Artificial neural network for modeling the elastic modulus of electrospun polycaprolactone/gelatin scaffolds

Scaffolds for tissue engineering (TE) require the consideration of multiple aspects, including polymeric composition and the structure and mechanical properties of the scaffolds, in order to mimic the native extracellular matrix of the tissue. Electrospun fibers are frequently utilized in TE due to their tunable physical, chemical, and mechanical properties and porosity. The mechanical properties of electrospun scaffolds made from specific polymers are highly dependent on the processing parameters, which can therefore be tuned for particular applications. Fiber diameter and orientation along with polymeric composition are the major factors that determine the elastic modulus of electrospun nano- and microfibers. Here we have developed a neural network model to investigate the simultaneous effects of composition, fiber diameter and fiber orientation of electrospun polycaprolactone/gelatin mats on the elastic modulus of the scaffolds under ambient and simulated physiological conditions. The model generated might assist bioengineers to fabricate electrospun scaffolds with defined fiber diameters, orientations and constituents, thereby replicating the mechanical properties of the native target tissue.     

Engineering the niche for stem cells

Abstract

Much has been made about the potential for stem cells in regenerative medicine but the reality is that the development of actual therapies has been slow. Adult stem cells rely heavily on the assortment of biochemical and biophysical elements that constitute the local microenvironment in which they exist. One goal of biomedicine is to create an artificial yet biofunctional niche to support multipotency, differentiation and proliferation. Such tools would facilitate more conclusive experimentation by biologists, pharmaceutical scientists and tissue engineers. While many bioengineering techniques and platforms are already in use, technological innovations now allow this to be done at a higher resolution and specificity. Ultimately, the multidisciplinary integration of engineering and biology will allow the niche to be generated at a scale that can be clinically exploited. Using the systems that constitute the intestinal, hematopoietic and epidermal tissues, this article summarizes the various approaches and tools currently employed to recreate stem cell niches and also explores recent advances in the field.     

Biocompatibility of subcutaneously implanted marine macromolecules cross-linked bio-composite scaffold for cartilage tissue engineering applications

There is an intense interest in developing innovative biomaterials which support the invasion and proliferation of living cells for potential applications in tissue engineering and regenerative medicine. Present study demonstrated the in vivo biocompatibility and toxicity of a macromolecules cross-linked biocomposite scaffold composed of hydroxyapatite, alginate, chitosan and fucoidan abbreviated as HACF. The in vivo biocompatibility and toxicity of HACF scaffold were tested by comparing them with those of a biocompatible surgical metal implant (SMI) in a subcutaneous rat model. Following the implantation, animals were sacrificed and the scaffolds were resected at 1st, 4th, and 8th weeks; the surrounding tissue along with the implant was removed to evaluate its biocompatibility. The effects of implanted biomaterial scaffolds on vital organ systems such as liver, kidney, etc., have been studied by hematology and serum biochemistry. The activities of pro-inflammatory marker enzymes such as COX, 5-LOX, 15-LOX, and NOS were normal in rats implanted with HACF scaffold. Hematological parameters, antioxidant and lipid peroxidation status were also found to be normal in implanted rats same as that of control and SMI. The modulatory effect of implanted scaffold over inflammatory and stress signaling cascades were confirmed by the normalized mRNA expressions of NF-κB, TNF-α and IL-6. The histopathological analysis of liver, kidney and tissue support our results. Taken together, these results demonstrated that HACF biocomposite scaffold signifies its suitability for further research as a scaffold material for cartilage tissue engineering applications.     

Decellularization and genipin crosslinking of amniotic membrane suitable for tissue engineering applications

Abstract

Amniotic membrane has the potential to be used as scaffold in various tissue engineering applications. However, increasing its biostability at the same time maintaining its biocompatibility is important to enhance its usage as a scaffold. This studied characteristics genipin-crosslinked amniotic membrane as a bioscaffold. Redundant human amniotic membranes (HAM) divided into native (nAM), decellularized (dAM) and genipin-crosslinked (clAM) groups. The dAM and clAM group were decellularized using thermolysin (TL) and sodium hydroxide (NaOH) solution. Next, clAM group was crosslinked with 0.5% and 1.0% (w/v) genipin. The HAM was then studied for in vitro degradation, percentage of swelling, optical clarity, ultrastructure and mechanical strength. Meanwhile, fibroblasts isolated from nasal turbinates were then seeded onto nAM, dAM and clAM for biocompatibility studies. clAM had the slowest degradation rate and were still morphologically intact after 30 days of incubation in 0.01% collagenase type 1 solution. The dAM had a significantly highest percentage of swelling than other groups (p?<?0.05). Besides, the dAM retained the collagen content at similar level of nAM. Although the dAM had highest mechanical strength compared to the rest of the groups, the differences were statistically insignificant. Cell attachment on dAM and 0.5% clAM was higher compared to that on nAM and 1.0% clAM. In conclusion, clAM have better biostability and biocompatibility compared to the nAM and dAM. Together with other suitable characteristics of the clAM such as percentage of swelling, structural integrity and ECM content, clAM is suitable as scaffold for various tissue engineering applications.     

Balancing mechanical strength with bioactivity in chitosan–calcium phosphate 3D microsphere scaffolds for bone tissue engineering: air- vs. freeze-drying processes

The objective of this study was to evaluate the potential benefit of 3D composite scaffolds composed of chitosan and calcium phosphate for bone tissue engineering. Additionally, incorporation of mechanically weak lyophilized microspheres within those air-dried (AD) was considered for enhanced bioactivity. AD microsphere, alone, and air- and freeze-dried microsphere (FDAD) 3D scaffolds were evaluated in vitro using a 28-day osteogenic culture model with the Saos-2 cell line. Mechanical testing, quantitative microscopy, and lysozyme-driven enzymatic degradation of the scaffolds were also studied. FDAD scaffold showed a higher concentration (p?<?0.01) in cells per scaffold mass vs. AD constructs. Collagen was ～31% greater (p?<?0.01) on FDAD compared to AD scaffolds not evident in microscopy of microsphere surfaces. Alternatively, AD scaffolds demonstrated a superior threefold increase in compressive strength over FDAD (12 vs. 4?MPa) with minimal degradation. Inclusion of FD spheres within the FDAD scaffolds allowed increased cellular activity through improved seeding, proliferation, and extracellular matrix production (as collagen), although mechanical strength was sacrificed through introduction of the less stiff, porous FD spheres.     

Usefulness of a Three‐Dimensional‐Printed Model in the Treatment of Irreducible Atlantoaxial Dislocation with Transoral Atlantoaxial Reduction Plate

ObjectiveTo evaluate the usefulness of a 3D‐printed model for transoral atlantoaxial reduction plate (TARP) surgery in the treatment of irreducible atlantoaxial dislocation (IAAD).MethodsA retrospective review was conducted of 23 patients (13 men, 10 women; mean age 58.17 ± 5.27 years) with IAAD who underwent TARP from January 2015 to July 2017. Patients were divided into a 3D group (12 patients) and a non‐3D group (11 patients). A preoperative simulation process was undertaken for the patients in the 3D group, with preselection of the TARP system using a 3D‐printed 1:1 scale model, while only imaging data was used for the non‐3D group. Complications, clinical outcomes (Japanese Orthopaedic Association [JOA] and visual analogue score [VAS]), and image measurements (atlas–dens interval [ADI], cervicomedullary angle [CMA], and clivus‐canal angle [CCA]) were noted preoperatively and at the last follow up.ResultsA total of 23 patients with a follow‐up time of 16.26 ± 4.27 months were included in the present study. The surgery duration, intraoperative blood loss, and fluoroscopy times in the 3D group were found to be shorter than those in non‐3D group, with statistical significance. The surgery duration was 3.29 ± 0.45 h in the 3D group and 4.68 ± 0.90 h in the non‐3D group, and the estimated intraoperative blood loss was 131.67 ± 43.03 mL in the 3D group and 185.45 ± 42.28 mL in the non‐3D group. No patients received blood transfusions. The intraoperative fluoroscopy times were 5.67 ± 0.89 in the 3D group and 7.91 ± 1.45 in the non‐3D group. Preoperatively and at last follow up, JOA and VAS scores and ADI, CCA, and CMA were improved significantly within the two groups. However, no statistical difference was observed between the two groups. However, surgical site infection occurred in 1 patient in the 3D group, who underwent an emergency revision operation of the removal of TARP device and posterior occipitocervical fixation; the patient recovered 2 weeks after the surgery. In 2 patients in the traditional group, a mistake occurred in the placement of screws, with no neurological symptoms related to the misplacement.ConclusionPreoperative surgical simulation using a 3D‐printed real‐size model is an intuitive and effective aid for TARP surgery for treating IAAD. The 3D‐printed biomodel precisely replicated patient‐specific anatomy for use in complicated craniovertebral junction surgery. The information was more useful than that available with 3D reconstructed images.     

Tissue‐Engineered Tracheal Reconstruction Using Three‐Dimensionally Printed Artificial Tracheal Graft: Preliminary Report

Three‐dimensional printing has come into the spotlight in the realm of tissue engineering. We intended to evaluate the plausibility of 3D‐printed (3DP) scaffold coated with mesenchymal stem cells (MSCs) seeded in fibrin for the repair of partial tracheal defects. MSCs from rabbit bone marrow were expanded and cultured. A half‐pipe‐shaped 3DP polycaprolactone scaffold was coated with the MSCs seeded in fibrin. The half‐pipe tracheal graft was implanted on a 10 × 10‐mm artificial tracheal defect in four rabbits. Four and eight weeks after the operation, the reconstructed sites were evaluated bronchoscopically, radiologically, histologically, and functionally. None of the four rabbits showed any sign of respiratory distress. Endoscopic examination and computed tomography showed successful reconstruction of trachea without any collapse or blockage. The replaced tracheas were completely covered with regenerated respiratory mucosa. Histologic analysis showed that the implanted 3DP tracheal grafts were successfully integrated with the adjacent trachea without disruption or granulation tissue formation. Neo‐cartilage formation inside the implanted graft was sufficient to maintain the patency of the reconstructed trachea. Scanning electron microscope examination confirmed the regeneration of the cilia, and beating frequency of regenerated cilia was not different from those of the normal adjacent mucosa. The shape and function of reconstructed trachea using 3DP scaffold coated with MSCs seeded in fibrin were restored successfully without any graft rejection.