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One of the leading causes of failure for any bone implant is implant-associated infections. The implant-bone interface is in fact the crucial site of infection where both the microorganisms and cells compete to populate the newly introduced implant surface. Most of the work dealing with this issue has focused on the design of implant coatings capable of preventing infection while ignoring cell proliferation or vice versa. The present study is therefore focused on investigating the antibacterial and biological properties of nanocomposite coatings based on an amorphous hydrocarbon (a-C:H) matrix containing silver nanoparticles (AgNPs). a-C:H coatings with varying silver concentrations were generated directly on medical grade titanium substrates using a combination of a gas aggregation source (GAS) and a plasma-enhanced chemical vapor deposition (PE-CVD) process. The obtained results revealed that the surface silver content increased from 1.3 at % to 5.3 at % by increasing the used DC magnetron current in the GAS from 200 to 500 mA. The in vitro antibacterial assays revealed that the nanocomposites with the highest number of silver content exhibited excellent antibacterial activities resulting in a 6-log reduction of Escherichia coli and a 4-log reduction of Staphylococcus aureus after 24 h of incubation. An MTT assay, fluorescence live/dead staining, and SEM microscopy observations of MC3T3 cells seeded on the uncoated and coated Ti substrates also showed that increasing the amount of AgNPs in the nanocomposites had no notable impact on their cytocompatibility, while improved cell proliferation was especially observed for the nanocomposites possessing a low amount of AgNPs. These controllable Ag/a-C:H nanocomposites on Ti substrates, which simultaneously provide an excellent antibacterial performance and good biocompatibility, could thus have promising applications in orthopedics and other biomedical implants.

Infection associated with titanium based implants remains the most serious problem in implant surgery hence it is important to find optimal strategies to prevent infections. In the present study, we investigated the surface properties, antibacterial activity and biocompatibility of nanocomposite coatings based on an amorphous hydrocarbon (a-C:H) film containing copper nanoparticles (CuNPs) deposited on Ti discs via a gas aggregation cluster source. Three different Cu/a-C:H coatings with approximately the same amount of embedded CuNPs with and without barrier a-C:H layer were fabricated. The obtained results revealed that different structures of the produced coatings have significantly different release rates of Cu ions from the coatings into the aqueous media. This subsequently influences the antibacterial efficiency and osteoblast cell viability of the treated coatings. Coatings with the highest number of CuNPs resulted in excellent antibacterial activity exhibiting approximately 4 log reduction of E.coli and S.aureus after 24 h incubation. The cytotoxicity study revealed that after 7 day cell seeding, even the coating with the highest Cu at.% (4 at.%) showed a cell viability of 90%. Consequently, the coating, formed with a properly tailored number of CuNPs and a-C:H barrier thickness offer a strong antibacterial effect without any harm to osteoblast cells.

Given the complex calcified nature of the fibrous bone tissue, a combinatorial approach merging specific topographical/biochemical cues was adopted to design bone tissue-engineered scaffolds. Coral having a Ca-enriched structure was added to electrospun chitosan (CS)/polyethylene oxide (PEO) nanofibers that were subjected to plasma surface modifications using a medium pressure Ar, air or N2 dielectric barrier discharge. Plasma incorporated oxygen- and nitrogen-containing functionalities onto the nanofibers surface thus enhancing their wettability. Plasma treatment enhanced the performance of osteoblasts and the interplay between plasma treatment and coral was shown to boost initial cell adhesion. The fibers capacity to trigger calcium phosphate growth was predicted via immersion in simulated body fluid. Globular carbonate apatite nanocrystals were deposited on plasma-treated CS/PEO NFs while thicker layers of flake-like nanocrystals were covering plasma-treated Coral/CS/PEO fibers without blocking the interfibrous pores. Overall, the exclusive multifaceted plasma-treated Coral/CS/PEO nanofibers are believed to revolutionize the bone tissue engineering field.

In this study, chitosan (CS)/polyethylene oxide (PEO) nanofibrous mats (O: 166 ± 43 nm) were fabricated by electrospinning and subsequently surface-modified by a dielectric barrier discharge (DBD) sustained in argon, ammonia/helium or nitrogen. The surface properties of the CS/PEO nanofibers (NFs) before and after plasma treatment were characterized using contact angle measurements, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Additionally, the mechanical properties and PEO leaching in aqueous conditions of the different NFs under study were examined by tensile tests and nuclear magnetic resonance (1H NMR) spectroscopy respectively. Finally, cell behavior and cell morphology of human foreskin fibroblasts (HFFs) on the CS/PEO NFs were evaluated via live/dead fluorescence microscopy, MTT assays and SEM. The obtained results revealed that the surface free energy of the CS/PEO NFs was significantly increased after plasma modification, which was correlated to an enrichment in surface oxygen (Ar, N2, NH3/He) and nitrogen (N2, NH3/He) functional groups. All performed plasma treatments also led to an increase in ultimate tensile strength, most likely due to an increased fiber-to-fiber friction. Additionally, it was also observed that N2 plasma treatment resulted in a decrease in PEO release, which could be attributed to more pronounced surface cross-linking. Cellular interactions on the CS/PEO NFs also significantly increased due to the performed plasma treatments. The best cellular response was noted for the Ar plasma modification although the surface hydrophilicity was the lowest in this case. These observations thus suggest that not only the wettability characteristics but also the presence of distinct functional groups on plasma-treated CS/PEO NFs have a significant influence on the observed enhanced cellular interactions.

In this work, a dielectric barrier discharge (DBD) operated at medium to atmospheric pressure has been used for the deposition of thin polyallylamine (PAA) films on ultra-high molecular weight polyethylene (UHMWPE) substrates. The effect of treatment time (1–5 min), discharge power (5.7–24.0 W), monomer concentration (1–2 g/h) and pressure (10–100 kPa) on the films properties, aging and stability behaviors have been investigated. The used characterization techniques are X-ray photoelectron spectroscopy, water contact angle and optical reflectance spectroscopy. In this paper, it is shown that plasma treatment time does not affect the coatings chemistry; whereas plasma power, monomer concentration and pressure control the coatings properties. It is also shown that the deposition rate of the deposited films changes with varying W/FM values. At low W/FM values, high deposition rates of up to 2 nm/s are observed. Plasma treatments were also characterized by their amino efficiency ([NH2]/[C] in %) and amino selectivity ([NH2]/[N] in %). Depending on the used parameters, these varied between 12.3% and 20% and between 71.2% and 91.1%, respectively. For the aging study, coatings that preserved most of their hydrophilicity were obtained at power ≤11.3 W, monomer concentration ≥1.5 g/h and pressure ≥50 kPa. For the stability study, coatings that showed the highest [N] (%) and lowest percentage of thickness decrease were obtained at ≤2 min, 24.0 W, 1 g/h and pressure ≤50 kPa. One can therefore control the deposition rate as well as the properties, aging and stability behaviors of the deposited coating by carefully choosing the plasma parameters.

The objective of this study was the development of Ag-rich antibacterial coatings on titanium to prevent post-operative infections. A series of Ag-doped TiO2 coatings were synthesized on Ti discs by plasma electrolytic oxidation in an electrolyte containing AgNPs. The incorporation, distribution and chemical composition of the AgNPs on Ti were determined using scanning electron microscopy-energy dispersive spectroscopy. The crystalline structure and wettability of the coating was characterized by X-ray diffraction and water contact angle analysis respectively. Surface roughness and hardness of the coating were examined using surface profilometry and Knoop indentation test respectively, while silver ion release was quantified using inductively coupled plasma-mass spectroscopy. Following PEO, the surface of the Ti substrate was converted to TiO2 composed of anatase and rutile phases. The SEM micrographs showed that the AgNPs were distributed throughout the oxide layer, without changing the morphology of the coating. The coatings also revealed an increased surface roughness, microhardness and improved surface wettability relative to untreated Ti substrates. Furthermore, the incorporation of Ag into the coating did not alter the phase component, roughness, microhardness and wettability. A series of in-vitro antibacterial assays indicated that increasing the number of AgNPs in the electrolyte led to excellent antibacterial activities.

The success of an orthopedic implant therapy depends on successful bone integration and the prevention of microbial infections. In this work, plasma electrolytic oxidation (PEO) was performed to deposit TiO2 coatings enriched with Ca, P, and Ag on titanium to improve its surface properties and antibacterial blasts efficacy while maintaining normal biological functions and thus to enhance the performance of orthopedic implants. After PEO treatment, the surface of Ti was converted to anatase and rutile TiO2, hydroxyapatite, and calcium titanate phases. The presence of these crystalline phases was further increased with an increased Ag content in the coatings. The developed coatings also exhibited a more porous morphology with an improved surface wettability, roughness, microhardness, and frictional coefficient. In vitro antibacterial assays indicated that the Ag-doped coatings can significantly prevent the growth of both Staphylococcus aureus and Escherichia coli by releasing Ag+ ions, and the ability to prevent these bacteria was enhanced by increasing the Ag content in the coatings, resulting in a maximal 6-log reduction of E. coli and a maximal 5-log reduction of S. aureus after 24 h of incubation. Moreover, the in vitro cytocompatibility evaluation of the coatings showed that the osteoblast (MC3T3) cell integration on the PEO-based coatings was greatly improved compared to untreated Ti and no notable impact on their cytocompatibility was observed on increasing the amount of Ag in the coating. In conclusion, the coating with favorable physicochemical and mechanical properties along with controlled silver ion release can offer an excellent antibacterial performance and osteocompatibility and can thus become a prospective coating strategy to face current challenges in orthopedics.

Traditional wet chemistry offers a great magnitude of methods for surface modification and surface coatings for nanostructured materials. However, most methods require solvents and purification steps, and generate waste and byproducts. An interesting alternative set of methods involves the use of nonthermal or low-temperature plasmas (LTP) toward making and modifying nanostructured biomaterials. In this current opinion piece, some of the recent literature in this area is highlighted, and current perspectives are given. Emphasis is noted for the role of LTP for surface modification of nanofibrous scaffolds and plasma electrolytic oxidation (PEO) for surface-nanostructuring of metallic implants. The morphological nanofeaturing in fibrous mats as an extracellular matrix mimicking scaffold is presented along with recent perspectives of using LTP and plasma electrolytic oxidation for surface structuring for enhanced biointegration via cell/surface interactions with plasma processed implants/scaffolds constructs.

The prominent success of polycaprolactone (PCL) electrospun nanofibrous mats (ENM) has expanded the use of PCL over other polymers for tissue engineering applications. However, the major challenge in the design of a nanofibrous scaffold is to modify its surface properties while preserving its bulk properties. Therefore, the first part of the study is focused on the fabrication of PCL-ENMs by alternating-current electrospinning using the following solvent systems: formic acid, formic acid/acetic acid (1/1) and formic acid/acetic acid/acetone (1/1/1). While the second part is focused on an nm-thick surface chemical modification via medium pressure argon and nitrogen plasma treatment, and the third part is dedicated to investigating the morphology, wettability, surface functional groups, crystallite size, crystallinity, crystallization, and melting temperature of plasma-treated nanofibers. Samples were characterized using scanning electron microscopy (SEM), water contact angle analysis (WCA), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), and differential scanning calorimetry (DSC). WCA and SEM results showed that plasma treatments significantly improve the wettability of the PCL ENMs without compromising their surface morphology. XPS analysis revealed that argon and nitrogen gases are responsible for a substantial increase in polar oxygen and nitrogen functional groups respectively. Out of the six plasma-treated PCL ENMs understudy, the argon plasma-treated sample showed superior hydrophilicity (from 136° to ~35°) followed by nitrogen plasma treatment (from 136° to ~42°). It was also found from XRD that the crystallite size was not significantly affected by the conducted plasma treatments. Moreover, the degree of crystallinity was also not altered by the plasma treatments, as was observed by DSC and FTIR. The conducted experiments showed that the surface properties of the PCL ENMs could be positively affected while maintaining their beneficial bulk properties thereby making these plasma-modified ENMs excellent candidates in multiple biomedical and tissue engineering applications.

Bacterial infections associated with titanium implants remain a common problem in the orthopedic field. To overcome this, antibacterial plasma polymer nanocomposites have been studied for years due to their antibacterial potency1. Unfortunately, the application of these nanocomposites is often hindered by the fact that they are soft and not mechanically stable. Therefore, a hard plasma polymer layer is crucial that can withstand wear abrasion and at the same time shows antibacterial potency2, In this study, a low-pressure plasma-based method was employed for the deposition of hard polymeric nanocomposite coatings containing Ag nanoparticles (AgNPs) on Ti substrates. This method uses a gas aggregation source (GAS) for the formation and deposition of Ag nanoparticles and combines it with plasma enhanced chemical vapor deposition of an amorphous hydrocarbon matrix (a-C:H) that is deposited in a mixture of Ar and n-hexane on substrates placed on a powered RF electrode. The matrix properties can be modified by adapting the applied RF power while the amount of incorporated Ag nanoparticles can be altered by the operational parameters of the GAS. The focus of this study is to deposit an a-C:H matrix containing Ag nanoparticles on Ti substrates and to optimize the working parameters to achieve a mechanically stable coating possessing anti -bacterial properties. Three different types of nanocomposite layers are studied: 1) nanocomposite films by simultaneous deposition of AgNPs and an a-C:H matrix 2) sandwich structures with base and top layers of a-C:H and an AgNP interlayer 3) quasi sandwich films with a base layer of a-C:H and a second layer of simultaneous deposition of AgNPs and an a-C:H matrix.

Biofilm growth on the implant surface is the number one cause of the failure of the implants. Biofilms on implant surfaces are hard to eliminate by antibiotics due to the protection offered by the exopolymeric substances that embed the organisms in a matrix, impenetrable for most antibiotics and immune cells. Application of metals in nanoscale is considered to resolve biofilm formation. Here we studied the effect of iron-oxide nanoparticles over biofilm formation on different biomaterial surfaces and pluronic coated surfaces. Bacterial adhesion for 30 min showed significant reduction in bacterial adhesion on pluronic coated surfaces compared to other surfaces. Subsequently, bacteria were allowed to grow for 24 h in the presence of different concentrations of iron-oxide nanoparticles. A significant reduction in biofilm growth was observed in the presence of the highest concentration of iron-oxide nanoparticles on pluronic coated surfaces compared to other surfaces. Therefore, combination of polymer brush coating and iron-oxide nanoparticles could show a significant reduction in biofilm formation.