Evaluation of the effect of co-transplantation of collagen-hydroxyapatite bio-scaffold containing nanolycopene and human endometrial mesenchymal stem cell derived exosomes to regenerate bone in rat critical size calvarial defect.

This study aimed to evaluate the effect of nanoparticles based on the PLGA and biomolecule of lycopene (i.e. NLcp) and exosomes loaded on hydroxyapatite/collagen-based scaffolds (HA/Coll), on human endometrial MSCs (hEnMSCs) differentiation into osteoblast cells. To this end, after synthesizing NLcp and isolating hEnMSC-derived exosomes, and studying their characterizations, HA/Coll scaffold with/without NLcp and exosome was fabricated. In following, the rat skull-defect model was created on 54 male Sprague-Dawley rats (12 weeks old) which were classified into 6 groups [control group (4 healthy rats), negative control group: bone defect without grafting (10 rats), and experimental groups including bone defect grafted with HA/Coll scaffold (10 rats), HA/Coll/NLcp scaffold (10 rats), HA/Coll scaffold + exosome (10 rats), and HA/Coll-NLcp scaffold + exosome (10 rats)]. Finally, the grafted membrane along with its surrounding tissues was removed at 90 days after surgery, to assess the amount of defect repair by Hematoxylin and eosin staining. Moreover, immunohistochemical and X-ray Micro-Computed Tomography (Micro-CT) analyses were performed to assess osteocalcin and mean bone volume fraction (BVF). Based on the results, although, the existence of the exosome in the scaffold network can significantly increase mean BVF compared to HA/Coll scaffold and HA/Coll-NLcp scaffold (2.25-fold and 1.5-fold, respectively). However, the combination of NLcp and exosome indicated more effect on mean BVF; so that the HA/Coll-NLcp scaffold + exosome led to a 15.95 % increase in mean BVF than the HA/Coll scaffold + exosome. Hence, synthesized NLcp in this study can act as a suitable bioactive to stimulate the osteogenic, promotion of cell proliferation and its differentiation when used in the polymer scaffold structure or loaded into polymeric carriers containing the exosome.

[Construction of a novel tissue engineered meniscus scaffold based on low temperature deposition three-dimenisonal printing technology].

Objective: To investigate the construction of a novel tissue engineered meniscus scaffold based on low temperature deposition three-dimenisonal (3D) printing technology and evaluate its biocompatibility. Methods: The fresh pig meniscus was decellularized by improved physicochemical method to obtain decellularized meniscus matrix homogenate. Gross observation, HE staining, and DAPI staining were used to observe the decellularization effect. Toluidine blue staining, safranin O staining, and sirius red staining were used to evaluate the retention of mucopolysaccharide and collagen. Then, the decellularized meniscus matrix bioink was prepared, and the new tissue engineered meniscus scaffold was prepared by low temperature deposition 3D printing technology. Scanning electron microscopy was used to observe the microstructure. After co-culture with adipose-derived stem cells, the cell compatibility of the scaffolds was observed by cell counting kit 8 (CCK-8), and the cell activity and morphology were observed by dead/live cell staining and cytoskeleton staining. The inflammatory cell infiltration and degradation of the scaffolds were evaluated by subcutaneous experiment in rats. Results: The decellularized meniscus matrix homogenate appeared as a transparent gel. DAPI and histological staining showed that the immunogenic nucleic acids were effectively removed and the active components of mucopolysaccharide and collagen were remained. The new tissue engineered meniscus scaffolds was constructed by low temperature deposition 3D printing technology and it had macroporous-microporous microstructures under scanning electron microscopy. CCK-8 test showed that the scaffolds had good cell compatibility. Dead/live cell staining showed that the scaffold could effectively maintain cell viability (>90%). Cytoskeleton staining showed that the scaffolds were benefit for cell adhesion and spreading. After 1 week of subcutaneous implantation of the scaffolds in rats, there was a mild inflammatory response, but no significant inflammatory response was observed after 3 weeks, and the scaffolds gradually degraded. Conclusion: The novel tissue engineered meniscus scaffold constructed by low temperature deposition 3D printing technology has a graded macroporous-microporous microstructure and good cytocompatibility, which is conducive to cell adhesion and growth, laying the foundation for the in vivo research of tissue engineered meniscus scaffolds in the next step.

[Research progress of three-dimensional bioprinting technology in auricle repair and reconstruction].

Objective: To review the research progress on the application of three-dimensional (3D) bioprinting technology in auricle repair and reconstruction. Methods: The recent domestic and international research literature on 3D printing and auricle repair and reconstruction was extensively reviewed, and the concept of 3D bioprinting technology and research progress in auricle repair and reconstruction were summarized. Results: The auricle possesses intricate anatomical structure and functionality, necessitating precise tissue reconstruction and morphological replication. Hence, 3D printing technology holds immense potential in auricle reconstruction. In contrast to conventional 3D printing technology, 3D bioprinting technology not only enables the simulation of auricular outer shape but also facilitates the precise distribution of cells within the scaffold during fabrication by incorporating cells into bioink. This approach mimics the composition and structure of natural tissues, thereby favoring the construction of biologically active auricular tissues and enhancing tissue repair outcomes. Conclusion: 3D bioprinting technology enables the reconstruction of auricular tissues, avoiding potential complications associated with traditional autologous cartilage grafting. The primary challenge in current research lies in identifying bioinks that meet both the mechanical requirements of complex tissues and biological criteria.

Research and analysis of the properties of bredigite-based 3D-printed bone scaffolds.

The use of bone tissue-engineered scaffolds for repairing bone defects has become extremely common. Bone tissue-engineered scaffolds should have good mechanical properties, a pore structure similar to that of natural bone, appropriate biodegradability, and good biocompatibility to provide attachment sites for growth factors and seed cells. They also need to exhibit special functions such as osteoconductivity and osteoinduction. In this study, the mechanical, degradation, and biological properties of bredigite were studied by using a triply periodic minimal surface (TPMS) model structure. Pressure tests on bone tissue-engineered scaffolds showed that the mechanical properties of TPMS scaffolds were significantly better than those of open-rod scaffolds with the same porosity. By analyzing the biological properties, we found that the TPMS model had better protein adsorption ability than the open-rod model, the cells could better adsorb on the surface of the TPMS scaffold, and the proliferation number and proliferation rate of the TPMS model were higher than those of the open-ended rod model.

Experimental HER2-Targeted Therapy Using ADAPT6-ABD-mcDM1 in Mice Bearing SKOV3 Ovarian Cancer Xenografts: Efficacy and Selection of Companion Imaging Counterpart.

Overexpression of the human epidermal growth factor receptor 2 (HER2) in breast and gastric cancer is exploited for targeted therapy using monoclonal antibodies and antibody-drug conjugates. Small engineered scaffold proteins, such as the albumin binding domain (ABD) derived affinity proteins (ADAPTs), are a promising new format of targeting probes for development of drug conjugates with well-defined structure and tunable pharmacokinetics. Radiolabeled ADAPT6 has shown excellent tumor-targeting properties in clinical trials. Recently, we developed a drug conjugate based on the HER2-targeting ADAPT6 fused to an albumin binding domain (ABD) for increased bioavailability and conjugated to DM1 for cytotoxic action, designated as ADAPT6-ABD-mcDM1. In this study, we investigated the therapeutic efficacy of this conjugate in mice bearing HER2-expressing SKOV3 ovarian cancer xenografts. A secondary aim was to evaluate several formats of imaging probes for visualization of HER2 expression in tumors. Administration of ADAPT6-ABD-mcDM1 provided a significant delay of tumor growth and increased the median survival of the mice, in comparison with both a non-targeting homologous construct (ADAPTNeg-ABD-mcDM1) and the vehicle-treated groups, without inducing toxicity to liver or kidneys. Moreover, the evaluation of imaging probes showed that small scaffold proteins, such as 99mTc(CO)3-ADAPT6 or the affibody molecule 99mTc-ZHER2:41071, are well suited as diagnostic companions for potential stratification of patients for ADAPT6-ABD-mcDM1-based therapy.

Redesigning of 3-Dimensional Vascular-Muscle Structure Using ADSCs/HUVECs Co-Culture and VEGF on Engineered Skeletal Muscle ECM.

OBJECTIVE: The main objective of this study is to determine the myogenic effects of skeletal muscle extracellular matrix, vascular endothelial growth factor and human umbilical vein endothelial cells on adipose-derived stem cells to achieve a 3-dimensional engineered vascular-muscle structure. MATERIALS AND METHODS: The present experimental research was designed based on two main groups, i.e. monoculture of adipose tissue-derived stem cells (ADSCs) and co-culture of ADSCs and human umbilical vein endothelial cells (HUVECs) in a ratio of 1:1. Skeletal muscle tissue was isolated, decellularized and its surface was electrospun using polycaprolactone/gelatin parallel nanofibers and then matrix topography was evaluated through H and E, trichrome staining and SEM. The expression of MyHC2 gene and tropomyosin protein were examined through real-time reverse transcription polymerase chain reaction (RT-PCR) and immunofluorescence, respectively. Finally, the morphology of mesenchymal and endothelial cells and their relationship with each other and with the engineered scaffold were examined by scanning electron microscopy (SEM). RESULTS: According to H and E and Masson's Trichrome staining, muscle tissue was completely decellularized. SEM showed parallel Polycaprolactone (PCL)/gelatin nanofibers with an average diameter of about 300 nm. The immunofluorescence proved that tropomyosin was positive in the ADSCs monoculture and the ADSCs/HUVECs coculture in horse serum (HS) and HS/VEGF groups. There was a significant difference in the expression of the MyHC2 gene between the ADSCs and ADSCs/HUVECs culture groups (P<0.05) and between the 2D and 3D models in HS/ VEGF differentiation groups (P<001). Moreover, a significant increase existed between the HS/VEGF group and other groups in terms of endothelial cells growth and proliferation as well as their relationship with differentiated myoblasts (P<0.05). CONCLUSION: Co-culture of ADSCs/HUVECs on the engineered cell-free muscle scaffold and the dual effects of VEGF can lead to formation of a favorable engineered vascular-muscular tissue. These engineered structures can be used as an acceptable tool for tissue implantation in muscle injuries and regeneration, especially in challenging injuries such as volumetric muscle loss, which also require vascular repair.

Shape-Memory Polymers Hallmarks and Their Biomedical Applications in the Form of Nanofibers.

Shape-Memory Polymers (SMPs) are considered a kind of smart material able to modify size, shape, stiffness and strain in response to different external (heat, electric and magnetic field, water or light) stimuli including the physiologic ones such as pH, body temperature and ions concentration. The ability of SMPs is to memorize their original shape before triggered exposure and after deformation, in the absence of the stimulus, and to recover their original shape without any help. SMPs nanofibers (SMPNs) have been increasingly investigated for biomedical applications due to nanofiber's favorable properties such as high surface area per volume unit, high porosity, small diameter, low density, desirable fiber orientation and nanoarchitecture mimicking native Extra Cellular Matrix (ECM). This review focuses on the main properties of SMPs, their classification and shape-memory effects. Moreover, advantages in the use of SMPNs and different biomedical application fields are reported and discussed.

Poly(Lactic Acid)/Graphite Nanoplatelet Nanocomposite Filaments for Ligament Scaffolds.

The anterior cruciate ligament (ACL) is one of the most prone to injury in the human body. Due to its insufficient vascularization and low regenerative capacity, surgery is often required when it is ruptured. Most of the current tissue engineering (TE) strategies are based on scaffolds produced with fibers due to the natural ligament's fibrous structure. In the present work, composite filaments based on poly(L-lactic acid) (PLA) reinforced with graphite nanoplatelets (PLA+EG) as received, chemically functionalized (PLA+f-EG), or functionalized and decorated with silver nanoparticles [PLA+((f-EG)+Ag)] were produced by melt mixing, ensuring good filler dispersion. These filaments were produced with diameters of 0.25 mm and 1.75 mm for textile-engineered and 3D-printed ligament scaffolds, respectively. The resulting composite filaments are thermally stable, and the incorporation of graphite increases the stiffness of the composites and decreases the electrical resistivity, as compared to PLA. None of the filaments suffered significant degradation after 27 days. The composite filaments were processed into 3D scaffolds with finely controlled dimensions and porosity by textile-engineered and additive fabrication techniques, demonstrating their potential for ligament TE applications.

Poly(lactide-co-ε-caprolactone) scaffold promotes equivalent tissue integration and supports skin grafts compared to a predicate collagen scaffold.

Dermal scarring from motor vehicle accidents, severe burns, military blasts, etc. is a major problem affecting over 80 million people worldwide annually, many of whom suffer from debilitating hypertrophic scar contractures. These stiff, shrunken scars limit mobility, impact quality of life, and cost millions of dollars each year in surgical treatment and physical therapy. Current tissue engineered scaffolds have mechanical properties akin to unwounded skin, but these collagen-based scaffolds rapidly degrade over 2 months, premature to dampen contracture occurring 6-12 months after injury. This study demonstrates a tissue engineered scaffold can be manufactured from a slow-degrading viscoelastic copolymer, poly(ι-lactide-co-ε-caprolactone), with physical and mechanical characteristics to promote tissue ingrowth and support skin-grafts. Copolymers were synthesized via ring-opening polymerization. Solvent casting/particulate leaching was used to manufacture 3D porous scaffolds by mixing copolymers with particles in an organic solvent followed by casting into molds and subsequent particle leaching with water. Scaffolds characterized through SEM, micro-CT, and tensile testing confirmed the required thickness, pore size, porosity, modulus, and strength for promoting skin-graft bioincorporation and dampening fibrosis in vivo. Scaffolds were Oxygen Plasma Treatment and collagen coated to encourage cellular proliferation. Porosity ranging from 70% to 90% was investigated in a subcutaneous murine model and found to have no clinical effect on tissue ingrowth. A swine full-thickness skin wound model confirmed through histology and Computer Planimetry that scaffolds promote skin-graft survival, with or without collagen coating, with equal safety and efficacy as a commercially available tissue engineered scaffold. This study validates a scalable method to create poly(ι-lactide-co-ε-caprolactone) scaffolds with appropriate characteristics and confirms in mouse and swine wound models that the scaffolds are safe and effective at supporting skin-grafts. The results of this study have brought us closer towards developing an alternative technology that supports skin grafts with the potential to investigate long-term hypertrophic scar contractures.

Hyaluronic acid oligosaccharides modified mineralized collagen and chitosan with enhanced osteoinductive properties for bone tissue engineering.

In this study, we prepared a biomimetic hyaluronic acid oligosaccharides (oHAs)-based composite scaffold to develop a bone tissue-engineered scaffold for stimulating osteogenesis and endothelialization. The functional oHAs products were firstly synthesized, namely collagen/hyaluronic acid oligosaccharides/hydroxyapatite (Col/oHAs/HAP), chitosan/hyaluronic acid oligosaccharides (CTS/oHAs), and then uniformly distributed in poly (lactic-co-glycolic acid) (PLGA) solution followed by freeze-drying to obtain three-dimensional interconnected scaffolds as temporary templates for bone regeneration. The morphology, physicochemical properties, compressive strength, and degradation behavior of the fabricated scaffolds, as well as in vitro cell responses seeded on these scaffolds and in vivo biocompatibility, were investigated to evaluate the potential for bone tissue engineering. The results indicated that the oHAs-based scaffolds can promote the attachment of endothelial cells, facilitate the osteogenic differentiation of MC3T3-E1 and BMSCs, and have ideal biocompatibility and tissue regenerative capacity, suggesting their potential to serve as alternative candidates for bone tissue engineering applications.

Fabrication and assessment of chondroitin sulfate-modified collagen nanofibers for small-diameter vascular tissue engineering applications.

Chondroitin sulfate (ChS) has shown promising results in promoting cell proliferation and antithrombogenic activity. To engineered develop a dual-function vascular scaffold with antithrombosis and endothelialization, ChS was tethered to collagen to accelerate the growth of endothelial cells and prevent platelet activation. First, ChS was used to conjugate with collagen to generate glycosylated products (ChS-COL) via reductive amination. Then, the fabricated ChS-COL conjugates were electrospun into nanofibers and their morphologies and physicochemical characteristics, cell-scaffold responses and platelet behaviors upon ChS-COL nanofibers were comprehensively characterized to evaluate their potential use for small-diameter vascular tissue-engineered scaffolds. The experimental results demonstrated that the ChS modified collagen electrospun nanofibers were stimulatory of endothelial cell behavior, alleviated thrombocyte activation and maintained an antithrombotic effect in vivo in 10-day post-transplantation. The ChS-COL scaffolds encouraged rapid endothelialization, thus probably ensuring the antithrombotic function in long-term implantation, suggesting their promise for small-diameter vascular tissue engineering applications.

Optimization of the coaxial cell printing performance of bioink and printing of tissue-engineered scaffolds with vascular-like structure / 中国组织工程研究

BACKGROUND: Cells cannot survive in the area 200 µm away from nutrients in vitro. Vascular network construction is crucial for thick tissue and organ regeneration in tissue engineering. Coaxial cell printing provides a new way to construct vascular-like channels in vitro. OBJECTIVE: To optimize the coaxial cell printing performance of bioink and to build the tissue-engineered scaffolds with vascular-like structure. METHODS: The aseptic sodium alginate solution was prepared by intermittent pasteurization and then frozen. Freeze-dried powder of aseptic silk fibroin was prepared from degummed silk and sealed. The thawed sodium alginate solution was added to the silk fibroin protein freeze-dried powder and human umbilical vein endothelial cells were added to prepare the bioink. The outer axis of the biological three-dimensional printer was connected with the bioink, and the inner axis was connected with the crosslinking agent. The scaffolds were prepared by coaxial printing, and performed by optical coherence tomography, scanning electron microscopy observation and tensile test. Coaxial scaffolds were made by freeze-preserved sodium alginate solution for 7 days with human umbilical vein endothelial cells. Coaxial scaffolds were also made by freeze-dried sodium alginate solution for 7 days with human umbilical vein endothelial cells and silk fibroin protein sealed for 6 months. The cell survival rate was detected by dead and alive staining after 24 hours of culture in vitro. Vascular-like scaffolds with series and parallel structures were designed and printed. The cell proliferation was detected after 1, 3, 7, 10, and 14 days of culture. RESULTS AND CONCLUSIONS: (1) The optical coherence tomography showed that the maximum printing height of the bioink was 9 layers and the overall thickness was about 4.4 mm. Scanning electron microscopy showed that the outer wall of hollow fiber-filament of vascular-like scaffolds presented irregular strip-shaped crimp with micron-scale internal connected pore structure, while the inner wall of hollow fiber-filament had denser pore structure. (2) The elastic modulus of silk protein freeze-dried scaffold was higher than that of sodium alginate solution (P < 0.05). (3) The cell survival rate of scaffolds treated with sodium alginate solution for 7 days was (86.7±3.4)%, and that of scaffolds treated with silk protein freeze-dried powder for 7 days was (98.1±1.2)%, indicating that the sodium alginate solution freeze- preserved for 7 days was free of bacteria and the shelf-life of silk protein could be up to 6 months. (4) The proliferation activity of cells cultured with parallel structure for 7, 10, and 14 days was higher than that with series structure (P < 0.05). (5) These results imply that the scaffolds have good biocompatibility and mechanical properties.

Testing a novel nanofibre scaffold for utility in bone tissue regeneration.

Many variables serve to alter the process of bone remodelling and diminish regeneration including the size and nature of the wound bed and health status of the individual. To overcome these inhibitory factors, tissue-engineered osteoconductive scaffolds paired with various growth factors have been utilized clinically. However, many limitations still remain, for example, bone morphogenetic protein 2 (BMP2) can lead to rampant inflammation, ectopic bone formation, and graft failure. Here, we studied the ability for a nanofiber scaffold (Talymed) to accelerate BMP2 growth factor-induced bone healing compared with the traditional absorbable collagen sponge (ACS) delivery system. One hundred fifty-five adult wild type mice were arranged in 16 groups by time, 4 and 8 weeks, and treatment, ACS or Talymed, loaded with control, low, medium, or high dosages of BMP2. Skulls were subjected to microCT, biomechanical, and histological analysis to assess bone regeneration. The use of Talymed within the defect site was found to decrease the bone volume, bone formation rate, and alkaline phosphatase activity compared with ACS/BMP2 combinations. Interestingly, though Talymed regenerated less bone, the regenerate was found to have a greater hardness value than that of bone within the ACS groups. However, the difference in bone hardness between scaffolds was not detectable by 8 weeks. Based on these results, we found that the nanofiber scaffold generated a better quality of bone regenerate at 4 weeks but, due to the lack of overall bone formation and the inhibition of normal remodelling processes, was not as efficacious as the current clinical standard ACS/BMP2 therapy.

Eumelanin Coated PLA Electrospun Micro Fibers as Bioinspired Cradle for SH-SY5Y Neuroblastoma Cells Growth and Maturation.

Within the framework of neurodegenerative disorder therapies, the fabrication of 3D eumelanin architectures represents a novel strategy to realize tissue-engineering scaffolds for neuronal cell growth and control by providing both mechanical support and biological signals. Here, an appropriate procedure combining electrospinning, spin coating and solid-state polymerization process is established to realize the scaffolds. For biological analysis, a human derived cell line SH-SY5Y from neuroblastoma is used. Cell maturation on eumelanin microfibers, random and aligned, is evaluated by using confocal analysis and specific markers of differentiating neurons (ßIII tubulin and GAP-43 expression). Cell morphology is tested by SEM analysis and immunofluorescence techniques. As results, eumelanin coated microfibers prove capable to support biological response in terms of cell survival, adhesion and spreading and to promote cell differentiation toward a more mature neuronal phenotype as confirmed by GAP-43 expression over the culture.

Low-temperature deposition manufacturing: A novel and promising rapid prototyping technology for the fabrication of tissue-engineered scaffold.

Developed in recent years, low-temperature deposition manufacturing (LDM) represents one of the most promising rapid prototyping technologies. It is not only based on rapid deposition manufacturing process but also combined with phase separation process. Besides the controlled macropore size, tissue-engineered scaffold fabricated by LDM has inter-connected micropores in the deposited lines. More importantly, it is a green manufacturing process that involves non-heating liquefying of materials. It has been employed to fabricate tissue-engineered scaffolds for bone, cartilage, blood vessel and nerve tissue regenerations. It is a promising technology in the fabrication of tissue-engineered scaffold similar to ideal scaffold and the design of complex organs. In the current paper, this novel LDM technology is introduced, and its control parameters, biomedical applications and challenges are included and discussed as well.

Carboxymethyl cellulose enables silk fibroin nanofibrous scaffold with enhanced biomimetic potential for bone tissue engineering application.

Novel silk fibroin (SF) and carboxymethyl cellulose (CMC) composite nanofibrous scaffold (SFC) were developed to investigate their ability to nucleate bioactive nanosized calcium phosphate (Ca/P) by biomineralization for bone tissue engineering application. The composite nanofibrous scaffold was prepared by free liquid surface electrospinning method. The developed composite nanofibrous scaffold was observed to control the size of Ca/P particle (≤100nm) as well as uniform nucleation of Ca/P over the surface. The obtained nanofibrous scaffolds were fully characterized for their functional, structural and mechanical property. The XRD and EDX analysis depicted the development of apatite like crystals over SFC scaffolds of nanospherical in morphology and distributed uniformly throughout the surface of scaffold. Additionally, hydrophilicity as a measure of contact angle and water uptake capacity is higher than pure SF scaffold representing the superior cell supporting property of the SF/CMC scaffold. The effect of biomimetic Ca/P on osteogenic differentiation of umbilical cord blood derived human mesenchymal stem cells (hMSCs) studied in early and late stage of differentiation shows the improved osteoblastic differentiation capability as compared to pure silk fibroin. The obtained result confirms the positive correlation of alkaline phosphatase activity, alizarin staining and expression of runt-related transcription factor 2, osteocalcin and type1 collagen representing the biomimetic property of the scaffolds. Thus, the developed composite has been demonstrated to be a potential scaffold for bone tissue engineering application.

[PREPARATION AND BIOCOMPATIBILITY OF IN SITU CROSSLINKING HYALURONIC ACID HYDROGEL].

OBJECTIVE: To fabricate in situ crosslinking hyaluronic acid hydrogel and evaluate its biocompatibility in vitro. METHODS: The acrylic acid chloride and polyethylene glycol were added to prepare crosslinking agent polyethylene glycol acrylate (PEGDA), and the molecular structure of PEGDA was analyzed by Flourier transformation infrared spectroscopy and 1H nuclear magnetic resonance spectroscopy. Hyaluronic acid hydrogel was chemically modified to prepare hyaluronic acid thiolation (HA-SH). And the degree of HA-SH was analyzed qualitatively and quantitatively by Ellman method. HA-SH solution in concentrations (W/V) of 0.5%, 1.0%, and 1.5% and PEGDA solution in concentrations (W/V) of 2%, 4%, and 6% were prepared with PBS. The two solutions were mixed in different ratios, and in situ crosslinking hyaluronic acid hydrogel was obtained; the crosslinking time was recorded. The cellular toxicity of in situ crosslinking hyaluronic acid hydrogel (1.5% HA-SH and 4% PEGDA mixed) was tested by L929 cells. Meanwhile, the biocompatibility of hydrogel was tested by co-cultured with human bone mesenchymal stem cells (hBMSCs). RESULTS: Flourier transformation infrared spectroscopy showed that most hydroxyl groups were replaced by acrylate groups; 1H nuclear magnetic resonance spectroscopy showed 3 characteristic peaks of hydrogen representing acrylate and olefinic bond at 5-7 ppm. The thiolation yield of HA-SH was 65.4%. In situ crosslinking time of hyaluronic acid hydrogel was 2 to 70 minutes in the PEGDA concentrations of 2%-6% and HA-SH concentrations of 0.5%-1.5%. The hyaluronic acid hydrogel appeared to be transparent. The toxicity grade of leaching solution of hydrogel was grade 1. hBMSCs grew well and distributed evenly in hydrogel with a very high viability. CONCLUSIONS: In situ crosslinking hyaluronic acid hydrogel has low cytotoxicity, good biocompatibility, and controllable crosslinking time, so it could be used as a potential tissue engineered scaffold or repairing material for tissue regeneration.

[NEW PROGRESS OF ACELLULAR FISH SKIN AS NOVEL TISSUE ENGINEERED SCAFFOLD].

OBJECTIVE: To review the recent research progress of acellular fish skin as a tissue engineered scaffold, and to analyze the feasibility and risk management in clinical application. METHODS: The research and development, application status of acellular fish skin as a tissue engineered scaffold were comprehensively analyzed, and then several key points were put forward. RESULTS: Acellular fish skin has a huge potential in clinical practice as novel acellular extracellular matrix, but there have been no related research reports up to now in China. As an emerging point of translational medicine, investigation of acellular fish skin is mainly focused on artificial skin, surgical patch, and wound dressings. CONCLUSIONS: Development of acellular fish skin-based new products is concerned to be clinical feasible and necessary, but a lot of applied basic researches should be carried out.

Quantification of fluid shear stress in bone tissue engineering scaffolds with spherical and cubical pore architectures.

Recent studies have shown that mechanical stimulation, in the form of fluid perfusion and mechanical compression, can enhance osteogenic differentiation of mesenchymal stem cells and bone cells within tissue engineering scaffolds in vitro. The precise nature of mechanical stimulation within tissue engineering scaffolds is not only dictated by the exogenously applied loading regime, but also depends on the geometric features of the scaffold, in particular architecture, pore size and porosity. However, the precise contribution of each geometric feature towards the resulting mechanical stimulation within a scaffold is difficult to characterise due to the wide range of interacting parameters. In this study, we have applied a fluid-structure interaction model to investigate the role of scaffold geometry (architecture, pore size and porosity) on pore wall shear stress (WSS) under a range of different loading scenarios: fluid perfusion, mechanical compression and a combination of perfusion and compression. It is found that scaffold geometry (spherical and cubical pores), in particular the pore size, has a significant influence on the stimulation within scaffolds. Furthermore, we observed an amplified WSS within scaffolds under a combination of fluid perfusion and mechanical compression, which exceeded that caused by individual fluid perfusion or mechanical compression approximately threefold. By conducting this comprehensive parametric variation study, an expression was generated to allow the design and optimisation of 3D TE scaffolds and inform experimental loading regimes so that a desired level of mechanical stimulation, in terms of WSS is generated within the scaffold.

In Vivo Microcomputed Tomography of Nanocrystal-Doped Tissue Engineered Scaffolds.

Tissue engineered scaffolds (TES) hold promise for improving the outcome of cell-based therapeutic strategies for a variety of biomedical scenarios, including musculoskeletal injuries, soft tissue repair, and spinal cord injury. Key to TES research and development, and clinical use, is the ability to longitudinally monitor TES location, orientation, integrity, and microstructure following implantation. Here, we describe a strategy for using microcomputed tomography (microCT) to visualize TES following implantation into mice. TES were doped with highly radiopaque gadolinium oxide nanocrystals and were implanted into the hind limbs of mice. Mice underwent serial microCT over 23 weeks. TES were clearly visible over the entire time course. Alginate scaffolds underwent a 20% volume reduction over the first 6 weeks, stabilizing over the next 17 weeks. Agarose scaffold volumes were unchanged. TES attenuation was also unchanged over the entire time course, indicating a lack of nanocrystal dissolution or leakage. Histology at the implant site showed the presence of very mild inflammation, typical for a mild foreign body reaction. Blood work indicated marked elevation in liver enzymes, and hematology measured significant reduction in white blood cell counts. While extrapolation of the X-ray induced effects on hematopoiesis in these mice to humans is not straightforward, clearly this is an area for careful monitoring. Taken together, these data lend strong support that doping TES with radiopaque nanocrystals and performing microCT imaging, represents a possible strategy for enabling serial in vivo monitoring of TES.