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Rupture of anterior cruciate ligament (ACL) is a common injury, generally treated by reconstruction surgery. Despite good clinical outcomes, achieving a long-term success for this procedure is still a challenge: young patients could face in fact early degenerative processes, including knee osteoarthritis (OA). The altered biomechanics of the reconstructed joint could affect knee anatomical structures varying – for instance – the loads on the intra-articular cartilage, definitely inducing its degeneration. To better understand the factors that can compromise the long-term success of this procedure, this study investigated the ACL transtibial reconstruction effects on overall knee biomechanics and on articular cartilage, by integrating dynamic radiostereophotogrammetry, inferior limb multi-body modelling and MRI T2 mapping, in order to correlate knee joint loads to its physiopathological status

In this work, an interdisciplinary approach was employed to investigate the impact on thermoplastic catheters from the deposition of a thin (180 nm), metallic silver film by a pulsed ablation technique. Our characterization firstly involved tensile and bending tests, each one accompanied by finite element modeling aiming to elucidate the contributions resulting from bulk and coating to the device&rsquo, s mechanical behavior. The morphological assessment of the surface before and after the deposition was performed by atomic force microscopy, specifically implemented to visualize the nanostructured character of the film surface and the extent to which the polymer was modified by the deposition process, focusing on coating delamination due to tensile stress. Finally, thermogravimetric&ndash, differential thermal analysis was carried out to evaluate whether silver deposition has affected the physiochemical structure of the polymer matrix. Our results establish that the deposition does not significantly alter the physical and chemical properties of the device. The presented characterization sets a useful precedent for elucidating how structural properties of polymeric materials may change after coating by electronic ablation techniques, highlighting the importance of employing a comprehensive approach for clarifying the effects of additive manufacturing on medical devices.

Biomimetic bone apatite coatings were realized for the first time by the novel Ionized Jet Deposition technique. Bone coatings were deposited on titanium alloy substrates by pulsed electron ablation of deproteinized bovine bone shafts in order to resemble bone apatite as closely as possible. The composition, morphology and mechanical properties of the coatings were characterized by GI-XRD, FT-IR, SEM-EDS, AFM, contact angle measurements, micro-scratch and screw-insertion tests. Different post-treatment annealing conditions (from 350 °C to 425 °C) were investigated. Bone apatite coatings exhibited a nanostructured surface morphology and a composition closely resembling that of the deposition target (i.e. natural bone apatite), also regarding the presence of magnesium and sodium ions. Crystallinity and composition of the coatings were strongly influenced by annealing temperature and duration; in particular, upon annealing at 400 °C and above, a crystallinity similar to that of bone was achieved. Finally, adhesion to the titanium substrate and hydrophilicity were significantly enhanced upon annealing, all characteristics being known to have a strong positive impact on promoting host cells attachment, proliferation and differentiation.

Due to poor mechanical properties and brittleness of bioactive glasses, the deposition of bioactive glass coatings on bioinert metallic implants for bone regeneration is a promising route to combine the high bioactivity of the glassy phase with the mechanical strength of metallic substrate. The Pulsed Electron Deposition (PED) technique has been recently demonstrated to be an effective method to fabricate highly-adherent and nanostructured bioactive thin films and coatings, with fine control over film composition. In this paper, we investigated the deposition by PED of 45S5 Bioglass ® and of a novel CaO-rich bioactive glass, also containing potassium oxide. Composition, microstructure, surface morphology, wettability and adhesion to the titanium substrate were assessed for both as-deposited and annealed coatings. All samples exhibited a nanostructured surface morphology and high hydrophilicity, both positive features for biological applications. In particular, annealed samples exhibited increased roughness and adhesion degree to the titanium substrate compared to the as-deposited ones. The results showed in this paper suggest that bioactive glass coatings deposited by PED are promising for being further investigated as bioactive coatings for bone implants.

In orthopedics and dentistry, novel approaches for fabricating biomimetic and mechanically robust bioactive coatings are highly desirable in order to truly improve the clinical results of coated implants compared to uncoated ones. In this paper, a biological-like apatite coating is deposited for the first time by plasma-assisted deposition of a natural apatite source. Specifically, we deposited bone apatite-like (BAL) thin films from bone apatite targets by pulsed electron deposition (PED). Morphology, composition, structure and mechanical properties of as-deposited and annealed BAL and stoichiometric hydroxyapatite (HA) films were investigated. While as-deposited BAL and HA films were poorly crystalline at room temperature, they crystallized to an extent very close to that of natural apatite when annealed at 400 °C. In addition, FTIR analysis pointed out that BAL films closely resembled the composition of the starting natural apatite target. Finally, nanoindentation tests indicated that BAL films with high mechanical properties could be deposited by PED.

Nanoindentation has been emerging as a powerful tool for the investigation of the quality of bone tissue, as it allows to relate compositional/structural heterogeneity to mechanical variations at the micro- and nano-scale. To date, the investigation of nanomechanical properties of bone has been almost exclusively limited to healthy or pathologic tissues, while very few studies attempted to evaluate the mechanical properties of the tissue during the regeneration process. Here, we report the analysis by nanoindentation of the mechanical properties of healing tissue considering different animal models (rabbit and sheep), anatomical regions (condylar osteochondral interface and femoral trabecular bone), comparing pre-existent (i.e. native) and newly-formed (i.e. engineered) tissue according to different engineering approaches. In particular, we focused on bone tissue regenerated by means of nanostructured multi-layered biomimetic scaffolds or macroporous hydroxyapatite scaffolds implanted in critical-size bone defects. Our data confirm that nanoindentation represents an extremely useful tool to follow the degree of maturation of bone tissue during the healing process, for instance allowing the comparison of the efficacy of different regenerative approaches. In addition, the knowledge of the level of reconstruction of the osteochondral interface by revealing the (nano-)mechanical gradient can provide clinically relevant information to predict the correct load transfer from the cartilage to the underlying bone tissue

Nanostructured thin films of silver (Ag) are receiving attention in many production fields requiring adaptation to different substrate materials and fine control over surface texture, such as hi-tech industry and biomedicine. Here we report the deposition at room temperature of Ag thin films by pulsed electron ablation, the films thickness ranging from tens to hundreds of nanometers. Films micro- and nanostructure were investigated by means of AFM, STM and XRD, and chemical composition assessed by XPS. The data were elaborated and discussed in the context of depositions under non-local growth effects, and compared with pulsed electron ablation of different target materials. Our films resulted nanometrically smooth and homogeneous, with high degree of purity and characterized by a narrow distribution of grains of nanometric size at all the thicknesses considered. We suggest that a balance between the efficiency of the ablation process and the unique properties of Ag as a metal accounts for the overall reduction of the system size, and is at the origin of the observed nanostructuration. Our results are interesting in the perspective of metals ablation and provide an optimal platform for the study of functional surfaces with high surface-to-volume ratio.

Anterior Cruciate Ligament (ACL) is one of the main ligaments within the knee. ACL is a dense fibrous tissue, its nonlinear stress-strain behaviour is related to fibres uncrimping, reorienting and tensioning, which inherently define its functional properties. Aim of this study was to design a setup able to acquire the 3D fibrous microstructure of ACL samples evolving under strain. A specific tensioning device – consisting in two clamps to hold the sample, a linear guide moved by a threaded rod for sample elongation, a load cell to measure reaction force and an aluminum frame – was designed to be inserted into the chamber of a high resolution micro-CT system (Skyscan 1176). Once clamped, ACL underwent 1, 2, 3, 4, 6 and 8% of elongation to reveal toe and linear region of the stress-strain curve. At each specific strain, specimen was scanned with a nominal resolution of 9 μm to non-destructively obtain 3D microstructure. Before testing, collagen fibres were highlighted by an optimized contrasting protocol which included the staining of ACL in a solution of 2% PTA in H2O. With the specific contrasting procedure and micro-CT resolution, it was possible to show the effect of strain variation on the different fibres bundles. Presented procedure makes it possible to obtain fundamental information about mechanical and microstructural characteristics, simultaneously addressing clinical and engineering issues related to ACL reconstruction. Current work is related to micro-CT image processing, in order to perform a 3D morphometric analysis on the fibres bundle changes in relation to their mechanical behaviour.

Realizing hard ceramic coatings on the plastic component of a joint prosthesis can be strategic for the mechanical preservation of the whole implant and to extend its lifetime. Recently, thanks to the Plasma Pulsed Deposition (PPD) method, zirconia coatings on ultra-high molecular weight polyethylene (UHMWPE) substrates resulted in a feasible outcome. Focusing on both the highly specific requirements defined by the biomedical application and the effective possibilities given by the deposition method in the perspectives of technological transfer, it is mandatory to optimize the coating in terms of load bearing capacity. The main goal of this study was to identify through Finite Element Analysis (FEA) the optimal coating thickness that would be able to minimize UHMWPE strain, possible insurgence of cracks within the coating and stresses at coating-substrate interface. Simulations of nanoindentation and microindentation tests were specifically carried out. FEA findings demonstrated that, in general, thickening the zirconia coating strongly reduced the strains in the UHMWPE substrate, although the 1 μm thickness value was identified as critical for the presence of high stresses within the coating and at the interface with the substrate. Therefore, the optimal thickness resulted to be highly dependent on the specific loading condition and final applications.

This work aims to develop a tool to quantitatively connect the surfaces of a thin film and the substrate underneath during growth. To this purpose, it is suggested that at microscopic scales the surface of a rough substrate can be conveniently treated as a set of spatial wavelengths, whose periodicities undergo a gradual modification upon arrival of the depositing species and consequent formation of the front roughness. This enables the implementation of approximate models based on local roughening of surfaces to follow the evolution of morphology during growth. Focused primarily on situations in which growth models based on idealized deposition conditions are no longer valid, as typically happens under shadowing instability, the methodology detailed here is potentially capable to cover a broad class of thin-film processes with impact on many technological and industrial applications. As an example, two different batches of thin films, namely a ceramic (zirconia) and a metal (silver) deposited by pulsed electron ablation on rough substrates, are investigated. Our results agree well with expectations related to the different response to ablation of the used materials and, at the same time, match with the previously observed kinetic of formation of the surfaces under mainly nonideal conditions.

The use of ceramic coatings to improve mechanical, chemical, and biological properties of a large variety of materials including polymers and metals has often produced technologically attractive as well as problematic surfaces to study, because of their complicate morphology compared to smooth surfaces obtained, for example, by atomistic processes. In this work we deposited thin films of zirconia by a new generation pulsed electron deposition system named Ionized Jet Deposition onto four materials, different from each other by structure and surface texture, and applied methods of fractal geometry to investigate their microstructure and roughening mechanism at different thickness values. Our findings show that the film growth does not follow any known class of universality, but is strongly influenced by non-local effects inherent to deposition technique. In this context, we show that deposition onto rough materials is dominated by a strong memory effect that leads to uniform surface coverages that microscopically retain the shape of the substrate. This circumstance is potentially useful for deposition of conformal coatings in view of applications of such plasma-based deposition technique to cases of technological interest.

Herein the preparation of Sr2+-doped calcium phosphate (CaP) coatings on poly(etheretherketone) (PEEK) substrates by pulsed electron deposition (PED) was investigated. Hydroxyapatites (HA) substituted with tailored amounts of Sr2+ up to 9 wt% were synthesized to generate the deposition targets. Dense and uniform amorphous CaP films having Sr/Ca molar ratios close to that of targets were achieved. The roughness and the wettability of the bare PEEK were significantly enhanced after coating deposition. The presence of Sr2+ led to a slight increase of the particles size while it did not mainly affect the RMS of the coatings that consisted of nanostructured aggregates of globular shape. After a mild annealing treatment at 130 degrees C for 6 h, the amorphous coatings transformed into nanocrystalline HA films incorporating sr(2+) having Sr/Ca molar ratios close to those of the as-deposited films. The annealing did not affect the topography and the roughness of the coatings, while improved the hardness of the films un-doped and doped at low-extent. This study shows that PED is feasible technique to coat PEEK implants with CaP films with control over the Sr/Ca ratio, which could improve bone fixation and in vivo stability especially under osteoporotic conditions thanks to the anabolic effect of Sr2+. (C) 2017 Elsevier B.V. All rights reserved.

Deposition of nanostructured and low-wear zirconia (ZrO2) thin films on the metallic component of a total joint implant is envisaged to reduce wear of the soft ultra-high molecular weight polyethylene (UHMWPE) counterpart. In this work, morphological surface features, wear resistance and in vitro-biocompatibility of zirconia thin films deposited by the novel Pulsed Plasma Deposition (PPD) method have been investigated. Film thickness, roughness and wettability were found to be strongly dependent on deposition gas pressure. Interestingly, wear rate of UHMWPE disks coupled to zirconia-coated titanium spheres was only poorly correlated to the contact angle values, while film roughness and thickness seemed not to affect it. Furthermore, wear of UHMWPE, when coupled with zirconia coated-titanium spheres, significantly decreased with respect to uncoated spheres under dry or NaCl-lubricated conditions; besides, when using bovine serum, similar results were obtained for coated and uncoated spheres. Finally, suitable mesenchymal stem and osteoblast cells adhesion, proliferation and viability were observed, suggesting good biocompatibility of the nanostructured zirconia films. Taken together, the results shown in this work indicate that zirconia thin films deposited by the PPD method deserve further investigations as low-wear materials for biomedical applications such as total joint replacement.