Journal of Applied Biomaterials & Biomechanics最新文献

Purpose: The aim of this work is to develop a 3D finite elements model to study the nanomechanical behavior of mineralized collagen microfibrils, which consists of three phases, (i) collagen phase formed by five tropocollagen (TC) molecules linked together with cross-links, (ii) a mineral phase (Hydroxyapatite), and (iii) impure mineral phase, and to investigate the important role of individual properties of every constituent.

Methods: The mechanical and geometric properties (TC molecule diameter) of both tropocollagen and mineral were taken into consideration as well as cross-links, which was represented by spring elements with adjusted properties based on experimental data. In this paper an equivalent homogenized model was developed to assess the whole microfibril mechanical properties (Young's modulus and Poisson's ratio) under varying mechanical properties of each phase.

Results: In this study, both equivalent Young's modulus and Poisson's ratio, which were expressed as functions of Young's modulus of each phase, were obtained under tensile load with symmetric and periodic boundary conditions.

Purpose: Experimental tests have played a major role in the assessment of fatigue endurance of orthopedic prostheses; however, cyclic tests on devices entail high costs. Here, a multiaxial fatigue criterion coupled with computational simulations and material properties measurements has been employed to predict fatigue life of the tibial component of a polymeric PMMA spacer. The ultimate aim is to obtain valid information on fatigue behavior avoiding fatigue tests on the device.

Methods: First, an accurate measurement of the static and fatigue properties of PMMA samples is performed. Then, numeric simulations of the fatigue behavior of the PMMA spacer reproducing the experimental test conditions according to ISO 14879-1 were carried out in order to calculate the stress field throughout the device. Finally, a Risk Index was calculated by using a proper multiaxial fatigue criterion for brittle materials (Kakuno-Kawada) for the assessment of the device fatigue behavior by predicting the F-N curves.

Results: The numeric results were validated by comparing the predictions against experimental data already published by our group. The multiaxial fatigue criterion was able to predict the most critical point on the spacer upper surface and the fatigue behavior of the device that nicely matched the experimental curves.

Conclusions: This approach represents a valuable tool to investigate the mechanical reliability of implantable devices; nevertheless, the use of advanced and specific failure criteria coupled with accurate data of the device’s material is mandatory to represent a real alternative to the experimental approach in fatigue life prediction.??Key words: Acrylic bone cement, Fatigue endurance, Finite element analyses, Knee spacer.

Purpose: The aim of this study was to screen specific adherent matrix for endothelial progenitor cells (EPCs), which can be used for antibody capturing stents.

Methods: In this study, the adhesion of EPCs on different matrices containing three different antibodies, VEGFR-2, CD34, CD133, was observed under shear stress in a flow chamber. Nitric oxide (NO) release, cell proliferation and the retention rate of EPCs, were measured separately.

Results: The results demonstrated that shear stress within a certain range can promote proliferation and NO secretion of EPCs. Under the same shear stress, the EPCs showed stronger adhesion on matrix-containing CD133 antibody than on the other matrices.

Conclusions: CD133 antibody has the potential application for EPCs capture.

Purpose: To assess both the in vitro and in vivo biological response of a laser modified surface in an integrated manner. A combined innovative approach applies lasers to macrostructure as well as to oxidize the surface of titanium alloy implants.

Materials and methods: A Nd:YAG marking and ArF excimer lasers were used for macrostructuring and UV-oxidizing the surface of Ti6Al4V discs, respectively. Human fetal osteoblastic cell culture and a sheep tibia model were used to assess the cell response and the osseogeneration capability of as-machined, laser macrostructured and laser macrostructured and oxidized surfaces.

Results: In vitro: Laser macrostructuration alone did not promote cell response. Cellular proliferation was enhanced by the additional UV laser oxidation. In vivo: A greater significant percentage of bone-implant contact was obtained for both laser treated surfaces compared to machine-turned control samples, three months after implantation, in spite of the low cellular response for macrostructured samples. The use of sheep model for six months appears to be less adequate for a comparison because of the high level of bone integration in all samples. In spite of the often reported positive effect of titanium oxidation on the triggering of faster osseointegration, in this experiment the additional UV laser oxidation did not lead to a significant in vivo improvement.

Conclusions: Laser macrostructuration of titanium alloy surfaces appears to promote bone apposition and may therefore constitute a promising surface modification strategy. In animal models, the natural process of titanium surface oxidation, because of physiologic fluids, alters properties observed in vitro with cells.

Purpose: Since bacterial pollution is more troublesome than other nonbiologic air pollutants, the need to control airborne micro-organisms has led to renewed interest in filter media for air filtration in indoor environments. Although mechanical filtration of aerosols by HEPA systems is the most common method for particle removal, these filters characterized by high efficiency usually reveal a higher drop in pressure and noise and are very expensive. On this basis, we aimed to develop novel, very effective air filters for removal of airborne bacteria from confined environments.

Methods: Parallelepiped filters surrounded by a cardboard frame were manufactured by aligning strips of corrugated cardboard and were assessed in terms of airflow rate reduction. Cardboard filters were soaked in isopropanol or used untreated in in vitro experiments for assessment of their antibacterial effect against E. coli and in a testing chamber for assessment of airborne bacterial removal. The surface morphology of cardboard specimens was also investigated by Scanning Electron Microscopy (SEM).

Results: Cardboard filters determined a very low decrease in airflow rate. Although specimens showed no antimicrobial behavior, untreated filters showed a maximum of 77% abatement of the airborne bacteria and the alcohol treatment of filters further increased their effectiveness by 14% probably because of their more convoluted surface.

Conclusions: This work disclosed corrugated cardboard-based filters as promising tools for the air treatment of indoor environments because of their excellent microbial abatement properties. Moreover, cardboard is lightweight, inexpensive, and eco-friendly material, and corrugated cardboard-based air filters are very simple in shaping, mounting, and replacing existing ventilation systems.

The use of biomaterials in dentistry is more widespread than in any other medical field in terms of both amount and variety. Most of them were not originally designed for dental applications but for other medical applications or, sometimes, for no medical purposes. Among these materials, biodegradable materials play an important role, especially in bone regeneration and in periodontal surgery. This paper briefly reviews some degradable polymers developed as tools for the treatment of periodontal and bone diseases. We discuss materials previously applied in other industrials contexts, such as polyesters, methylcellulose, and chitosan and we provide perspectives for their use in periodontal regeneration.

A complete morphologic characterization of porous scaffolds for tissue engineering application is fundamental, as the architectural parameters, in particular porosity, strongly affect the mechanical and biological performance of the structures. Therefore, appropriate techniques for this purpose need to be selected. Several techniques for the assessment of scaffold porosity have been proposed, including Scanning Electron Microscopy observation, mercury and liquid extrusion porosimetry, gas pycnometry, and capillary flow porometry. Each of these techniques has several drawbacks and, a combination of different techniques is often required so as to achieve an in depth study of the morphologic properties of the scaffold. A single technique is often limited and suitable only for the assessment of a specific parameter. To overcome this limit, the most attractive option would be a single nondestructive technique, yet capable of providing a comprehensive set of data. It appears that micro-computed tomography (micro-CT) can potentially fulfill this role. Initially developed to characterize the 3D trabecular microarchitecture of bone, its use has been recently exploited by researchers for the morphologic characterization of porous biomaterials, as it enables obtaining a full assessment of the porous structures both in terms of pore size and interconnected porosity. This review aims to explore the use of micro-CT in scaffold characterization, comparing it with other previously developed techniques; we also focus on the contribution of this innovative tool to the development of scaffold-based tissue engineering application.

Genomics is the study of an organism's genome aimed at the functional specification of the different parts of the sequence that comprise the blueprint of the living cell to unveil the mechanisms of the physiology of the cell and its basic, developmental, and tissue-specific processes. Proteomics is the comprehensive study of the executive molecules of the cell coded by the genome, further raising the level of complexity, because of the large amplification in the number, going from genes to proteins, and to the sophisticated structural and functional characterization of protein products, which confer specific biochemical properties. While continuous progress in technology provides new experimental solutions to study and measure the behavior of genes and proteins in the cell, the analysis and the management of biological data cannot be uncoupled from the use of mathematics, statistics, and informatics disciplines that play a key role in modern molecular biology.Together, genomics and proteomics, meant as complementary approaches, delineate the framework of modern molecular medicine, where the knowledge of the functional mechanisms on a subcellular scale, both under physiologic and pathologic conditions, may lead to an improvement in diagnosis, therapy, and drug development.