General Surgery of Nanfang Hospital, in Guangzhou, to develop an injectable hydrogel which is more likely to be retained by tissues. It can be used to seal wounds and dries within five seconds under ultraviolet light to prevent it sticking to surrounding healthy tissues. “We are working with Changzhou Hualian Health Dressing Company on clinical translation of these materials,“ Huang says.
Cardiac muscles are developed on a chip to study the growth and function of muscle cells.Credit: Southern Medical University
Skeletal muscles on a chip are developed to test drugs for injury.Credit: Southern Medical University
The team has also done a great deal of research and experimentation to prepare 3D bioprinting materials with enhanced mechanical and surface properties, and that have high compatibility with human cells and tissues. By combining 3D bioprinting and microfluidic chip techique, Huang’s team has also developed organ-on-chip models to study organ function and test drugs.
Rapid growth
Huang’s research hints at some of the potential of the printing techniques. “3D printing technology is set to revolutionize the future of health care,” he says. The global sales revenue related to 3D printing reached US$12.5 billion in 2020 — with the healthcare industry accounting for 13.9% of that — a figure that is expected to grow in coming years.
The team at Southern Medical University 3D-prints metal samples.Credit: Southern Medical University
Huang’s team has been awarded many patents, and has close collaborations with medical device companies to drive commercialization of products. Recently, they have developed an orthotic device to treat ear abnormalities, along with Zhuhai Sailner 3D Technology Company. They have developed a personalized 3D metal prosthesis with Changzhou Geasure Medical Apparatus and Instruments Company.
The researchers have also participated in the creation of industrial standards that seek to regulate 3D bioprinting in China. Huang has taken the lead in standardizing the application of bioprinting technology in precision surgeries to repair broken fingers, injured muscles and bones, and in minimally invasive spinal surgery.
To help upskill researchers on medical 3D printing, the university has run a series of training courses on its uses in orthopaedics. The SMU researchers have also published China’s first monograph on the topic, 3D Orthopaedics, as well as a series of popular science books to enhance awareness of medical uses of 3D printing.
Based on the university’s Guangdong Provincial Key Laboratory of Medical Biomechanics, and Guangdong Provincial Key Laboratory of Construction and Detection in Tissue Engineering, SMU has established an interdisciplinary collaboration of university researchers across fields of medical anatomy, digital medicine and 3D printing to fuel future growth.
The university has founded two academic associations, two research centres, and 21 nationwide technology support units affiliated with clinics and corporates, to push the frontiers of biomedical research and innovation.
“I believe 3D printing will change the world, and I will continue to explore its possibilities in the medical field,” Huang says.