Preparation，properties and applications of hydroxyapatite/synthetic polymer composites

随着生物医用材料的需求量日趋增大,磷灰石与人工合成高分子的复合材料成为组织修复和替代材料的研究热点。以不同单体分类,综述了磷灰石与合成的非降解高分子、可降解高分子复合材料的研究进展;对羟基磷灰石/合成高分子复合材料的制备方法、性能及其应用等方面进行研究,并对此复合材料存在的问题和发展前景进行讨论。说明从分子水平设计出具有良好力学性能、生物活性和生物相容性的医学材料,具有十分重要的意义。     

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.     

Fabrication and characterization of hybrid coating on Mg–Zn–Ca Mg alloy for enhanced corrosion and degradation resistance as medical implant

Magnesium (Mg)-based alloys have appealing properties as promising implants for medical applications. However, their clinical applications are hindered due to the rapid corrosion and degradation rate in the physiological environment. In this investigation, we reported a novel interfacial engineering approach for the fabrication of polymer/ceramic hybrid coating on Mg–Zn–Ca Mg alloy. Firstly, hydroxyapatite (HA) coating was fabricated on the Mg–Zn–Ca sample followed by an alkali treatment that was performed in 1 M NaOH solution at 60 °C. Finally, polycaprolactone (PCL) coating was synthesized using a dip-coating approach on the top of the HA-coated Mg–Zn–Ca specimen. Microhardness test and adhesion test revealed that PCL/HA hybrid coating significantly improved mechanical properties and enhanced biointerface property between the substrate and coating. The immersion tests showed that the hybrid coating considerably slowed down the degradation in the simulated body fluid (SBF) solution. In addition, in vitro electrochemical investigations confirmed that PCL/HA coating significantly improved corrosion resistance and greatly reduced corrosion rate by about 10 times compared to HA coating and about 900 times to untreated Mg–Zn–Ca sample. Moreover, cytotoxicity assessment exhibited PCL/HA hybrid coating enhanced biocompatibility and bioactivity due to adopting a suitable interfacial engineering approach.     

Nanocomposites of Polymeric Biomaterials Containing Carbonate Groups: An Overview

The modification of biomaterials using nanoadditives can lead to the development of novel materials for a wide variety of biomedical applications such as drug administration systems, tissue engineering, bioresistance coatings, and biomedical instruments. Moreover, a further improvement of mechanical and thermal properties of aforementioned biomaterials while maintaining their dimensional stability is a goal of major scientific researches. Aliphatic polycarbonates (APCs) containing carbonate groups such as poly(trimethylene carbonate), poly(propylene carbonate), poly(ethylene carbonate), poly(dimethyl trimethylene carbonate), etc., have become much more interesting compared to other biodegradable materials due to their unique physical and chemical properties. This review presents the effect of applying different kinds of nanoparticles (NPs) on the mechanical, thermal, and viscoelastic properties as well as dimensional stability and biocompatibility of APCs. The dispersion process of nanofillers within polymer matrices has been divided into two groups, solution and melt mixing techniques. Moreover, synthesis procedures of APC loaded NPs for drug delivery systems and electrospinning of nanofiber mats have also been reviewed. In order to clarify the effect of NPs on the overall characteristics of the APC biomaterials, the detailed mechanism of improving process have been extensively discussed.     

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。     

Research progress of surface modification of biomedical magnesium

由于镁具有优异的生物相容性、可生物降解性及适宜的力学性能而成为潜在的生物医用材料。本文对镁作为生物材料的优缺点进行了综合的评价,分类综述了用不同的表面改性技术在镁及其合金表面制备不同的涂层,包括电化学沉积法及阴极沉积法、离子注入及离子电镀法、阳极氧化及微弧氧化法以及化学转化法,评述了这些涂层对镁的腐蚀性能与生物活性的影响,并对镁作为一种新型可降解的硬组织植入材料的应用前景进行了展望。     

Emerging Perspectives in the Synthesis of Novel Degradable Biomedical Copolymers

Biodegradable polymer is playing an increasingly significant role in the development of biomedical materials due to its good biocompatibility and biodegradability, and is undoubtedly the focus in the biomedical fields, such as controlled drug delivery, tissue engineering, and regenerative medicine. In this review, some new degradable biomedical copolymers reported over the past 5 years are introduced and discussed in combination with some our research results. The molecular design, chemical structures and related properties of these novel biodegradable copolymers are reported. In summarizing the review, the development, potential applications and future directions of the degradable biomedical copolymers are discussed.     

Reactive oxygen species-responsive degradable poly(amino acid)s for biomedical use

A series of reactive oxygen species-responsive degradable poly(amino acid)s (PAAs) was synthesized via in situ melting polycondensation. The PAAs were characterized by X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, differential scanning calorimetry, thermogravimetric analysis, and mechanical property analysis. The degradation and biocompatibility of the PAAs were also studied to evaluate their applicability as biomedical materials. The results show that the PAAs possessed semicrystalline amide structures, and the PAA melting temperature decreased gradually with increasing methionine loading. The incorporation of methionine decreased the thermal stability of the matrix, leading to decreases in both the initial and maximum degradation temperatures. The mechanical properties of the PAAs deteriorated as the content of methionine increased. The content of methionine had an obvious effect on PAA degradation, and the PAAs were responsive to the reactive oxygen-rich environment, suggesting that the incorporation of methionine is effective at improving the degradation of PAAs. The PAAs showed great in vitro and in vivo biocompatibilities. Based on the results, these polymers show promise as high-performance materials for biomedical applications.     

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.     

The Effect of Antibacterial Particle Incorporation on the Mechanical Properties,Biodegradability, and Biocompatibility of PLA and PHBV Composites

The composites based on polylactide (PLA) and poly (3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) with the addition of antibacterial particles: silver (Ag) and copper oxide (CuO) are characterized. Basic mechanical properties and biodegradation processes, as well as biocompatibility of materials with human cells are determined. The addition of Ag or CuO to the polymers do not significantly affect their mechanical properties, flammability, or biodegradation rate. However, several differences between the base materials are observed. PLA‐based composites have higher tensile and impact strength values, while PHBV‐based ones have a higher modulus of elasticity, as well as better mechanical properties at elevated temperatures. Concerning biocompatibility, each of the tested materials support the growth of fibroblasts over time, although large differences are observed in the initial cell attachment. The analysis of hydrolytic degradation effects on the structure of materials shows that PHBV degrades much faster than PLA. The results of this study confirm the good potential of the investigated biodegradable polymer composites with antibacterial particles for future biomedical applications.     

Comparison of Selective Laser Melted Titanium and Magnesium Implants Coated with PCL

Degradable implant material for bone remodeling that corresponds to the physiological stability of bone has still not been developed. Promising degradable materials with good mechanical properties are magnesium and magnesium alloys. However, excessive gas production due to corrosion can lower the biocompatibility. In the present study we used the polymer coating polycaprolactone (PCL), intended to lower the corrosion rate of magnesium. Additionally, improvement of implant geometry can increase bone remodeling. Porous structures are known to support vessel ingrowth and thus increase osseointegration. With the selective laser melting (SLM) process, defined open porous structures can be created. Recently, highly reactive magnesium has also been processed by SLM. We performed studies with a flat magnesium layer and with porous magnesium implants coated with polymers. The SLM produced magnesium was compared with the titanium alloy TiAl6V4, as titanium is already established for the SLM-process. For testing the biocompatibility, we used primary murine osteoblasts. Results showed a reduced corrosion rate and good biocompatibility of the SLM produced magnesium with PCL coating.     

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.     

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     

A comprehensive review of hydroxyapatite-based coatings adhesion on metallic biomaterials

Metallic biomaterials have been employed in replacing and reconstructing the structural parts of the human physical structure due to their high mechanical properties, superior biocompatibility, and high corrosion resistance. The most common metallic biomaterials that have been used in implants include magnesium, stainless steel, cobalt-based alloy, titanium, and titanium-based alloy. Hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂) is one of the ceramic biomaterials considered as ideal materials for coating on metallic biomaterials as it possesses almost the closest similarity in chemical composition and excellent biocompatibility with natural bone tissue. Recently, the HAp-based coating has increasingly drawn attention to improve the adhesion quality in metallic biomaterials. This study comprehensively reviews the current progress in the adhesion qualities of HAp-based coatings on metallic biomaterials specifically for the biomedical application. It has been observed that a surface that meets the minimum unique characteristics will enhance the bonding force between the coating and metallic biomaterial as the substrate. Critical factors of coating/substrate materials, coating techniques, and coating thickness that determine the adhesion quality are thoroughly identified and discussed. The surface structure and microstructure of HAp-based coating are also reviewed to confirm the findings.     

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.     

Silk proteins for biomedical applications: Bioengineering perspectives

Biomaterials of either natural or synthetic origin are used to fabricate implantable devices, as carriers for bioactive molecules or as substrates to facilitate tissue regeneration. For the design of medical devices it is fundamental to use materials characterized by non-immunogenicity, biocompatibility, slow and/or controllable biodegradability, non-toxicity, and structural integrity. The success of biomaterial-derived biodevices tends to be based on the biomimetic architecture of the materials. Recently, proteins from natural precursors that are essentially structural and functional polymers, have gained popularity as biomaterials. The silks produced by silkworms or spiders are of particular interest as versatile protein polymers. These form the basis for diverse biomedical applications that exploit their unique biochemical nature, biocompatibility and high mechanical strength. This review discusses and summarizes the latest advances in the engineering of silk-based biomaterials, focusing specifically on the fabrication of diverse bio-mimetic structures such as films, hydrogels, scaffolds, nanofibers and nanoparticles; their functionalization and potential for biomedical applications.     

Current advances concerning the most cited metal ions doped bioceramics and silicate-based bioactive glasses for bone tissue engineering

Studies related to biomaterials that stimulate the repair of living tissue have increased considerably, improving the quality of many people's lives that require surgery due to traumatic accidents, bone diseases, bone defects, and reconstructions. Among these biomaterials, bioceramics and bioactive glasses (BGs) have proved to be suitable for coating materials, cement, scaffolds, and nanoparticles, once they present good biocompatibility and degradability, able to generate osteoconduction on the surrounding tissue. However, the role of biomaterials in hard tissue engineering is not restricted to a structural replacement or for guiding tissue regeneration. Nowadays, it is expected that biomaterials develop a multifunctional role when implanted, orchestrating the process of tissue regeneration and providing to the body the capacity to heal itself. In this way, the incorporation of specific metal ions in bioceramics and BGs structure, including magnesium, silver, strontium, lithium, copper, iron, zinc, cobalt, and manganese are currently receiving enhanced interest as biomaterials for biomedical applications. When an ion is incorporated into the bioceramic structure, a new category of material is created, which has several unique properties that overcome the disadvantages of primitive material and favors its use in different biomedical applications. The doping can enhance handling properties, angiogenic and osteogenic performance, and antimicrobial activity. Therefore, this review aims to summarize the effect of selected metal ion dopants into bioceramics and silicate-based BGs in bone tissue engineering. Furthermore, new applications for doped bioceramics and BGs are highlighted, including cancer treatment and drug delivery.     

Functional copolymer coatings on electrospun fibers via photo-initiated chemical vapor deposition

With the increasing use of implantable patches in biomedical applications, the significance of surface modification techniques in improving biocompatibility, enhancing adhesion, and regulating drug release has grown. A significant challenge that these methods must address is ensuring that the process does not harm the delicate fibers or therapeutic agents they contain. Here, we report surface functionalization of implantable, curcumin loaded Polycaprolactone (PCL) patches with pH-responsive poly(2-hydroxyethyl methacrylate-co-4-vinylpyridine), p(HEMA-co-4VP) polymer thin film. The polymer was coated on the patch surface via photo-initiated chemical vapor deposition (piCVD) where the polymerization was initiated by the UV degradation of the initiator tert-butyl peroxide (TBPO) and the monomer HEMA. Additionally, the piCVD method was utilized to crosslink the HEMA without the use of additional crosslinkers. The pH-responsiveness of the coating was achieved by incorporating 4VP into the copolymer structure. The effect of the coating was demonstrated through degradation and drug release studies. The presence of the polymer coating decelerated the fiber degradation and the pH-dependent swelling of the coating allowed for the control of drug release rates from the patches. The innovative use of piCVD as a coating method provides a platform for advancing tailored surface modifications in various biomedical applications.     

Biodegradation of Silk Biomaterials

Silk fibroin from the silkworm, Bombyx mori, has excellent properties such as biocompatibility, biodegradation, non-toxicity, adsorption properties, etc. As a kind of ideal biomaterial, silk fibroin has been widely used since it was first utilized for sutures a long time ago. The degradation behavior of silk biomaterials is obviously important for medical applications. This article will focus on silk-based biomaterials and review the degradation behaviors of silk materials.     

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.