Effect of titanium dioxide intermediate layer on scratch and corrosion resistance of sol-gel-derived HA coating applied on Ti-6Al-4V substrate.

Modification of dental and orthopedic implants' surface by coating them with bioactive materials, such as hydroxyapatite (HA), diminishes the implants' fixation time. Appropriate adhesion to the substrate and stability in biological conditions are essential requirements for these coatings. In this study, sol-gel-derived HA coating was applied on the Ti-6Al-4 V substrate, which is a high-performance alloy for manufacturing bone implants. Also, titanium dioxide (TiO2) which was prepared by the sol-gel method was used as an intermediate layer between HA coating and the substrate. The nano-scratch and potentiodynamic polarization tests were employed to evaluate the effectiveness of TiO2 intermediate layer on improving the scratch resistance, as an indicator of coating adhesion strength, and the corrosion resistance of the coated samples. The quality of the coating bonded to the substrate was studied by cross-sectional SEM images. The XRD tests indicated that HA and TiO2 coatings were formed with predetermined phase compositions. The biocompatibility of sol-gel-derived HA coating was established by simulated body fluid (SBF) immersion tests. The SEM images, along with the results of electrochemical and nano-scratch tests, proved the significant effect of a TiO2 intermediate layer on improving the scratch resistance and stability of HA coating on titanium alloy substrate.

Enhancing degradability, bioactivity, and osteocompatibility of poly (propylene fumarate) bone filler by incorporation of Mg-Ca-P nanoparticles.

As an alternative for polymethyl methacrylate, poly(propylene fumarate) (PPF) has been considered as injectable and biodegradable bone cement; however, its mechanical and biological properties need more attention. Hence, the current study aimed to develop the properties by compositing PPF with magnesium calcium phosphate (MCP) nano-powders. In this regard, the pure PPF was compared with PPF/MCP by evaluating their composition, mechanical properties, hydrophilicity, and biodegradability. Furthermore, their bioactivity in the simulated body fluid (SBF) and, via applying MG-63 cells, their cell interaction, including proliferation, adhesion, differentiation, and mineralization, were assessed. The addition of MCP improved compressive strength and elastic modulus of PPF, e.g., 10 wt% MCP increased them to 32.7 and 403 MPa, respectively. Also, hydrophilicity and biodegradation of PPF were enhanced in the presence of MCP; so that the highest hydrophilicity, 42% higher than PPF, was achieved at the presence of 20 wt% MCP. In this condition, after 21-day immersion in SBF, the surface of the sample was covered with a dense and continuous layer of hydroxyapatite. The composite proliferation, adhesion, differentiation, and mineralization of MG-63 cells improved in comparison to the pure PPF. Hence, controllable strength and biodegradation of the composite, along with its proved bioactivity and osteoconductivity, make PPF/MCP as a candidate for bone therapeutic application.

Poly(propylene fumarate)/magnesium calcium phosphate injectable bone composite: Effect of filler size and its weight fraction on mechanical properties.

This study aimed to produce a composite of poly(propylene fumarate)/magnesium calcium phosphate as a substitutional implant in the treatment of trabecular bone defects. So, the effect of magnesium calcium phosphate particle size, magnesium calcium phosphate:poly(propylene fumarate) weight ratio on compressive strength, Young's modulus, and toughness was assessed by considering effective fracture mechanisms. Micro-sized (∼30 µm) and nano-sized (∼50 nm) magnesium calcium phosphate particles were synthesized via emulsion precipitation and planetary milling methods, respectively, and added to poly(propylene fumarate) up to 20 wt.%. Compressive strength, Young's modulus, and toughness of the composites were measured by compressive test, and effective fracture mechanisms were evaluated by imaging fracture surface. In both micro- and nano-composites, the highest compressive strength was obtained by adding 10 wt.% magnesium calcium phosphate particles, and the enhancement in nano-composite was superior to micro-one. The micrographs of fracture surface revealed different mechanisms such as crack pinning, void plastic growth, and particle cleavage. According to the results, the produced composite can be considered as a candidate for substituting hard tissue.

Evaluation of setting time and compressive strength of a new bone cement precursor powder containing Mg-Na-Ca.

Taking the advantage of a novel magnesium phosphate precursor containing Na and Ca, the cementation rate of the cement, including only Mg/Mg-Na-Ca, was studied. Besides, two effective parameters, that is, calcination temperature, 650 °C and 800 °C, and powder-to-cement liquid ratio, 1 and 1.5 g/mL, were assessed. X-ray diffraction, scanning electron microscopy, ion chromatography, particle size analyser, Vicat needle and compression test were used to characterize the powders and obtained cements. The sample containing Mg-Na-Ca, calcined at 800 °C with powder-to-cement liquid ratio of 1.5, obtained the highest compressive strength, 20 MPa, but set fast. To control the kinetics of cementation, the powder containing Mg-Na-Ca calcined at 950 °C with powder-to-cement liquid ratio of 1.5 and 2 g/mL was assessed and the one with 2 g/mL set in 9 min possessing 22 MPa compressive strength was selected as optimal condition to be used as a candidate, injectable bone cement.

Influence of RGD grafting on biocompatibility of oxidized cellulose scaffold.

Cellulose powder was oxidized by NO2 gas and the porous scaffold was fabricated by dry pressing. RGD peptide was immobilized on the surface of scaffold by grafting to make a hybrid scaffold. The hybrid scaffold was characterized by SEM and FTIR and its biocompatibility was examined through MTT assay. FTIR results proved oxidization of cellulose and bonding between scaffold surface and RGD. Porous microstructure having suitable size was confirmed by SEM. The results by MTT showed significant increase of viable cells on hybrid scaffold. Porous structure and high biocompatibility were the benefits of scaffold in bone tissue engineering.

Preparation of a novel biodegradable nanocomposite scaffold based on poly (3-hydroxybutyrate)/bioglass nanoparticles for bone tissue engineering.

One of the most important challenges in composite scaffolds is pore architecture. In this study, poly (3-hydroxybutyrate) with 10% bioglass nanoparticles was prepared by the salt leaching processing technique, as a nanocomposite scaffold. The scaffolds were characterized by SEM, FTIR and DTA. The SEM images demonstrated uniformed porosities of appropriate sizes (about 250-300 microm) which are interconnected. Furthermore, higher magnification SEM images showed that the scaffold possesses less agglomeration and has rough surfaces that may improve cell attachment. In addition, the FTIR and DTA results showed favorable interaction between polymer and bioglass nanoparticles which improved interfaces in the samples. Moreover, the porosity of the scaffold was assessed, and the results demonstrated that the scaffold has uniform and high porosity in its structure (about 84%). Finally it can be concluded that this scaffold has acceptable porosity and morphologic character paving the way for further studies to be conducted from the perspective of bone tissue engineering.