Bioprinting on the operating table
Fixation of traumatic injuries to the skin and bones of the face and skull is difficult due to the many layers of different types of tissues involved in the process. Researchers from the University of Pennsylvania restored such defects in rat models using bioprinting during surgery.
This work is of great clinical importance, as it makes it possible to fix both hard and soft tissues at the same time. Currently, the use of a graft from another part of the patient's body or cadaveric material is required to fix injuries to the bones of the head. The bone must be covered with transplanted soft tissue with sufficient blood supply, otherwise the bone tissue will die. Then surgeons need to restore soft tissues and skin.
Ibrahim Ozbolat and his colleagues used extrusion and drip bioprinting of mixtures of cells and carrier materials to restore both bone and soft tissue.
First, the researchers solved the problem of bone replacement. The "solid" ink was created from collagen, chitosan, nanohydroxyapatite and other compounds and mesenchymal stem cells – multipotent bone marrow cells that create bone and cartilage tissue.
Solid fabric ink is supplied at room temperature, but when applied, it heats up to body temperature. This creates a physical crosslinking of collagen and other ink components without any chemical changes or the need for a stapler additive.
To create a soft tissue, the researchers used drip printing. They alternated layers of collagen and fibrinogen with cross-linking and growth-enhancing compounds. Each layer of the skin, including the epidermis and dermis, is different, so the printed layers of soft tissues differed in composition. Experiments to restore a 6-millimeter skin defect were successful.
Diagram of the skin and bone bioprinting process.
After the researchers created the skin and bones separately, they moved on to reconstruct both structures during a single surgical procedure.
After careful visualization, to determine the geometry of the defect, the researchers laid the bone layer. Then they applied a barrier layer that mimics the periosteum. It was necessary so that cells from the skin layers would not migrate to the bone area and begin to grow there. After installing the barrier, the researchers printed layers of dermis and then epidermis.
It took the bioprinter less than 5 minutes to lay the bone layer and soft tissues.
The researchers closed more than 50 defects and achieved 100% soft tissue repair in four weeks and 80% bone repair in six weeks, but Ozbolat noted that even with bone transplantation, defect repair usually does not reach 100% in six weeks.
According to the researchers, blood flow to the bone is especially important, and the inclusion of vascularizing compounds is the next step. They also plan to transfer this research to human tissues and continue to work with neurosurgeons, craniofacial and plastic surgeons.
Article by K.K.Moncal et al. Intra-Operative Bioprinting of Hard, Soft, and Hard/Soft Composite Tissues for Craniomaxillofacial Reconstruction is published in the journal Advanced Functional Materials.
Aminat Adzhieva, portal "Eternal Youth" http://vechnayamolodost.ru based on Penn State: Skin and bones repaired by bioprinting during surgery.