Samaneh Saber-Samandari

Efficient removal of lead (II) ions and methylene blue from aqueous solution using chitosan/Fe-hydroxyapatite nanocomposite beads.

Chitosan is a well-known sorbent and effective in the uptake of anionic or reactive dyes, but it has deficiency in adsorption of basic dyes. In this work, chitosan/Fe-substituted hydroxyapatite composite beads were prepared in a different ratio via embedding of hydroxyapatite into chitosan solution for removal of basic dye and heavy metal from aqueous solution. The composite beads were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy in order to reveal their composition and surface morphology. In this particular study, methylene blue (MB) and lead (Pb (II)) ions were selected as representatives of dye and a heavy metal, respectively. The various experimental conditions affecting dye adsorption were explored to achieve maximum adsorption capacity. Moreover, the kinetic, thermodynamic and adsorption isotherm models were employed for the description of the heavy metal and dye adsorption processes. The results indicated that the prepared hydrogel is an efficient adsorbent for the aforementioned dye and metal concomitant with the ability of regeneration without losing the original activity and stability for water treatment applications.

Micro-Raman spectroscopy shows how the coating process affects the characteristics of hydroxylapatite

The diversity in the structural and chemical state of apatites allows implant manufacturers to fine-tune implant properties. This requires suitable manufacturing processes and characterization tools to adjust the amorphous phase and hydroxyl content from the source hydroxylapatite. Hydroxylapatite was processed by high-velocity oxy-fuel spraying, plasma spraying and flame spraying, and primarily analyzed by Raman spectroscopy. Investigation of rounded splats, the building blocks of thermal spray coatings, allowed correlation between the visual identity of the splat surface and the Raman spectra. Splats were heat-treated to crystallize any remaining amorphous phase. The ν1 PO4 stretching peak at 950-970 cm(-1) displayed the crystalline order, but the hydroxyl peak at 3572 cm(-1) followed the degree of dehydroxylation. Hydroxyl loss was greatest for flame-sprayed particles, which create the longest residence time for the melted particle. Higher-frequency hydroxyl peaks in flame- and plasma-sprayed splats indicated a lower structural order for the recrystallized hydroxylapatite within the splats. Crystallization at 700 °C has shown potential for revealing hydroxyl ions previously trapped in amorphous calcium phosphate. This work compares Fourier transform infrared and Raman spectroscopy to measure the hydroxyl content in rapidly solidified apatites and shows that Raman spectroscopy is more suitable.

Efficient Removal of Anionic and Cationic Dyes from an Aqueous Solution Using Pullulan-graft-Polyacrylamide Porous Hydrogel

A pullulan-graft-polyacrylamide porous hydrogel was prepared by radical polymerization in the presence of a crosslinking agent (N,N′-methylenebisacrylamide). Then, the swelling behavior of the hydrogel and the kinetics of swelling were investigated. The novel synthesized hydrogel was used as an adsorbent for removal of dyes from aqueous solutions. In this study, methylene blue (MB) and reactive blue 2 (RB) were selected as representative cationic and anionic dyes, respectively. The synthesized porous hydrogel exhibited excellent adsorption ability for both dyes. Various experimental conditions affecting the dye adsorption were explored to achieve maximum removal of both dye molecules. In addition, kinetic, thermodynamic, and adsorption isotherm models were employed to describe the dye adsorption process. The results indicated that the prepared hydrogel is an efficient adsorbent for dyes and possesses the ability to be regenerated without losing its original activity and stability for water treatment applications.

Removal of Mercury (II) from Aqueous Solution using Chitosan-graft-Polyacrylamide Semi-IPN Hydrogels

Chitosan-graft-polyacrylamide semi-interpenetrating polymer network (IPN) superabsorbent hydrogel was prepared via UV irradiation and N, N′-methylene-bis-acrylamide was used as crosslinker. The product was characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction analysis (XRD), and scanning electron microscopy (SEM). The hydrogels were observed to exhibit as much as 2580.2% swelling under optimum reaction conditions. The hydrogel is an efficient selective sorbent for the removal of mercuric ions (Hg(II)) from aqueous solutions. The mercury sorption capacity under non-buffered conditions is achieved around 9.98 mmol · g−1 (or 2001.8 mg (mercury)/g (hydrogel)) via the colorimetric method. The kinetic data were fitted to the pseudo second order model. Furthermore, the influence of pH, hydrogel dose, and initial mercury concentration on adsorption capacity of the semi-IPN hydrogel was evaluated. Also, the isothermal adsorption equilibrium data was described using the Langmuir model. Finally, the mercury loaded hydrogel was regenerated without losing its original activity and stability.

The impact of functionalized CNT in the network of sodium alginate-based nanocomposite beads on the removal of Co(II) ions from aqueous solutions.

Significant efforts have been made to develop highly efficient adsorbents to remove radioactive Co(II) ion pollutants from medical and industrial wastewaters. In this study, amide group functionalized multi-walled carbon nanotube (CNT-CONH2) imprinted in the network of sodium alginate containing hydroxyapatite, and new nanocomposite beads were synthesized. Then, they were characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction analysis (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS). The prepared nanocomposite beads were used as an adsorbent of Co(II) ions from an aqueous solution. The presence and distribution of Co(II) ions in the surface of the nanocomposite beads was confirmed using FESEM, EDS and metal mapping analysis. The effect of various experimental conditions such as time, pH, and initial concentration of the adsorbate solution and temperature on the adsorption capacity of the nanocomposite beads were explored. The maximum Co(II) ions adsorption capacity of the prepared nanocomposite beads with the largest surface area of 163.4m(2)g(-1) was 347.8mgg(-1) in the optimized condition. The adsorption mechanism followed a pseudo-second-order kinetic model. Furthermore, the Freundlich appears to produce better fit than the Langmuir adsorption isotherm. Finally, thermodynamic studies suggest that endothermic adsorption process of Co(II) ions is spontaneous and thermodynamically favorable.

In vitro evaluation for apatite-forming ability of cellulose-based nanocomposite scaffolds for bone tissue engineering.

Research on synthetic bioactive bone graft materials has significantly expanded in the past decade. In this study, the nanocomposite scaffold of semi-interpenetrating networks (semi-IPN) cellulose-graft-polyacrylamide/nano-hydroxyapatite was synthesized through free radical polymerization. The scaffolds were fabricated by the freeze-drying technique. The prepared semi-IPN nanocomposite scaffolds were characterized by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and X-ray diffraction (XRD) analysis. In addition, the mechanical properties (i.e., elastic modulus and compressive strength) of the scaffolds were investigated. The SEM images showed that the pores of the scaffolds were interconnected, and their sizes ranged from 120 μm to 190 μm. Under optimum conditions, the prepared scaffolds had a compressive strength of 4.80 MPa, an elastic modulus of 0.29 GPa and a value of 47.37% porosity. Furthermore, the apatite-forming ability of the scaffolds was determined using simulated body fluid (SBF) for 28 days. The results revealed that the new apatite particles could grow on the surface of the scaffolds after a 14-day immersion in SBF. Finally, this study suggests that the prepared semi-IPN nanocomposites that closely mimic the properties of bone tissue could be a promising scaffold for bone tissue engineering.

Cellular compatibility of nanocomposite scaffolds based on hydroxyapatite entrapped in cellulose network for bone repair

In the past few decades, artificial graft materials for bone tissue engineering have gained much importance. In this study, novel porous 3D nanocomposite scaffolds composed of polyacrylamide grafted cellulose and hydroxyapatite were proposed. They were characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction analysis (XRD). The swelling behavior of the scaffolds was examined in both water and phosphate buffer saline (PBS) solution. The cytotoxicity of the scaffolds was determined by MTT assays on human fibroblast gum (HuGu) cells. Results showed that the nanocomposite scaffolds were highly porous with maximum porosity of 85.7% interconnected with a pore size of around 72-125μm. The results of cell culture experiments showed that the scaffolds extracts do not have cytotoxicity in any concentration. Obtained results suggested that the introduced scaffolds are comparable with the trabecular bone from the compositional, structural, and mechanical perspectives and have a great potential as a bone substitute.

Biocompatible nanocomposite scaffolds based on copolymer-grafted chitosan for bone tissue engineering with drug delivery capability

Significant efforts have been made to develop a suitable biocompatible scaffold for bone tissue engineering. In this work, a chitosan-graft-poly(acrylic acid-co-acrylamide)/hydroxyapatite nanocomposite scaffold was synthesized through a novel multi-step route. The prepared scaffolds were characterized for crystallinity, morphology, elemental analysis, chemical bonds, and pores size in their structure. The mechanical properties (i.e. compressive strength and elastic modulus) of the scaffolds were examined. Further, the biocompatibility of scaffolds was determined by MTT assays on HUGU cells. The result of cell culture experiments demonstrated that the prepared scaffolds have good cytocompatibility without any cytotoxicity, and with the incorporation of hydroxyapatite in their structure improves cell viability and proliferation. Finally, celecoxib as a model drug was efficiently loaded into the prepared scaffolds because of the large specific surface area. The in vitro release of the drug displayed a biphasic pattern with a low initial burst and a sustained release of up to 14days. Furthermore, different release kinetic models were employed for the description of the release process. The results suggested that the prepared cytocompatible and non-toxic nanocomposite scaffolds might be efficient implants and drug carriers in bone-tissue engineering.

Synthesis, Characterization and Application of Cellulose Based Nano-Biocomposite Hydrogels

Nano-hydroxyapatite/cellulose-graft-polyacrylamide biocomposite hydrogels of different molar ratios were prepared to examine their potential application as a carrier for colon targeted drug delivery in vitro. The particle size of the synthesized nano-hydroxyapatite was found to be 122 nm. The swelling behavior of the composite hydrogels was observed in acidic and basic aqueous solution that simulated lower small intestine, colon and stomach fluids. The hydrogel could be applied in drug-delivery systems and acetylsalicylic acid was used as a model compound to test such a possibility. Finally, the synthesized biocomposite hydrogels with the 96.97% maximum encapsulation and 85.67% release efficiency in the basic medium were found to be a suitable candidate to carry and release of colon-targeted drugs.

Photoinduced Graft Copolymerization onto Chitosan Under Heterogeneous Conditions

Photoinitiated graft copolymerization of acrylamide onto chitosan under heterogeneous conditions and in the absence of a photo initiator was investigated. The effect of irradiation time, the amount of chitosan and monomer concentration on the extent of grafting was examined. The maximum grafting percentage obtained was 294%. The copolymer was characterized using carbon-13 nuclear magnetic resonance (13C-NMR) spectroscopy, X-ray diffraction analysis (XRD), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The system designed allows synthesis of grafted chitosan with free amine groups which are otherwise possible only by chemical protection. The swelling properties of copolymer were followed in aqueous solution.