Prosthetic joint infections represent complications connected to the implantation of biomedical devices, they have high incidence, interfere with osseointegration, and lead to a high societal burden. The microbial biofilm, which is a complex structure of microbial cells firmly attached to a surface, is one of the main issues causing infections. Biofilm- forming bacteria are acquiring more and more resistances to common clinical treatments due to the abuse of antibiotics administration. Therefore, there is increasing need to develop alternative methods exerting antibacterial activities against multidrug-resistant biofilm-forming bacteria. In this context, metal-based coatings with antimicrobial activities have been investigated and are currently used in the clinical practice. However, traditional coatings exhibit some drawbacks related to the insufficient adhesion to the substrate, scarce uniformity and scarce control over the toxic metal release reducing their efficacy. Here, we propose the use of antimicrobial silver-based nanostructured thin films to discourage bacterial infections. Coatings are obtained by Ionized Jet Deposition, a plasma-assisted technique that permits to manufacture films of submicrometric thickness having a nanostructured surface texture, allow tuning silver release, and avoid delamination. To mitigate interference with osseointegration, here silver composites with bone apatite and hydroxyapatite were explored. The antibacterial efficacy of silver films was tested in vitro against gram- positive and gram-negative species to determine the optimal coatings characteristics by assessing reduction of bacterial viability, adhesion to substrate, and biofilm formation. Efficacy was tested in an in vivo rabbit model, using a multidrug-resistant strain of Staphylococcus aureus showing significant reduction of the bacterial load on the silver prosthesis both when coated with the metal only (>99% reduction) and when in combination with bone apatite (>86% reduction). These studies indicate that IJD films are highly tunable and can be a promising route to overcome the main challenges in orthopedic prostheses.

Calcium phosphates-based (CaPs) nanocoatings on metallic prosthesis are widely studied in orthopedics and dentistry because they mimic the mineral component of native human bone and favor the osseointegration process. Despite the fact that different calcium phosphates have different properties (composition, crystallinity, and ion release), only stoichiometric hydroxyapatite (HA) films have been analyzed in deep. Here, we have realized films of different CaPs (HA, beta-tricalcium phosphate (β-TCP) and brushite (DCPD)) onto Ti6Al4V microrough substrates by Ionized Jet Deposition (IJD). We have implemented the heating of substrates at 400°C during deposition to see the effect on coating properties.

Different film features are evaluated: morphology and topography (FEG-SEM, AFM), physical-chemical composition (FT-IR and EDS), dissolution profile and adhesion to substrate (scratch test), with a focus on how the different CaPs and temperature changed the coating features. After coating optimization, we have studied the in vitro BM-MSC behavior, in term of viability and early adhesion.

We have obtained good transfer of fidelity in composition from target to coating for all CaPs, with nanostructured films formed by globular aggregates (~300 nm diameter), with homogeneous and uniform coverage of the substrate surface, without cracks. The heating during deposition has increased the adhesion of the films to the substrate, with higher stability in medium immersion and wettability, features that can improve the biological behavior of cells. All CaP coatings have showed excellent biocompatibility, with DCPD coating that promote higher cells viability at 14 days respect to HA and β- TCP films. About the early cell adhesion, the BM-MSC have showed switch from a globular to an elongated morphology at 6 hours in all coatings respect to the uncoated titanium, sign of better adhesion.

From these results, the fabrication of different CaP nanocoatings with IJD can be a promising for applications in orthopedics and dentistry.

Prosthetic joint infections represent complications connected to the implantation of biomedical devices, they have high incidence, interfere with osseointegration, and lead to a high societal burden. The microbial biofilm, which is a complex structure of microbial cells firmly attached to a surface, is one of the main issues causing infections. Biofilm- forming bacteria are acquiring more and more resistances to common clinical treatments due to the abuse of antibiotics administration. Therefore, there is increasing need to develop alternative methods exerting antibacterial activities against multidrug-resistant biofilm-forming bacteria. In this context, metal-based coatings with antimicrobial activities have been investigated and are currently used in the clinical practice. However, traditional coatings exhibit some drawbacks related to the insufficient adhesion to the substrate, scarce uniformity and scarce control over the toxic metal release reducing their efficacy. Here, we propose the use of antimicrobial silver-based nanostructured thin films to discourage bacterial infections. Coatings are obtained by Ionized Jet Deposition, a plasma-assisted technique that permits to manufacture films of submicrometric thickness having a nanostructured surface texture, allow tuning silver release, and avoid delamination. To mitigate interference with osseointegration, here silver composites with bone apatite and hydroxyapatite were explored. The antibacterial efficacy of silver films was tested in vitro against gram- positive and gram-negative species to determine the optimal coatings characteristics by assessing reduction of bacterial viability, adhesion to substrate, and biofilm formation. Efficacy was tested in an in vivo rabbit model, using a multidrug-resistant strain of Staphylococcus aureus showing significant reduction of the bacterial load on the silver prosthesis both when coated with the metal only (>99% reduction) and when in combination with bone apatite (>86% reduction). These studies indicate that IJD films are highly tunable and can be a promising route to overcome the main challenges in orthopedic prostheses.

Infection in orthopedics is a challenge, since it has high incidence (rates can be up to 15-20%, also depending on the surgical procedure and on comorbidities), interferes with osseointegration and brings severe complications to the patients and high societal burden. In particular, infection rates are high in oncologic surgery, when biomedical devices are used to fill bone gaps created to remove tumors. To increase osseointegration, calcium phosphates coatings are used. To prevent infection, metal- and mainly silver-based coatings are the most diffused option. However, traditional techniques present some drawbacks, including scarce adhesion to the substrate, detachments, and/or poor control over metal ions release, all leading to cytotoxicity and/or interfering with osteointegration. Since important cross-relations exist among infection, osseointegration and tumors, solutions capable of addressing all would be a breakthrough innovation in the field and could improve clinical practice.

Here, for the first time, we propose the use antimicrobial silver-based nanostructured thin films to simultaneously discourage infection and bone metastases. Coatings are obtained by Ionized Jet Deposition, a plasma-assisted technique that permits to manufacture films of submicrometric thickness having a nanostructured surface texture. These characteristics, in turn, allow tuning silver release and avoid delamination, thus preventing toxicity. In addition, to mitigate interference with osseointegration, here silver composites with bone apatite are explored. Indeed, capability of bone apatite coatings to promote osseointegration had been previously demonstrated in vitro and in vivo. Here, antibacterial efficacy and biocompatibility of silver-based films are tested in vitro and in vivo. Finally, for the first time, a proof-of-concept of antitumor efficacy of the silver-based films is shown in vitro.

Coatings are obtained by silver and silver-bone apatite composite targets. Both standard and custom-made (porous) vertebral titanium alloy prostheses are used as substrates.

Films composition and morphology depending on the deposition parameters are investigated and optimized. Antibacterial efficacy of silver films is tested in vitro against gram+ and gram- species (E. coli, P. aeruginosa, S. aureus, E. faecalis), to determine the optimal coatings characteristics, by assessing reduction of bacterial viability, adhesion to substrate and biofilm formation. Biocompatibility is tested in vitro on fibroblasts and MSCs and, in vivo on rat models. Efficacy is also tested in an in vivo rabbit model, using a multidrug resistant strain of S. aureus (MRSA, S. aureus USA 300). Absence of nanotoxicity is assessed in vivo by measuring possible presence of Ag in the blood or in target organs (ICP-MS). Then, possible antitumor effect of the films is preliminary assessed in vitro using MDA-MB-231 cells, live/dead assay and scanning electron microscopy (FEG-SEM). Statistical analysis is performed and data are reported as Mean ± standard Deviation at a significance level of p <0.05. Silver and silver-bone apatite films show high efficacy in vitro against all the tested strains (complete inhibition of planktonic growth, reduction of biofilm formation > 50%), without causing cytotoxicity. Biocompatibility is also confirmed in vivo.

In vivo, Ag and Ag-bone apatite films can inhibit the MRSA strain (>99% and >86% reduction against ctr, respectively). Residual antibacterial activity is retained after explant (at 1 month). These studies indicate that IJD films are highly tunable and can be a promising route to overcome the main challenges in orthopedic prostheses.

Favoring osseointegration and avoiding bacterial contamination are the key challenges in the design of implantable devices for orthopedic applications. To meet these goals, a promising route is to tune the biointerface of the devices, that can regulate interactions with the host cells and bacteria, by using nanostructured antibacterial and bioactive coatings. Indeed, the selection of adequate metal-based coatings permits to discourage infection while avoiding the development of bacterial resistance and nanostructuring permits to tune the release of the antimicrobial compounds, allowing high efficacy and decreasing possible cytotoxic effects. In addition, metal-doped calcium phosphates-based nanostructured coatings permit to tune both composition and morphology of the biointerfaces, allowing to regulate host cells and bacteria response. To tune the biointerfaces of implantable devices, nanostructured coatings can be used, but their use is challenging when the substrate is heat-sensitive and/or porous.

Here, we propose the use of Ionized Jet Deposition (IJD) to deposit metallic and ion-doped calcium phosphates materials onto different polymeric substrates, without heating and damaging the substrate morphology. 3D printed scaffolds in polylactic acid (PLA) and polyurethane (PU), and electrospun matrices in polycaprolactone (PCL) and PLA were used as substrates. Biogenic apatite (HA), ion doped (zinc, copper and iron) tricalcium phosphate (TCP) and silver (Ag) coatings were obtained on porous and custom-made polymeric substrates.

Chemical analyses confirmed that coatings composition matches that of the target materials, both in terms of main phase (HA or TCP) and ion doping (presence of Cu, Zn or Fe ion). Deposition parameters, and especially its duration time, influence the coating features (morphology and thickness) and substrate damage. Indeed, SEM/EDS observations show the presence of nanostructured agglomerates on substrates surface. The dimensions of the aggregates and the thickness of the coating films increase increasing the deposition time, without affecting the substrate morphology (no porosity alteration or fibers damaging). The possible substrate damage is influenced by target and substrate material, but it can be avoided modulating deposition time.

Once the parameters are optimized, the models show suitable in vitro biological efficacy for applications in bone models, regenerative medicine and infection. Indeed, HA-based coatings favor cells adhesion on printed and electrospun fibers. For antibacterial applications, the ion doped TCP coatings can reduce the bacterial growth and adhesion (E.coli and S.aureus) on electrospun matrices.

To conclude, it is possible achieve different properties applying nanostructured coatings with IJD technique on polymeric substrates, modulating deposition conditions to avoid substrate damage.

Introduction and Objective

The choice of appropriate characteristics is crucial to favor a firm bonding between orthopedic implants and the host bone and to permit bone regeneration. In particular, the morphology and composition of the biointerface plays a crucial role in orchestrating precise cellular responses. Here, to modulate the biointerface, we propose new biomimetic coatings, having multi-scale nano- to micro- morphological cues and a composition mimicking the mineral phase of bone.

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.

Fabrication of biogenic coatings with suitable mechanical properties is a key goal in orthopedics, to overcome the limitations of currently available coatings and improve the clinical results of coated implants compared to uncoated ones. In this paper, biological-like apatite coatings were deposited from a natural bone-apatite source by a pulsed electron deposition technique (PED).

Bone apatite-like (BAL) films were deposited directly from bone targets, obtained by standard deproteinization of bovine tibial cortical shafts and compared to films deposited by sintered stoichiometric-hydroxyapatite targets (HA). Deposition was performed at room temperature by PED in the Ionized Jet Deposition (IJD) version. Half of the samples was annealed at 400°C for 1h (BAL_400 and HA_400). As-deposited and annealed coatings were characterized in terms of composition and crystallinity (XRD, FT-IR), microstructure and morphology (SEM-EDS, AFM) and mechanical properties (nanoindentation and micro-scratch). For the biological tests, human dental pulp stem cells (hDPSCs) were isolated from dental pulp from patients undergoing a routine tooth extraction, plated on the samples (2500 cells/cm2) and cultured for 3 weeks, when the expression of typical osteogenic markers Runx-2, osteopontin, Osx and Osteocalcin in hDPSCs was evaluated.

Results showed that deposition by PED allows for a close transfer of the targets” composition. As-deposited coatings exhibited low cristallinity, that was significantly increased by post-deposition annealing, up to resembling that of biogenic apatite target. As a result of annealing, mechanical properties increased up to values comparable to those of commercial plasma-sprayed HA-coatings.

In vitro biological tests indicated that BAL_400 promotes hDPSCs proliferation to a higher extent compared to non-annealed bone coating and HA-references. Furher, immunofluorescence and western blot analyses revealed that the typical osteogenic markers were expressed, indicating that BAL_400 alone can efficiently promote the osteogenic commitment of the cells, even in absence of an osteogenic medium.

In conclusion, bone-like apatite coatings were deposited by PED, which closely resembled composition and structure of natural-apatite. Upon annealing at 400°C, the coatings exhibited satisfactory mechanical properties and were capable of providing a suitable microenvironment for hDPSCs adherence and proliferation and for them to reach osteogenic commitment.

These results suggest that bone apatite-like thin films obtained by biogenic source may represent an innovative platform to boost bone regeneration in the orthopedic, maxillofacial and odontoiatric 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].

Introduction

Protective hard coatings are appealing for several technological applications like solar cells, organic electronics, fuel cells, cutting tools and even for orthopaedic implants and prosthetic devices. At present for what concerns the application to prosthetic components, the coating of the surface of the metallic part with low-friction and low-wear materials has been proposed [1]. Concerning the use of ceramic materials in joint arthroplasty, zirconia-toughned-alumina (ZTA) reported high strength, fracture toughness, elasticity, hardness, and wear resistance [2]. The main goal of this study was to directly deposit ZTA coating by using a novel sputter-based electron deposition technique, namely Pulsed Plasma Deposition (PPD) [3]. The realized coatings have been preliminary characterized from the point of view of morphology, wettability, adhesion and friction coefficients.

Wear of the ultra-high molecular weight polyethylene (UHMWPE) insert is one of the major issue related to orthopaedic implants. In this study, the tribo-mechanical properties of zirconia-coated UHMWPE deposited by means of Pulsed Plasma Deposition (PPD) technique were analyzed. Specifically, strength to local plastic deformation, indentation work portioning and creep behavior were evaluated through nanoindentation and micro-scratch tests, whereas preliminary wear data were obtained by tribology tests. A strong reduction of plastic deformation and a drop of the creep phenomenon for the zirconia-coated UHMWPE were evidenced, whereas - in spite of similar wear data - different wear mechanism was also detected. This study supported the use of hard ceramic thin films to enhance the mechanical performance of the plastic inserts used in orthopaedics.