3D printing has been used in the medical field for six or seven years, with some interesting cases that demonstrate the potential of additive technology. It was back in 2014 that surgeons at Texas Children’s Hospital in Houston, U.S. first produced 3D-printed color-coded 3D models of organs and skeletons in exquisite detail. This level of detail enabled surgeons to separate out two conjugated twin girls. The surgical procedure lasted for 26 hours.
Across healthcare, 3D printing is being used to produce low-cost, made-to-measure implants including jaws, pieces of skulls, hearing aids, and hips.
In pharmaceuticals, the area where 3D printing is likely to have the greatest impact is with tablet production. While the technology is currently prohibitively expensive for mass produced tablets (such as common pain killer drugs), there is a market for 3D printing and the production of personalized medicines.
This overcomes the need to purchase large and expensive machinery that will only be used to produce small runs of a niche medicine; in contrast one 3D printer can produce a range of personalized medicines through different software codes being activated.
The first 3D-printed approved medicine was in 2015, when the U.S. FDA (Food and Drug Administration) approved the medicine Spritam, which is a reformulation of the anti-epileptic seizure drug levetiracetam.
Since Spritam if formed from a layered, highly porous structure that takes in liquid quickly, it cannot be made using traditional tablet manufacturing methods. This is where 3D printing provided a solution. Additive manufacturing was key to creating the medicine in the form of lattice.
The process used takes a powder containing the drug. A powder layer is placed onto a surface, which moves along a conveyor belt and the moves underneath an inkjet printhead. This produces a binding liquid at specific locations along the powdered sheet, functioning to bind the powdered layer together. After this, a second layer of powder is laid down and printed for a second time at the same location. In the case of Spritam, this was undertaken up to 40 times. The advantage of this that when the latticework touches a sip of water it disperses in the mouth rapidly, enabling the medicine to take effect quickly.
A further innovation with tableting and 3D printing is with the production of polypills. These are single tablets containing multiple drugs (in order to reduce the number of different tablets a patient takes ). The complication with this is considerable, based on compatibility issues relating to how active pharmaceutical ingredients and incipient materials interact and the rate at which different active ingredients need to be released once the tablet has been ingested and has reached the digestive system.
The solution presented by 3D printing is with containing multiple drugs in a compartmentalized form within the single tablet. To overcome the release process, this is controlled by where a particular medicine is located within the tablet. Tests show that ingredients located in the center of the tablet are released first, with ingredients towards the edges of a tablet released second. This happens by varying the concentration gradient of the different ingredients through the use of paste extrusion 3D printing technology. These types of 3D printers are different to the fused deposition modelling types used to create thermoplastics molds in different shapes and sizes.
Fused deposition 3D printers can also play a role in the production of medicines. It is possible to embeds a drug into a plastic using hot-melt extrusion (where drug molecules are mixed with polymers under mechanical pressure). The resulting filament can be loaded into a print head and then printed. The degree to which this technology can be used depends on the type of drug and its thermal degradation properties. For example, some anticancer drugs can be produced this way, whereas no antibiotic could.
In relation to antimicrobials, an alternative 3D printing process based on stereolithography has proven to be more successful. This form of 3D printing involves taking the active ingredient and positioning.
There will no doubt be further innovations, building on the examples outlined in this article, with 3D printing to produce medicines.
