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Polyvinyl alcohol (PVA) hydrogel is favored by researchers due to its good biocompatibility, high mechanical strength, low friction coefficient, and suitable water content. The widely distributed hydroxyl side chains on the PVA molecule allow the hydrogels to be branched with various functional groups. By improving the synthesis method and changing the hydrogel structure, PVA-based hydrogels can obtain excellent cytocompatibility, flexibility, electrical conductivity, viscoelasticity, and antimicrobial properties, representing a good candidate for articular cartilage restoration, electronic skin, wound dressing, and other fields. This review introduces various preparation methods of PVA-based hydrogels and their wide applications in the biomedical field. [ABSTRACT FROM AUTHOR]

Abstract Intracranial aneurysms (ICAs) are focal dilations in the brain's arteries. When left untreated, ICAs can grow to the point of rupture, accounting for 50–80% of subarachnoid hemorrhage cases. Current treatments include surgical clipping and endovascular coil embolization to block circulation into the aneurysmal space for preventing aneurysm rupture. As for endovascular embolization, patients could experience aneurysm recurrence due to an incomplete coil filling or compaction over time. The use of shape memory polymers (SMPs) in place of conventional platinum coils could provide more control and predictability for mitigating these complications. This study was focused on characterization of an aliphatic urethane-based SMP to evaluate its potential as a novel biomaterial for endovascular embolization. Twelve compositions of the SMP were synthesized and their thermomechanical properties together with the shape recovery behavior were comprehensively investigated. Our results showed that the SMPs experienced a significant decrease in storage and loss moduli as heated above their glass transition temperatures (32.3–83.2 °C), and that all SMPs were thermally stable up to 265 °C. Moreover, the SMPs exhibited both composition-dependent stress relaxation and a decrease in elastic modulus during cyclic loading. The shape recovery time was less than 11 s for all SMP compositions, which is sufficiently short for shape changing during embolization procedures. Several candidate compositions were identified, which possess a glass transition temperature above body temperature (37 °C) and below the threshold of causing tissue damage (45 °C). They also exhibit high material strength and low stress relaxation behavior, suggesting their potential applicability to endovascular embolization of ICAs. Graphical abstract fx1 Highlights • A detailed experimental procedure has been developed for the synthesis of aliphatic urethane-based shape memory polymers. • Comprehensive thermomechanical characterizations on a variety of SMP compositions have been performed. • Investigations of the polymer's working temperature, thermal stability and their mechanical behavior have been made. • Recovery tests has demonstrated superb shape recovery of the SMPs desirable for the endovascular embolization procedure. • SMP compositions that meet our criteria have been identified with their great potential for individualized ICA treatment. [ABSTRACT FROM AUTHOR]

Abstract Finite element models of biomedical applications increasingly use anisotropic hyperelastic material formulations. Appropriate material parameters are essential for a reliable outcome of these simulations, which is why planar biaxial testing of soft biological tissues is gaining importance. However, much is still to be learned regarding the ideal methodology for performing this type of test and the subsequent parameter fitting procedure. This paper focuses on the effect of an unknown sample orientation or a mistake in the sample orientation in a planar biaxial test using rakes. To this end, finite element simulations were conducted with various degrees of misalignment. Variations to the test method and subsequent fitting procedures are compared and evaluated. For a perfectly aligned sample and for a slightly misaligned sample, the parameters of the Gasser-Ogden-Holzapfel model can be found to a reasonable accuracy using a planar biaxial test with rakes and a parameter fitting procedure that takes into account the boundary conditions. However, after a certain threshold of misalignment, reliable parameters can no longer be found. The level of this threshold seems to be material dependent. For a sample with unknown sample orientation, material parameters could theoretically be obtained by increasing the degrees of freedom along which test data is obtained, e.g. by adding the data of a rail shear test. However, in the situation and the material model studied here, the inhomogeneous boundary conditions of the test set-ups render it impossible to obtain the correct parameters, even when using the parameter fitting method that takes into account boundary conditions. To conclude, it is always important to carefully track the sample orientation during harvesting and preparation and to minimize the misalignment during mounting. For transversely isotropic samples with an unknown orientation, we advise against parameter fitting based on a planar biaxial test, even when combined with a rail shear test. [ABSTRACT FROM AUTHOR]

Abstract In this research, a new metal matrix nanocomposite with enhanced capability for biomedical applications was fabricated by incorporation of nano-sized hydroxyapatite (HA) particles within the titanium substrate using multi-pass friction-stir processing (FSP). These n-HA particles were dispersed effectively within the titanium matrix. Titanium metal-matrix was processed without introducing the HA nanoparticles, as well, for the aim of comparison. The results showed the formation of different regions with various microstructural features and mechanical property across the processed materials. A thin layer with ultra-fine grain structure and indentation hardness value of up to ~400 HV was formed on the surface after FSP modification of coarse-grained titanium substrate. This was due to severe shear deformation induced by the rotating shoulder as well as the surface absorption of N and O elements from the atmosphere inside the layer. Incorporation of nanoparticles and subsequent grain structural refinement owing to operative dynamic recrystallization mechanisms leads to a maximum hardness improvement of up to ~250 HV in the lower regions (as compared to the average hardness value of base metal ~150 HV). The FSP modified pure titanium exhibited a good combination of strength and ductility by refining the grain structure with a well-developed dimple-like structure on the fracture surface. For the nanocomposite specimen, the trend of the tensile property was found deteriorative showing the impaired features on the fracture surface. This is attributed to the complex structure of HA compound and low quality of interfacial bonding between the nanoparticles and titanium matrix. [ABSTRACT FROM AUTHOR]

Abstract Considering that micromotions generated at the bone-implant interface under physiological loading introduce mechanical strain on the tissue and surface of the implant and that strain can be introduced during processing of the biomedical device, we elucidate here the interplay between mechanically-induced nanoscale twinning in austenitic stainless steel on osteoblast functions. Mechanically-induced nanoscale twinning significantly impacted cell attachment, cell-substrate interactions, proliferation, and subsequent synthesis of prominent proteins (fibronectin, actin, and vinculin). Twinning was beneficial in favorably modulating cellular activity and contributed to small differences in hydrophilicity and nanoscale roughness in relation to the untwinned surface. [ABSTRACT FROM AUTHOR]

In this study, chitosan-poly(methacrylic acid-co- N -isopropylacrylamide) [chitosan-p(MAA-co-NIPAM)] hydrogels were synthesized by emulsion polymerization. In order to be used as a carrier for drug delivery systems, the hydrogels had to be biocompatible, biodegradable and multi-responsive. The polymerization was performed by copolymerize MAA and NIPAM with chitosan polymer to produce a chitosan-based hydrogel. Due to instability during synthesis and complexity of components to produce the hydrogel, further study at different times of reaction is important to observe the synthesis process, the effect of end product on swelling behaviour and the most important is to find the best way to control the hydrogel synthesis in order to have an optimal swelling behaviour for drug release application. Studied by using Fourier transform infra-red (FTIR) spectroscopy found that, the synthesized was successfully produced stable chitosan-based hydrogel with PNIPAM continuously covered the outer surface of hydrogel which influenced much on the stability during synthesis. The chitosan and PMAA increased the zeta potential of the hydrogel and the chitosan capable to control shrinkage above human body temperature. The chitosan-p(MAA-co-NIPAM) hydrogels also responses to pH and temperature thus improved the ability to performance as a drug carrier. [ABSTRACT FROM AUTHOR]

Despite the significant efforts in the synthesis of new polymers, the mechanical properties of polymer matrices can be considered modest in most cases, which limits their application in demanding areas. The isolation of graphene and evaluation of its outstanding properties, such as high thermal conductivity, superior mechanical properties, and high electronic transport, have attracted academic and industrial interest, and opened good perspectives for the integration of graphene as a filler in polymer matrices to form advanced multifunctional composites. Graphene‐based nanomaterials have prompted the development of flexible nanocomposites for emerging applications that require superior mechanical, thermal, electrical, optical, and chemical performance. These multifunctional nanocomposites may be tailored to synergistically combine the characteristics of both components if proper structural and interfacial organization is achieved. The investigations carried out in this aim have combined graphene with different polymers, leading to a variety of graphene‐based nanocomposites. The extensive research on graphene and its functionalization, as well as polymer graphene composites, aiming at applications in the biomedical field, are reviewed in this paper. An overview of the polymer matrices adequate for the biomedical area and the production techniques of graphene composites is presented. Finally, the applications of such nanocomposites in the biomedical field, particularly in drug delivery, wound healing, and biosensing, are discussed. [ABSTRACT FROM AUTHOR]

The materials used to manufacture prosthetic components must meet the conditions of biocompatibility imposed by the human body, to be mechanically resistant, to present a good resistance to corrosion, to be resistant to aging process and not to generate flows of attrition particles. This paper aims the selection and analising of some biocompatible metallic materials (the austenitic stainless steel and titanium alloys). Thus, various prosthetic elements made by rapid prototyping (RP) technologies from Ti6Al4V alloys obtained using laser selective melting (SLS Technology) have a major advantage in the special geometric form for medicine, creating a personalized implant for each patient and with superior properties on the quality of the material used. Studies in recent years have led to the conclusion that the biocompatibility of an implant depends on many factors such as: the general health status of the patient, age, tissue permeability, immunological factors, but also the implant characteristics (roughness and porosity of the material, chemical composition, corrosion properties, toxicity, etc.). For this reason, samples of 316L stainless steel and Ti6Al4V titanium alloy were analyzed. [ABSTRACT FROM AUTHOR]

Porous structures, manufactured of a biocompatible metal, mimicking human bone structure are the future of orthopedic implantology. Fully porous materials, however, suffer from certain drawbacks. To overcome these, gradient in structure can be prepared. With gradient in porosity mechanical properties can be optimized to an appropriate value, implant can be attributed a similar gradient macrostructure as bone, tissue adhesion may be promoted and also various modification with organic or inorganic substances are possible. In this study, additive technology selective laser melting (SLM) was used to produce three types of gradient porosity model specimens of titanium alloy Ti-6Al-4V. As this technology has the potential to prepare complex structures in the near-net form, to control porosity, pore size and shape, it represents a promising option. The first part of the research work was focused on the characterization of the material itself in the as-produced state, only with heat treatment applied. The second part dealt with the influence of porosity on mechanical properties. The study has shown SLM brings significant changes in the surface chemistry. Despite this finding, titanium alloy retained its cytocompatibility, as it was outlined by in vitro tests with U-2 OS cells. With introduced porosity yield strength, ultimate strength and stiffness showed linear decrease, both in tension and compression. With respect to the future use in the form of orthopedic implant, especially reduction in Young's modulus down to the human bone value (30.5±2 GPa) is very appreciated as the stress-shielding effect followed by possible implant loosening is limited. [ABSTRACT FROM AUTHOR]

ABSTRACT BACKGROUND Microcarrier based cell culture offers many advantages when compared with conventional cell cultures, and this technology has been widely used in the production of many important biological materials. In this work, microcarriers were produced using materials and methods that are relatively simple and low-cost. RESULTS Polystyrene ( PS) microspheres were prepared by using an emulsion solvent-evaporation method and the effects of process conditions on the size of microspheres were investigated. The mean size of microspheres decreased with increasing agitation speed, concentration of polyvinyl alcohol ( PVA) and polymer to solvent ratios but increased with increasing oil to water phase ratios. To enhance its cell attachment abilities, surfaces of PS microspheres were loaded with oxygen functional groups by using an ultraviolet/ozone ( UVO3) system. Analysis by Fourier transform infrared ( FTIR), energy dispersive X-ray spectroscopy ( EDX), toluidine blue O ( TBO) assay and relative contact angle measurements showed increased surface oxygen concentration after UVO3 treatment. Results from spinner flask culture revealed that UVO3 treated PS microspheres support the growth of Vero cells to high cell density. CONCLUSION UVO3 treatment successfully rendered the hydrophobic surface of PS microspheres hydrophilic. This newly developed microcarrier could serve as a low-cost alternative to commercial microcarriers available in the market today. © 2015 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Plant-derived nanostructures and nanoparticles (NPs) have functional applications in numerous disciplines such as health care, food and feed, cosmetics, biomedical science, energy science, drug-gene delivery, environmental health, and so on. Consequently, it is imperative for researchers to understand that plants are cost-effective, sustainable and renewable platforms, and therefore, they are ideal sources for production of natural NPs. This critical review discusses significant recent developments pertaining to plant-derived nanostructures, their classes, and vital applications. The aim is to provide insight into the use of plants as bio-renewable, sustainable, diversified resources and as platforms for the production of useful nanostructures and NPs, with functions in various fields including medicine, industry, agriculture, and pharmaceuticals. [ABSTRACT FROM AUTHOR]

Purpose - The purpose of this paper is to develop a process chain for design and manufacture of endplates of intervertebral disc implants, with specific emphasis on designing footprint profiles and matching endplate geometry. Design/methodology/approach - Existing techniques for acquiring patient-specific information from CT scan data was and a user-friendly software solution was developed to facilitate pre-surgical planning and semi-automated design. The steps in the process chain were validated experimentally by manufacturing Ti6Al4?V endplates by means of Direct Metal Laser Sintering to match vertebrae of a cadaver and were tested for accuracy of the implant-to-bone fitment. Findings - Intervertebral disc endplates were successfully designed and rapid manufactured using a biocompatible material. Accuracy within 0.37?mm was achieved. User-friendly, semi-automated design software offers an opportunity for surgeons to become more easily involved in the design process and speeds up the process to more accurately develop a custom-made implant. Research limitations/implications - This research is limited to the design and manufacture of the bone-implant contacting interface. Other design features, such as keels which are commonly used for implant fixation as well as the functionality of the implant joint mechanics were not considered as there may be several feasible design alternatives. Practical implications - This research may change the way that current intervertebral disc implants are designed and manufactured. Originality/value - Apart from other areas of application (cranial, maxillofacial, hip, knee, foot) and recent research on customized disc nucleus replacement, very little work has been done to develop patient-specific implants for the spine. This research was conducted to contribute and provide much needed progress in this area of application. [ABSTRACT FROM AUTHOR]

Abstract: Biomanufacturing integrates life science and engineering fundamentals to produce biocompatible products enhancing the quality of life. The state-of-the-art of this rapidly evolving manufacturing sector is presented and discussed, in particular the additive electrical, chemical and physical processes currently being applied to produce synthetic and biological parts. This fabrication strategy is strongly material-dependent, so the main classes of biomaterials are detailed. It is explained the potential to process composite materials combining synthetic and biological materials, such as cells, proteins and growth factors, as well the interdependences between materials and processes. The techniques commonly used to increase the bioactivity of clinical implants and improve the interface characteristics between biological tissues and implants are also presented. [Copyright &y& Elsevier]

Well-defined microcapsules with polyamide-polyurea as a hybrid shell have been described for biomedical applications. Interfacial polymerization method with surfactant and cosurfactant was developed for the preparation of the hybrid microcapsules. After reaction, centrifugation, and freeze drying processes, the polyamide-polyurea hybrid microcapsules with porous membranes were successfully fabricated. Compared with previous researches of the single polyamide or polyurea microcapsules, experimental data showed that the hybrid microcapsules have a thicker shell and excellent mechanical property. Various diameters and morphologies for the hybrid microcapsules can be obtained by changing the stirring rate, drying method, and surfactant content. [ABSTRACT FROM AUTHOR]

The article discusses the development of novel biomaterials that provide cells with a steady supply of oxygen and their use in various applications, including the regeneration of cardiac muscle after a heart attack. Topics include the challenges of creating vascularised tissues with a plentiful blood supply, the use of oxygen-releasing biomaterials for tissue engineering applications, and liquid and solid oxygen-releasing reagents, such as hydrogen peroxide (H2O2).

The work aims to present the methods of processing the biological material (of human and animal origin) used in our laboratory in the Department of Biochemistry and Radiobiology of Cancer Disease within the Institute of Oncology Bucharest, for carrying out several biochemical and immunochemical determinations: sialic acid, oxidative stress parameters (products of lipid peroxidation, total thiols, celuloplasin oxidizing activity), immuno-phenotyping, assessment of cell cycle and apoptosis. The biological material provided to our laboratory comes from patients from our clinic, with various types of cancer (blood, urine) and experimental animals: mice, experimental tumour-bearing rats (blood, organs, tumour ascites, and solid tumours). Since the way of processing and preserving biological products has a decisive influence on the results of subsequent determinations, we hope that this work will prove useful and attract the interest of many practitioners in the field. [ABSTRACT FROM AUTHOR]