A 3D Printable Electroconductive Biocomposite Bioink Based on Silk Fibroin-Conjugated Graphene Oxide.

Reduced graphene oxide (rGO) has wide application as a nanofiller in the fabrication of electroconductive biocomposites due to its exceptional properties. However, the hydrophobicity and chemical stability of rGO limit its ability to be incorporated into precursor polymers for physical mixing during biocomposite fabrication. Moreover, until now, no suitable rGO-combining biomaterials that are stable, soluble, biocompatible, and 3D printable have been developed. In this study, we fabricated digital light processing (DLP) printable bioink (SGOB1), through covalent reduction of graphene oxide (GO) by glycidyl methacrylated silk fibroin (SB). Compositional analyses showed that SGOB1 contains approximately 8.42% GO in its reduced state. Our results also showed that the rGO content of SGOB1 became more thermally stable and highly soluble. SGOB1 hydrogels demonstrated superior mechanical, electroconductive, and neurogenic properties than (SB). Furthermore, the photocurable bioink supported Neuro2a cell proliferation and viability. Therefore, SGOB1 could be a suitable biocomposite for neural tissue engineering.

Fabrication of a Urea Biosensor for Real-Time Dynamic Fluid Measurement.

In this study, a portable urea sensor that monitors the urea concentration in flow conditions was fabricated. We propose an electrochemical sensor that continually measures the urea concentration of samples flowing through it at a constant flow rate in real time. For the electrochemical sensing, a porous silk fibroin membrane with immobilized urease was mounted in a polydimethylsiloxane (PDMS) sensor housing. The fabricated urea sensor elicited linear current⁻concentration characteristics in the clinically significant concentration range (0.1⁻20 mM) based on peritoneal dialysis. The sensor maintained the linear current⁻concentration characteristics during operation in flow conditions.

Digital light processing 3D printed silk fibroin hydrogel for cartilage tissue engineering.

Three-dimensional printing with Digital Lighting Processing (DLP) printer has come into the new wave in the tissue engineering for regenerative medicine. Especially for the clinical application, it needs to develop of bio-ink with biocompatibility, biodegradability and printability. Therefore, we demonstrated that Silk fibroin as a natural polymer fabricated with glycidyl-methacrylate (Silk-GMA) for DLP 3D printing. The ability of chondrogenesis with chondrocyte-laden Silk-GMA evaluated in vitro culture system and applied in vivo. DLP 3D printing system provided 3D product with even cell distribution due to rapid printing speed and photopolymerization of DLP 3D printer. Up to 4 weeks in vitro cultivation of Silk-GMA hydrogel allows to ensure of viability, proliferation and differentiation to chondrogenesis of encapsulated cells. Moreover, in vivo experiments against partially defected trachea rabbit model demonstrated that new cartilage like tissue and epithelium found surrounding transplanted Silk-GMA hydrogel. This study promises the fabricated Silk GMA hydrogel using DLP 3D printer could be applied to the fields of tissue engineering needing mechanical properties like cartilage regeneration.

4D-bioprinted silk hydrogels for tissue engineering.

Recently, four-dimensional (4D) printing is emerging as the next-generation biofabrication technology. However, current 4D bioprinting lacks biocompatibility or multi-component printability. In addition, suitable implantable targets capable of applying 4D bioprinted products have not yet been established, except theoretical and in vitro study. Herein, we describe a cell-friendly and biocompatible 4D bioprinting system including more than two cell types based on digital light processing (DLP) and photocurable silk fibroin (Sil-MA) hydrogel. The shape changes of 3D printed bilayered Sil-MA hydrogels were controlled by modulating their interior or exterior properties in physiological conditions. We used finite element analysis (FEA) simulations to explore the possible changes in the complex structure. Finally, we made trachea mimetic tissue with two cell types using this 4D bioprinting system and implanted it into a damaged trachea of rabbit for 8 weeks. The implants were integrated with the host trachea naturally, and both epithelium and cartilage were formed at the predicted sites. These findings demonstrate that 4D bioprinting system could make tissue mimetic scaffold biologically and suggest the potential value of the 4D bioprinting system for tissue engineering and the clinical application.

Recirculating peritoneal dialysis system using urease-fixed silk fibroin membrane filter with spherical carbonaceous adsorbent.

The chronic kidney disease (CKD) patients are undergoing continuous ambulatory peritoneal dialysis (CAPD). However, there are some constraints, the frequent exchange of the dialysate and limitation of outside activity, associated with CAPD remain to be solved. In this study, we designed the wearable artificial kidney (WAK) system for peritoneal dialysis (PD) using urease-immobilized silk fibroin (SF) membrane and polymer-based spherical carbonaceous adsorbent (PSCA). We evaluated this kit's removal abilities of uremic toxins such as urea, creatinine, uric acid, phosphorus, and ß2-microglobulin from the dialysate of end-stage renal disease (ESRD) patients in vitro. The uremic toxins including urea, creatinine, uric acid, and phosphorus were removed about 99% by immobilized SF membrane and PSCA filter after 24 h treatment. However, only 50% of ß2-microglobulin was removed by this filtering system after 24 h treatment. In vivo study result shows that our filtering system has more uremic toxins removal efficiency than exchanged dialysate at every 6 h. We suggest that recirculating PD system using urease-immobilized SF membrane with PSCA could be more efficient than traditional dialysate exchange system for a WAK for PD.

A 4-Axis Technique for Three-Dimensional Printing of an Artificial Trachea.

BACKGROUND: Several types of three-dimensional (3D)-printed tracheal scaffolds have been reported. Nonetheless, most of these studies concentrated only on application of the final product to an in vivo animal study and could not show the effects of various 3D printing methods, materials, or parameters for creation of an optimal 3D-printed tracheal scaffold. The purpose of this study was to characterize polycaprolactone (PCL) tracheal scaffolds 3D-printed by the 4-axis fused deposition modeling (FDM) method and determine the differences in the scaffold depending on the additive manufacturing method. METHODS: The standard 3D trachea model for FDM was applied to a 4-axis FDM scaffold and conventional FDM scaffold. The scaffold morphology, mechanical properties, porosity, and cytotoxicity were evaluated. Scaffolds were implanted into a 7 × 10-mm artificial tracheal defect in rabbits. Four and 8 weeks after the operation, the reconstructed sites were evaluated by bronchoscopic, radiological, and histological analyses. RESULTS: The 4-axis FDM provided greater dimensional accuracy and was significantly closer to CAD software-based designs with a predefined pore size and pore interconnectivity as compared to the conventional scaffold. The 4-axis tracheal scaffold showed superior mechanical properties. CONCLUSION: We suggest that the 4-axis FDM process is more suitable for the development of an accurate and mechanically superior trachea scaffold.

Novel transparent collagen film patch derived from duck's feet for tympanic membrane perforation.

To increase healing rate of tympanic membrane (TM) perforations, patching procedure has been commonly conducted. Biocompatible, biodegradable patching materials which is not limited across cultures is needed. The authors evaluated the effectiveness of novel transparent duck's feet collagen film (DCF) patch in acute traumatic TM perforation. This procedure was compared with spontaneous healing and paper patching. Cell proliferation features were observed in paper and DCF patches. Forty-eight TMs of 24 rats were used for animal experiment, perforations were made on each TMs, and divided into three groups according to treatment modality. Sixteen were spontaneously healed, 16 were paper patched and 16 were DCF patched. The gross and histological healing results were analyzed. Both paper and DCF patch showed no cytotoxicity, but cell proliferations were more active in DCF than paper in early stage. In animal study, the healing of TM perforations were completed within 14 days in all three groups, but found to be faster in DCF patch group than paper patch or spontaneous healing group. The DCF patches were transparent and size of DCF patches were gradually decreased, so there were no need to remove the DCF patches to check the wound status or after the completion of healing. According to this result, authors concluded that DCF patch is transparent, biocompatible and biodegradable material, and can induce fast healing in acute traumatic TM perforations.

Fabrication and characterization of the porous duck's feet collagen sponge for wound healing applications.

There are several artificial dermis commonly use to cover the wound and promote healing. The major goal of wound management is fast and scarless healing. However, there is no ideal skin substitute, that is effective to accelerate wound healing without scar formation. Artificial dermis substitute also has some drawbacks, such as high cost, insufficient available period and donor pathogen infection. To overcome these problems, we developed duck's feet collagen (DFC) sponge as artificial dermal substitutes for the treatment of full-thickness skin defects. We measured these DFC sponge's comparative characteristics and performances with an artificial dermis Colladerm by carried out SEM-EDX analyze, water-binding abilities and porosity test. Biocompatibility test was also performed using CCK-8 cytotoxicity assay. We also evaluated its wound healing effects for a full-thickness skin wound and compared with Colladerm in a rat model. Histological studies were carried via hematoxylin and eosin and Masson's Trichrome staining. Although the wound healing effect of the DFC sponge was almost similar to that of Colladerm, the DFC sponge did not induce scar formation and wound contracture like Colladerm. We suggest that DFC sponge can be used as an ideal dermal substitute to the treatment of full-thickness skin wound.

Development of an omentum-cultured oesophageal scaffold reinforced by a 3D-printed ring: feasibility of an in vivo bioreactor.

Current treatments of oesophageal diseases, such as carcinoma, congenital abnormality or trauma, require surgical intervention and oesophageal reconstruction with the stomach, jejunum or colon. However, serious side effects are possible with each treatment option. Despite tissue engineering promising to be an effective regenerative strategy, no functional solution currently exists for oesophageal reconstruction. Here, we developed an omentum-cultured oesophageal scaffold reinforced by a 3D-printed ring. The nano-structured scaffolds were wrapped into the omentum of rats and orthotopically transplanted for the repair of circumferential oesophageal defects two weeks later. The artificial oesophagus exhibited complete healing of the surgically created circumferential defects by the second week. The integration of the omentum-cultured oesophageal scaffold and the regenerative tissue remained intact. Macroscopically, there was no evidence of a fistula, perforation, abscess formation or surrounding soft-tissue necrosis. The omentum-cultured nano-structure scaffold reinforced by a 3D-printed ring is a more practical model with better vascularization for artificial neo-oesophagus reconstruction in a rat model.

Precisely printable and biocompatible silk fibroin bioink for digital light processing 3D printing.

Although three-dimensional (3D) bioprinting technology has gained much attention in the field of tissue engineering, there are still several significant engineering challenges to overcome, including lack of bioink with biocompatibility and printability. Here, we show a bioink created from silk fibroin (SF) for digital light processing (DLP) 3D bioprinting in tissue engineering applications. The SF-based bioink (Sil-MA) was produced by a methacrylation process using glycidyl methacrylate (GMA) during the fabrication of SF solution. The mechanical and rheological properties of Sil-MA hydrogel proved to be outstanding in experimental testing and can be modulated by varying the Sil-MA contents. This Sil-MA bioink allowed us to build highly complex organ structures, including the heart, vessel, brain, trachea and ear with excellent structural stability and reliable biocompatibility. Sil-MA bioink is well-suited for use in DLP printing process and could be applied to tissue and organ engineering depending on the specific biological requirements.

Publisher Correction: Precisely printable and biocompatible silk fibroin bioink for digital light processing 3D printing.

The original version of this Article contained errors in Figs. 5 and 6. In Fig. 5b, the second panel on the bottom row was stretched out of proportion. In Fig. 6d, the first panel was also stretched out of proportion. In Fig. 6f, the fifth panel inadvertently repeated the fourth. This has been corrected in both the PDF and HTML versions of the Article.

In vitro and in vivo evaluation of the duck's feet collagen sponge for hemostatic applications.

Recently different hemostatic agents have been developed, but most of them are ineffective in severe bleeding and expensive or cause safety concerns. In this study, we fabricated duck's feet collagen-based porous sponges and investigated its use as a hemostatic agent. We determined the sponge's physical and biological characteristics and compared with Avitene via scanning electron microscope analysis, water-uptake abilities and porosity test, and cytotoxicity assay. The duck's feet collagen/silk sponge showed a larger interconnected porous structure compared to others sponges. The duck's feet collagen/silk sponge also exhibited significantly higher porosity than Avitene. Hemostatic properties of the sponges were evaluated by whole blood clotting and rat femoral artery hemorrhage experiment. The addition of silk to duck's feet collagen showed better blood clotting ability than Avitene in vitro. However, rat femoral artery hemorrhage test showed a similar hemostatic property between the duck's feet collagen-based sponges and Avitene. We suggest that duck's feet collagen-based sponge can be effectively used for hemostatic applications.