Pectin-chitosan-PVA nanofibrous scaffold made by electrospinning and its potential use as a skin tissue scaffold

Scaffolds made of chitosan nanofibers are often too mechanically weak for their application and often their manufacturing processes involve the use of harmful and flammable organic solvents. In the attempt to improve the mechanical properties of nanofibrous scaffolds made of chitosan without the use of harmful chemicals, pectin, an anionic polymer was blended with chitosan, a cationic polymer, to form a polyelectrolyte complex and electrospun into nanofibers for the first time. The electrospun chitosan-pectin scaffolds, when compared to electrospun chitosan scaffolds, had a 58% larger diameter, a 21% higher Young’s modulus, a 162% larger strain at break, and a 104% higher ultimate tensile strength. Compared to the chitosan scaffolds, the chitosan-pectin scaffolds’ swelling ratios decreased by 55% after 60?min in a saline solution and more quickly released the preloaded tetracycline HCl. The L929 fibroblast cells proliferated slightly slower on the chitosan-pectin scaffolds than on the chitosan scaffolds. Nonetheless, cells on both materials deposited similar levels of extracellular type I collagen on a per DNA basis. In conclusion, a novel chitosan-pectin nanofibrous scaffold with superior mechanical properties than a chitosan nanofibrous scaffold was successfully made without the use of harmful solvents.     

Surface characteristics and biocompatibility of lactide-based poly(ethylene glycol) scaffolds for tissue engineering

Novel lactide-based poly(ethylene glycol) (PEG) polymer networks (GL9-PEGs) were prepared by UV copolymerization of a glycerol-lactide triacrylate (GL9-Ac) with PEG monoacrylate (PEG-Ac) to use as scaffolds in tissue engineering, and the surface properties and biocompatibility of these networks were investigated as a function of PEG molecular weight and content. Analysis by ATR-FTIR and ESCA reveled that PEG was incorporated well within the GL9-PEG polymer networks and was enriched at the surfaces. From the results of SEM, AFM, and contact angle analyses, GL9-PEG networks showed relatively rough and irregular surfaces compared to GL9 network, but the mobile PEG chains coupled at their termini were readily exposed toward the aqueous environment when contacting water such that the surfaces became smoother and more hydrophilic. This reorientation and increase in hydrophilicity were more extensive with increasing PEG molecular weight and content. As compared to GL9 network lacking PEG, protein adsorption as well as platelet and S. epidermidis adhesion to GL9-PEG networks were significantly reduced as the molecular weight and content of PEG was increased, indicating that GL9-PEG networks are more biocompatible than the GL9 network due to PEG's passivity. Based on the physical and biological characterization reported, the GL9-PEG materials would appear to be interesting candidates as matrices for tissue engineering.     

Regenerative Endodontic Therapy in Mature Teeth Using Human-Derived Composite Amnion-Chorion Membrane as a Bioactive Scaffold: A Pilot Animal Investigation

IntroductionHuman-derived composite amnion-chorion membrane (ACM) has been used for various regenerative treatments. The aim of this pilot study was to investigate the effectiveness of the ACM as a scaffold for pulp regeneration in mature canine teeth.MethodsA total of 24 roots from mature premolars in dogs were included for regenerative procedures using blood clots (BC) (group 1, n = 8), collagen membrane (CM) (group 2, n = 8), and ACM (group 3, n = 8). Each tooth was left open through a buccal access to induce root canal infection and inflammation. The root canals were disinfected with 1.5% NaOCl and calcium hydroxide intracanal medicament. After 2 weeks, bleeding was evoked to induce blood clot formation (group 1) or before the placement of the membranes (groups 2 and 3). After 12 weeks, the animals were euthanized for histologic assessment. The histologic data including intracanal fibrous connective tissue, odontoblast-like cell lining, intracanal mineralized tissue, periapical inflammation, and apical closure were qualitatively and quantitively analyzed.ResultsHistologic analysis revealed that intracanal fibrous connective tissue was identified in all groups, but a higher volume of the fibrous tissues was formed in the ACM group. Odontoblast-like cells were only observed in the ACM group. The intracanal mineralized tissue was observed only in the BC and CM groups. The BC group showed more periapical inflammation than the ACM group (P < .05). Apical closure was more often found in the CM group than the BC group (P < .05).ConclusionsMore intracanal fibrous tissue and odontoblast-like cell lining, and less periapical inflammation were observed after regenerative endodontic treatment in mature teeth using the ACM than blood clot alone or blood clot with collagen membrane. The use of the ACM may be useful for a cell-homing–based pulp regeneration in mature teeth.     

聚乳酸⁃羟基乙酸共聚物在牙髓疾病治疗中的应用前景

材料学的发展对牙髓疾病的治疗有重要意义,聚乳酸?羟基乙酸共聚物[poly(lactic?co?glycolic acid),PLGA]是一种被广泛应用于生物医用材料制备的有机高分子化合物。近年来,作为载药/分子系统和组织再生支架在牙髓疾病治疗中展现出应用前景,本文将对PLGA在牙髓疾病治疗中的应用作一综述,为其进一步开发利用提供参考。文献复习结果表明,PLGA作为药物/分子输送系统主要应用于盖髓材料、根管消毒剂和根尖诱导成形剂的改良。PLGA改良盖髓材料能延长药物作用时间、降低毒性;改良根管消毒剂能实现药物缓释,使药物深入更细微的结构,与致病菌有更广泛的接触;改良根尖诱导成形剂能为根尖诱导提供更便捷的给药方式。PLGA作为组织工程支架主要应用于牙髓再生的研究,通过PLGA物理性能、作用环境的不断优化为种子细胞提供更适宜增殖分化的微环境。如何合理利用PLGA的优势,研制出更适宜根管内应用的材料,还需要进一步的研究。     

3D打印技术在牙髓再生领域的研究进展

近年来,牙髓再生成为了口腔医学领域的研究热点,3D打印能实现支架结构和形状的精准调控,为种子细胞黏附和生长因子释放提供基础,通过3D打印组织工程支架构建的3D打印“牙髓复合体”为牙髓再生研究提供了新的方向。本文就3D打印技术应用于牙髓再生的研究作一综述。文献复习结果表明,3D打印“牙髓复合体”中的支架材料、种子细胞和生长因子在牙髓再生的研究中都扮演着重要角色,其中,支架材料能发挥载体作用负载种子细胞和生长因子,并为其提供合适微环境;牙髓干细胞、根尖乳头干细胞和人脱落乳牙牙髓干细胞等常用种子细胞为牙髓再生提供细胞基础;生长因子的引入可以进一步支持牙髓组织的分化和牙髓血管重建,促进牙髓再生。目前,3D打印“牙髓复合体”在牙髓再生的研究中取得了一定进展,在实验室阶段可诱导牙髓样组织的形成,但制备生物活性良好且具有仿生血管和神经效果的3D打印“牙髓复合体”,为根管内细胞提供氧气和营养物质仍是一个巨大的挑战,需进一步的探索和研究。     

神经干细胞与脊髓脱细胞支架体外共培养的可行性

目的 观察大鼠神经干细胞(NSCs)在脊髓脱细胞支架(SCAS)上黏附、生长和分化情况,评价其构建脊髓组织工程的可行性。 方法 新生Sprague-Dawley大鼠大脑皮质来源NSCs传代培养并鉴定;Sprague-Dawley雌性大鼠脊髓组织改良物理振荡结合化学萃取法制备SCAS,并行基础评估;将第三代NSCs种植在SCAS上,体外共培养,免疫荧光、免疫组化和扫描电镜观察支架上细胞形态。 结果 共培养的细胞为能增殖、分化的NSCs。制备的SCAS孔隙率、含水率、酶解率都明显高于正常脊髓(|t| > 4.679, P < 0.01);SCAS基质结构呈疏松网络状,基质上可见极少量残留细胞核。NSCs在SCAS上黏附、生长良好,可分化为神经元和神经胶质细胞。 结论 制备的SCAS脱细胞较彻底,具有多通道空间结构,适合NSCs黏附、生长和分化,可用于脊髓组织工程。     

In vitro and in vivo evaluation of heparin mediated growth factor release from tissue‐engineered constructs for anterior cruciate ligament reconstruction

Anterior cruciate ligament (ACL) rupture is a common injury often necessitating surgical treatment with graft reconstruction. Due to limitations associated with current graft options, there is interest in a tissue‐engineered substitute for use in ACL regeneration. While they represent an important step in translation to clinical practice, relatively few in vivo studies have been performed to evaluate tissue‐engineered ACL grafts. In the present study, we immobilized heparin onto electrospun polycaprolactone scaffolds as a means of incorporating basic fibroblast growth factor (bFGF) onto the scaffold. In vitro, we demonstrated that human foreskin fibroblasts (HFFs) cultured on bFGF‐coated scaffolds had significantly greater cell proliferation. In vivo, we implanted electrospun polycaprolactone grafts with and without bFGF into athymic rat knees. We analyzed the regenerated ACL using histological methods up to 16 weeks post‐implantation. Hematoxylin and eosin staining demonstrated infiltration of the grafts with cells, and picrosirius red staining demonstrated aligned collagen fibers. At 16 weeks postop, mechanical testing of the grafts demonstrated that the grafts had approximately 30% the maximum load to failure of the native ACL. However, there were no significant differences observed between the graft groups with or without heparin‐immobilized bFGF. While this study demonstrates the potential of a regenerative medicine approach to treatment of ACL rupture, it also demonstrates that in vitro results do not always predict what will occur in vivo. © 2014 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:229–236, 2015.     

Electron beam sterilization does not have a detrimental effect on the ability of extracellular matrix scaffolds to support in vivo ligament healing

Extracellular matrix (ECM) scaffolds have been used to enhance anterior cruciate ligament (ACL) repair in large animal models. To translate this technology to clinical care, identifying a method which effectively sterilizes the material without significantly impairing in vivo function is desirable. Sixteen Yorkshire pigs underwent ACL transection and were randomly assigned to bridge‐enhanced ACL repair—primary suture repair of the ACL with addition of autologous blood soaked ECM scaffold—with either (i) an aseptically processed ECM scaffold, or (ii) an electron beam irradiated ECM scaffold. Primary outcome measures included sterility of the scaffold and biomechanical properties of the scaffold itself and the repaired ligament at 8 weeks after surgery. Scaffolds treated with 15 kGy electron beam irradiation had no bacterial or fungal growth noted, while aseptically processed scaffolds had bacterial growth in all tested samples. The mean biomechanical properties of the scaffold and healing ligament were lower in the electron beam group; however, differences were not statistically significant. Electron beam irradiation was able to effectively sterilize the scaffolds. In addition, this technique had only a minimal impact on the in vivo function of the scaffolds when used for ligament healing in the porcine model. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:1015–1023, 2015.     

Semi‐xenotransplantation: the regenerative medicine‐based approach to immunosuppression‐free transplantation and to meet the organ demand

Although xenografts have always held immeasurable potential as an inexhaustible source of donor organs, immunological barriers and physiological incompatibility have proved to be formidable obstacles to clinical utility. An exciting, new regenerative medicine‐based approach termed “semi‐xenotransplantation” (SX) seeks to overcome these obstacles by combining the availability and reproducibility of animal organs with the biocompatibility and functionality of human allografts. Compared to conventional xenotransplantation wherein the whole organ is animal‐derived, SX grafts are cleansed of their antigenic cellular compartment to produce whole‐organ extracellular matrix scaffolds that retain their innate structure and vascular channels. These scaffolds are then repopulated with recipient or donor human stem cells to generate biocompatible semi‐xenografts with the structure and function of native human organs. While numerous hurdles must be still overcome in order for SX to become a viable treatment option for end‐stage organ failure, the immense potential of SX for meeting the urgent needs for a new source of organs and immunosuppression‐free transplantation justifies the interest that the transplant community is committing to the field.     

Monitoring nutrient transport in tissue‐engineered grafts

Limited nutrient diffusion in three‐dimensional (3D) constructs is a major concern in tissue engineering. Therefore, monitoring nutrient availability and diffusion within a scaffold is an important asset. Since nutrients come in various forms, we have investigated the diffusion of the oxygen, luciferin and dextran molecules within tissue‐engineered constructs using optical imaging technologies. First, oxygen availability and diffusion were investigated, using transgenic cell lines in which a hypoxia‐responsive element drives expression of the green fluorescent protein gene. Using confocal imaging, we observed oxygen limitation, starting at around 200 µm from the periphery in the context of agarose gel with 1 million CHO cells. Diffusion of luciferin was monitored real‐time in agarose gels using a cell line in which the luciferase gene was driven by a constitutively active CMV promoter. Gel concentration affected the diffusion rate of luciferin. Furthermore, we assessed the diffusion rates of fluorescent dextran molecules of different molecular weights in biomaterials by fluorescence recovery after photobleaching (FRAP) and observed that diffusion depended on both molecular size and gel concentration. In conclusion, we have validated a set of efficient tools to investigate molecular diffusion of a range of molecules and to optimize biomaterials design in order to improve nutrient delivery. Copyright © 2013 John Wiley & Sons, Ltd.