Bioactive and antibacterial coatings on stainless steel substrates were developed and characterized in this study. Silver nanocluster-silica composite coatings of 60-150 nm thickness were deposited using radio frequency (RF) co-sputtering on PEEK/bioactive glass (BG) layers (of 80-90 μm thickness) which had been electrophoretically deposited onto stainless steel. Two sputtering conditions were used by varying the deposition time (15 and 40 min); the resulting microstructure, composition, adhesion strength, in vitro bioactivity, and antibacterial activity were investigated. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and energy dispersive spectroscopy (EDX) confirmed the presence of silver nanoclusters, which were homogeneously embedded in the silica matrix. The isoelectric point of the coatings and their charge at physiological pH were determined by zeta potential measurements. The presence of BG particles in the PEEK/BG layer allows the coatings to form apatite-like crystals upon immersion in simulated body fluid (SBF). Moreover, silver nanoclusters embedded in the silica matrix as a top layer provided an antibacterial effect against Escherichia coli and Staphylococcus carnosus.

Mesoporous bioactive glasses have been widely investigated for applications in bone tissue regeneration and, more recently, in soft tissue repair and wound healing. In this study we produced mesoporous bioactive glass nanoparticles (MBGNs) based on the SiO2–CaO system. With the intention of adding subsidiary biological function, MBGNs were doped with Zn2+ ions. Zn-MBGNs with 8 mol% ZnO content were synthesized via microemulsion assisted sol-gel method. The synthesized particles were homogeneous in shape and size. They exhibited spherical shape, good dispersity, and a size of 130 ± 10 nm. The addition of zinc precursors did not affect the morphology of particles, while their specific surface area increased in comparison to MBGNs. The presence of Zn2+ ions inhibited the formation of hydroxycarbonate apatite (HCAp) on the particles after immersion in simulated body fluid (SBF). No formation of HCAp crystals on the surface of Zn-MBGNs could be observed after 14 days of immersion. Interestingly, powders containing relatively high amount of zinc released Zn2+ ions in low concentration (0.6–1.2 mg L−1) but in a sustained manner. This releasing feature enables Zn-MBGNs to avoid potentially toxic levels of Zn2+ ions, indeed Zn-MBGNs were seen to improve the differentiation of osteoblast-like cells (MG-63). Additionally, Zn-MBGNs showed higher ability to adsorb proteins in comparison to MBGNs, which could indicate a favourable later attachment of cells. Due to their advantageous morphological and physiochemical properties, Zn-MBGNs show great potential as bioactive fillers or drug delivery systems in a variety of applications including bone regeneration and wound healing.

Mesoporous bioactive glass (BG) nanoparticles based in the system: SiO-PO-CaO-MnO were synthesized via a modified Stöber process at various concentrations of Mn (0-7 mol %). The synthesized manganese-doped BG nanoparticles were characterized in terms of morphology, composition, in vitro bioactivity and antibacterial activity. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Brunauer-Emmett-Teller (BET) analysis confirmed that the particles had spherical morphology (mean particle size: 110 nm) with disordered mesoporous structure. Energy dispersive X-ray spectroscopy (EDX) confirmed the presence of Mn, Ca, Si and P in the synthesized Mn-doped BG particles. Moreover, X-ray diffraction (XRD) analysis showed that Mn has been incorporated in the amorphous silica network (bioactive glass). Moreover, it was found that manganese-doped BG particles form apatite crystals upon immersion in simulated body fluid (SBF). Inductively coupled plasma atomic emission spectroscopy (ICP-OES) measurements confirmed that Mn is released in a sustained manner, which provided antibacterial effect against Bacillus subtilis, Pseudomonas aeruginosa and Staphylococcus aureus. The results indicate that the incorporation of Mn in the bioactive glass network is an effective strategy to develop novel multifunctional BG nanoparticles for bone tissue engineering.

In this study, chitosan/bioactive glass (BG)/lawsone coatings were deposited by electrophoretic deposition (EPD) on polyetheretherketone (PEEK)/BG layers (previously deposited by EPD on 316-L stainless steel) to produce bioactive and antibacterial coatings. First, the EPD of chitosan/BG/lawsone was optimized on stainless steel in terms of suspension stability, homogeneity and thickness of coatings. Subsequently, the optimized EPD parameters were used to produce bioresorbable chitosan/bioactive glass (BG)/lawsone coatings on PEEK/BG layers. The produced layered coatings were characterized in terms of composition, microstructure, corrosion resistance, in vitro bioactivity, drug release kinetics and antibacterial activity. Ultraviolet/Visible (UV/VIS) spectroscopic analyses confirmed the release of lawsone from the coatings. Moreover, the deposition of chitosan/BG coatings was confirmed by Scanning Electron Microscopy (SEM) and Fourier Transform Infrared spectroscopy (FTIR). The coated specimens presented higher corrosion resistance (10 times) in comparison to that of bare 316-L stainless steel and showed convenient wettability for initial protein attachment. The presence of lawsone in the top layer provided antibacterial effects against Staphylococcus carnosus. Moreover, the developed coatings formed apatite-like crystals upon immersion in simulated body fluid, indicating the possibility of achieving close interaction between the coating surface and bone. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 3111-3122, 2018.

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The question how bioactive glasses (BGs) influence the viability and osteogenic differentiation of human osteogenic cells has already been addressed by several studies.However, a literature review revealed great differences in the type of cells used for these experiments. Primary human osteoblasts (hOBs) represent the desired standard, but possess the limitation of patient variability and time-consuming isolation protocols. Therefore, several alternative cell types have been used including primary mesenchymal stromal cells (BMSCs) and the "osteoblast-like" cell lines MG-63, Saos-2, HOS, and U2OS. The aim of our study was the identification of the cell type most suitable for tissue engineering projects involving BGs by comparative analysis of cell viability and osteogenic differentiation in response to crystallized 45S5-BG. We observed that hOBs, BMSCs, and MG-63 cells were resistant to 45S5-BG induced cytotoxicity, while the viability of Saos-2, HOS, and U2OS cells was significantly reduced. In addition, we detected alkaline phosphatase activity, except in U2OS cells, that increased upon 45S5-BG cocultivation, demonstrating the induction of osteogenic differentiation. Our data and the fact that the donor-dependent variations can be avoided when using MG-63 cells suggest that these are a promising alternative to primary cells and remain an important cell line for future BG related studies.