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.

Silk Fibroin-Based Biomaterials for Hemostatic Applications.

Hemostasis plays an essential role in all surgical procedures. Uncontrolled hemorrhage is the primary cause of death during surgeries, and effective blood loss control can significantly reduce mortality. For modern surgeons to select the right agent at the right time, they must understand the mechanisms of action, the effectiveness, and the possible adverse effects of each agent. Over the past decade, various hemostatic agents have grown intensely. These agents vary from absorbable topical hemostats, including collagen, gelatins, microfibrillar, and regenerated oxidized cellulose, to biologically active topical hemostats such as thrombin, biological adhesives, and other combined agents. Commercially available products have since expanded to include topical hemostats, surgical sealants, and adhesives. Silk is a natural protein consisting of fibroin and sericin. Silk fibroin (SF), derived from silkworm Bombyx mori, is a fibrous protein that has been used mostly in fashion textiles and surgical sutures. Additionally, SF has been widely applied as a potential biomaterial in several biomedical and biotechnological fields. Furthermore, SF has been employed as a hemostatic agent in several studies. In this review, we summarize the several morphologic forms of SF and the latest technological advances on the use of SF-based hemostatic agents.

A Feasibility Study for 3D-printed Poly(methyl methacrylate)-resin Tracheostomy Tube Using a Hamster Cheek Pouch Model.

BACKGROUND/AIM: A three-dimensional (3D) printed tracheostomy tube has potential application for patients who require a specialized tube. The aim of this study was to evaluate the characteristics of various 3D printing materials and determine their use in producing 3D-printed tracheostomy tube. MATERIALS AND METHODS: Mechanical, chemical, and microbiological in vivo changes in the scaffolds were analyzed using a hamster cheek pouch (HCP) model. RESULTS: The poly methyl methacylate (PMMA)-resin showed superior pre- and post-insertion mechanical properties and a relatively consistent lower biofilm formation compared with other scaffolds. PMMA-resin was successfully 3D-printed with dimensional accuracy without a support system. The use of a 3D-printed PMMA tracheostomy tube in a rabbit trachea showed no definite signs of infection, allergy or foreign body reaction. CONCLUSION: PMMA-resin can be proposed as an alternative for a 3D-printed tracheostomy tube material. In addition, we suggest HCPs as an in vivo model for evaluating indwelling medical devices.

Cytocompatibility of Modified Silk Fibroin with Glycidyl Methacrylate for Tissue Engineering and Biomedical Applications.

Hydrogel with chemical modification has been used for 3D printing in the biomedical field of cell and tissue-based regeneration because it provides a good cellular microenvironment and mechanical supportive ability. As a scaffold and a matrix, hydrogel itself has to be modified chemically and physically to form a ß-sheet crosslinking structure for the strength of the biomaterials. These chemical modifications could affect the biological damage done to encapsulated cells or surrounding tissues due to unreacted chemical residues. Biological assessment, including assessment of the cytocompatibility of hydrogel in clinical trials, must involve testing with cytotoxicity, irritation, and sensitization. Here, we modified silk fibroin and glycidyl methacrylate (Silk-GMA) and evaluated the physical characterizations, residual chemical detection, and the biological effect of residual GMA depending on dialysis periods. Silk-GMA depending on each dialysis period had a typical ß-sheet structure in the characterization analysis and residual GMA decreased from dialysis day 1. Moreover, cell proliferation and viability rate gradually increased; additionally, necrotic and apoptotic cells decreased from dialysis day 2. These results indicate that the dialysis periods during chemical modification of natural polymer are important for removing unreacted chemical residues and for the potential application of the manufacturing standardization for chemically modified hydrogel for the clinical transplantation for tissue engineering and biomedical applications.

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.

New concept of 3D printed bone clip (polylactic acid/hydroxyapatite/silk composite) for internal fixation of bone fractures.

Open reduction with internal fixation is commonly used for the treatment of bone fractures. However, postoperative infection associated with internal fixation devices (intramedullary nails, plates, and screws) remains a significant complication, and it is technically difficult to fix multiple fragmented bony fractures using internal fixation devices. In addition, drilling in the bone to install devices can lead to secondary fracture, bone necrosis associated with postoperative infection. In this study, we developed bone clip type internal fixation device using three- dimensional (3D) printing technology. Standard 3D model of the bone clip was generated based on computed tomography (CT) scan of the femur in the rat. Polylacticacid (PLA), hydroxyapatite (HA), and silk were used for bone clip material. The purpose of this study was to characterize 3D printed PLA, PLA/HA, and PLA/HA/Silk composite bone clip and evaluate the feasibility of these bone clips as an internal fixation device. Based on the results, PLA/HA/Silk composite bone clip showed similar mechanical property, and superior biocompatibility compared to other types of the bone clip. PLA/HA/Silk composite bone clip demonstrated excellent alignment of the bony segments across the femur fracture site with well-positioned bone clip in an animal study. Our 3D printed bone clips have several advantages: (1) relatively noninvasive (drilling in the bone is not necessary), (2) patient-specific design (3) mechanically stable device, and (4) it provides high biocompatibility. Therefore, we suggest that our 3D printed PLA/HA/Silk composite bone clip is a possible internal fixation device.

An omentum-cultured 3D-printed artificial trachea: in vivo bioreactor.

The purpose of this study was to evaluate whether the prior implantation of a 3D-printed polycaprolactone (PCL) artificial trachea in the omentum is beneficial for revascularization of the scaffold and reduces associated complications in the reconstruction of a circumferential tracheal defect. Ten New Zealand rabbits were divided into 2 groups: (1) PCL-OC group (PCL scaffold cultured in omentum for 2 weeks before transplantation) and (2) PCL group. In the PCL-OC group, newly formed connective tissue completely covered the luminal surface of the scaffold with mild inflammation at 2 weeks postoperatively; a minor degree of stenosis was noted at 8 weeks postoperatively. The PCL group showed scaffold exposure without any tissue regeneration at 2 weeks postoperatively, and a moderate degree of luminal stenosis 6 weeks after implantation. Histology revealed highly organized regenerated tissue composed of ciliated respiratory epithelium, and submucosal layer in the PCL-OC group. Neo-cartilage regeneration was noted in part of the regenerated tissue. The PCL group demonstrated severe inflammation and an unorganized structure compared to that of the PCL-OC group. In vivo omentum culture of the tracheal scaffold before transplantation is beneficial for rapid re-epithelialization and revascularization of the scaffold. It also prevents postoperative luminal stenosis.