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The biodegradability of magnesium (Mg) metal implants necessitates surface modification to mitigate the high corrosion rate in the body's physiological environment. This study focuses on synthesizing and applying a nanocomposite coating of polydimethylsiloxane-nanosized bioactive glass (PDMS-nBG) on the surface of a plasma electrolytic oxidation (PEO)-modified AZ91 Mg alloy. The PDMS-1 wt% nBG nanocomposite coating was deposited on the PEO-treated substrate using the dip-coating method. Surface and cross-sectional morphologies of the nanocomposite coatings were examined using field emission scanning electron microscopy (FESEM). Corrosion behavior of the AZ91 substrate, PEO coating, and double-layer PEO/PDMS-nBG coating was investigated using electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) tests. Results showed that the corrosion resistance and corrosion current density of Mg substrates increased and decreased from 4815 Ω.cm2 and 8.96 µA.cm− 2 to 18 MΩ.cm2 and 0.00016 µA.cm− 2 for AZ91 and PEO/PDMS-nBG coating, respectively. Additionally, the morphology and adhesion of cultured human mesenchymal cells on the PEO-modified AZ91 substrates with a single PDMS polymer coating and a PDMS-nBG nanocomposite coating were investigated using fluorescent light microscopy and FESEM. The PEO/PDMS-nBG bilayer coating effectively addressed the limitations of magnesium alloys and holds potential for biomedical applications, particularly in orthopedic implants, due to the enhanced biocompatibility and bioactivity of Mg alloys. [ABSTRACT FROM AUTHOR]

To improve the corrosion behavior of a magnesium alloy, two-step coatings have been fabricated through plasma electrolytic oxidation coating (PEO) under constant voltage conditions applied to the AZ91 substrate surface in the silicate electrolyte. A polymeric layer [Polydimethylsiloxane (PDMS)] has been successfully implemented by the immersion method on both bare AZ91 alloy and pre-treated samples by the PEO process. PEO coating contains MgO, MgSiO3, and Mg2SiO4 phases detected by X-ray diffraction patterns (XRD). The surface morphology observation investigated using the field emission scanning electron microscopy (FESEM) showed a porous and non-porous layer on the substrate for PEO and PEO/PDMS coatings, respectively. The topography and roughness of the PEO coating evaluated by atomic force microscopy (AFM) revealed a high roughness for the PEO coating. The chemical composition of coatings was determined using X-ray energy distribution spectroscopy (EDS), and the corrosion behavior of the AZ91 substrates with/without coating was studied by the potentiodynamic polarization test in the Ringer solution. The results showed that the corrosion (Ecorr) potential of the AZ91 substrate increased compared to a single-layer PDMS coating from − 1.48 to − 1.47 V, and their corrosion current density (icorr) reduced from 4.3 to 0.486 µA·cm−2 in the order given. However, by applying PEO coating as a pre-treatment utilizing the PEO/PDMS composite coating, these values were obtained − 0.75 V and 0.9 nA·cm−2, respectively. So, applying PEO/PDMS hybrid coating may effectively reduce the high corrosion rates of magnesium alloys as the main limitations in the physiological environment. [ABSTRACT FROM AUTHOR]

This research aimed at fabrication of baghdadite scaffolds with chitosan coating via combining of polymeric sponge replication and dip-coating methods with improved mechanical and biological properties. The composite was characterized using x-ray diffraction, Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). Porosity, compressive strength, in vitro bioactivity and biological responses of human bone marrow mesenchymal stem cells were evaluated. The porosity percentage and compressive strength values were 79 ± 0.87 and 2.88 ± 0.34, respectively. The results showed chitosan coating could largely enhance the mechanical strength of baghdadite scaffolds. Also apatite-like layer formation was observed. Based on the MTT assay and SEM micrographs, human bone marrow mesenchymal stem cells were spread and attached well on the surface of the scaffold, which indicated a high biocompatibility. The results showed that this composite scaffold has the potential to be used as a temporary substrate for bone tissue engineering applications. [ABSTRACT FROM AUTHOR]

Bioceramic coatings have had a significant impact on the realm of biomaterials and medical devices in recent decades. In this study, synthesized hardystonite coating (Ca2ZnSi2O7) by sol–gel method was applied on titanium substrate (Ti-6Al-4V) using electrophoretic deposition method. XRD patterns and EDX result confirm the pure hardystonite phase structure. Transmission electron microscopy was confirmed the appeared round morphology and nanometer size of the synthesized hardystonite particles. Additionally SEM analysis was approved that the hardystonite coating is able to make a uniform and flawless apatite with needle-like and cauliflower forms during prolonged exposure to SBF. The Ringer’s solution Tafel test results were indicated that the corrosion resistance of twice-coated samples is increased by increasing the voltage to 50 Voltages so that the corrosion current density in the twice coated samples is less than the bare samples. In vitro evaluation by MTT assay was confirmed the viability of the bone marrow stem cells so that hardystonite increases the vitality and reproduction of stem cells at low concentration which makes the hardystonite coating a suitable candidate for clinical applications. [ABSTRACT FROM AUTHOR]

Recently, porous bioceramics are widely used in bone tissue engineering in order to the regeneration of damaged tissues. Piezoelectric effect in bone plays a very important role in bone regeneration. Therefore, the purpose of this study was the fabrication of porous barium titanate (BT)/nanobioglass (nBG) scaffold (vol.% BT = 75% and 90%) with high piezoelectric coefficient by freeze casting technique. For this purpose, BT and nBG powders were synthesized using solid-state and sol–gel methods, respectively. Partial recrystallization of nBG phase during sintering process occurred. The highly oriented lamellar microstructure of the fabricated BT90/nBG10 scaffold with open/interconnected porosities observed. The BT75/nBG25 composite scaffold exhibited higher value of density (1.18 ± 0.1 g/cm3) and lower amount of porosities (77 ± 1%) compared to the BT90/nBG10 scaffold (0.99 ± 0.1 g/cm3 and 82 ± 1%). The piezoelectric coefficients of the BT90/nBG10 and BT75/nBG25 composite scaffolds obtained 36 pC/N and 24 pC/N which were much higher than that of the natural human bone. The BT75/nBG25 scaffold showed more compressive strength (16.9 ± 1.1 MPa) than that of BT90/nBG10 composite scaffold (8.1 ± 0.3 MPa). The MTT results after 24, 72 and 168 h of culture showed that both composites had acceptable cell viability and cells were able to adhere, proliferate and migrate into pores of the scaffolds. Furthermore, cell density and adhesion were little bit higher in the BT75/nBG25 composite. These results indicated that highly porous barium titanate scaffolds have great potential in tissue engineering applications for bone tissue repair and regeneration. [ABSTRACT FROM AUTHOR]

In this study, the effect of grain size on the mechanical properties and hydrogen embrittlement of a NiTi shape memory alloy (SMA) was investigated. Samples with different grain sizes were prepared through different annealing processes. For creating and evaluating hydrogen embrittlement, samples were immersed in an aqueous solution of 2% acidulated phosphate fluoride (APF) for 8, 16, and 72 h. Optical microscopy (OM), scanning electron microscopy (SEM), tensile test, and three-point bending test were conducted to characterize the samples. Results demonstrated samples with large grain sizes to be more susceptible to hydrogen embrittlement. Improvement in shape memory properties was achieved at smaller grain sizes. Besides, with increasing the immersion time, fracture stress reduced, while detwinning stress increased. Overall, the results of this study have demonstrated that grain refinement can bring about improved mechanical properties and abated hydrogen embrittlement in NiTi alloys, which can be of vital importance in biomedical applications. [ABSTRACT FROM AUTHOR]

Polycaprolactone (PCL) based nanocomposite scaffolds containing graphene (Gr) and baghdadite (BAG) nanoparticles were fabricated using the electrospinning method. Mechanical properties of the scaffolds were evaluated. Viability and adhesion of cells on the scaffolds were confirmed using fluorescence optical microscopy, MTT and FE-SEM analysis methods. The results indicated that incorporation of various concentrations of BAG from 1 to 3 wt% notably improved the mechanical properties. Cell adhesion assay revealed that the addition of BAG nanoparticles to PCL-Gr scaffold caused further adhesion, viability, and proliferation of the cells. [ABSTRACT FROM AUTHOR]