Gingival mesenchymal stem cell-derived exosomes are immunosuppressive in preventing collagen-induced arthritis.

Due to the unsatisfied effects of clinical drugs used in rheumatoid arthritis (RA), investigators shifted their focus on the biotherapy. Although human gingival mesenchymal stem cells (GMSC) have the potential to be used in treating RA, GMSC-based therapy has some inevitable side effects such as immunogenicity and tumorigenicity. As one of the most important paracrine mediators, GMSC-derived exosomes (GMSC-Exo) exhibit therapeutic effects via immunomodulation in a variety of disease models, bypassing potential shortcomings of the direct use of MSCs. Furthermore, exosomes are not sensitive to freezing and thawing, and can be readily available for use. GMSC-Exo has been reported to promote tissue regeneration and wound healing, but have not been reported to be effective against autoimmune diseases. We herein compare the immunomodulatory functions of GMSC-Exo and GMSC in collagen-induced arthritis (CIA) model and in vitro CD4+ T-cell co-culture model. The results show that GMSC-Exo has the same or stronger effects compared with GMSC in inhibiting IL-17A and promoting IL-10, reducing incidences and bone erosion of arthritis, via inhibiting IL-17RA-Act1-TRAF6-NF-κB signal pathway. Our results suggest that GMSC-Exo has many advantages in treating CIA, and may offer a promising new cell-free therapy strategy for RA and other autoimmune diseases.

Characteristics of Marine Biomaterials and Their Applications in Biomedicine.

Oceans have vast potential to develop high-value bioactive substances and biomaterials. In the past decades, many biomaterials have come from marine organisms, but due to the wide variety of organisms living in the oceans, the great diversity of marine-derived materials remains explored. The marine biomaterials that have been found and studied have excellent biological activity, unique chemical structure, good biocompatibility, low toxicity, and suitable degradation, and can be used as attractive tissue material engineering and regenerative medicine applications. In this review, we give an overview of the extraction and processing methods and chemical and biological characteristics of common marine polysaccharides and proteins. This review also briefly explains their important applications in anticancer, antiviral, drug delivery, tissue engineering, and other fields.

Preparation of Alginate-Based Biomaterials and Their Applications in Biomedicine.

Alginates are naturally occurring polysaccharides extracted from brown marine algae and bacteria. Being biocompatible, biodegradable, non-toxic and easy to gel, alginates can be processed into various forms, such as hydrogels, microspheres, fibers and sponges, and have been widely applied in biomedical field. The present review provides an overview of the properties and processing methods of alginates, as well as their applications in wound healing, tissue repair and drug delivery in recent years.

Polymeric Micelles in Cancer Immunotherapy.

Cancer immunotherapies have generated some miracles in the clinic by orchestrating our immune system to combat cancer cells. However, the safety and efficacy concerns of the systemic delivery of these immunostimulatory agents has limited their application. Nanomedicine-based delivery strategies (e.g., liposomes, polymeric nanoparticles, silico, etc.) play an essential role in improving cancer immunotherapies, either by enhancing the anti-tumor immune response, or reducing their systemic adverse effects. The versatility of working with biocompatible polymers helps these polymeric nanoparticles stand out as a key carrier to improve bioavailability and achieve specific delivery at the site of action. This review provides a summary of the latest advancements in the use of polymeric micelles for cancer immunotherapy, including their application in delivering immunological checkpoint inhibitors, immunostimulatory molecules, engineered T cells, and cancer vaccines.

Biopolymer-Based Nanomedicine for Cancer Therapy: Opportunities and Challenges.

Cancer, as the foremost challenge among human diseases, has plagued medical professionals for many years. While there have been numerous treatment approaches in clinical practice, they often cause additional harm to patients. The emergence of nanotechnology has brought new directions for cancer treatment, which can deliver anticancer drugs specifically to tumor areas. This article first introduces the application scenarios of nanotherapies and treatment strategies of nanomedicine. Then, the noteworthy characteristics exhibited by biopolymer materials were described, which make biopolymers stand out in polymeric nanomedicine delivery. Next, we focus on summarizing the state-of-art studies of five categories of proteins (Albumin, Gelatin, Silk fibroin, Zein, Ferritin), nine varieties of polysaccharides (Chitosan, Starch, Hyaluronic acid, Dextran, cellulose, Fucoidan, Carrageenan, Lignin, Pectin) and liposomes in the field of anticancer drug delivery. Finally, we also provide a summary of the advantages and limitations of these biopolymers, discuss the prevailing impediments to their application, and discuss in detail the prospective research directions. This review not only helps readers understand the current development status of nano anticancer drug delivery systems based on biopolymers, but also is helpful for readers to understand the properties of various biopolymers and find suitable solutions in this field through comparative reading.

Enhancing neuroinduction activity of PLCL-based nerve conduits through native epineurium integration.

Autologous nerve grafts have been considered the gold standard for peripheral nerve grafts. However, due to drawbacks such as functional loss in the donor area and a shortage of donor sources, nerve conduits are increasingly being considered as an alternative approach. Polymer materials have been widely studied as nerve repair materials due to their excellent processing performance. However, their limited biocompatibility has restricted further clinical applications. The epineurium is a natural extra-neural wrapping structure. After undergoing decellularization, the epineurium not only reduces immune rejection but also retains certain bioactive components. In this study, decellularized epineurium (DEP) derived from the sciatic nerve of mammals was prepared, and a bilayer nerve conduit was created by electrospinning a poly (l-lactide-co-ε-caprolactone) (PLCL) membrane layer onto the outer surface of the DEP. Components of the DEP were examined; the physical properties and biosafety of the bilayer nerve conduit were evaluated; and the functionality of the nerve conduit was evaluated in rats. The results demonstrate that the developed bilayer nerve conduit exhibits excellent biocompatibility and mechanical properties. Furthermore, this bilayer nerve conduit shows significantly superior therapeutic effects for sciatic nerve defects in rats compared to the pure PLCL nerve conduit. In conclusion, this research provides a novel strategy for the design of nerve regeneration materials and holds promising potential for further clinical translation.

Preparation of PLCL/ECM nerve conduits by electrostatic spinning technique and evaluationin vitroandin vivo.

Objective. Artificial nerve scaffolds composed of polymers have attracted great attention as an alternative for autologous nerve grafts recently. Due to their poor bioactivity, satisfactory nerve repair could not be achieved. To solve this problem, we introduced extracellular matrix (ECM) to optimize the materials.Approach.In this study, the ECM extracted from porcine nerves was mixed with Poly(L-Lactide-co-ϵ-caprolactone) (PLCL), and the innovative PLCL/ECM nerve repair conduits were prepared by electrostatic spinning technology. The novel conduits were characterized by scanning electron microscopy (SEM), tensile properties, and suture retention strength test for micromorphology and mechanical strength. The biosafety and biocompatibility of PLCL/ECM nerve conduits were evaluated by cytotoxicity assay with Mouse fibroblast cells and cell adhesion assay with RSC 96 cells, and the effects of PLCL/ECM nerve conduits on the gene expression in Schwann cells was analyzed by real-time polymerase chain reaction (RT-PCR). Moreover, a 10 mm rat (Male Wistar rat) sciatic defect was bridged with a PLCL/ECM nerve conduit, and nerve regeneration was evaluated by walking track, mid-shank circumference, electrophysiology, and histomorphology analyses.Main results.The results showed that PLCL/ECM conduits have similar microstructure and mechanical strength compared with PLCL conduits. The cytotoxicity assay demonstrates better biosafety and biocompatibility of PLCL/ECM nerve conduits. And the cell adhesion assay further verifies that the addition of ECM is more beneficial to cell adhesion and proliferation. RT-PCR showed that the PLCL/ECM nerve conduit was more favorable to the gene expression of functional proteins of Schwann cells. Thein vivoresults indicated that PLCL/ECM nerve conduits possess excellent biocompatibility and exhibit a superior capacity to promote peripheral nerve repair.Significance.The addition of ECM significantly improved the biocompatibility and bioactivity of PLCL, while the PLCL/ECM nerve conduit gained the appropriate mechanical strength from PLCL, which has great potential for clinical repair of peripheral nerve injuries.

Analysis of Individualized Silicone Rubber Bolus Using Fan Beam Computed Tomography in Postmastectomy Radiotherapy: A Dosimetric Evaluation and Skin Acute Radiation Dermatitis Survey.

Objective: To investigate the dosimetric effects of using individualized silicone rubber (SR) bolus on the target area and organs at risk (OARs) during postmastectomy radiotherapy (PMRT), as well as evaluate skin acute radiation dermatitis (ARD). Methods: A retrospective study was performed on 30 patients with breast cancer. Each patient was prepared with an individualized SR bolus of 3 mm thickness. Fan-beam computed tomography (FBCT) was performed at the first and second fractions, and then once a week for a total of 5 times. Dosimetric metrics such as homogeneity index (HI), conformity index (CI), skin dose (SD), and OARs including the heart, lungs, and spinal cord were compared between the original plan and the FBCTs. The acute side effects were recorded. Results: In targets' dosimetric metrics, there were no significant differences in Dmean and V105% between planning computed tomography (CT) and actual treatments (P > .05), while the differences in D95%, V95%, HI, and CI were statistically significant (P < .05). In OARs, there were no significant differences between the Dmean, V5, and V20 of the affected lung, V5 of the heart and Dmax of the spinal cord (P > .05) except the V30 of affected lung, which was slightly lower than the planning CT (P < .05). In SD, both Dmax and Dmean in actual treatments were increased than plan A, and the difference was statistically significant (P < .05), while the skin-V20 and skin-V30 has no difference. Among the 30 patients, only one patient had no skin ARD, and 5 patients developed ARD of grade 2, while the remaining 24 patients were grade 1. Conclusion: The OR bolus showed good anastomoses and high interfraction reproducibility with the chest wall, and did not cause deformation during irradiation. It ensured accurate dose delivery of the target and OARs during the treatment, which may increase SD by over 101%. In this study, no cases of grade 3 skin ARD were observed. However, the potential of using OR bolus to reduce grade 1 and 2 skin ARD warrants further investigation with a larger sample size.

Manufacture and preliminary evaluation of acellular tooth roots as allografts for alveolar ridge augmentation.

Alveolar ridge augmentation can be used to obtain appropriate alveolar ridge for dental implantation. A variety of bone graft materials including autogenous bone, allograft, xenograft, and alloplastic material are used in alveolar ridge augmentation. Autogenous tooth-derived bone graft material has received much attention for the past few years, because the structure and physicochemical characteristics of tooth are similar to those of bones. Compared to autogenous tooth, allogenic tooth has the advantage of extensive resources. However, the problem of cell-derived immunological rejection of allogenic tooth remains unresolved. In the present study, acellular tooth root (ATR) is obtained by an innovative combination procedure. The biocompatibility of ATR is assessed using cytotoxicity test, hemolysis test, intracutaneous reactivity test, and acute systemic toxicity test. Osseointegration is evaluated in vivo by implanting ATR into the rat tibia defect as an allograft material. The results show that the ATR has fine biocompatibility, and there is an osseointegration between ATR and bone bed at 8 weeks post operation. This study demonstrates that the ATR could be used in alveolar ridge augmentation as a kind of new tooth-derived bone graft material.

Preparation of chitosan films using different neutralizing solutions to improve endothelial cell compatibility.

The development of chitosan-based constructs for application in large-size defects or highly vascularized tissues is still a challenging issue. The poor endothelial cell compatibility of chitosan hinders the colonization of vascular endothelial cells in the chitosan-based constructs, and retards the establishment of a functional microvascular network following implantation. The aim of the present study is to prepare chitosan films with different neutralization methods to improve their endothelial cell compatibility. Chitosan salt films were neutralized with either sodium hydroxide (NaOH) aqueous solution, NaOH ethanol solution, or ethanol solution without NaOH. The physicochemical properties and endothelial cell compatibility of the chitosan films were investigated. Results indicated that neutralization with different solutions affected the surface chemistry, swelling ratio, crystalline conformation, nanotopography, and mechanical properties of the chitosan films. The NaOH ethanol solution-neutralized chitosan film (Chi-NaOH/EtOH film) displayed a nanofiber-dominant surface, while the NaOH aqueous solution-neutralized film (Chi-NaOH/H(2)O film) and the ethanol solution-neutralized film (Chi-EtOH film) displayed nanoparticle-dominant surfaces. Moreover, the Chi-NaOH/EtOH films exhibited a higher stiffness as compared to the Chi-NaOH/H(2)O and Chi-EtOH films. Endothelial cell compatibility of the chitosan films was evaluated with a human microvascular endothelial cell line, HMEC-1. Compared with the Chi-NaOH/H(2)O and Chi-EtOH films, HMECs cultured on the Chi-NaOH/EtOH films fully spread and exhibited significantly higher levels of adhesion and proliferation, with retention of the endothelial phenotype and function. Our findings suggest that the surface nanotopography and mechanical properties contribute to determining the endothelial cell compatibility of chitosan films. The nature of the neutralizing solutions can affect the physicochemical properties and endothelial cell compatibility of chitosan films. Therefore, selection of suitable neutralization methods is highly important for the application of chitosan in tissue engineering.

Xenogeneic Decellularized Extracellular Matrix-based Biomaterials For Peripheral Nerve Repair and Regeneration.

Peripheral nerve injury could lead to either impairment or a complete loss of function for affected patients, and a variety of nerve repair materials have been developed for surgical approaches to repair it. Although autologous or autologous tissue-derived biomaterials remain preferred treatment for peripheral nerve injury, the lack of donor sources has led biomedical researchers to explore more other biomaterials. As a reliable alternative, xenogeneic decellularized extracellular matrix (dECM)-based biomaterials have been widely employed for surgical nerve repair. The dECM derived from animal donors is an attractive and unlimited source for xenotransplantation. Meanwhile, as an increasingly popular technique, decellularization could retain a variety of bioactive components in native ECM, such as polysaccharides, proteins, and growth factors. The resulting dECM-based biomaterials preserve a tissue's native microenvironment, promote Schwann cells proliferation and differentiation, and provide cues for nerve regeneration. Although the potential of dECM-based biomaterials as a therapeutic agent is rising, there are many limitations of this material restricting its use. Herein, this review discusses the decellularization techniques that have been applied to create dECM-based biomaterials, the main components of nerve ECM, and the recent progress in the utilization of xenogeneic dECM-based biomaterials through applications as a hydrogel, wrap, and guidance conduit in nerve tissue engineering. In the end, the existing bottlenecks of xenogeneic dECM-based biomaterials and developing technologies that could be eliminated to be helpful for utilization in the future have been elaborated.

Chitosan capping of CuO nanoparticles: Facile chemical preparation, biological analysis, and applications in dentistry.

This investigation is vital contribution to the healthcare system utilizing techniques of nanobiotechnology. It interestingly applies chitosan capped CuO nanoparticles in the field of medicine and restorative dentistry. The CuO nanoparticles and CuO-Chitosan nanoparticles are prepared by co-precipitation, and their characterization is performed using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray (EDX). The average crystallite size of these nanoparticles has been found to be in the dimensions of <40 nm and <35 nm, respectively. CuO-Chitosan nanoparticles show significant enhancement in in vitro antibacterial, antioxidant, cytotoxic, and antidiabetic activity as compared to CuO nanoparticles. In addition, the successful amalgamation of CuO nanoparticles and CuO-Chitosan nanoparticles into dentine bonding agents results in providing efficient remedy against secondary caries. CuO-Chitosan nanoparticles reinforced dental adhesive discs cause significant upsurge in reduction of Lactobacillus acidophillus and Streptococcus mutans. Also, the augmentation of mechanical properties, water sorption and solubility plus slow and sustained release profile and slight variation of shear bond strength is attained. Taken together, the chemically synthesized CuO nanoparticles and CuO-Chitosan nanoparticles have proven to be promising candidates having enormous potential to be utilized in drug delivery and nanotheranostics.

Chitosan encapsulated ZnO nanocomposites: Fabrication, characterization, and functionalization of bio-dental approaches.

Current report is paramount contribution via nanotechnology to the existing remedies of health diseases. The lag in application of capped metallic oxide nanoparticles in restorative dentistry exist which is covered by this promising study. The uncapped and chitosan encapsulated ZnO nanoparticles were fabricated by facile co-precipitation method, and characterized using various biophysical strategies including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and Energy dispersive x-ray (EDX). ZnO nanoparticles and ZnO-Citosan nanoparticles were estimated to be <30 nm and <25 nm in size on respective basis. Significant in vitro antibacterial, antioxidant, cytotoxic and antidiabetic activity of ZnO nanoparticles has been elucidated that is enhanced by capping with chitosan polymer. 90% cytotoxicity against brine shrimps, 69.6% antidiabetic activity against α-amylase, and noteworthy antioxidation power by chitosan decorated ZnO nanoparticles has been effectively illustrated. Furthermore, the effective secondary caries remediation approach has been established by an amalgamation of ZnO nanoparticles and ZnO-Chitosan nanoparticles into dentine bonding agents. A remarkable reduction in Streptococcus mutans and Lactobacillus acidophillus strains has been observed, in-specific boosted by chitosan capped ZnO nanoparticles reinforced dental adhesive discs. Additionally, augmented mechanical properties, greater resistance to water sorption and solubility, notably high release profile, and slight variation of shear bond strength values have been obtained. In short, the prepared nanoparticles reported are detected to be auspicious theranostic agents for combating wide array of human pathogens in healthcare system.

Tracing Carbon Nanotubes (CNTs) in Rat Peripheral Nerve Regenerated with Conductive Conduits Composed of Poly(lactide-co-glycolide) and Fluorescent CNTs.

Nerve regeneration can be promoted using nerve guide conduits (NGCs). Carbon nanotubes (CNTs) are often used to prepare conductive NGCs, however, the major concern for their applications is the final location of the implanted CNTs in vivo. Herein, photoluminescent multiwalled CNTs (MWCNTs) were prepared and electrospun with poly(lactide-co-glycolide) (PLGA), followed by shaping into multichannel NGCs for repairing of injured rat sciatic nerve, thereby the distribution of CNTs in vivo could be detected via bioimaging. Photoluminescent MWCNTs (MWCNT-FITC) were prepared by functionalization with poly(glycidyl methacrylate) (PGMA) and fluorescein-isothiocyanate-isomer I (FITC) subsequently. The conductivity of the PLGA/MWCNT-FITC fibers was approx. 10-4 S/cm at 3 wt % MWCNTs. Compared with PLGA fibers, Schwann cells on PLGA/MWCNT-FITC fibers matured at a faster rate, accordingly, nerve regeneration was promoted by the PLGA/MWCNT-FITC NGC. With a confocal laser scanning microscope and small-animal imaging system, the location of MWCNTs was detected. Alongside the degradation of PLGA, MWCNTs intended to aggregate and were entrapped in the regenerated nerve tissue without migrating into surrounding tissues and other organs (liver, kidneys, and spleen). This study provides a useful characterization method for MWCNTs and the guidance for in vivo applications of MWCNTs in tissue engineering.

Fabrication and Evaluation of a Xenogeneic Decellularized Nerve-Derived Material: Preclinical Studies of a New Strategy for Nerve Repair.

The repair and regeneration of transected peripheral nerves is an important area of clinical research, and the adhesion of anastomosis sites to surrounding tissues is a vital factor affecting the quality of nerve recovery after nerve anastomosis. This study involves the generation of a novel nerve repair membrane derived from decellularized porcine nerves using a unique, innovative technique. The decellularized nerve matrix was verified to be effective in eliminating cellular components, and it still retained some neural extracellular matrix components and bioactive molecules (collagens, glycosaminoglycans, laminin, fibronectin, TGF-ß, etc.), which were mainly determined by proteomic analysis, histochemistry, immunohistochemistry, and enzyme-linked immunosorbent assay. Cytotoxicity, intracutaneous reactivity, hemolysis, and cell affinity analyses were conducted to confirm the biosecurity of the nerve repair membrane. The in vivo functionality was assessed in a rat sciatic nerve transection model, and indices of functional nerve recovery, including the measurement of the claw-spread reflex, nerve anastomosis site adhesion, electrophysiological properties, and the number of regenerated nerve fibers, were evaluated. The results indicated that the nerve repair membrane could effectively prevent adhesion between the nerve anastomosis sites and the surrounding tissues and enhance nerve regeneration, which could be attributed to its various bioactive components. In conclusion, the novel nerve repair membrane derived from xenogeneic decellularized nerves described in this study shows great potential auxiliary clinical treatment for peripheral nerve injuries.

In vitro and in vivo biocompatibility study on acellular sheep periosteum for guided bone regeneration.

This study addresses the fabrication of an extracellular matrix material of the acellular sheep periosteum and the systematic evaluation of its biocompatibility to explore its potential application in guided bone regeneration. Sheep periosteum was harvested and decellularized by a combined decellularization protocol. The effectiveness of cell removal was proved and residual α-Gal antigen was also quantitatively detected. Then, mouse MC3T3-E1 cells were seeded onto the acellular periosteum. A scanning electron microscope (SEM) was used to record the whole process of cell adhesion. The CCK-8 assay suggested that the acellular periosteum not only had zero toxic effect on pre-osteoblasts, but played a positive role in cell proliferation. We also tested whether the acellular periosteum possesses favorable osteogenesis induction activity using an alkaline phosphatase (ALP) assay and a quantitative real-time PCR (Col I, Runx2, OCN) assay. An in vivo study of a subcutaneous implantation test using Sprague Dawley (SD) rats was performed to detect the changes in IL-2, IFN-γ and IL-4 in serum and elucidate the host's local response to acellular periosteum through hematoxylin and eosin (HE) and immunohistochemical staining. The results show that acellular sheep periosteum did not elicit a severe immunogenic response via the Th1 pathway, unlike fresh sheep periosteum. In conclusion, acellular sheep periosteum possesses favorable biocompatibility to be employed for guided bone regeneration.

Preparation and characterization of a multilayer biomimetic scaffold for bone tissue engineering.

In scaffold based bone tissue engineering, both the pore size and the mechanical properties of the scaffold are of great importance. However, an increase in pore size is generally accompanied by a decrease in mechanical properties. In order to achieve both suitable mechanical properties and porosity, a multilayer scaffold is designed to mimic the structure of cancellous bone and cortical bone. A porous nano-hydroxyapatite-chitosan composite scaffold with a multilayer structure is fabricated and encased in a smooth compact chitosan membrane layer to prevent fibrous tissue ingrowth. The exterior tube is shown to have a small pore size (15-40 microm in diameter) for the enhancement of mechanical properties, while the core of the multilayer scaffold has a large pore size (predominantly 70-150 microm in diameter) for nutrition supply and bone formation. Compared with the uniform porous scaffold, the multilayer scaffold with the same size shows an enhanced mechanical strength and larger pore size in the center. More cells are shown to grow into the center of the multilayer scaffold in vitro than into the uniform porous scaffold under the same seeding condition. Finally, the scaffolds are implanted into a rabbit fibula defect to evaluate the osteoconductivity of the scaffold and the efficacy of the scaffold as a barrier to fibrous tissue ingrowth. At 12 weeks post operation, affluent blood vessels and bone formation are found in the center of the scaffold and little fibrous tissue is noted in the defect site.

Chitosan nerve conduits seeded with autologous bone marrow mononuclear cells for 30 mm goat peroneal nerve defect.

In the current research, to find if the combination of chitosan nerve conduits seeded with autologous bone marrow mononuclear cells (BM-MNCs) can be used to bridge 30 mm long peroneal nerve defects in goats, 15 animals were separated into BM-MNC group (n = 5), vehicle group (n = 5), and autologous nerve graft group (n = 5). 12 months after the surgery, animals were evaluated by behavioral observation, magnetic resonance imaging tests, histomorphological and electrophysiological analysis. Results revealed that animals in BM-MNC group and autologous nerve graft group achieved fine functional recovery; magnetic resonance imaging tests and histomorphometry analysis showed that the nerve defect was bridged by myelinated nerve axons in those animals. No significant difference was found between the two groups concerning myelinated axon density, axon diameter, myelin sheath thickness and peroneal nerve action potential. Animals in vehicle group failed to achieve significant functional recovery. The results indicated that chitosan nerve conduits seeded with autologous bone marrow mononuclear cells have strong potential in bridging long peripheral nerve defects and could be applied in future clinical trials.

Manufacture of multimicrotubule chitosan nerve conduits with novel molds and characterization in vitro.

Multimicrotubule chitosan conduits (M-conduits) were fabricated using novel molds and a thermal-induced phase-separation technique. Hollow chitosan conduits (H-conduits) with an inner diameter of 1-5 mm and a wall thickness of 0.2-1.0 mm were made, and then a novel mold composed of a styrofoam insulating pedestal with several holes and a stainless steel cover plate was used to make M-conduits. In brief, corresponding H-conduits were inserted upright into the holes of the styrofoam pedestal, and filled with chitosan solution, then rapidly covered with the precooled stainless steel cover plate, and then placed in a freezer. The styrofoam insulating pedestal enclosing the conduits could reduce the heat transfer through the side wall of the conduits. Gradual phase separation then occurred uniaxially in the presence of a unidirectional temperature gradient from the top end to the bottom end of the chitosan conduits. The phase-separated polymer/solvent systems were then dried in a freeze-dryer. The microtubule diameters were controlled by adjusting the polymer concentration and cooling temperature. In vitro characterization demonstrated that the mold-based multimicrotubule chitosan conduits possessed suitable mechanical strength, microtubule diameter distribution, porosity, swelling, biodegradability, and nerve cell affinity, and so they showed potential for application as nerve tissue engineering scaffolds.

A sandwich tubular scaffold derived from chitosan for blood vessel tissue engineering.

Many materials have been investigated in blood vessel tissue engineering, such as PGA, PLGA, P4HB. However, chitosan is not mentioned in the arena. This study aimed to develop a chitosan-based tubular scaffold and examine its feasibility of being applied in this field. Briefly, a knitted chitosan tube was dipped into chitosan solution (2%, w/v) and dried, then its inner and outer surface was mantled with a layer of chitosan/gelatin (4:1, w/w) complex solution, and then freeze-dehydrated. In vitro characterization showed that the scaffold had a wall of 1.0 mm in thickness with a sandwich structure, and a porosity of 81.2%. The pore diameter was 50-150 microm and could be regulated by varying freezing conditions. The scaffold possessed proper swelling property, burst strength of almost 4000 mmHg, and high suture-retention strength. After degradation for 2 months, the scaffold could maintain enough mechanical strength with an average mass loss of 18.7%. Vascular smooth muscle cells could spread and grow very well on the scaffold. This study provided a novel method to fabricate chitosan and its complex into a tubular scaffold and demonstrated the feasibility of the scaffold employed in the field of blood vessel tissue engineering.