Hydroxyapatite–Polyphosphazane Composites Prepared at Low Temperatures

Owing to their similarities to bone apatite, calcium phosphate bioceramics, such as hydroxyapatite (HAp), are used as biomaterials for hard tissue replacements. Composites of bioceramics and biomedical polymers can mimic bone structure and properties. The characteristics of composites comprising HAp and a biomedical polymer and prepared at low temperatures are described. The kinetics of HAp formation in the presence of a polyphosphazene polymer that carries carboxylic acid moieties (acid-PCPP) were established at temperatures from 25° to 50°C. Evolution in the compositions of the solids present, solution chemistry, and microstructure development were established as functions of reaction time and temperature. The polymer participated in HAp formation affecting its rates of nucleation and growth through the formation of calcium cross links. The presence of polymer also enhanced ductility.     

Boron-containing bioactive glasses in bone and soft tissue engineering

Boron is considered to influence the performance of several metabolic enzymes and boron deficiency is associated with impaired growth and abnormal bone development. As such, boron is a beneficial bioactive element for animals and humans. It is also well known that boron stimulates wound healing and improves bone health. The addition of boron in different proportions to bioactive glasses has significant effects on glass structure, glass processing parameters, biodegradability, biocompatibility, bioactivity and cytotoxicity. Different compositions of bioactive glasses (BGs) containing boron, including boron-doped, borosilicate and borate glasses, are being investigated for bone and soft tissue engineering under the premise that these BGs are suitable carriers of boron, indicating controlled release of B species in the biological environment. This paper reviews up to date research and applications of borate, borosilicate, and boron doped silicate and phosphate BGs focussing on their physical, structural, degradation and biological properties for hard and soft tissue regeneration.     

Reversible control of biomaterial properties for dynamically tuning cell behavior

In the past decade, significant advances in chemistry and manufacturing have enabled the development of increasingly complex and controllable biomaterials. A key innovation is the design of dynamic biomaterials that allow for user-specified, reversible, temporal control over material properties. In this review, we provide an overview of recent advancements in reversible biomaterials, including control of stiffness, chemistry, ligand presentation, and topography. These systems have wide-ranging applications within biomedical engineering, including in vitro disease models and tissue-engineered scaffolds to guide multistep biological processes.     

Advanced graphene ceramics and their future in bone regenerative engineering

The outstanding properties of graphene materials rely on an exceptional two-dimensional honeycombed lattice. The lattice allows for electrical, thermal, and mechanical reinforcement effects when applied to the ceramic matrix. The biocompatibility of the material allows for providing multifunctional bioceramics applications. However, the potential of graphene lies in its ability to be homogenously distributed as part of a ceramic matrix. Therefore, appropriate processing techniques are important for attaining desired graphene ceramic properties applicable for regenerative biomedical purposes. This article provides an inclusive review of the current knowledge of advanced graphene-based ceramics for bone regenerative engineering. In this review, the opportunities and challenges in utilizing graphene materials in combination with ceramics suitable for applications in load-bearing bone defects are discussed.     

Silicone-based biomaterials for biomedical applications: Antimicrobial strategies and 3D printing technologies

Silicone is a synthetic polymer widely used in the biomedical industry as implantable devices since 1940, owing to its excellent mechanical properties and biocompatibility. Silicone biomaterials are renowned for their biocompatibility due to their inert nature and hydrophobic surface. A timeline illustration shows critical development periods of using silicone in varied biomedical applications. In this review, silicone properties are discussed along with several biomedical applications, including medical inserts, speciality contact lenses, drains and shunts, urinary catheters, reconstructive gel fillers, craniofacial prosthesis, nerve conduits, and metatarsophalangeal joint implants. Silicones are prone to microbial infections when exposed and interactions with the host tissue. As in the case of medical inserts, the development of specific antimicrobial strategies is essential. The review highlights silicone implants' interaction with soft and bone tissue and various antimicrobial strategies, including surface coating, physical or chemical modifications, treating with antibiotics or plasma-activated surfaces to develop the resistance to bacterial infection. Finally, 3D printing technology, tissue engineering, regenerative medicine applications, and future trends are also critically presented, indicating the silicone's potential as a biomaterial.     

Synthesis, properties and biomedical applications of poly(glycerol sebacate) (PGS): A review

Poly(glycerol sebacate) (PGS) is a biodegradable polymer increasingly used in a variety of biomedical applications. This polyester is prepared by polycondensation of glycerol and sebacic acid. PGS exhibits biocompatibility and biodegradability, both highly relevant properties in biomedical applications. PGS also involves cost effective production with the possibility of up scaling to industrial production. In addition, the mechanical properties and degradation kinetics of PGS can be tailored to match the requirements of intended applications by controlling curing time, curing temperature, reactants concentration and the degree of acrylation in acrylated PGS. Because of the flexible and elastomeric nature of PGS, its biomedical applications have mainly targeted soft tissue replacement and the engineering of soft tissues, such as cardiac muscle, blood, nerve, cartilage and retina. However, applications of PGS are being expanded to include drug delivery, tissue adhesive and hard tissue (i.e., bone) regeneration. The design and fabrication of PGS based devices for applications that mimic native physiological conditions are also being pursued. Novel designs range from accordion-like honeycomb structures for cardiac patches, gecko-like surfaces for tissue adhesives to PGS (nano) fibers for extra cellular matrix (ECM) like constructs; new design avenues are being investigated to meet the ever growing demand for replacement tissues and organs. In less than a decade PGS has become a material of great scrutiny and interest by the biomedical research community. In this review we consolidate the valuable existing knowledge in the fields of synthesis, properties and biomedical applications of PGS and PGS-related biomaterials and devices.     

无机生物涂层材料研究进展及应用

无机生物涂层材料是综合利用金属基体的高强度、高韧性、高塑性以及生物陶瓷的表面活性和生物相容性的优点，成为材料科学领域及生物医学工程领域研究的热点。文章详细介绍了惰性生物陶瓷涂层材料、生物活性玻璃涂层和生物陶瓷涂层的分类、性能及其应用。另外，对无机生物涂层材料的各种制备方法作了详细介绍，最后对无机生物涂层材料的研究前景作了展望。     

Biological and mechanical enhancement of zirconium dioxide for medical applications

Extensive research in global biomedical industry has been driven rapidly due to problems faced in bone implants such as loosening of implants in knee and hip prosthesis as well as short service life of orthopaedic implants. Advances in biomedical engineering have resulted in formation of various materials utilized for orthopaedic transplants and artificial implants. Among the various available materials zirconium dioxide is observed as potential material for biomedical application due to its superior biocompatibility, good compression resistance (2000 MPa), good viability of cell culture, good opacity, and radiopacifying capacity showcasing it's diverse applications in bone and tissue regeneration, orthopaedic implants as well as bone resorption. Bone tissue regenerative modifications is accompanied with coating of zirconium dioxide on metal alloys or 316 L SS substrate, composite formation with silica carbide or organic acids (usnic acid), surface propargylation achieved using chemical treatment of propargyl bromide, electrochemical treatment of zirconium dioxide to evaluate corrosion resistance, etc. Zirconium dioxide is also recorded for exhibiting enhanced mechanical properties as well as biocompatibility in hip arthroplasty as well as bone implants; it also serves application in bone cement to provide adhesion between the biomedical implants. The review paper majorly focuses on effective utilization of zirconium dioxide with various additive materials and functionalization techniques used for enhancement of properties, enabling the application of material in orthopaedic implants as well as bone tissue applications. The mechanical and biological performance analysis of various orthopaedic implants containing zirconium dioxide has been elaborately discussed along with possible measures implemented to enlarge the life of biomedical implant.     

Calcium zirconium silicate (baghdadite) ceramic as a biomaterial

Bioceramics have been widely used for many years to restore and replace hard tissues including bones, teeth and mineralized matrices such as calcified cartilages at osteochondral interfaces, mainly because of their physicochemical similarity with these tissues. Calcium silicate based bioceramics have been shown to possess high bioactivity due to having high apatite-forming ability and stimulating cell proliferation, as well as biodegradability at rates appropriate to hard tissue regeneration. The outstanding biological properties of these ceramics have made them the most studied hard tissue engineering biomaterials along with calcium phosphates and bioactive glasses. Baghdadite is a calcium silicate containing zirconium ions which promotes the proliferation and differentiation of human osteoblasts and consequently increases mineral metabolism and ossification. Recently, it has attracted considerable attention in academic community and widely studied in the form of porous scaffolds, coatings, bone cement and void fillers, microspheres and nanoparticles mostly in orthopedic, dental and maxillofacial applications. This review paper is aimed to summarize and discuss the most relevant studies on the mechanical properties, apatite formation ability, dissolution behavior, and in vitro and in vivo biological properties of baghdadite as a biomaterial for hard tissue regeneration applications.     

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.     

Cobalt-containing bioactive glasses reduce human mesenchymal stem cell chondrogenic differentiation despite HIF-1α stabilisation

Bioactive glasses (BGs) are excellent delivery systems for the sustained release of therapeutic ions and have been extensively studied in the context of bone tissue engineering. More recently, due to their osteogenic properties and expanding application to soft tissue repair, BGs have been proposed as promising materials for use at the osteochondral interface. Since hypoxia plays a critical role during cartilage formation, we sought to investigate the influence of BGs releasing the hypoxia-mimicking agent cobalt (CoBGs) on human mesenchymal stem cell (hMSC) chondrogenesis, as a novel approach that may guide future osteochondral scaffold design. The CoBG dissolution products significantly increased the level of hypoxia-inducible factor-1 alpha in hMSCs in a cobalt dose-dependent manner. Continued exposure to the cobalt-containing BG extracts significantly reduced hMSC proliferation and metabolic activity, as well as chondrogenic differentiation. Overall, this study demonstrates that prolonged exposure to cobalt warrants careful consideration for cartilage repair applications.     

高分子复合生物材料的研究进展

本文综述了近年来用于骨修复的各类高分子复合生物材料的研究状况,并从力学性能的改善和降解速率的可调性等角度,总结了高分子复合生物材料与单一组分的材料相比在生物医用领域应用中所表现出的综合使用性能的优越性,提出将与人骨中磷灰石微晶类似的无机纳米粒子与具有降解性能的有机生物材料进行复合,能够得到具有优越骨修复性能的新型骨生物材料。     

Chemical Modifications of Chitosan and Its Applications

Chitosan is considered as a promising material in the pharmaceutical and biomedical fields based on its unique biological properties. This review presents chemical modifications of chitosan via using photosensitizers, dendrimers, sugars, cyclodextrins and crown ethers as modifiers and places an emphasis on the applications of chitosan derivatives as carriers in drug delivery systems, as supporting materials for tissue engineering, as dye removing agents and as metal ion adsorbents. Recently, the progress on chemical modifications of chitosan is quite rapid and we are confident that a more extensive range of applications of chitosan derivatives could be expected in the near future.     

Review on calcium silicate-based bioceramics in bone tissue engineering

Calcium (Ca) and silica (Si) ions have attracted intense interest in biomedical applications. The two ions are directly involved in many biological processes; for instance, Ca plays a key role in regulating cellular responses to bioceramics, promoting cell growth, and differentiation into osteoblasts. Si plays a significant role in bone calcification and is helpful for bone density improvement and inhibiting osteoporosis. Calcium silicate ceramics including a large group of trace metal containing calcium silicate-based compounds are involved in biomedical applications such as repairing hard tissue texture, bone scaffolds, bone cements, or implant coatings. The aim of the study is to provide a comprehensive overview of developments in research on calcium silicate-based ceramics, such as wollastonite (CaSiO₃), diopside (CaMgSi₂O₆), akermanite (Ca₂MgSi₂O₇), bredigite (Ca₇Mg(SiO₄)₄), merwinite (Ca₃MgSi₂O₈), monticellite (CaMgSiO₄), hardystonite (Ca₂Zn(Si₂O₇), and baghdadite (Ca₃ZrSi₂O₉), including degradation, apatite mineralization, and mechanical properties. Finally, the biological in vitro and in vivo presentation for bone tissue repair are summarized, which show promise with regard to application of calcium silicate-based ceramics as bone repair and replacement materials.     

PVA-based hydrogels for tissue engineering: A review

Poly (vinyl alcohol) (PVA) is a hydrophilic polymer with excellent biocompatibility and has been applied in various biomedical areas due to its favorable properties. PVA-based hydrogels have been recognized as promising biomaterials and suitable candidates for tissue engineering applications and can be manipulated to act various critical roles. However, due to some disadvantages (i.e., lack of cell-adhesive property), they needs further modification for desired and targeted applications. This review highlights recent progress in the design and fabrication of PVA-based hydrogels, including crosslinking and processing techniques. Finally, major challenges and future perspectives in tissue engineering are briefly discussed.     

Polymeric nanostructured materials for biomedical applications

Polymeric nanostructured materials (PNMs), which are polymeric materials in nanoscale or polymer composites containing nanomaterials, have become increasingly useful for biomedical applications. In specific, advances in polymer-related nanoscience and nanotechnology have brought a revolutionary change to produce new biomaterials with tailored properties and functionalities for targeted biomedical applications. These materials, including micelles, polymersomes, nanoparticles, nanocapsules, nanogels, nanofibers, dendrimers and nanocomposites, have been widely used in drug delivery, gene therapy, bioimage, tissue engineering and regenerative medicine. This review presents a comprehensive overview on the various types of PNMs, their fabrication methods and biomedical applications, as well as the challenges in research and development of future PNMs.     

Recent advances on akermanite calcium-silicate ceramic for biomedical applications

Owing to great biocompatibility and high capacity of apatite formation, bioceramics, especially calcium silicate-based compounds, were extensively employed in orthopedic and dental uses concerning biomedical applications. Lately, akermanite (AK; Ca₂MgSi₂O₇), as a bioceramic containing Ca-, Mg- and Si, has gained an increased level of attention because of its more tunable mechanical characteristics and degradation rate. All studies indicate that this magnesium incorporating Ca-silicate ceramic has a great capacity to use as a bone graft material to fulfill the necessity of bone reconstruction. Despite the rising interest in using these materials in biomedical fields, there has not yet been an extensive overview of this bioceramic property and its potential benefits. Thus, it has been speculated that this concept and the emergence of akermanite bioactive ceramics might lead to significant upcoming advancements in the field of bone tissue engineering (BTE). Definitely, the approach still requires additional advances to considerably better respond to the vital concerns regarding the clinical application. The review tackles the present research trends on akermanite ceramics for biomedical purposes such as bone scaffold, coating materials, bone cement, and treatment of osteoporotic bone defects, commencing with recent status and shifting to upcoming developments.     

Homology of selenium (Se) and tellurium (Te) endow the functional similarity of Se-doped and Te-doped mesoporous bioactive glass nanoparticles in bone tissue engineering

The focus of bone tissue engineering is to realize the regeneration of new functional bone through the synergistic combination of biomaterials, therapeutic agents and cells. Doping of mesoporous bioactive glass (MBG) nanoparticles with therapeutic ions to give them special properties is gaining increasing interest in the design of biomaterials for bone tissue engineering. In this study, we synthesized Se-doped and Te-doped MBG nanoparticles using the sol-gel method, and demonstrated for the first time that the homology of Se and Te endows the functional similarity of bone tissue engineering, and also obtains the desired properties by guiding cell behavior and changing the physicochemical properties of the biomaterial. Results found that MBG nanoparticles doped with Se and Te respectively can be gained similar structure, and thus endowed their similar properties as expected, such as drug sustained release, anticancer and antibacterial properties in a dose-dependent manner. This study provides a feasible strategy for the development of homologous group ions doped nanobiomaterials and their evaluation and basic research in bone tissue engineering.     

骨组织工程支架材料

寻找理想的支架材料是目前骨组织工程研究的热点。本文对用于骨组织工程支架材抖的天然生物衍生材料、聚合物类材料、陶瓷材料及其复合材料等的研究现状进行综述，分析了这些材料的优缺点，并对骨组织工程支架材料发展趋势进行了展望。     

Review of crosslinked and non‐crosslinked copolyesters for tissue engineering and drug delivery

Novel degradable biomedical materials are found to have huge potential applications in fields such as drug delivery and release, orthopedic fixation support and tissue engineering. Utilization of polymers as biomaterials has greatly impacted the advancement of modern medicine. In this review, some new degradable biomedical copolyesters reported in recent years are introduced and discussed in combination with some of our research results, including non‐crosslinked copolyesters, crosslinked copolyesters and their corresponding derivatives. The molecular design, chemical structures and related properties of these biodegradable copolyesters are reported. In summarizing the review, the development, potential applications and future directions of degradable biomedical copolyesters are discussed. © 2013 Society of Chemical Industry