Infections are among the main complications connected to implantation of biomedical devices, having high incidence rate and severe outcome. Since their treatment is challenging, prevention must be preferred. For this reason, solutions capable of exerting suitable efficacy while not causing toxicity and/or development of resistant bacterial strains are needed. To address infection, inorganic antibacterial coatings, and in particular silver coatings, have been extensively studied and used in the clinical practice, but some drawbacks have been evidenced, such as scarce adhesion to the substrate, delamination, or scarce control over silver release.

Here, antibacterial nanostructured silver-based thin films are proposed, obtained by a novel plasma-assisted technique, Ionized Jet Deposition (IJD). Coatings are obtained by deposition of metallic silver targets. Films thickness is selected based on previous results aimed at measuring extent and duration of silver release and at evaluating toxicity to host cells (fibroblasts). Here, composition (grazing incidence XRD) and morphology (SEM) of the obtained coatings are characterized for deposition onto different substrates, both metallic and polymeric. For heat sensitive substrates, possible alterations caused by coatings deposition in terms of morphology (SEM) and composition (FT-IR) is assessed. Then, a proof-of-concept study of the capability of these films to inhibit microbial biofilm formation is performed by using two different supports i.e., the Calgary Biofilm Device and the microplates. To the best of the Authors knowledge, this is the first study describing the application of specific anti-biofilm analyses to nanostructured coatings. In particular, anti-biofilm activities are tested against the following pathogenic strains: Escherichia (E.) coli NCTC12923, Staphylococcus (S.) aureus ATCC29213 and S. aureus 86. Among these, the strain 86 is not only pathogen but it also possesses several antibiotic resistance genes, allowing the evaluation of the utilization of nanostructured coatings as an alternative anti-microbial system to face the global threat of antibiotic resistance.

Results indicate that films deposited from silver targets are composed of nanosized aggregates of metallic silver, indicating a perfect transfer of composition from the deposition target to the coatings.

Results obtained here indicate that the films have significant antibacterial and antibiofilm activity. In addition, they prove that the system can be successfully applied for evaluation of coatings antibacterial efficacy for biomedical applications.

Calcium phosphates-based coatings have been widely studied to favour a firm bonding between orthopaedic implants and the host bone. To this aim, thin films (thickness below 1 μm) having high adhesion to the substrate and a nanostructured surface texture are desired, capable of boosting platelet, proteins and cells adhesion. In addition, a tunable composition is required to resemble as closely as possible the composition of mineralized tissues and/or to intentionally substitute ions having possible therapeutic functions. The authors demonstrated nanostructured films having high surface roughness and a composition perfectly resembling the deposition target one can be achieved by Ionized Jet Deposition (IJD). Highly adhesive nanostructured coatings were obtained by depositing bone-apatite like thin films by ablation of deproteinized bovine bone, capable of promoting host cells attachment, proliferation and differentiation. Here, biomimetic films are deposited by IJD, using biogenic and synthetic apatite targets. Since IJD deposition can be carried out without heating the substrate, application on heat sensitive polymeric substrate, i.e. 3D printed porous scaffolds, is investigated.

Biogenic apatite coatings are obtained by deposition of deproteinized bone (bovine, ovine, equine, porcine) and compared to ones of stoichiometry hydroxyapatite (HAp). Coatings composition (FT-IR-ATR, FT-IR microscopy, XRD, EDS) and morphology (SEM, AFM) are tested for deposition onto metallic and 3D-printed polymeric substrates (polyurethane (PU)). Different post-treatment annealing procedures for metallic substrates are compared (350–425°C), to optimize crystallinity. Then, uniformity of substrate coverage and possible damage caused to the polymeric substrate are studied by SEM, DSC and FT-IR microscopy.

Biogenic coatings are composed by carbonated HAp (XRD, FT-IR). Trace ions Na⁺ and Mg²⁺ are transferred from deposition target to coating. All coatings are nanostructured, composed by nano-sized globular aggregates, of which morphology and dimensions depend on the target characteristics. As-deposited coatings are amorphous, but crystallinity can be tuned by post-treatment annealing. A bone-like crystallinity can be achieved for heating at ≥400°C, also depending on duration. When deposited on 3D-printed PU scaffolds, coatings, owing to sub-micrometric thickness, coat them entirely, without altering their fibre shape and porosity.

Obtained biomimetic bone apatite coatings can be deposited onto a variety of metallic and polymeric biomedical devices, thus finding several perspective applications in biomedical field.

A critical bone defect may be more frequently the consequence of a trauma, especially when a fracture occurs with wide exposure, but also of an infection, of a neoplasm or congenital deformities. This defect needs to be treated in order to restore the limb function. The treatments most commonly performed are represented by implantation of autologous or homologous bone, vascularized fibular grafting with autologous or use of external fixators; all these treatments are characterized by several limitations.

Nowadays bone tissue engineering is looking forward new solutions: magnetic scaffolds have recently attracted significant attention. These scaffolds can improve bone formation by acting as a “fixed station” able to accumulate/release targeted growth factors and other soluble mediators in the defect area under the influence of an external magnetic field. Further, magnetic scaffolds are envisaged to improve implant fixation when compared to not-magnetic implants.

We performed a series of experimental studies to evaluate bone regeneration in rabbit femoral condyle defect by implanting hydroxyapatite (HA), polycaprolactone (PCL) and collagen/HA hybrid scaffolds in combination with permanent magnets.

Our results showed that ostetoconductive properties of the scaffolds are well preserved despite the presence of a magnetic component. Interestingly, we noticed that, using bio-resorbable collagen/HA magnetic scaffolds, under the effect of the static magnetic field generated by the permanent magnet, the reorganization of the magnetized collagen fibers produces a highly-peculiar bone pattern, with highly-interconnected trabeculae orthogonally oriented with respect to the magnetic field lines. Only partial healing of the defect was seen within the not magnetic control groups.

Magnetic scaffolds developed open new perspectives on the possibility to exploiting magnetic forces to improve implant fixation, stimulate bone formation and control the bone morphology of regenerated bone by synergically combining static magnetic fields and magnetized biomaterials. Moreover magnetic forces can be exploited to guide targeted drug delivery of growth factors functionalized with nanoparticles.

Introduction

Protective hard coatings are appealing for several technological applications and even for orthopaedic implants and prosthetic devices. For what concerns the application to prosthetic components, coating of the surface of the metallic part with low-friction and low-wear materials has been proposed [1, 2]; at the same time, concerning use of ceramic materials in joint arthroplasty, zirconia-toughned-alumina (ZTA) ceramic material has shown high strength, fracture toughness, elasticity, hardness, and wear resistance [3, 4]. The purpose of this study was to directly deposit ZTA coatings by using a novel sputter-based electron deposition technique, namely Pulsed Plasma Deposition (PPD) [5]. Preliminary characterization of realized coatings from the point of view of morphology, wettability, adhesion and friction coefficients was performed.

Introduction

Total joint arthroplasty is frequently necessary when a traumatic or degenerative disease leads to develop osteoarthritis (OA). Nowadays, the main reason for long term prosthesis failure is due to osteolysys and aseptic loosening of the implant itself, that are related to UHMWPE wear debris [1–3]. Different solutions to overcome this issue have been proposed, including different couplings like metal-on-metal and ceramic-on-ceramic. Our hypothesis was that a hard ceramic thin film realized on the plastic component (i.e. UHMWPE) could improve the friction and wear performance in a prosthetic coupling. The purpose of the presented study was therefore to characterize from the point of view of structure and mechanical performance of this ceramic-coated plastic component. The thin films were specifically realized by means of the novel Pulsed Plasma Deposition (PPD) technique [4].