[Application of microcarrier technology in cartilage repairing: a review].

Cartilage has poor self-recovery because of its characteristics of no blood vessels and high extracellular matrix. In clinical treatment, physical therapy or drug therapy is usually used for mild cartilage defects, and surgical treatment is needed for severe ones. In recent years, cartilage tissue engineering technology provides a new way for the treatment of cartilage defects. Compared with the traditional surgical treatment, cartilage tissue engineering technology has the advantages of small wound and good recovery. The application of microcarrier technology in the design of tissue engineering scaffolds further expands the function of scaffolds and promotes cartilage regeneration. This review summarized the main preparation methods and development of microcarrier technology in recent years. Subsequently, the properties and specific application scenarios of microcarriers with different materials and functions were introduced according to the materials and functions of microcarriers used in cartilage repair. Based on our research on osteochondral integrated layered scaffolds, we proposed an idea of optimizing the performance of layered scaffolds through microcarriers, which is expected to prepare bionic scaffolds that are more suitable for the structural characteristics of natural cartilage.

High-cytocompatible semi-IPN bio-ink with wide molecular weight distribution for extrusion 3D bioprinting.

The development of 3D printing has recently attracted significant attention on constructing complex three-dimensional physiological microenvironments. However, it is very challenging to provide a bio-ink with cell-harmless and high mold accuracy during extrusion in 3D printing. To overcome this issue, a technique improving the shear-thinning performance of semi-IPN bio-ink, which is universally applicable to all alginate/gelatin-based materials, was developed. Semi-IPN bio-ink prepared by cyclic heating-cooling treatment in this study can reduce the cell damage without sacrificing the accuracy of the scaffolds for its excellent shear-thinning performance. A more than 15% increase in post-printing Cell viability verified the feasibility of the strategy. Moreover, the bio-ink with low molecular weight and wide molecular weight distribution also promoted a uniform cell distribution and cell proliferation in clusters. Overall, this strategy revealed the effects of molecular parameters of semi-IPN bio-inks on printing performance, and the cell activity was studied and it could be widely applicable to construct the simulated extracellular matrix with various bio-inks.

Viscoelastic Silk Fibroin Hydrogels with Tunable Strength.

Hydrogels are often used as synthetic extracellular matrices (ECMs) for biomedical applications. Natural ECMs are viscoelastic and exhibit partial stress relaxation. However, commonly used hydrogels are typically elastic. Hydrogels developed from ECM-based proteins are viscoelastic, but they often have weak mechanical properties. Here, biocompatible viscoelastic hydrogels with excellent mechanical performance are fabricated by an all aqueous process at body or room temperature. These hydrogels offer obvious stress relaxation and tunable mechanical properties and gelation kinetics. Their compressive modulus can be controlled between 2 kPa and 1.2 MPa, covering a significant portion of the properties of native tissues. Investigation of the gelation mechanism revealed that silk fibroin gelation is caused by the synergistic effects of hydrophobic interaction and hydrogen bonding between silk fibroin molecules. Newly formed crystals serve as the cross-link sites and form a network endowing the hydrogel with stable structure, and the flexible noncrystalline silk nanofibers connect disparate silk fibroin crystals, endowing hydrogels with viscoelastic properties. The all aqueous gelation process avoids complex chemical and physical treatments and is beneficial for encapsulating cells or biomolecules. Encapsulation of chondrocytes results in high initial survival rate (95% ± 1%). These silk fibroin-based viscoelastic hydrogels, combined with superior biocompatible and tunable mechanical properties, represent an exciting option for tissue engineering and regenerative medicine.

3D Poly(Lactic-co-glycolic acid) Scaffolds for Treating Spinal Cord Injury.

In this paper, poly(lactic-co-glycolic acid) (PLGA) was used to fabricate spinal cord scaffolds using low temperature deposition manufacturing (LDM) technology. The PLGA scaffolds were characterized as having good porosity, hydrophilicity and considerable biodegradability. The effects of the PLGA scaffolds on cell proliferation and cytotoxicity were evaluated by culturing Schwann cells (SCs) on the surfaces of the scaffolds. The results showed that the SCs spread and proliferated well on the PLGA scaffolds. Histological assessment including Glia fibrillary acidic protein (GFAP) staining, Nissl staining, Luxol fast blue (LFB) staining and Bielschowsky silver staining showed that the spinal cord recoveries considerably improved with the PLGA scaffolds, indicating that the PLGA scaffolds exhibited potential for applications in the management of spinal cord injuries.

[Rapid manufacturing of degradable porous polymer bone scaffold].

Making bone scaffold through tissue engineering method presents a new choice for both the patients and the doctors of orthopaedics. The biodegradable polymer PLA is chosen to make porous fundus scaffold jetting through special designed nozzle on multi-functional rapid prototyping machine controlled by computer according to the CT data CAD model. The scaffold is then chemically aggregated to compound with collagen-hydroxyapatite, and the ideal bone repair material is obtained. Animal experiment has indicated the correctness of this conclusion.

The research of laryngeal joints to reconstruction and modeling.

Larynx has a complex structure with joints and multiple functions. In order to study the artificial larynx and artificial auricle scaffold, a three-dimensional digital model of laryngeal joint is established in this paper using MIMICS with its biomechanical properties analyzed and calculated by using the finite element method. This model is based on the CT scanned images of 281 layers with an interlamellar spacing of 1.25 mm. The obtained data are denoised, segmented and smoothed before being loaded into MIMICS. By further optimizations, an accurate and complete 3D model can be obtained. Subsequently, a 3D FEM of the normal larynx joint is performed which allows observations from any dimensions and angles. Compared with natural laryngeal joint, this model has good geometric similarity and mechanically similar throat voicing functions.

[Computer-assisted manufacture of individual auricular framework and the experimental study for ear reconstruction].

OBJECTIVE: To manufacture the individual polyurethane (PUR) auricular framework using the rapid prototyping (RP) technique and to evaluate its feasibility in ear reconstruction. METHODS: 3-D models of the patient's auricle were reconstructed according to the computed tomography (CT) data. The supporting and drainage structures were created. Then the individual PUR auricular frameworks were manufactured using RP technique. The frameworks were tested for the fatigue strength and elasticity. The frameworks were also put at the subcutaneous layer of rat. At 1, 2, 4, 8, 12 weeks after operation, the shape of the reconstructed ears was observed and the histological examination was performed. RESULTS: The PUR framework had good elasticity and a much better fatigue strength than high density polyethylene (HDPE) framework. The shape of reconstructed ear matched the prototype very well. The around tissue grew into the implant pore and adhered tightly to the framework 2 weeks after implantation. Histologic examination showed integrated capsule four weeks later without lymphocytes infiltration. The shape kept very well twelve weeks later. CONCLUSIONS: PUR auricular framework manufactured by the 3D reconstruction and RP techniques has very good shape, intensity and elasticity. It can be selected to replace the autograft of rib cartilage framework.