Florida Atlantic University: 3D Printing Flexible Self-Expanding Stents for Esophageal Cancer Patients

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Researchers from Florida Atlantic University are exploring new ways to make stents for patients undergoing palliation therapy due to dysphagia, a condition that makes it difficult to swallow—especially individuals suffering esophageal cancers that are inoperable.

In ‘3D-printed flexible polymer stents for potential applications in inoperable esophageal malignancies,’ authors Maohua Lin, Negar Firoozi, Chi-Tay Tsai, Michael B. Wallace, and Yunqing Kang sought to offer improvements over metal and plastic stents typically offered to patients today, also citing statistics regarding esophageal cancer as:

“…the sixth leading cause of cancer-related deaths worldwide and recognized as one of the most difficult and challenging malignancies to cure [1]. The five-year survival rate for patients with esophageal cancer is less than 20%. For those patients with inoperable esophageal malignancies, esopha- geal stents offer effective palliative therapy to allow per-oral drink- ing and feeding as well as swallowing of saliva.”

In an effort to find ways to help patients avoid side effects from implants such as tumor ingrowth, and complications like stent migration, the researchers 3D printed a tubular, flexible polymer stent with spirals that could be digitally optimized. The authors explain in their paper that 3D printed stents without spirals acted as controls in the experiment, along with:

  • Properties characterized in an ex vivo esophagus
  • Tests carried out in both neutral and acidic gastric buffers
  • Cytotoxicity of the new stent was examined through the viability test of human esophagus epithelial cells

Other efforts to improve on today’s stents have resulted in experiments with biodegradable stents too, as medical professionals and researchers realize the need ‘to avoid the complications of reinterventions for stent removal…’ These devices can be problematic also because often they do migrate (and in many cases, earlier), prompting negative reactions. Here, the researchers created a tubular, polymeric stent made of medical flexible thermoplastic polyurethane (TPU), offering the necessary toughness, durability, and biostability—and, PLA, offering mechanical strength and biodegradable properties.

Finite element analysis of PLA/TPU stents. (A) The simulation model when the stent is placed in an esophagus (i); the stent model with an obtuse, right and acute angle (ii); local stress versus acute, right and obtuse angle with 15PLA85TPU stent (iii). (B) The stents with spiral thicknesses of 0.3 mm, 0.6 mm, 0.9 mm, 1.2 mm and 1.5 mm (i); The circumferential stress of 15PLA85TPU stent versus circumferential deformation (ii). (C) The stent with spiral number 3, 4, 5, 6, 7, 8, 9, 10 (i); frictional force versus spiral number with 100TPU, 5PLA95TPU, 10PLA90TPU and 15PLA85TPU stents (ii).

Four types of stents were 3D printed at weights of 0, 5%, 10%, and 15% and respectively named 100TPU, 5PLA95TPU, 10PLA90TPU, and 15PLA85TPU. Several different prototypes were created, in different sizes, and some with color. They also noticed that the 3D printed stents were pliable, reverting to their original shapes after being released—leaving the scientists to notice the potential for self-expansion. This would make placing them far easier. The 15PLA85TPU stent with spirals expanded the most:

The whole parameter of the designed PLA/TPU stent (A). A PLA/TPU stent was being printed (B). Different types of 3D-printed stents with different structures and material ratios. (color was from added dyes) (C). The stent was compressed and then recovered to the original shape after it was released (D).

“Spiral stents opened larger luminal size than non-spiral stents when they had the same contents of PLA and TPU. The luminal size of the esophagus opened by the TPU stent without spirals is smallest in all the groups,” stated the researchers.

They measured the compression force with a mechanical tester, and the expansion force using a pig esophagus. All stents increased in compression force in direct response to the level of strain. In terms of decreasing migration, the researchers noted the stent with 10 percent PLA as the best candidate for anti-migration—along with better performance in expansion and cell viability too.

The new, upward spiral structure of the 3D-printed polymer stent has a significantly higher anti-migration force compared to non-spiraled stents. The spiral structure remarkably decreases the migration distance,” concluded the researchers. “The flexibility and rigidity of the composite polymer stent bring an adjustable self-expansion force. Importantly, such a functional polymer stent can be produced by 3D-printing and tailored to meet the treatment needs of different esophagus conditions and could be combined with other technologies in the future. In summary, the 3D-printed flexible polymer stent with unique structures has promising potential to potentially treat inoperable esophageal malignancies.”

Many health issues—both acute and chronic—can be challenging, but the sensations of not being able to swallow or feeling like one is choking can be terrifying, traumatic experiences. Researchers are continually seeking ways to offset the symptoms of dysphagia, with the development of 3D printed foods to aid with eating, along with splints and implants. What do you think of this news? Let us know your thoughts! Join the discussion of this and other 3D printing topics at 3DPrintBoard.com.

Expansion test of PLA/TPU stents. (A) The stent was compressed in a catheter (i); the stent was pushed out in the middle (ii); the stent was completely released from the catheter (iii). (B) The stent was guided into the esophagus by a catheter (i); the stent was released into the esophagus (ii); the esophagus with stent and without stent (iii). (C) The diameter of the esophagus in the middle was around 12–14 mm after the insertion of PLA/TPU stents with/without spirals. (D) The esophagus diameter at the two-ends part was significantly enlarged by the stents with spirals, compared to the stents without spirals. Higher content of PLA increased the larger diameter of the esophagus (n = 3).

[Source / Images: From Florida Atlantic University – ‘3D-printed flexible polymer stents for potential applications in inoperable esophageal malignancies’]

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