Hydroxyapatite/polyurethane composites as promising biomaterials

The biomaterials are intended to augment or replace the function of tissues or organs in human body. Every year millions of people require soft- or hard-tissue regeneration worldwide. Polymers and their composites are a large class of biomaterials appreciated for tissue regeneration. Polyurethane (PUR) is an organic synthetic multifunctional polymer with established biomedical applications. The hydroxyapatite (HA) is one of the biocompatible ceramic materials similar to natural bone material. The amalgamation of hydroxyapatite with polyurethane enhances the bioactivity of final product along with the combination of individual properties. Here, we review the synthesis, characterization, and applications studies of HA/PUR-based biomaterials. We initiate this review with a brief and representative compilation of the chemical composition and methods of preparation for HA/PUR biomaterials. Then, moving ahead, first, we review the simple HA/PUR biomaterials and use of PUR templates. Second, we review the significance of modified HA and PUR in these biomaterials. Third, we discuss the potential of bio-based PUR and inclusion of third constituent in the HA/PUR biomaterials. Then, we appraise the involvement of trace nutrient in deposition of HA on PUR scaffolds. Finally, we consider the other expedient applications of HA/PUR composites such as drug delivery system and sorbent of pollutants.     

Multiscale modeling and simulations of protein adsorption: progresses and perspectives

Protein adsorption, which shows wide prospects in many practical applications such as biosensors, biofuel cells, and biomaterials, has long been identified as a very complex problem in interface science. Here, we present a review on the multiscale modeling and simulation methods of protein adsorption on surfaces with different properties. First, various simulation algorithms (replica exchange, metadynamics, TIGER2A, and PSOVina) and protein models (colloidal, coarse-grained, and all-atom models) are introduced. Then, recent molecular simulation progresses about protein adsorption on different material surfaces (such as charged, hydrophobic, hydrophilic, and responsive surfaces) are retrospected. It has been demonstrated that the adsorption orientation of proteins on charged surfaces and hydrophobic surfaces can be controlled by the electrical dipole and the hydrophobic dipole of proteins, respectively. Superhydrophilic zwitterionic surfaces can resist protein adsorption because of the strong hydration. Under the stimuli of external conditions, the surface properties of materials can be modulated, and thus, the adsorption/desorption of proteins on responsive surfaces can be controlled. Finally, the future directions of molecular simulation study of protein adsorption are discussed.     

Designing Gelatin Based Blood Compatible Materials with Hydrophilic and Hydrophobic Macromolecular Chains

Polymer matrices based on poly 2-hydroxyethyl methacrylate (PHEMA) have emerged as promising materials for developing applications in biomedical and tissue engineering fields. The major criteria of a material to be used as a support matrix in tissue engineering application rests on its biocompatible, hydrophilic, and mechanically strong nature. Although a great deal of research efforts have been put into designing such materials, achieving these properties together for such a material still remains a challenge. Thus, by a judicious combination of natural and synthetic polymers, such as gelatin and copolymers of PHEMA and PAN, respectively, it has been attempted to synthesize a polymer material by redox polymerization method. The prepared polymer matrix was characterized by FTIR, scanning electron microscopy (SEM), and differential scanning calorimetry (DSC) techniques. The prepared polymeric biomaterials were assessed for their water sorption potential under varying experimental conditions such as chemical composition, pH, and temperature of the swelling bath. The diffusion mechanism of transport of water molecules arising due to solvent–polymer interaction was analyzed to predict the behavior of continuously relaxing macromolecular chains. The in vitro blood compatibility of the prepared polymeric materials was determined by methods such as blood clot formation, platelet adhesion, percent hemolysis assay, and protein–adsorption on the surface of the prepared biomaterials.     

新一代生物医用材料

第一代生物医用材料是生物相容和生物惰性材料;第二代生物医用材料是生物活性或可生物降解吸收材料;第三代生物医用材料是同时具有生物活性和生物降解性的新一代生物医用材料。作为细胞外基质,它们可在分子水平上激活基因、刺激细胞增殖、诱导其组织分化进而构筑成新的组织和器官。     

Reactive supramolecular assemblies of mucopolysaccharide,polypyrrole and protein as controllable biocomposites for a new generation of ‘intelligent biomaterials’

A method for the simple synthesis of supramolecular composites of polypyrrole, complex mucopolysaccharides and protein is described. These materials have interesting hydrogel-like properties such as high water content and biocompatibility. In addition they are capable of trapping protein in their structure during synthesis and releasing this protein in response to electrical stimuli. The materials are also electroconductive and electroactive. The improved mechanical properties of polypyrrole films over hydrogels and the facile control of their properties by the application of small electrical potentials make them interesting candidates for the design and synthesis of a new generation of ‘smarter’ biomaterials.     

Electrospinning of Hyperbranched Poly-L-Lysine/Polyaniline Nanofibers for Application in Cardiac Tissue Engineering

Electrospun polyaniline nanofibers are one of the most promising materials for cardiac tissue engineering due to their tunable electroactive properties. Moreover, the biocompatibility of polyaniline nanofibes can be improved by grafting of adhesive peptides during the synthesis. In this paper, we describe the biocompatible properties and cardiomyocytes proliferation on polyaniline electrospun nanofibers modified by hyperbranched poly-L-lysine dendrimers (HPLys). The microstructure characterization of the HPLys/polyaniline nanofibers was carried out by scanning electron microscopy (SEM). It was observed that the application of electrical current stimulates the differentiation of cardiac cells cultured on the nanofiber scaffolds. Both electroactivity and biocompatibility of the HPLys based nanofibers suggest the use this material for culture of cardiac cells and opens the possibility of using this material as a biocompatible electroactive 3-D matrix in cardiac tissue engineering.     

Engineering Mechanical Strong Biomaterials Inspired by Structural Building Blocks in Nature

The intricate multiscale architectures in natural structural building blocks provide many sources of inspiration for the designs of artificial biomaterials. In nature, the assembly of highly ordered molecular crystals and amorphous aggregates often derives from inter- and intra-molecular interactions of biomacromolecules, e.g., proteinaceous materials. The structural biomaterials derived from the protein self-assembly behave with remarkable mechanical performance. However, there is still a grand challenge to mimic the mechanical properties of natural protein-based biomaterials in a rational design fashion to yield comparable man-made synthetic ensembles. In this review, a brief perspective on current challenges and advances in terms of bioinspired structural materials is presented. We outline a framework for mimicking protein self-assembly of natural building blocks across multiscale and highlight the critical role of synthetic biology and chemical modifications in material biosynthesis. Particularly, we focus on the design and promising applications of protein-based fibers, adhesives, dynamic hydrogels and engineered living materials, in which natural mechanical functions are effectively reproduced.     

Synthesis and Characterization of PEG‐Based Drug‐Responsive Biohybrid Hydrogels

Interactive materials being responsive to a biocompatible stimulus represent a promising approach for future therapeutic applications. In this study, we present a novel biohybrid material synthesized from biocompatible components being stimulus‐responsive to the pharmaceutically approved small‐molecule novobiocin. The hydrogel design is based on the gyrase B (GyrB) protein, which is covalently grafted to multi‐arm polyethylene glycol (PEG) using a Michael‐type addition reaction. Upon addition of the GyrB‐dimerizing substance coumermycin, stable hydrogels form which can be dissolved in a dose‐adjustable manner by the antibiotic novobiocin. The switchable properties of this PEG‐based hydrogel are favorable for future applications in tissue engineering and as externally controlled drug depot.     

Preparation of new biomedical materials and their application in clinics

Biomaterials – tissues interaction is important to study in biomaterials science. The information is indispensable to make medical devises and artificial organs and to predict their performance. It is also very useful to consider a hypothesis to design new biomaterials. New materials have brought big progress in the society as we know. There are few biomaterials specially designed to use in biomedical fields. The most important effort must be preparation of biocompatible materials, that must be essential to develop new type high performance devices and artificial organs. Preparation of new dental biomaterials used in bonding of prostheses to dentinal tissues that require fundamental change in modern dentistry and a new methacrylate, MPC, to develop promising several kinds of biomaterials with unusually excellent biocompatibility and functions are going to present. Topics in tissue engineering are also discussed.     

Amyloid-Like Assembly to Form Film at Interfaces: Structural Transformation and Application

Protein-based biomaterials are attracting broad interest for their remarkable structural and functional properties. Disturbing the native protein's three-dimensional structural stability in vitro and controlling subsequent aggregation is an effective strategy to design and construct protein-based biomaterials. One of the recent developments in regulating protein structural transformation to ordered aggregation is amyloid assembly, which generates fibril-based 1D to 3D nanostructures as functional materials. Especially, the amyloid-like assembly to form films at interfaces has been reported, which is induced by the effective reduction of the intramolecular disulfide bond. The main contribution of this amyloid-like assembly is the large-scale formation of protein films at interfaces and excellent adhesion to target substrates. This review presents the research progress of the amyloid-like assembly to form films and related applications and thereby provides a guide to exploiting protein-based biomaterials.     

Smart Porous Multi-Stimulus Polysaccharide-Based Biomaterials for Tissue Engineering

Recently, tissue engineering and regenerative medicine studies have evaluated smart biomaterials as implantable scaffolds and their interaction with cells for biomedical applications. Porous materials have been used in tissue engineering as synthetic extracellular matrices, promoting the attachment and migration of host cells to induce the in vitro regeneration of different tissues. Biomimetic 3D scaffold systems allow control over biophysical and biochemical cues, modulating the extracellular environment through mechanical, electrical, and biochemical stimulation of cells, driving their molecular reprogramming. In this review, first we outline the main advantages of using polysaccharides as raw materials for porous scaffolds, as well as the most common processing pathways to obtain the adequate textural properties, allowing the integration and attachment of cells. The second approach focuses on the tunable characteristics of the synthetic matrix, emphasizing the effect of their mechanical properties and the modification with conducting polymers in the cell response. The use and influence of polysaccharide-based porous materials as drug delivery systems for biochemical stimulation of cells is also described. Overall, engineered biomaterials are proposed as an effective strategy to improve in vitro tissue regeneration and future research directions of modified polysaccharide-based materials in the biomedical field are suggested.     

Functional biointerface materials inspired from nature

Controlling the interfacial chemical and physical properties, and thus modulating the behaviours of cells and biomolecules on material surfaces, form an important foundation for the development of high-performance biomaterials and devices. Biological systems in nature exhibit unique features in this aspect. The first one is that the superior properties of natural biomaterials are normally not determined by their bulk properties, but more related to the multi-scale micro- and nanostructures on the surface; the second is that biological systems usually utilize highly specific weak interactions (e.g. hydrogen bonding interaction, hydrophobic interaction, etc.) to solve the problems of biomolecule interactions; the third is that the biomolecules in nature are often chiral molecules and show high preference for one specific enantiomorphous configuration, suggesting a distinctive chiral recognition mechanism in biological systems. These features bring much inspiration to design novel biointerface materials with special functionalities, e.g. structural biointerface materials, smart biointerface materials and chiral biointerface materials. The purpose of this critical review is to give a brief introduction of recent advances in these aspects (90 references).     

Surface perspectives in the biomedical applications of poly(α-hydroxy acid)s and their associated copolymers

Impressive advances in biotechnology, bioengineering, and biomaterials with unique properties have led to increased interest in polymers and other novel materials in biological and biomedical research and development over the past two decades. Although biomaterials have already made an enormous impact in biomedical research and clinical practice, there is a need for better understanding of the surface and interfacial chemistry between tissue (or cells) and biomedical materials. This is because the detailed physicochemical events related to the biological response to the surface of materials still often remain obscure, even though surface properties are important determinants of biomedical material function. In this regard, data available in the literature show the complexity of the interactions (surface reorganization, non-specific/specific protein adsorption, and chemical reactions such as acid-base, ion pairing, ion exchange, hydrogen bonding, divalent-ion bridging) and the interrelationship between biological environments, interfacial properties, and surface functional groups responsible for the biological responses. Because of the multidisciplinary nature of surface and interfacial phenomena at the surface of biomedical polymers, this review focuses on several aspects of current work published on poly(alpha-hydroxy acid)s and their associated copolymers:surface structure-biomedical function relationships;physicochemical strategies for surface modification; and, finally,synthetic strategies to increase biocompatibility for specific in-vivo and/or in-vitro biomedical applications.     

Customized PEG-derived copolymers for tissue-engineering applications

PEG-containing copolymers play a prominent role as biomaterials for different applications ranging from drug delivery to tissue engineering. These custom-designed materials offer enormous possibilities to change the overall characteristics of biomaterials by improving their biocompatibility and solubility, as well as their ability to crystallize in polymer blends and to resist protein adsorption. This article demonstrates various principles of PEG-based material design that are applied to fine tune the properties of biomaterials for different tissue engineering applications. More specifically, strategies are described to develop PEG copolymers with various block compositions and specific bulk properties, including low melting points and improved surface hydrophilicity. Highly hydrated polymer gel networks for promoting cellular growth or suppressing protein adsorption and cell adhesion are introduced. By incorporating selectively cleavable cross-links, these hydrophilic polymers can also serve as smart hydrogel scaffolds, mimicking the natural extracellular matrix for cell cultivation and tissue growth. Ultimately, these developments lead to the creation of biomimetic materials to immobilize bioactive compounds, allowing precise control of cellular adhesion and tissue growth. [image: see text]     

Properties and applications of proteins encapsulated within sol-gel derived materials

The last decade has seen a revolution in the area of sol-gel-derived materials since the demonstration that these materials can be used to encapsulate biological species such as enzymes, antibodies and other proteins in a functional state. The interactions between the biomolecule and the inorganic, organic or hybrid nanocomposite material determines the degree to which the biomolecule retains its native properties, and such interactions can be tuned to provide optimised biomaterials that are suitable for a variety of applications. Typical applications of sol-gel derived biomaterials include selective coatings for optical and electrochemical biosensors, stationary phases for affinity chromatography, immunoadsorbent and solid-phase extraction materials, controlled release agents, solid-phase biosynthesis, and unique matrices for biophysical studies. Through careful selection of precursors and additives, these materials can be designed for specific applications, and can produce useful, robust devices with good analytical parameters of merit. Indeed, current advances in the development of nanocomposite and mesostructured materials suggest that major improvements in bioimmobilisation are on the horizon, and should result in substantial improvements in bioanalytical devices over the next decade.     

Two-dimensional oxides: multifunctional materials for advanced technologies

The last decade has seen spectacular progress in the design, preparation, and characterization down to the atomic scale of oxide ultrathin films of few nanometers thickness grown on a different material. This has paved the way towards several sophisticated applications in advanced technologies. By playing around with the low-dimensionality of the oxide layer, which sometimes leads to truly two-dimensional systems, one can exploit new properties and functionalities that are not present in the corresponding bulk materials or thick films. In this review we provide some clues about the most recent advances in the design of these systems based on modern electronic structure theory and on their preparation and characterization with specifically developed growth techniques and analytical methods. We show how two-dimensional oxides can be used in mature technologies by providing added value to existing materials, or in new technologies based on completely new paradigms. The fields in which two-dimensional oxides are used are classified based on the properties that are exploited, chemical or physical. With respect to chemical properties we discuss use of oxide ultrathin films in catalysis, solid oxide fuel cells, gas sensors, corrosion protection, and biocompatible materials; regarding the physical properties we discuss metal-oxide field effect transistors and memristors, spintronic devices, ferroelectrics and thermoelectrics, and solar energy materials.     

Surface modification and property analysis of biomedical polymers used for tissue engineering

The response of host organism in macroscopic, cellular and protein levels to biomaterials is, in most cases, closely associated with the materials’ surface properties. In tissue engineering, regenerative medicine and many other biomedical fields, surface engineering of the bio-inert synthetic polymers is often required to introduce bioactive species that can promote cell adhesion, proliferation, viability and enhanced ECM-secretion functions. Up to present, a large number of surface engineering techniques for improving biocompatibility have been well established, the work of which generally contains three main steps: (1) surface modification of the polymeric materials; (2) chemical and physical characterizations; and (3) biocompatibility assessment through cell culture. This review focuses on the principles and practices of surface engineering of biomedical polymers with regards to particular aspects depending on the authors’ research background and opinions. The review starts with an introduction of principles in designing polymeric biomaterial surfaces, followed by introduction of surface modification techniques to improve hydrophilicity, to introduce reactive functional groups and to immobilize functional protein molecules. The chemical and physical characterizations of the modified biomaterials are then discussed with emphasis on several important issues such as surface functional group density, functional layer thickness, protein surface density and bioactivity. Three most commonly used surface composition characterization techniques, i.e. ATR-FTIR, XPS, SIMS, are compared in terms of their penetration depth. Ellipsometry, CD, EPR, SPR and QCM's principles and applications in analyzing surface proteins are introduced. Finally discussed are frequently applied methods and their principles to evaluate biocompatibility of biomaterials via cell culture. In this section, current techniques and their developments to measure cell adhesion, proliferation, morphology, viability, migration and gene expression are reviewed.     

Sol–gel derived organic–inorganic hybrid materials: synthesis,characterizations and applications

Organic/inorganic hybrid materials prepared by the sol–gel approach have rapidly become a fascinating new field of research in materials science. The explosion of activity in this area in the past decade has made tremendous progress in both the fundamental understanding of the sol–gel process and the development and applications of new organic/inorganic hybrid materials. Polymer-inorganic nanocomposite present an interesting approach to improve the separation properties of polymer material because they possess properties of both organic and inorganic such as good permeability, selectivity, mechanical strength, and thermal and chemical stability. Composite material derived by combining the sol–gel approach and organic polymers synthesis of hybrid material were the focus area of review It has also been demonstrated in this review that a more complete understanding of their structure–property behavior can be gained by employing many of the standard tools that are utilized for developing similar structure–property relationships of organic polymers. This review article is introductory in nature and gives introduction to composite materials/nanocomposite, their applications and the methods commonly employed for their synthesis and characterization. A brief literature survey on the polysaccharide templated and polysaccharide/protein dual templated synthesis of silica composite materials is also presented in this review article.     

Current trends in spinel based modified polymer composite materials for electromagnetic shielding

The present article deals with current trends in spinel based modified polymer composite materials for applications in the field of electromagnetic shielding. The interaction between the various spinel based materials and polymers is an emerging field of studies among various researchers. The thermal stability, electrical conductivity, the bonding between the metal ferrites and the polymer plays an important role in the interaction of electromagnetic radiation. These properties also effect the mechanism of the EM waves for the shielding applications. Considering these all properties, polyaniline appears to be an suitable polymer for electromagnetic shielding applications. Polyaniline composites not only reinforced the properties of spinel materials but also enhanced the dielectric properties of the composite material. When carbon based materials such as graphene, graphene oxide and CNT was added along with spinel material in polyaniline based composite, they accelerate the electrical properties and enhances the shielding applications. In this paper the various synthesis methods, fabrication methods of polyaniline, and the properties of polyaniline based composites have been discussed. In addition, the various salient features and futuristic challenges of polyaniline based composite materials for EMI shielding applications were attempted to make a well equipped material for radar absorption.