62 / 2019-08-15 15:18:06

Design and Fabrication of Biodegradable External Airway Splints with Native-like Mechanical Properties

Design,External airway splints,Mechanical properties,Tracheomalacia (TM),Polycaprolactone (PCL)

全体主题 > Design and fabrication of biological systems

Suspending malacic tracheas with additively manufactured external airway splints that derived from degradable biopolymers is a promising strategy to treat tracheomalacia (TM). However, it is still changing for most of the existing splints to fully reproduce the lumen shapes as well as the mechanical properties of native tracheas. In this work, we designed and fabricated biodegradable external airway splints which possessed native-like lumen geometry and mechanical properties.
The contour shape of the external airway splints was designed according to the geometrical characteristics of native tracheas. Matchable mechanical properties were then realized by adjusting different pore shape and size of the splints, consisting of the hexagon (H) and diamond (D) pore shape with the inscribed circle diameters of 3 and 5 mm (Design parameters are shown in Fig.1a with H5 as an example). Selective laser sintering (SLS) was employed to fabricate the as-designed splints with polycaprolactone (PCL). The structural analysis of SLS-fabricated splints was characterized by micro-computed tomography (μ-CT, YXLON.CHEETAH, Germany) and a scanning electron microscope (SEM, Hitachi S-3000N, Japan). In order to examine the mechanical properties of the fabricated splints, compression testing was further performed in both radical and lateral directions using an electromechanical universal testing machine (Wance 103A, China).
Macro/micro structural characterisations of the SLS-fabricated PCL splints demonstrated well reproduction of the designs with nearly full density in a reproducible manner (Fig.1b-c). The radical and lateral compression results showed that the SLS-fabricated D3 splints exhibited very similar initial mechanical properties (stiffness of 2.2 ± 0.1 N/mm and 0.59 ± 0.05 N/mm) to those of native tracheas (stiffness of 2.2 ± 0.5 N/mm and 0.43 ± 0.18 N/mm) with the same length of 60 mm. Additionally, the intraluminal height and area of the splints can retrieve 83.0 ± 1.3% and 81.2 ± 5.0% even when the splints were periodically compressed under a radial deformation of 60% for 200 times. To further investigate their efficacy for animal survival, the D3 splints were implanted in a tracheomalacia dog model. X-ray images revealed that the tracheomalacia was mitigated immediately after the malacic tracheas were suspended with the splints, and the lumen of airways gradually restored normal patency within 1 week. The dogs survived for 5 weeks after the surgery without any sign of wheezing or dyspnea. In comparison, the dogs in the control group died due to the collapse of airways.
Here we designed and fabricated PCL external airway splints with different pore characterization by employing the SLS technique. The fabricated D3 external airway splints can successfully reproduce native-like mechanical properties of tracheas and prolong the life of dogs with TM, which could be clinically used for the treatment of tracheomalacia. Future studies should be conducted to incorporate bioactive or functional biomaterials into the splints for functionalization, so as to achieve specific properties such as controlled drug release for better treatment effect.