What is 3D Bioprinting and How Does it Work?

3D Bioprinting, also known as bioinks, is a form of additive manufacturing that uses cells and other biocompatible materials as 'inks' to print living structures layer-by-layer, which mimic the behaviour of natural living systems.

Bioprinted structures like an organ-on-a-chip can be used to study a human body's functions outside the body (in Vitro) in 3D. A 3D bioprinted structure's geometry is more similar to that of a naturally happening biological system than an in vitro study performed in 2D. It can be more biologically relevant to form a new organ. It's most commonly used in the fields of tissue engineering and bioengineering, and materials science.

3D bioprinting has been increasingly used for pharmaceutical development and drug validation. It will soon be used for medical applications in clinical settings such as 3D printed skin grafts, bone grafts, implants, biomedical devices, and even full 3D printed organs are all active bioprinting research topics.

How does 3D Bioprinting Function?

3D bioprinting starts with a recreated layer-by-layer model structure out of a bioink, combined with living cells, or seeded with cells after the print is complete. These models can come from anywhere, an MRI or CT scan, a computer-generated design (CAD) program, or a file downloaded from the internet.

That model file is then fed into a slicer, a computer program that analyses the model's geometry and generates a series of thin layers or slices. It forms the shape of the original model when stacked vertically. For example, Cura and slic3r are two commonly used slicers in 3D printing. Allevi also has a specialized slicer, explicitly optimized for bioprinting, created into Allevi Bioprint software.

If a model is sliced, the slices are transformed into path data, stored as a g-code file sent to a 3D bioprinter for printing. This bioprinter follows instructions in the g-code file in order. It includes instructions to control the extruders' temperature, bedplate temperature, extrusion pressure, crosslinking intensity and frequency, and the 3D movement path generated by the slicer. When all the g-codes commands are completed, the print is done and can be cultured or incorporated with cells as part of a biostudy.

3D Bioprinting Techniques Producing Human Organs

Following are the various techniques of 3D Bioprinting to create different Body parts:

Forming Artificial Bone Matrix

A team from Swansea University, UK, has developed a bioprinting process to create an artificial bone matrix, using durable, regenerative biomaterial.

Today, complex bone fractures are treated through bone grafting, a surgical procedure. It replaces missing or damaged bones with synthetic, cement-based materials. This technique has its limitations, too, as these structures can frequently have inappropriate mechanical integrity and disallow the formation of new bone tissues.

The bioprinted bones could be printed in the exact structure required with a durable and regenerative biomaterial, made from gelatine, agarose, collagen alginate, calcium phosphate, and polycaprolactone. These are capable of fusing with a patient's natural bones over time, ultimately being replaced by them.

Caring Damaged Joint

Researchers at BioFAB3D, an Australian biofabrication centre have built a handheld cartilage printing device called BioPen. It is filled with stem cells derived from a patient's fat that can produce and surgically implant custom scaffolds of living material into failing joints. Like 3D printed bones, the cartilage undergoes a process of growth and development within the body. Although it's been tested only on sheep so far, developers hope that BioPen can accelerate functional cartilage regeneration in human patients in the future.

Surgeons will use 3D printing technology in the handheld stylus to place the bioink into a damaged joint layer by layer. The ink layers consist of stem cells and specially-selected growth factors within a biopolymer matrix, form a structure in which a patient's reproducing cells will rapidly reinforce for lasting cartilage repair.

Healing Burnt Skin

A printer designed by Wake forest Schools of Medicine can print skin cells directly onto a burn wound.

The typical treatment for severe burns is skin grafting. In this process, healthy skin is harvested from an unburnt part of a patient's body. This method can be traumatic to heal from, and in some cases, there is not sufficient healthy skin left on the body to use.

In the newly developed technique, a patch of skin only 10% of the burn size can be used to enlarge cells for 3D printing. A scanner determines the wound's size and depth. Then the printer absorbs this information and prints dermic, hypodermic, and epidermic skin cells at the corresponding depths to cover the wound.

With trials of this technology move forward, the researchers hope to see if stem cells from amniotic fluid and placentas are as effective as patient skin in healing the wounds.

As bioprinting evolves, it will become possible to use a patient's own cells to 3D print skin and bone grafts, organ patches, and even full replacement organs. In the future, 3D bioprinting will provide doctors and researchers with the tools to better target treatments and improve patients' conditions.