NumericaI simuIation anaIysis of the internaI fIow fieId of a 3D bioIogicaI printhead based on FLUENT / 中国组织工程研究

BACKGROUND: With the development of 3D printing technology, organ and tissue construction can be achieved by constructing a three-dimensional scaffold that is conducive to cell growth. OBJECTIVE: To solve the scaffold over-accumulation during 3D printing.METHODS: Fluent, a finite element analysis software developed by ANSYS Company in the United States, was used to analyze the extrusion process of print heads and to obtain suitable viscosity and extrusion pressure of materials for the 3D printing of cellulose gel composites. We then compared simulation results with experimental results. RESULTS AND CONCLUSION: The error between simulation results and experimental results was less than 5%. The simulated values at a kinetic viscosity of 45 and a pressure of 0.10-0.12 MPa solved the phenomenon of over-accumulation of cellulose gel composites during the 3D printing process, ensuring enough space for the 3D printed scaffold.

Experimental study on the reconstruction of circumferential tracheal defects with novel prosthesis / 中华外科杂志

<p><b>OBJECTIVE</b>To investigate the feasibility of using new tracheal prosthesis made of biomaterials to replace extensive circumferential tracheal defects in mongrel dogs.</p><p><b>METHODS</b>Three types of tracheal prostheses were developed, whose basic skeleton of tubular mesh was knitted with polypropylene monofilament and poly (lactic-co-glycolic acid) fiber. The inner side of type-I tubular mesh was first coated with polyurethane solution and then with collagen. The exterior of type-I was then immobilized with collagen-hydroxyapatite composites. In contrast, the internal and external walls of type-II were coated with polyurethane solution, which produced a prosthesis similar to a nonporous one, while type-III was coated only with collagen solution. Surgical resection and replacement of a segment of the cervical trachea was performed in 16 adult mongrel dogs. The efficacy of the implanted prosthesis periodically evaluated postoperatively.</p><p><b>RESULTS</b>In group A, only one died from prosthetic dehiscence, another from anastomotic leakage, and the others had uneventful postoperative courses. The implanted prosthesis was completely incorporated with the recipient trachea, where different length of reepithelialization occurred on the luminal surface of the reconstructed trachea. Macroscopic examination showed scattered and different sizes of neo-ossification surrounding the implanted prosthesis. The prosthesis was roentgenopaque when exposed to routine X rays. In contrast, a relatively high number of complications occurred postoperatively in group B and C.</p><p><b>CONCLUSION</b>Type-I tracheal prosthesis may be used effectively for long-segment circumferential tracheal replacement, and appears very promising for clinical application, with further improvements in promoting the epithelialization.</p>

Experimental study on a novel esophageal prosthesis made of composite biomaterials / 中华外科杂志

<p><b>OBJECTIVE</b>To design and develop a novel esophageal prosthesis by selecting appropriate biomaterials, developing special manufacturing techniques, and investigating the feasibility of replacement of cervical esophagus in mongrel dogs.</p><p><b>METHODS</b>In accordance with the requirements of ideal esophageal substitutes, we designed a new type of esophageal prostheses. The inner stent were made with polyurethane of medical grade, and the outer surface of the prosthesis was coated with collagen-chitosan sponge. The silicone tube was used as a control. Thirteen adult mongrel dogs that were divided into two groups were used to establish the experimental models.</p><p><b>RESULTS</b>In the experimental group (n = 8), the esophageal prostheses were completely incorporated with the native esophagus and adherent to the surrounding host connective tissues. Epithelial linings of varying degrees were formed on the luminal surface, and complete epithelization was seen in 1 month postoperatively. The granulation at the sites of the anastomosis in this group was less significant than that of the control group. One dog has been surviving for 12 months up to now without any complications. In the control group (n = 5), esophageal epithelial was not observed on the luminal surface, constriction of the regenerated esophagus progressed and all the dogs died within 2 months after operation.</p><p><b>CONCLUSION</b>These observations suggest that this esophageal prosthesis made of composite biomaterials has high biocompatibility and potential for long-segment esophageal reconstruction, which is promising for the clinical repair of esophageal defects.</p>

Replacing dog cervical esophagus with polyurethane stent covered with collagen-chitosan sponge / 第二军医大学学报

Objective: To replace esophageal defects with artificially composed biodegradable materials and non-biodegradable materials. Met hods: A two-layered tube consisting of a collagen-chitosan sponge and an inner polyurethane stent was used to replace 5 cm esophageal segmental defect s in 15 dogs. The inner polyurethane stent was removed endoscopically at weekly intervals from 2 or 4 weeks. Results: Partial regeneration of es ophageal epithelia was observed in 5 dogs at week 2, and progressing constricti on occurred and the dogs became unable to swallow within 1 month. In the 10 dog s that the polyurethane stent was removed at week 4, regenerated esophageal tiss ue successfully replaced the defects, and complete epithelization was observed 1 month after surgery. Complete regeneration of esophageal mucosa structures, inc luding mucosal smooth muscle and mucosal glands were observed 3 months after surgery, and partial regeneration of esophageal muscle tissue was also observed 6 months after surgery. Conclusion: Our artificial prosthesis i n reconstruction of the cervical esophagus segment in dogs is feasible. Through temporary polyurethane tube, collagen-chitosan sponge provides a three-dimensi onal structure suitable for the regeneration and sufficient degradation time for the complete regeneration of esophagus.

Replacing dog cervical esophagus with polyurethane stent covered with collagen-chitosan sponge / 第二军医大学学报

Objective: To replace esophageal defects with artificially composed biodegradable materials and non-biodegradable materials. Met hods: A two-layered tube consisting of a collagen-chitosan sponge and an inner polyurethane stent was used to replace 5 cm esophageal segmental defect s in 15 dogs. The inner polyurethane stent was removed endoscopically at weekly intervals from 2 or 4 weeks. Results: Partial regeneration of es ophageal epithelia was observed in 5 dogs at week 2, and progressing constricti on occurred and the dogs became unable to swallow within 1 month. In the 10 dog s that the polyurethane stent was removed at week 4, regenerated esophageal tiss ue successfully replaced the defects, and complete epithelization was observed 1 month after surgery. Complete regeneration of esophageal mucosa structures, inc luding mucosal smooth muscle and mucosal glands were observed 3 months after surgery, and partial regeneration of esophageal muscle tissue was also observed 6 months after surgery. Conclusion: Our artificial prosthesis i n reconstruction of the cervical esophagus segment in dogs is feasible. Through temporary polyurethane tube, collagen-chitosan sponge provides a three-dimensi onal structure suitable for the regeneration and sufficient degradation time for the complete regeneration of esophagus.