Graphene functionalized decellularized scaffold promotes skin cell proliferation

An increasing number of new strategies for skin tissue engineering have been developed with the potential to mimic the biological properties of native tissue with a high degree of complexity, flexibility, and reproducibility. In this study, decellularized tissue (DT) was prepared from the bovine heart by using chemical treatments. However, the mechanical properties of the DT constructs were poorer than the extra cellular matrix of the skin tissue. To overcome this challenge, hybrid scaffolds of DT and graphene oxide (GO) were developed and the effects of the GO concentration on the morphology, pore size, porosity, mechanical strength, and water uptake capacity of the samples were evaluated. Moreover, the biocompatibility of hybrid scaffolds was studied by Live/Dead staining. The results show that a hybrid scaffold incorporating 3 % graphene oxide improved the mechanical strength and cell viability by ~25 % in comparison to the DT scaffolds. Cell viability results confirmed that the porous scaffolds could support cell adhesion, proliferation, and cell activity for 7 days. This study provides new insight into and opportunities for using graphene-based materials to develop biomimetic constructs for clinical applications.     

Tissue Engineering and Regenerative Medicine in Pediatric Urology: Urethral and Urinary Bladder Reconstruction

In the case of pediatric urology there are several congenital conditions, such as hypospadias and neurogenic bladder, which affect, respectively, the urethra and the urinary bladder. In fact, the gold standard consists of a urethroplasty procedure in the case of urethral malformations and enterocystoplasty in the case of urinary bladder disorders. However, both surgical procedures are associated with severe complications, such as fistulas, urethral strictures, and dehiscence of the repair or recurrence of chordee in the case of urethroplasty, and metabolic disturbances, stone formation, urine leakage, and chronic infections in the case of enterocystoplasty. With the aim of overcoming the issue related to the lack of sufficient and appropriate autologous tissue, increasing attention has been focused on tissue engineering. In this review, both the urethral and the urinary bladder reconstruction strategies were summarized, focusing on pediatric applications and evaluating all the biomaterials tested in both animal models and patients. Particular attention was paid to the capability for tissue regeneration in dependence on the eventual presence of seeded cell and growth factor combinations in several types of scaffolds. Moreover, the main critical features needed for urinary tissue engineering have been highlighted and specifically focused on for pediatric application.     

Polymeric scaffolds for cardiac tissue engineering: requirements and fabrication technologies

Cardiac tissue engineering (TE) is an emerging field, whose main goal is the development of innovative strategies for the treatment of heart diseases, with the aim of overcoming the drawbacks of traditional therapies. One of these strategies involves the implantation of three‐dimensional matrices (scaffolds) capable of supporting tissue formation. Scaffolds designed and fabricated for such application should meet several requirements, concerning both the scaffold‐forming materials and the properties of the scaffold itself. A scaffold for cardiac TE should be biocompatible and biodegradable, mimic the properties of the native cardiac tissue, provide a mechanical support to the regenerating heart and possess an interconnected porous structure to favour cell migration, nutrient and oxygen diffusion, and waste removal. Moreover, the mimesis of myocardium characteristic anisotropy is attracting increasing interest to provide engineered constructs with the possibility to be structurally and mechanically integrated in native tissue. Several conventional and non‐conventional fabrication techniques have been explored in the literature to produce polymeric scaffolds meeting all these requirements. This review describes these techniques, with a focus on their advantages and disadvantages, and their flexibility, with the final goal of providing the reader with the primal knowledge necessary to develop an effective strategy in cardiac TE. © 2013 Society of Chemical Industry     

Extracellular matrix regenerated: tissue engineering via electrospun biomimetic nanofibers

While electrospinning had seen intermittent use in the textile industry from the early twentieth century, it took the explosion of the field of tissue engineering, and its pursuit of biomimetic extracellular matrix (ECM) structures, to create an electrospinning renaissance. Over the past decade, a growing number of researchers in the tissue engineering community have embraced electrospinning as a polymer processing technique that effectively and routinely produces non‐woven structures of nanoscale fibers (sizes of 80 nm to 1.5 µm). These nanofibers are of physiological significance as they closely resemble the structure and size scale of the native ECM (fiber diameters of 50 to 500 nm). Attempts to replicate the many roles of native ECM have led to the electrospinning of a wide array of polymers, both synthetic (poly(glycolic acid), poly(lactic acid), polydioxanone, polycaprolactone, etc.) and natural (collagen, fibrinogen, elastin, etc.) in origin, for a multitude of different tissue applications. With various compositions, fiber dimensions and fiber orientations, the biological, chemical and mechanical properties of the electrospun materials can be tailored. In this review we highlight the role of electrospinning in the engineering of different tissues and applications (skin/wound healing, cartilage, bone, vascular tissue, urological tissues, nerve, and ligament), and discuss its potential role in future work. Copyright © 2007 Society of Chemical Industry     

膀胱全切回肠原位代膀胱改良术的疗效观察

目的评价膀胱全切除回肠原位代膀胱术的临床效果。方法回顾性分析2004年8月至2008年3月我院膀胱肿瘤行膀胱全切原位回肠代膀胱术18例的临床资料。结果所有病人均得到随访。患者除一例外均无瘤存活。手术时间为6～9 h,平均8h。术中出血量为800～1000mL,平均为950mL;代膀胱容量平均300mL,最大尿流率平均15mL/s;剩余尿量平均为30mL,代膀胱排尿状态良好。结论膀胱全切回肠原位代膀胱手术具有膀胱容量大、内压低、正位排尿、可控性能好等优点,是一种较理想的膀胱替代术式,值得临床推广应用。     

Nanofibrous MgO composites: structures,properties, and applications

ABSTRACT

Nanomaterials have become an established area of academic research and have gained commercial importance due to their valuable physicochemical properties, such as large surface area, high mechanical strength as well as unique optical and electrical features. Numerous nanosize architectures have been researched and reported to date including quantum dots, fullerenes, nanorods, nanowires, nanofibers, nanosheets, nanowalls, nanocoils, and nanoballs, etc. Among these materials, nanofibers are extremely valuable morphologies used across many industries spanning from textile to medical applications and beyond. This review article focuses on the various works and reports of MgO-based applications and its overlap with nanofiber-based structures. Comprehensive review of the growing number of reports to date provides a unified resource for researchers going forward. As the acceptance and broader set of applications continues its exponential growth in commercial and academic output, it is envisaged that MgO-based composites will play a central part in many future reports of nanofibrous composites and other composite architectures, e.g., particle-reinforced composites, metal matrix composites, ceramic matrix composites, etc., due to the wide variety of applications to which MgO is suited, as well as other peripheral properties such as cost, availability, ease-of-handling, and use, etc. Indeed, despite the many preliminary reports to date, there remains a great deal yet to discover and optimize for such systems.     

A Guide to Polysaccharide-Based Hydrogel Bioinks for 3D Bioprinting Applications

Three-dimensional (3D) bioprinting is an innovative technology in the biomedical field, allowing the fabrication of living constructs through an approach of layer-by-layer deposition of cell-laden inks, the so-called bioinks. An ideal bioink should possess proper mechanical, rheological, chemical, and biological characteristics to ensure high cell viability and the production of tissue constructs with dimensional stability and shape fidelity. Among the several types of bioinks, hydrogels are extremely appealing as they have many similarities with the extracellular matrix, providing a highly hydrated environment for cell proliferation and tunability in terms of mechanical and rheological properties. Hydrogels derived from natural polymers, and polysaccharides, in particular, are an excellent platform to mimic the extracellular matrix, given their low cytotoxicity, high hydrophilicity, and diversity of structures. In fact, polysaccharide-based hydrogels are trendy materials for 3D bioprinting since they are abundant and combine adequate physicochemical and biomimetic features for the development of novel bioinks. Thus, this review portrays the most relevant advances in polysaccharide-based hydrogel bioinks for 3D bioprinting, focusing on the last five years, with emphasis on their properties, advantages, and limitations, considering polysaccharide families classified according to their source, namely from seaweed, higher plants, microbial, and animal (particularly crustaceans) origin.     

Biodegradable zinc-based materials with a polymer coating designed for biomedical applications

Over the last decades, biodegradable metals have gained popularity for biomedical applications due to their ability to assist in tissue healing. These materials degrade in vivo, while the corrosion products formed are either absorbed or excreted by the body, and no further surgical intervention is required for removal. Intensive research has been carried out mainly on degradable biomaterials based on Mg and Fe. In recent years, zinc-based degradable biomaterials have been explored by the biomedical community for their intrinsic physiological relevance, desirable biocompatibility, intermediate degradation rate, tuneable mechanical properties and pro-regeneration properties. Since pure Zn does not exhibit sufficient mechanical properties for orthopedic applications, various Zn alloys with better properties are being developed. In this work, the combined effect of minor Fe addition to Zn and a polyethyleneglycol (PEG) coating on the surface morphology, degradation, cytotoxicity and mechanical properties of Zn-based materials was studied. There are several studies regarding the influence of the production of Zn alloys, but the effect of polymer coating on the properties of Zn-based materials has not been reported yet. A positive effect of Fe addition and polymer coating on the degradation rate and mechanical properties was observed. However, a reduction in biocompatibility was also detected.     

Aldehyde?Amine Chemistry Enables Tissue Adhesive Materials to Respond to Physiologic Variation and Pathologic States

Biomaterials science represents the next frontier in medical therapeutics. Innovations in materials design and formulation have helped create previously unimaginable interventions and composite devices with materials whose structure and function evolve with time. Yet, materials development has outstripped our ability to explain why, when, and how these materials work. Current characterization means are limited, especially for dynamic erodible materials that are specifically designed to fade away. This complexity and dynamism of emerging materials and the impact they have on tissue make it challenging to understand and predict material interactions with local tissues. Because tissue biomaterials interactions are determined not only by the innate properties of the materials, but also by the local microenvironment at the implantation site, we must now examine the impact of target tissue site, state, and incidence of a disease on material performance, efficacy, and biocompatibility. This issue becomes increasingly important when considering surface interacting materials, whose intimate interactions with tissues are dictated by local mechanical forces, tissue target site, and the modulation of tissue surface properties manifested by specific disease types and states. The mechanisms involved and the extent to which these parameters affect the in vivo performance of materials are mostly unknown. These open questions motivated us to explore the determinant factors that affect the efficacy of materials, using adhesive materials whose surface interactions with tissues make them an ideal material class for the assessment of tissue material interactions. As an example of this paradigm, we determined how tissue amines served as a natural binding site for material aldehydes, enabling tissue-specific binding that varied with natural changes in amine density from tissue to tissue and the physiologic environment, as well as with disease. The introduction of amines within the material also provides greater control over binding and material cohesion. This general mode will provide new tissue adhesives that can sense local tissue states and provide mechanical interactions titrated to context and need to enhance the desired effect and minimize local toxicity.     

An assessment of biopolymer‐ and synthetic polymer‐based scaffolds for bone and vascular tissue engineering

The promise of tissue engineering is the combination of a scaffold with cells to initiate the regeneration of tissues or organs. Engineering of scaffolds is critical for success and tailoring of polymer properties is essential for their good performance. Many different materials of natural and synthetic origins have been investigated, but the challenge is to find those that have the right mix of mechanical performance, biodegradability and biocompatibility for biological applications. This article reviews key polymeric properties for bone and vascular scaffold eligibility with focus on biopolymers, synthetic polymers and their blends. The limitations of these polymeric systems and ways and means to improve scaffold performance specifically for bone and vascular tissue engineering are discussed. © 2013 Society of Chemical Industry     

Changes in the Mechanical Properties of Alginate-Gelatin Hydrogels with the Addition of Pygeum africanum with Potential Application in Urology

New hydrogel materials developed to improve soft tissue healing are an alternative for medical applications, such as tissue regeneration or enhancing the biotolerance effect in the tissue-implant–body fluid system. The biggest advantages of hydrogel materials are the presence of a large amount of water and a polymeric structure that corresponds to the extracellular matrix, which allows to create healing conditions similar to physiological ones. The present work deals with the change in mechanical properties of sodium alginate mixed with gelatin containing Pygeum africanum. The work primarily concentrates on the evaluation of the mechanical properties of the hydrogel materials produced by the sol–gel method. The antimicrobial activity of the hydrogels was investigated based on the population growth dynamics of Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 25923, as well as the degree of degradation after contact with urine using an innovative method with a urine flow simulation stand. On the basis of mechanical tests, it was found that sodium alginate-based hydrogels with gelatin showed weaker mechanical properties than without the additive. In addition, gelatin accelerates the degradation process of the produced hydrogel materials. Antimicrobial studies have shown that the presence of African plum bark extract in the hydrogel enhances the inhibitory effect on Gram-positive and Gram-negative bacteria. The research topic was considered due to the increased demand from patients for medical devices to promote healing of urethral epithelial injuries in order to prevent the formation of urethral strictures.     

Effect of replacement of castor oil and polychloroprene by chlorinated paraffin in butyl compounds of tyre‐curing bladder

Ways are explored to increase the life and to reduce the cost of tyre‐curing bladders by improving their mechanical and ageing properties. Nine formulations have been designed which involve the partial replacement of polychloroprene (PC) and castor oil (CO), both individually and simultaneously, by chlorinated paraffin (CP) in the butyl bladder compound. The compounds have been tested for various cure properties such as initial torque, minimum torque, scorch time, optimum cure time, cure rate, maximum torque and reversion time. The vulcanized samples have been tested for mechanical properties such as tensile stress at 300 % elongation, tensile strength at break, ultimate elongation, rubber deterioration by dynamic fatigue test and Shore‐A hardness before and after ageing. The results show that tensile strength at break and ultimate elongation decrease, while tensile stress at 300 % elongation increase except in one case (when PC was partially replaced by CP). Simultaneous and individual replacement of CO by CP results in a decrease in hardness of up to 3 phr (base recipe CO 5 phr), whereas further replacement of CO by CP results in an increase in hardness. Tensile stress at 300 % elongation and Shore‐A hardness increase up to a limit while tensile strength at break and ultimate elongation decrease with ageing. © 2000 Society of Chemical Industry     

Hydrogels with Reversible Crosslinks for Improved Localised Stem Cell Retention: A Review

Successful stem cell applications could have a significant impact on the medical field, where many lives are at stake. However, the translation of stem cells to the clinic could be improved by overcoming challenges in stem cell transplantation and in vivo retention at the site of tissue damage. This review aims to showcase the most recent insights into developing hydrogels that can deliver, retain, and accommodate stem cells for tissue repair. Hydrogels can be used for tissue engineering, as their flexibility and water content makes them excellent substitutes for the native extracellular matrix. Moreover, the mechanical properties of hydrogels are highly tuneable, and recognition moieties to control cell behaviour and fate can quickly be introduced. This review covers the parameters necessary for the physicochemical design of adaptable hydrogels, the variety of (bio)materials that can be used in such hydrogels, their application in stem cell delivery and some recently developed chemistries for reversible crosslinking. Implementing physical and dynamic covalent chemistry has resulted in adaptable hydrogels that can mimic the dynamic nature of the extracellular matrix.     

Surface Modification of Bacterial Cellulose for Biomedical Applications

Bacterial cellulose is a naturally occurring polysaccharide with numerous biomedical applications that range from drug delivery platforms to tissue engineering strategies. BC possesses remarkable biocompatibility, microstructure, and mechanical properties that resemble native human tissues, making it suitable for the replacement of damaged or injured tissues. In this review, we will discuss the structure and mechanical properties of the BC and summarize the techniques used to characterize these properties. We will also discuss the functionalization of BC to yield nanocomposites and the surface modification of BC by plasma and irradiation-based methods to fabricate materials with improved functionalities such as bactericidal capabilities.     

The Role of Glycoside Hydrolases in Phytopathogenic Fungi and Oomycetes Virulence

Phytopathogenic fungi need to secrete different hydrolytic enzymes to break down complex polysaccharides in the plant cell wall in order to enter the host and develop the disease. Fungi produce various types of cell wall degrading enzymes (CWDEs) during infection. Most of the characterized CWDEs belong to glycoside hydrolases (GHs). These enzymes hydrolyze glycosidic bonds and have been identified in many fungal species sequenced to date. Many studies have shown that CWDEs belong to several GH families and play significant roles in the invasion and pathogenicity of fungi and oomycetes during infection on the plant host, but their mode of function in virulence is not yet fully understood. Moreover, some of the CWDEs that belong to different GH families act as pathogen-associated molecular patterns (PAMPs), which trigger plant immune responses. In this review, we summarize the most important GHs that have been described in eukaryotic phytopathogens and are involved in the establishment of a successful infection.     

Synthesis, preparation, in vitro degradation, and application of novel degradable bioelastomers—A review

Degradable bioelastomers are novel polymer biomaterials mainly applied in soft tissue engineering and drug delivery. Synthetic degradable bioelastomers present four remarkable features: three-dimensional crosslinking network structure similar to that of natural elastins, high flexibility and elasticity capable of providing mechanical stimuli for tissue engineering constructs, matched mechanical properties especially with soft body tissues, and broad biodegradability that can be adjusted directly by crosslink density. In this review, degradable bioelastomers are divided into chemically and physically crosslinked bioelastomers. In view of the influence of crosslinking structures on the properties of bioelastomers, chemically crosslinked bioelastomers are further classified into thermo-cured and photo-cured bioelastomers, and physically crosslinked bioelastomers correspond to thermoplastic bioelastomers. In this contribution, after a discussion on the definition of and design strategies for degradable bioelastomers is delivered, the recent advances in the synthesis, properties (especially the in vitro degradation), and potential biomedical applications of these materials are described. Simultaneously, some insights on degradable bioelastomers have also been illuminated. Degradable bioelastomers are sure to play an increasingly significant role in the future developments of polymer biomaterials.     

Past and Future Solid-State NMR Spectroscopy Studies at the Convergence Point between Biology and Materials Research

Many cellular events involve attachment of proteins to the surfaces of rigid or semi-rigid solid materials, such as the inorganic materials in the extracellular matrix of hard tissue, and the macromolecular scaffolds made of actin and tubulin filaments in the cytoskeleton. Understanding these processes on a fundamental level will have far-reaching repercussions for the design of biomaterials, biomedical research, and biomineralization. Numerous studies have reported structural changes experienced by proteins as they adhere to surfaces, yet there are only a few examples in which detailed views of protein conformation and alignment on surfaces were measured. Modern multidimensional solid-state NMR spectroscopy is timely situated to unveil molecular details of these processes and shed light on many fundamental questions related to recognition of surfaces by biomolecules. Targeting these questions is currently at the focal point of many research fields and can lead to insights and breakthroughs in biotechnology and in biomimetic material design.     

骨组织工程中的碳纤维材料

归纳了聚合物支架材料在提高其力学性能方面的一些研究工作,并综述了碳纤维材料在骨组织工程上应用的进展.分析表明,骨组织工程是修复骨缺损的有效方法之一,而碳纤维材料的结构性能优势使其成为提高组织工程支架性能的首选材料之一.在提高聚合物支架力学性能的同时,进一步提高材料的生物活性和促进骨的修复是目前研究的重点和难点.指出可通过对碳纤维材料的改性、有序排列等手段来进一步提高碳纤维材料的作用.     

The impact of rheology of human fibronectin-fibrinogen solutions on fibre extrusion for tissue engineering

Fibronectin-fibrinogen composite materials form a basis for natural constructs for applications in soft tissue engineering including skin repair, blood vessel replacement and nerve regeneration. Scaleable methods for the preparation of such scaffolds are a prerequisite for their widespread use. Here, we report data on the extrusion of fibronectin-based constructs in the form of fibres.The results suggested that events occurring in the extrusion head and coagulation bath were critical in determining the ultimate mechanical strength of the extruded fibres. These events were controlled by interaction between the rheology of the dope, the geometry of the extrusion device and the operating parameters of the extrusion process. The rheology of the dope was successfully controlled by incorporation of sodium alginate, and urea was added to the formulation to produce oriented fibres. We previously reported that oriented fibronectin fibres have the capacity to induce desirable cell responses.Measurements indicated that for a given formulation, the mechanical properties and morphological features depended on the diameter of the extruded fibre, the rate of shear in the extrusion pipe and the time of exposure to it.     

Morphology and Mechanical Properties of PLLA and PCL Scaffolds

Human tissue engineering, comprising methods and tools to create implants, is a promising although as yet a very underdeveloped field of research into the regeneration of specific damaged or necrotic tissue. Porous scaffolds play an important role in tissue engineering. The porous cell culture scaffolds in this study were produced through thermally induced phase separation (lyophilization). This technique yields considerable variations in scaffold microstructures (pore size and morphology) as a function of the polymer, solvent and thermal processing. PLLA and PCL were used with chloroform, 1,4-dioxane and water as solvent. We observed a decrease in mechanical properties with increasing pore size in the two polymers under study. However, we found that PLLA, which possesses larger pore sizes than PCL, showed superior mechanical properties, which we explain in terms of crystallinity.