MAE researchers help develop material for 3D printing inside the human body

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Depiction of tissue engineering structure being 3D printed directly on soft tissue
Depiction of tissue engineering structure being 3D printed directly on soft tissue

3D printing is commonly thought of being used in producing physical models and small structures. However, medical researchers have found ways to translate 3D printing capabilities to medical processes and treatments. Recently, a team of researchers have worked to develop the technology for 3D printing directly inside the human body.

David Hoelzle
Hoelzle

Mechanical and Aerospace engineering professor David Hoelzle, and PhD students Ali Asghari Adib and Andrej Simeunovic were part of a collaborative team that has developed a 3D printable biomaterial (bioink), that can be 3D printed intracorporeally, meaning directly inside the human body. 3D printing has been used previously to produce tissue engineering scaffolds for medical treatment, but most of these scaffolds are created in laboratories and later inserted surgically.

Asghari Adib noted that there is plenty of research on biomaterials for 3D printing of tissue engineering (TE) scaffolds. “But to the best of our knowledge,” said Asghari Adib, “none of them meet all the presumed intracorporal TE requirements.”

Ali Asghari Adib
Asghari Adib

The requirements are that the bioink needs to be printed at physiological temperature (37° C) and crosslinked using a method that is safe to native tissue. Hoelzle said that failing to be able to print at the right temperature could leave the bioink unable to hold its structure. These requirements are added to the conventional prerequisites of a biomaterial for TE, such as allowing viable cell growth.

“There were many challenges in developing this bioink,” said Asghari Adib.

These challenges included encapsulation of the cells in the biomaterial, shape fidelity and mechanical property testing of transparent soft materials, obtaining a printable bioink while keeping the cell viability high, and 3D printing on soft tissue interfaces.

simeunovic.1.jpg
Simeunovic

“We were able to overcome all these challenges with different scientific approaches,” said Asghari Adib. The team was able to develop a bioink that could be printed at body temperature, and crosslinked using safe visible light. The bioink scaffolds demonstrated consistent mechanical properties and high cell viability over 21 days.

Development of this bioink was a collaboration with two labs in the department of mechanical and aerospace engineering. One lab came into the project with expertise in cell culture. The other holds expertise in mechanical properties testing.

“Having an interdisciplinary team is critically important,” said Hoelzle. “It is very rare for a single lab to have all the facilities necessary for this type of study.”

The diversity in resources within MAE allowed the team access to traditional mechanical engineering experimental equipment, and to equipment in emerging areas of MAE such as facilities for cell culture and tissue engineering research. The group was also able to collaborate outside of the department with the Ohio State department of food science and technology to use necessary equipment.

Intracorporeal 3D printing process
Intracorporeal 3D printing process

The collaborative team was able to draw on previous research for the 3D printing of biomaterials. A key external collaborator was Ali Khademhosseini of the Teraski Institute. The Terasaki team contributed their visible light crosslinkable gelatin methacryloyl (GelMA), which is a natural hydrogel that is commonly used in tissue engineering. GelMA is known to be biocompatible, and have adjustable physiochemical properties. Visible light crosslinkable GelMA was the base material in the developed bioink.

However, “GelMA is not 3D printable at physiological temperature,” said Asghari Adib, “which is where our major contribution comes in.”

Having added the ability to 3D print the GelMA based bioink at the proper temperature is something that could have major impacts on medical treatment.

The team put the bioink to the test using a custom-built 3D printing system. With this configuration they were able to apply the bioink to soft materials, like raw chicken breasts, in a similar manner to construction caulk.

However, instead of sealing gaps in construction, the bioink was able to build interlocking structures directly on the soft surfaces. According to Hoelzle the structures can be printed in different ways, much like sewing stiches, that would give the bioprinted structures varying degrees of strength or flexibility.

These advances in biological printing could lead to safer and more cost-effective treatments for patients. The team hopes that this research will pave the way for minimally-invasive procedures that allow for patient-specific 3D printing of tissue engineering scaffolds directly inside the body. 

by Sam Cejda, Department of Mechanical and Aerospace Engineering