Magnetic-Oriented Nickel Particles and Nickel-Coated Carbon Nanotubes: An Efficient Tool for Enhancing Thermal Conductivity of PDMS Composites

In this study, PDMS composites are thermally cured with nickel particles and nickel-coated carbon nanotubes as fillers. Both fillers are oriented with the aim to increase the thermal conductivity of the silicone polymer network, due to the formation of a continuous thermal path. Scanning electron microscopy (SEM) gives a picture of the polymer network's morphology, proving the effective alignment of the nickel particles. Rheology and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) studies confirm the full curing of the silicon network and no influence in the curing kinetics of the type and content of fillers and their orientation. Dynamic mechanical thermal analysis (DMTA) and tensile analysis show instead different thermo-mechanical behavior of the polymer network due to the presence of different fillers, different fillers percentage, and orientation. Finally, the thermal transmittance coefficient (k) is studied by means of hot disk analysis, revealing the increment of almost 200% due to magnetic filler orientation

Electron beam structuring of Ti6Al4V: New insights on the metal surface properties influencing the bacterial adhesion

Soft tissue adhesion and infection prevention are currently challenging for dental transmucosal or percutaneous orthopedic implants. It has previously been shown that aligned micro-grooves obtained by Electron Beam (EB) can drive fibroblast alignment for improved soft tissue adhesion. In this work, evidence is presented that the same technique can also be effective for a reduction of the infection risk. Grooves 10-30 \u3bcm wide and around 0.2 \u3bcm deep were obtained on Ti6Al4V by EB. EB treatment changes the crystalline structure and microstructure in a surface layer that is thicker than the groove depth. Unexpectedly, a significant bacterial reduction was observed. The surfaces were characterized by field emission scanning electron microscopy, X-ray diffraction, confocal microscopy, contact profilometry, wettability and bacterial adhesion tests. The influence of surface topography, microstructure and crystallography on bacterial adhesion was systematically investigated: it was evidenced that the bacterial reduction after EB surface treatment is not correlated with the grooves, but with the microstructure induced by the EB treatment, with a significant bacterial reduction when the surface microstructure has a high density of grain boundaries. This correlation between microstructure and bacterial adhesion was reported for the first time for Ti alloys

Albumin and fibronectin adsorption on treated titanium surfaces for osseointegration: An advanced investigation

Protein adsorption has a central role in the outcome of implants. However, there is no consensus about the impact of the different surface properties on the material-protein interactions. Here, the adsorption of albumin and fibmnectin in near-physiological concentration is investigated on three differently treated titanium-based surfaces and compared after a thorough characterization. The different titanium surfaces have very different surface properties, in particular regarding roughness, oxide porosity, wettability, surface energy, and zeta potential, which are all known to deeply affect protein adsorption. By merging several characterization techniques, some conventional and some innovative, it was possible to discriminate the effect of surface properties on different aspects of protein adsorption. Despite forming a continuous layer on all samples, the amount of proteins bound to the surface is mainly due to surface roughness and topography, which can overcome the effect of wettability and surface energy. On the other hand, the secondary structure of albumin and fibmnectin and their orientation are determined by the hydroxyl groups exposed on the surfaces, depending on their surface concentration and acidic reactivity in the former, and the surface zeta potential in the latter

Competitive surface colonization of antibacterial and bioactive materials doped with strontium and/or silver ions

Nowadays, there is a large amount of research aimed at improving the multifunctional behavior of the biomaterials for bone contact, including the concomitant ability to induce apatite formation (bioactivity), fast and effective osteoblasts colonization, and antibacterial activity. The aim of this study is to develop antibacterial and bioactive surfaces (Ti6Al4V alloy and a silica-based bioactive glass) by chemical doping with strontium and/or silver ions. The surfaces were characterized by Scanning Electron Microscopy equipped with Energy Dispersive X ray Spectroscopy (SEM-EDS), X-ray photoelectron spectroscopy (XPS), and Transmission Electron Microscopy (TEM). To better focus on the cells–bacteria competition for the implant surface, in addition to the standard assays for the evaluation of the bacteria adhesion (ISO22196) and for single-cell cultures or biofilm formation, an innovative set of co-cultures of cells and bacteria is here proposed to simulate a competitive surface colonization. The results suggest that all the bioactive tested materials were cytocompatible toward the bone progenitor cells representative for the self-healing process, and that the doped ones were effective in reducing the surface colonization from a pathogenic drug-resistant strain of Staphylococcus aureus. The co-cultures experiments demonstrated that the doped surfaces were able to protect the adhered osteoblasts from the bacteria colonization as well as prevent the infection prior to the surface colonization by the osteoblasts

Advanced characterization of albumin adsorption on a chemically treated surface for osseointegration: An innovative experimental approach

Surface chemistry, charge, wettability, and roughness affect the adsorbed protein layer, influencing biocompatibility and functionality of implants. Material engineering seeks innovative, sensitive, and reliable characterization techniques for study the adsorbed proteins. These techniques must be suitable to be directly used on the surfaces of clinical interest. In this paper, the characterization of surfaces with topography and chemistry developed for osseointegration is performed by innovative surface analysis techniques to investigate the properties of adsorbed bovine serum albumin. Ti6Al4V alloy chemically treated with an oxidative process to obtain peculiar surface features (roughness and surface hydroxylation) was tested and compared with mirror-polished titanium. Albumin forms a continuous layer on both Ti surfaces when adsorbed from near physiological concentrations, as proved by Kelvin force probe microscopy. It was observed that the hydroxylation degree plays a pivotal role in determining the conformation of proteins after adsorption, where it strongly drives protein unfolding, as confirmed by Surface Enhanced Raman scattering, and in influencing the mechanism and chemical stability of protein-surface interactions, which was highlighted by zeta potential titration curves

Surface Properties and Antioxidant Activity of Silicate and Borosilicate Bioactive Glasses

Herein, silicate and borosilicate bioactive glasses are synthetized and characterized. The antioxidant activity, in the presence and absence of human osteoblasts' progenitor cells, of the different glass compositions, is correlated to the surface properties: wettability, zeta potential, hydroxylation degree, reactivity in simulated body fluid (SBF), and Tris buffer. An enhancing effect of boron in glass reactivity and a stabilizing role of Sr and Mg are evidenced. The scavenging potential of the analyzed bioactive glasses toward reactive oxygen species (ROS) is clearly proved. Moreover, cellular tests confirm the protective effect of the bioactive glasses toward viable cells acting as ROS/RNS species scavenger. The obtained results represent an original improvement of the knowledge concerning the intrinsic antioxidant ability of bioactive glasses with different compositions and the mechanisms involved

Influence of a Physiologically Formed Blood Clot on Pre-Osteoblastic Cells Grown on a BMP-7-Coated Nanoporous Titanium Surface

Titanium (Ti) nanotopography modulates the osteogenic response to exogenous bone morphogenetic protein 7 (BMP-7) in vitro, supporting enhanced alkaline phosphatase mRNA expression and activity, as well as higher osteopontin (OPN) mRNA and protein levels. As the biological effects of OPN protein are modulated by its proteolytic cleavage by serum proteases, this in vitro study evaluated the effects on osteogenic cells in the presence of a physiological blood clot previously formed on a BMP-7-coated nanostructured Ti surface obtained by chemical etching (Nano-Ti). Pre-osteoblastic MC3T3-E1 cells were cultured during 5 days on recombinant mouse (rm) BMP-7-coated Nano-Ti after it was implanted in adult female C57BI/6 mouse dorsal dermal tissue for 18 h. Nano-Ti without blood clot or with blood clot at time 0 were used as the controls. The presence of blood clots tended to inhibit the expression of key osteoblast markers, except for Opn, and rmBMP-7 functionalization resulted in a tendency towards relatively greater osteoblastic differentiation, which was corroborated by runt-related transcription factor 2 (RUNX2) amounts. Undetectable levels of OPN and phosphorylated suppressor of mothers against decapentaplegic (SMAD) 1/5/9 were noted in these groups, and the cleaved form of OPN was only detected in the blood clot immediately prior to cell plating. In conclusion, the strategy to mimic in vitro the initial interfacial in vivo events by forming a blood clot on a Ti nanoporous surface resulted in the inhibition of pre-osteoblastic differentiation, which was minimally reverted with an rmBMP-7 coating

Sudden neck swelling with rash as late manifestation of COVID-19: a case report

Background: Although there are reports of otolaryngological symptoms and manifestations of CoronaVirus Disease 19 (COVID-19), there have been no documented cases of sudden neck swelling with rash in patients with Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection described in literature. Case presentation: We report a case of a sudden neck swelling and rash likely due to late SARS-CoV-2 in a 64-year-old woman. The patient reported COVID-19 symptoms over the previous three weeks. Computed Tomography (CT) revealed a diffuse soft-tissue swelling and edema of subcutaneous tissue, hypodermis, and muscular and deep fascial planes. All the differential diagnoses were ruled out. Both the anamnestic history of the patient’s husband who had died of COVID-19 with and the collateral findings of pneumonia and esophageal wall edema suggested the association with COVID-19. This was confirmed by nasopharyngeal swab polymerase chain reaction. The patient was treated with lopinavir/ritonavir, hydroxychloroquine and piperacillin/tazobactam for 7 days. The neck swelling resolved in less than 24 h, while the erythema was still present up to two days later. The patient was discharged after seven days in good clinical condition and with a negative swab. Conclusion: Sudden neck swelling with rash may be a coincidental presentation, but, in the pandemic context, it is most likely a direct or indirect complication of COVID-19

Deposition of Antioxidant and Cytocompatible Caffeic Acid-Based Thin Films onto Ti6Al4V Alloys through Hexamethylenediamine-Mediated Crosslinking

A promising approach for advanced bone implants is thedepositionon titanium surfaces of organic thin films with improved therapeuticperformances. Herein, we reported the efficient dip-coating depositionof caffeic acid (CA)-based films on both polished and chemically pre-treatedTi6Al4V alloys by exploiting hexamethylenediamine (HMDA) crosslinkingability. The formation of benzacridine systems, resulting from theinteraction of CA with the amino groups of HMDA, as reported in previousstudies, was suggested by the yellow/green color of the coatings.The coated surfaces were characterized by means of the Folin-Ciocalteumethod, fluorescence microscopy, water contact angle measurements,X-ray photoelectron spectroscopy (XPS), zeta-potential measurements,and Fourier transform infrared spectroscopy, confirming the presenceof a uniform coating on the titanium surfaces. The optimal mechanicaladhesion of the coating, especially on the chemically pre-treatedsubstrate, was also demonstrated by the tape adhesion test. Interestingly,both films exhibited marked antioxidant properties (2,2-diphenyl-1-picrylhydrazyland ferric reducing antioxidant power assays) that persisted overtime and were not lost even after prolonged storage of the material.The feature of the coatings in terms of the exposed groups (XPS andzeta potential titration evidence) was apparently dependent on thesurface pre-treatment of the titanium substrate. Cytocompatibility,scavenger antioxidant activity, and antibacterial properties of thedeveloped coatings were evaluated. The most promising results wereobtained in the case of the chemically pre-treated CA/HMDA-based coatedsurface that showed good cytocompatibility and high reactive oxygenspecies' scavenging ability, preventing their intracellularaccumulation under pro-inflammatory conditions; moreover, an anti-foulingeffect preventing the formation of 3D biofilm-like bacterial aggregateswas observed by scanning electron microscopy. These results open newperspectives for the development of innovative titanium surfaces withthin coatings from naturally occurring phenols for bone contact implants