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.
