Erfan Salahinejad

Introduction: Epigallocatechin-3-gallate (EGCG) is a green-tea catechin with well-documented antiproliferative activity, but its short half-life and poor stability in physiological media limit its application. This study aimed to develop chitosan-coated poly(lactic-co-glycolic acid) (PLGA) core-shell nanoparticle carriers for EGCG, with assessing the effect of the chitosan shell on their release kinetics and concentration-response behavior in hepatic carcinoma and non-tumorigenic hepatic cells in vitro. Methods: EGCG-loaded PLGA nanoparticles were prepared by emulsion solvent evaporation at nominal loadings of 0.5, 1, and 1.5 wt% and then coated with chitosan. Morphology and size were characterized by field-emission scanning electron microscopy (FE-SEM), chemical composition by Fourier-transform infrared spectroscopy (FTIR), and EGCG release in phosphate-buffered saline (PBS) up to 30 days by UV-Vis spectroscopy. Release profiles were fitted to the zero-order, first-order, Higuchi and Korsmeyer-Peppas models. Metabolic cell viability was assessed by MTT assay in human hepatocellular carcinoma HepG2 cells and non-tumorigenic hepatic HepaRG cells until 5 days, and the concentration-response data were fitted with a Hill model. Results: The uncoated and chitosan-coated particles had mean diameters of 117 ± 8 and 144 ± 6 nm, respectively, giving an estimated dry shell thickness of 13.5 ± 5.0 nm. The application of the chitosan shell reduced the first 24 h burst release from 25.7 to 10.3– 15.6% and extended the profile to a plateau from 25 to 27 days. Release from the coated formulations was best described by the Higuchi model, with Korsmeyer-Peppas exponents of 0.55– 0.63 indicating anomalous (non-Fickian) transport, against n = 0.46 showing Fickian transport for the uncoated reference. Encapsulation efficiencies were 85.2– 88.8%, corresponding to delivered EGCG doses of 4.26– 12.98 μg mL^{− 1} at the applied nanoparticle concentration of 1 mg mL^{− 1}. HepG2 metabolic viability decreased in a concentration-dependent manner to 26.4 ± 1.8% of the untreated control on day 5, corresponding to 73.6% growth inhibition, with a fitted IC₅₀ of 8.2 μg mL^{− 1}. Over the same dose range, HepaRG viability remained at or above 92.4% and no IC₅₀ was reached (> 13 μg mL^{− 1}). The drug-free carrier was non-cytotoxic in both cell lines. Conclusion: A chitosan shell on EGCG-loaded PLGA nanoparticles suppresses burst release and shifts the transport mechanism from Fickian to anomalous, producing sustained release to 27 days. The resulting formulations reduce HepG2 metabolic viability in a concentration-dependent manner, while leaving HepaRG viability above the ISO 10993– 5 cytotoxicity threshold.

In this paper, the microstructure and mechanical properties of biocompatible Cr-Mn-N austenitic stainless steels produced by powder metallurgy are investigated. Processing is conducted by mechanical alloying of 74Fe-18Cr-8Mn (wt.%) powder mixture under a nitrogen atmosphere, followed by sintering at 1100 ºC for 20 h. The prepared materials are characterized by X-ray diffraction, scanning and transmission electron microscopy, suggesting the development of nanostructures with micron-sized spherical pores. It is also found that by increasing the milling time from 48 to 120 h, the densification is retarded; however, the hardness and compressive yield strength of the nanomaterials are enhanced.

In this paper, the effect of some parameters of a two-step surface-modification process, consisting of alkaline treatment followed by chitosan/bioactive glass nanocomposite coating, on the surface morphology of Ti-6Al-4V alloy is investigated. According to the results, the heat treatment of the alkaline-treated sample is critical to obtain a crack-free structure. It was also found that the deposition of three composite layers with the immersion time of 3 min for each layer is optimal to develop a desirable distribution of the composite nanoparticles on the surface. In other words, a coordinated optimization approach of composite-coating variables is required to control the morphology of the deposits.

One of the important parameters for bone regeneration scaffolds is their mechanical properties, which is the subject of this study in terms of a calcium magnesium silicate, namely bredigite. In this regard, bredigite powders were synthesized by a sol-gel process and then porous bredigite scaffolds were prepared using a polymer sponge method. Sintered bredigite scaffolds were afterwards coated with poly(lactic-co-glycolic acid) (PLGA), and the influence of the PLGA coating on the morphology, porosity and mechanical properties of the bredigite scaffold was investigated. The results showed that the PLGA-coated bredigite scaffolds maintained their porosity size and level required for bone tissue engineering. Typically, the compressive strength of the bredigite/PLGA scaffold was significantly improved compared to the pure bredigite scaffold due to the alteration of porosity.

Zirconium titanate powders were synthesized by a straightforward sol-gel method using zirconium and titanium chlorides as metal precursors, deionized water as solvent and oxygen donor, and a NaOH solution for adjusting pH to 7. According to transmission electron microscopy, amorphous particles of nearly 5 nm in size with a relatively spherical morphology were prepared. Thermogravimetry and differential scanning calorimetery analyses on the xerogel at a heating rate of 10 ºC/min indicated a crystallization temperature of 690 ºC, which is comparable with previous reports. Furthermore, via differential scanning calorimetery studies using the Kissinger's equation, the activation energy for ZrTiO4 crystallization was determined to be 850 kJ/mol. Structural evaluations in the isothermal regime, using X-ray diffraction experiments, implied the onset of ZrTiO4 crystallization at 550 °C.

In this research, a novel group of Ca-Mg oxyfluorosilicates containing different levels of fluoride substituting for oxide was synthesized by an inorganic salt coprecipitation process followed by calcination/sintering. The effects of the incorporation of fluoride on the resultant structural characteristics, apatite-forming ability and biodegradability were evaluated by Xray diffraction, transmission electron microscopy, scanning electron microscopy/energydispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, inductively coupled plasma spectroscopy and pH measurements. According to the results, the samples containing up to 2 mol% F present a single-phase structure of diopside (MgCaSi2O6) doped with F. It was also found that to meet the most biomineralization characteristic, the optimal value of fluoride in the homogeneous samples is 1 mol%. In this regard, on the one hand, the partial incorporation of fluoride into apatite (via forming fluorohydroxyapatite) and, on the other hand, the absence of fluorite (CaF2) as a consumer of Ca in the deposits are responsible for achieving the most apatite-forming ability circumstance controlled by an ion-exchange reaction mechanism. In conclusion, this study reflects the merit of the optimization of fluoride-doping into Ca-Mg silicates for development in biomedicine.

In this research, for the first time, the structure, bioactivity, biodegradation and biocompatibility of SiO2-MgO-CaO glasses doped with different levels of fluoride were studied. The glassy powder samples were synthesized by a coprecipitation method followed by calcination at 500 °C, where amorphicity and fluoride incorporation were verified by Xray diffraction and Raman spectroscopy, respectively. The in vitro biomineralization and biodegradation of the samples were also investigated by electron microscopy, Raman spectroscopy and inductively coupled plasma optical emission spectrometry. These assessments revealed that there is an optimum level of fluoride doping to meet the highest bioactivity. Remarkably, the same level of incorporation presented the foremost biocompatibility with respect to osteoblast-like MG-63 human cells, as realized by the MTT assay and cell attachment studies.

This paper for the first time investigates the sol-gel reaction of magnesium chloride and silicon tetrachloride, directed at the forsterite (Mg2SiO4) stoichiometry, using dry ethanol and glacial acetic acid as the solvent and chelating agent, respectively. The synthesized particles before and after calcination were characterized by transmission electron microscopy equipped with energy-dispersive X-ray spectroscopy mapping, X-ray diffraction and Fourier transform infrared spectroscopy. According to the results, the calcined nanoparticles showed a magnesia/forsterite structure along with silicon depletion, despite loading the forsterite stoichiometry. On the other hand, silicon-acetoxy bonds were detected in the xerogel (before calcination) as a result of the chelation reaction, albeit with a relatively uniform distribution of the essential elements. Since no non-alcoholyzed silicon-chlorine bond was detected in the xerogel, the development of the calcined structure was explained by the deficient sol-gel condensation and subsequent evaporation of silicon tetraacetate. It was inferred that the excessive amount of hydrogen chloride as the coproduct of the ethanolysis and chelation reactions of the precursors inhibits the condensation step, as confirmed by a supplementary test in an exaggerated circumstance. In conclusion, the silicon-containing species acts like a limiting reagent in the sol-gel condensation of forsterite using the chloride precursors and acetic acid chelator, in spite of loading the related stoichiometry.

Zirconium titanate multilayer thin films were prepared by an aqueous particulate sol–gel process followed by spin coating. The obtained structures were studied by transmission electron microscope, scanning electron microscope, atomic force microscope, and spectroscopic reflection analyses. According to the results, sound thin films up to three layers were developed, accompanied by an increase in thickness and roughness by increasing the number of the layers. It was also found that the coatings consist of globular nanoparticles with an average diameter of 50 nm. Considering the contribution of roughness to biological responses, the optimization of the surface characteristics to meet an optimal performance seems to be a challenging issue, which demands future studies.

One of the effective ways to overcome some of the drawbacks of oxide coatings for corrosion protection of metal surfaces is the incorporation of an organic component into the inorganic network, although, commonly, film adhesion is disadvantageously affected. In this work, for the first time, by exploiting both inorganic and organic–inorganic coatings, a new double-layer thin film, which comprises ZrTiO4 as the bottom layer and ZrTiO4–PMMA as the top layer, was deposited on a medical-grade stainless steel substrate via a sol–gel spin coating method. According to potentiodynamic polarization experiments in a simulated body fluid, the substrate coated with this film exhibited superior corrosion resistance, compared with the same steel coated with purely inorganic ZrTiO4 and hybrid ZrTiO4–PMMA films. The superior corrosion resistance of the newly developed coating was found to be due to simultaneously the good adhesion of the lower, inorganic film and the low defect density of the upper, hybrid film.