Formation mechanism of nano-hardystonite powder prepared by mechanochemical synthesis

Baghdadite: A Novel and Promising Calcium Silicate in Regenerative Dentistry and Medicine

For several years, ceramic biomaterials have been extensively utilized to rebuild and substitute for body tissues. Calcium silicates have been proven to exhibit excellent bioactivity due to apatite formation and cell proliferation stimulation, in addition to degradability at levels adequate for hard tissue formation. These ceramics' excellent biological characteristics have attracted researchers. Baghdadite is a calcium silicate incorporating zirconium ions that enhances human osteoblast multiplication and development, increasing mineralization, and ossification. It has currently received much interest in academic institutions and has been extensively explored in the form of permeable frameworks, varnishes, bone adhesive and gap fillings, microparticles, and nanospheres, particularly in a wide range of biomedical applications. This review article aims to summarize and analyze the most recent research on baghdadite's mechanical characteristics, apatite-forming capability, dissolution pattern, and physiochemical qualities as a scaffold for dentofacial tissuè regeneration purposes.

Intumescent Silicate Coatings with the Addition of Alkali-Activated Materials

Fireproof inorganic coatings based on sodium silicate solution with intumescent additions were prepared and tested to assess their ability to limit the negative effect of a fire. The intumescent materials were obtained by the alkali activation of waste glass powder (obtained by the grinding of recycled soda-lime culet) and slag (waste resulting from the metallurgical industry). The replacement of talc (used as filler in paint formulation) with the intumescent materials obtained by the alkaline activation of waste glass powder (WGP), determined an increase in the intumescence coefficient (up to 65%) and decreased the activation temperature of this process. To evaluate these coatings’ abilities to prevent or delay the temperature increase in metal structures, the paints were applied on steel plates and tested in direct contact with the flame of a butane burner for 60 min. The coatings prevented the increase in the steel substrate temperature over one considered critical (500°C) for steel mechanical properties; the combination of two coatings, with different intumescence activation temperatures, correlated with the increase in the coating’s thickness, sensibly reduced the rate of temperature increase (up to 75%) in the steel substrate.

CNT and rGO reinforced PMMA based bone cement for fixation of load bearing implants: Mechanical property and biological response

Polymethyl methacrylate (PMMA) bone cements (BCs) have some drawbacks, including limited bioactivity and bone formation, as well as inferior mechanical properties, which may result in failure of the BC. To deal with the mentioned issues, novel bioactive polymethyl methacrylate-hardystonite (PMMA-HT) bone cement (BC) reinforced with 0.25 and 0.5 wt% of carbon nanotube (CNT) and reduced graphene oxide (rGO) was synthesized. In this context, the obtained bone cements were evaluated in terms of their mechanical and biological characteristics. The rGO reinforced bone cement exhibited better mechanical properties to the extent that the addition of 0.5 wt% of rGO where its compressive and tensile strength of bioactive PMMA-HT/rGO cement escalated from 92.07 ± 0.72 MPa, and 40.02 ± 0.71 MPa to 187.48 ± 5.79 MPa and 64.92 ± 0.75 MPa, respectively. Besides, the mechanisms of toughening, apatite formation, and cell interaction in CNT and rGO encapsulated PMMA have been studied. Results showed that the existence of CNT and rGO in BCs led to increase of MG63 osteoblast viability, and proliferation. However, rGO reinforced bone cement was more successful in supporting MG63 cell attachment compared to the CNT counterpart due to its wrinkled surface, which made a suitable substrate for cell adhesion. Based on the results, PMMA-HT/rGO can be a proper bone cement for the fixation of load-bearing implants.

Bioactivity Behavior Evaluation of PCL-Chitosan-Nanobaghdadite Coating on AZ91 Magnesium Alloy in Simulated Body Fluid

Polymer–ceramic composite coatings on magnesium-based alloys have attracted lots of attention in recent years, to control the speed of degradability and to enhance bioactivity and biocompatibility. In this study, to decrease the corrosion rate in a simulated body fluid (SBF) solution for long periods, to control degradability, and to enhance bioactivity, polycaprolactone–chitosan composite coatings with different percentages of baghdadite (0 wt.%, 3 wt.%, and 5 wt.%) were applied to an anodized AZ91 alloy. According to the results of the immersion test of the composite coating containing 3 wt.% baghdadite in a phosphate buffer solution (PBS), the corrosion rate decreased from 0.45 (for the AZ91 sample) to 0.11 mg/cm2·h after seven days of immersion. To evaluate the apatite formation capability of specimens, samples were immersed in an SBF solution. The results showed that the samples were bioactive as apatite layers formed on the surface of specimens. The composite coating containing 3 wt.% baghdadite showed the highest apatite-formation capability, with a controlled release of ions, and the lowest corrosion rate in the SBF.

The influence of polycaporolacton fumarate coating on mechanical properties and in vitro behavior of porous diopside-hardystonite nano-composite scaffold

One of the significant challenges in bone tissue engineering is the fabrication of highly porous scaffolds with interconnected pores and appropriate mechanical properties. Artificial scaffolds which used in the field of medicine are usually made of single phase of polymer or ceramic. However, composition of these materials can produce the scaffolds with improve mechanical and biological properties.The aim of this study is to synthesize three-dimensional hardystonite-diopside (HT-Dio) porous scaffolds modified by polycaporolacton fumarate coating for low-load-bearing bone tissue engineering applications. The results showed that hardystonite scaffolds with 15 wt. % diopside and 6 w/v % polymer polycaporolacton fumarate (PCLF) had a significant bioactivity. The cell culture and cell attachment assay results revealed the well spreading of BMS cells on the surface of modified scaffolds which indicates the high biocompatibility of this scaffold. The modified scaffolds had a mean pore size, porosity, compressive strength, modules and toughness of 293.47 ± 5.51 μm, 74% ± 1.01, 3.37 ± 0.6 MPa, 151 ± 1.1 MPa and 31.3 ± 0.32 kJ/m³, respectively, which are in the appropriate range for spongy bone and hence can be a good candidate for bone tissue engineering applications.

In vitro evaluation of diopside/baghdadite bioceramic scaffolds modified by polycaprolactone fumarate polymer coating

Porous Si-based ceramic scaffolds are widely attracted in biomedical tissue engineering application. Despite the attractive properties of these materials, their weak mechanical properties and high degradability in vitro and in vivo environment can limit their application as biomedical devises. Applying a thin layer of polymer on the surface of porous scaffolds can improve the mechanical properties and control the degradation rate. In this study, we produced new modified scaffolds with polymers coating in order to improved mechanical and biological properties of Si-based ceramics scaffolds. The results showed that applying 6 wt% PCLF polymer on the surface of Bagh-15 wt%Dio scaffolds delayed apatite formation compared to unmodified scaffolds. On the other hand, in the modified scaffolds, apatite formation was observed. The degradation rate of unmodified scaffolds was decreased around 82% after 28 days soaking in PBS solution. Based on the MTT assay and SEM micrographs, the BMS cells were spread and attached well on the surface of the scaffolds, which indicated a good biocompatibility. The results showed that these scaffolds have the potential to be used as a temporary substrate for bone tissue engineering application.

A novel, doped calcium silicate bioceramic synthesized by sol-gel method: Investigation of setting time and biological properties

The aim of the current study was to synthesize a fast-setting ion-doped calcium silicate bioceramic by the sol-gel method and to characterize its in vitro apatite-forming ability and cell viability. Calcium silicate (CS), doped calcium silicate with zinc and magnesium, with Ca/Zn molar ratios of 6.7:1 (DCS1), and 4.5:1 (DCS2), were synthesized by the sol-gel method. Matreva white MTA (WMTA, Matreva, CA, Egypt) was used as a control. The synthesized powders were characterized by x-ray diffraction. Setting time was measured using the Gilmore needle indentation technique. The in vitro apatite-forming ability of the materials was evaluated by scanning electron microscope and energy dispersive X-ray. NIH3T3-E1 cells viability was tested using MTT assay. The ion release of Ca, Si, Zn, and Mg was measured using inductive coupled plasma-optical emission spectroscopy (ICP-OES). One-way ANOVA was used to analyze setting time results. The Tukey's HSD post hoc test was used to establish significance (p < 0.001). For nonparametric data, the Kruskal-Wallis H test with Dunn's correction for post hoc comparison was used (p < 0.05). CS, DCS1, and DCS2 showed a significant decrease in setting time 33 ± 1.63 min, 28 ± 1.63 min, and 41.75 ± 2.87 min, respectively, compared to WMTA 91 ± 3.16 min (p < 0.001). DCS1 showed the highest apatite-forming ability and cell viability compared to the other groups. Ca and Si ions release decreased in both DCS1 and DCS2. The physical and biological properties of CS can be successfully improved by the sol-gel synthesis and ions doping. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 108B:56-66, 2020.