It has been some time since 3D printers entered our collective consciousness as useful tools for more than toys and demonstration objects. Even firearms and certainly synthetic prosthetic limbs seem capable of being 3D-printed. As ageing societies face increasing shortages of donor organs for transplantation, the use of 3D print technology in medicine, although perhaps among the most obvious and compelling, is new but likely to disrupt synthetic biology as few tools have done before. Small wonder it won first prize 2016 at the international Genetically Engineered Machine (iGEM) contest, an MIT creation. The method enables printing intact tissues and potentially even entire organs using 3D bioINK tissue printing technology.
While printing biological material such as cartilage is already established state-of-the-art, printing complex cell tissue still presented notable challenges. They were resolved by printing layers of living cells with a 3D printer into a biocompatible matrix in a petri dish. In the past, hydrogels were used to supply a gelatin-like structure that is only later populated by cells. This “scaffolding” complicates printing and creates unnatural coherence between cells.
Instead, the students at two universities in Munich, Ludwig-Maximilian University and Technical University of Munich, developed a proprietary “biological ink” similar to a two-component adhesive to print living cells directly in 3D. Its main component is biotin, also known as vitamin H or B7 that is loaded onto the cellular surface. The second component, streptavidin, is a protein that binds biotin and thus provides the biochemical adhesive proper. In addition, high-volume proteins were equipped with biotin groups in order to create cross-networking structures. When a suspension of these cells is “printed” into a concentrated solution of the protein components, they form the requisite 3D structure and the bioINK tissue printer forms layers of scalable, formable tissue of living cells, ready for transplant.