Materials Science and Technology

The primary challenge in the delivery of a drug to a tumour site is to target the anticancer drug specifically into and around tumours at concentrations that will decrease their growth and/or viability. Excellent vehicles to achieve targeted drug delivery are magnetic nanocarriers. A approach to accomplish this objective is to fabricate a novel temperature and pH-responsive magnetic nanocarrier that combines tumour targeting and controlled release. In addition to controlled release, these carriers simultaneously offer the possibility of imaging the delivery process by magnetic resonance imaging. The novel aspect of this approach is the combination of thermal and pH sensitivity of the drug containing shell with magnetic properties of the core in a single unit. Furthermore, application of an external magnetic field will heat the nanoparticles and thus nanoparticle containing cells. The targeted heat will aid in the killing of tumour cells.

Polymer–clay nanocomposites have attracted great attention worldwide from both academic and industrial points of view. This review aims at reporting on very recent developments in types of polymer–clay nanocomposites, their constituents, synthetic routes, properties and their uses as carriers for drug delivery. This new family of composite materials frequently exhibits remarkable improvements of material properties when compared with the matrix polymers alone or conventional micro- and macrocomposites. Pharmaceutically, interesting improvements include increased mechanical and rheological properties, reduced drug permeability and water uptake and controlled release characteristics. On the basis of these properties, polymer–clay nanocomposites are extending their applicability to the design of new drug release dosage forms with highly specific technological and biopharmaceutical properties, such as swelling, film forming, bioadhesion, and cell uptake. Overall, there is an essential requirement directed towards a more comprehensive understanding of the supramolecular structure, drug loading and release mechanisms of these hybrid materials.

Biomedical materials have always been a priority issue in the healthcare sector. In the orthopaedic field, skeletal replacements, in particularly, hips, knees and shoulders, have become a major health concern, affecting both the young and the older population. There is not yet a clear consensus on a generic material for use in bone tissue engineering applications and the search continues for improved biomaterials, providing the potential for long lasting implants which benefit both patients and surgeons. Materials design thus presents an enormous challenge from both the perspectives of selection and processing. The present paper will address the various material categories such as metals, ceramics, polymers and composites currently being used for the treatment of bone fractures. The new research directions and future for bone regenerative medicine will also be discussed.

Tissue engineering, a field which focusses on the replacement, repair and regeneration of damaged or diseased tissue by the application of biomaterials, cells and associated biological molecules, has advanced rapidly due to the intense demand for tissue substitutes. A key principle in tissue engineering involves growing the appropriate cells in vitro for the desired application before delivery into the body of a patient. The implantable devices, biological constructs or scaffolds, developed in tissue engineering aim to provide the initial architecture required for supporting the cells as well as define the micro and macrostructure of the final engineered product. Furthermore, these scaffolds may be exploited to release drugs and/or growth factors in a controlled manner, thus facilitating the repair and regeneration of the target tissue. Microparticles, spherical carrier scaffolds, have recently received extensive interest for their potential therapeutic applications in a diverse range of clinical and regenerative medical settings. Not only can these versatile subunits be used as cell culture scaffolds, their innate structure reduces the degradation of encapsulated biologically active molecules and also allows their exploitation as a localised injectable delivery system. The purpose of the present article is to review the tissue engineering applications of these microparticles and to provide a brief overview of the critical factors considered during their formulation and use – including the range of materials used and the different modification protocols and technologies exploited to improve and enhance their mechanical properties and biocompatibility for regenerative medicine.

Although extensive efforts have been put into the development of porous scaffolds from natural materials for bone regeneration with encouraging results, they still have a common limitation: the inherent lack of strength associated with porosity. That is to say, they are not strong enough to meet the specific requirements of load bearing applications. The authors have reported a series studies on possible application of a natural material, zein protein from maize, as a new kind of biomaterial for tissue engineering. The result showed a good cell compatibility and biodegradability in tissue within eight months. To improve its mechanical property (especially the brittleness), stearic acid or oleic acid was added. The mechanical properties, especially the tensile and flexible properties were improved significantly. The possible mechanism is discussed.

Chitosan is a natural cationic copolymer of N-acetyl glucosamine and D-glucosamine, varying in composition, sequence and molecular chain length. Because of its bio- and cyto-compatibility, biodegradability and bioresorbability, chitosan has been investigated for application in various biomedical fields such as drug and gene delivery, tissue engineering, wound healing, and for use in antimicrobial, antiviral and immunoadjuvant strategies. With the rise of nanotechnology, chitosan together with bioactive nanoparticles are fabricated into various bionanocomposites, providing alternatives to new era of regenerative medicine and drug delivery vesicles. The present paper will review the preparations and biomedical applications of such chitosan composites, their current achievements, limitations and future perspectives. In this respect, the effect of chitosan properties on the interaction with nanoparticles and its consequences for applicability of the resulting composites will be discussed.

Tissue engineering (TE) is an interdisciplinary field involving principles of engineering and biological sciences to fabricate new tissue and organs using cells and scaffolds. It is expected to play an important role in the therapeutic approach in the current and future medicine. In the coming years, there will be an increased emphasis on the usage of biomaterials that can be integrated forming a renewable interface with prosthetic implants for regenerated medicine and cell based TE on a long term basis. In this regard, significant consideration is being given to natural cationic chitosan as a matrix for TE. Chitosan is a linear polysaccharide, produced from crustacean sources. Recent studies suggest that chitosan based matrixes are promising for TE applications. The authors describe here the uniqueness and versatility of chitosan in bone and cartilage TE in terms of structure–property relationship of chitosan scaffolds.

Membrane separation technology, owing to its low energy consumption, operational simplicity, ease of control and scale-up, has gained increasing interest. The rapid development requires highly selective membranes with high through rates and chemical/mechanical stability. Chitosan, a relatively inert biomaterial with film forming ability, has been rapidly recognised for its potential in separation and purification technology in recent decades. Because of its hydrophilicity, cationicity, biocompatibility, ease of modification, remarkable affinity to dyes, metals and proteins, chitosan membranes have become a promising candidate for several applications. In the present review, the pervaporation of azeotropic mixtures and protein purification and separation of gaseous mixtures using chitosan membranes are discussed. The general overview of the preparation of different chitosan membranes, its capabilities in the separation of various solvents, gases and biomacromolecules are presented. Finally, the opportunities, challenges and perspectives in these areas are discussed.

As natural aminopolysaccharides, chitin and chitosan show high intrinsic sorption affinity for dyes, metal ions, chiral molecules and several biomacromolecules. They have been extensively investigated as the high selective, low cost and environment friendly adsorbents. The separation performance of chitin and chitosan can be further improved by physical or chemical modifications designed for a specific application. The present article provides a review of the recent progress in the material preparation, experimental methodologies and mechanisms for the biosorption applications of chitin and chitosan, with the focus on the separation of proteins, lipids, lipopolysaccharides (endotoxins) and chiral molecules. The prospects and challenges in those applications are also discussed.

Biopolymers such as chitosan, pectin, alginate, ı -carrageenan and gelatin, can be assembled to layered solids by direct intercalation via ion exchange in the case of smectites or a ‘co-organised assembly’ method in the case of layered double hydroxides (LDHs). Layered perovskites can be delaminated and combined with the biopolymers following a delamination/restacking procedure. The starting cationic exchange ability of smectites such as montmorillonite is turned into an anionic exchange capacity due to the intercalated chitosan excess, while an opposite effect is observed in the case of the LDHs after incorporation of alginate, pectin or ı -carrageenan. This fact, combined with the good mechanical properties of these bionanocomposites, allows their use as the sensing phase of potentiometric sensors applied to the recognition of cationic or anionic species in aqueous solution. Besides, perovskite–gelatin bionanocomposites can be processed as robust translucent films with highly oriented two-dimensional particles exhibiting elevated dielectric permittivity values.

Porous biodegradable polymeric scaffolds are essential for tissue engineering application since they should provide the adequate three-dimensional structure for cellular attachment and tissue development. In particular, pore size and shape and overall porosity are key structural features in controlling neotissue formation. Since scaffolds structural properties play a relevant role in all processes involved in tissue genesis including cell adhesion, migration, proliferation, growth, differentiation and biosynthesis, an accurate control over the pore size and its distribution, pore shape, pore interconnectivity, and overall porosity of scaffolds is mandatory for the success of any tissue engineering approach. Several methods have been proposed to tailor make porous scaffolds to obtain the desired pore structure. Here, three techniques to emboss a controlled pattern of porosity in biodegradable polymers, particulate leaching, phase separation and gas foaming along with their combinations, are critically reviewed highlighting process–structure–property relationship.

Gene therapy is a powerful treatment for inborn and acquired diseases. The development of safe and effective gene delivery systems is a great challenge to make the human gene therapy a reality. Viral vectors have been commonly employed due to the high transfection efficiency, however, their application to the human body is often frustrated by immunogenicity, potential infectivity, complicated production, and inflammation. Non-viral vectors have been widely proposed as safer alternatives to viral vectors by reason of unique advantages such as less immune reaction against repeated administration, ease of synthesis, cell/tissue targeting, unrestricted plasmid size, and low cost. Among non-viral systems, cationic polymers have gained increasing attention because they can easily form self-assembly with DNA. Polyethylenimine (PEI) is one of the most popular cationic polymers investigated in non-viral gene therapy due to its ability to generate elevated levels of gene expression in vitro and in vivo compared to another non-viral carriers. However, the PEI showed high cytotoxicity, which depends on the molecular weight of the PEI. Recently, the degradable PEIs were synthesised to have high transfection efficiency with low cytotoxicity. The present review describes recent progress on the development of degradable PEIs as non-viral vectors. The present paper also summarises structure of degradable PEIs–transfection relationship to provide a novel insight with respect to this type of gene delivery system. First, linear degradable polymers based on linear PEIs are represented. Second, branched polymers based on branched PEIs are discussed. Third, grafted degradable copolymers based on branched PEIs are explained.

Despite advances in stent design, expansion techniques and anti-thrombotic agents to improve pharmacological control of subacute thrombosis (SAT) and to reduce to 2 the occlusive thrombosis rates, a significant risk of mortality associated with thrombotic vascular occlusion due to the adhesion of blood constituents remains a problem for patients with more complex lesions. The adhesion process is greatly governed by the surface characteristics, mainly the surface chemical composition, surface morphology, presence of charge, surface wettability and surface roughness. Surface chemical inertness (reduced interaction with chemicals and biological components) subsequently became the primary criteria which guided the development of non thrombotic stents as well as other blood-contacting materials. A number of strategies have been adopted in an effort to coat the stent with or without the use of a drug delivery system, to overcome the thrombus formation, to minimize the stent occlusion and to improve the overall hemocompatibility of the device. This paper aims at reviewing the clinical outcomes of main non-pharmaceutical stent coating procedures and their clinical outcomes. New stents which combine the anti-thrombotic coating with the drug delivery ability, such as radioactive stents, degradable stents and some new challenging trends which are mostly at research and development stage for stent surface coatings are also introduced.

Human bone is typically a hierarchical organisation at different length scales ranging from nanoscale to mesoscale. Synthetic biomaterials mimicking this structural aspect of the bone and thereby facilitating structure and function of damaged or dysfunctional tissues is the current trend in designing of biomaterials. Under such trend artificial biomaterials with biocompatible surface coatings and engineered three-dimensional features ranging from nanoscale to mesosclae to support cells and tissue growth is becoming a reality. In light of this, the present review provides a description of laser induced coating techniques, one of several methods of design and synthesis of biosurfaces. Especially, the laser induced coating technique to produce a bioactive and biomimetic calcium phosphate (Ca–P) based ceramic coating on Ti based alloys is the focus of present discussion. The two common coating methodologies namely, the pulsed laser deposition and direct melting using a pulsed and continuous wave laser are the subject of discussion. The formation of multiscale features, microstructures and phase evolution due to such coatings are discussed. Finally, the concept of laser based interference patterning as a future tool to explore these kinds of coatings is highlighted. Attempts are also made to demonstrate the effectiveness of these coatings in bioenvironment.

Atomic force microscopy can yield valuable information concerning basic physical properties as well as alterations of human red blood cells. Erythropoietin is a hormone that is naturally produced in the kidney to stimulate the growth of red blood cells. Administration of genetically engineered synthetic erythropoietin stimulates the production of additional red blood cells. Therefore erythropoietin is used for blood doping in serious sports. The present study aims at investigating any differences in structure and stiffness of red blood cells which are produced body own or with synthetic erythropoietin. The samples are prepared via standard methods, and atomic force spectroscopy with trigger forces of three micronewtons is performed in ambient air. The penetration depth does not reveal statistically relevant differences in the two types of red blood cells. Furthermore, cells with a penetration depth four times as large as healthy ones are encountered in the samples of one donor. Subsequent medical examination revealed a rare type of diabetes. Atomic force spectroscopy shall serve as fast screening method for nanodiagnostics of diseases that alter surface nanomechanical properties.