Andreea Madalina Pandele

Synthesis, characterization, and in vitro studies of graphene oxide/chitosan-polyvinyl alcohol films.

Nanocomposites based on chitosan-polyvinyl alcohol (CS-PVA) and graphene oxide (GO) were prepared by casting the stable aqueous mixture of the components. SEM, TEM and X-ray diffraction showed that graphene oxide is largely dispersed on molecular scale within CS-PVA matrix. FTIR investigation indicated the occurrence of some interaction between graphene oxide nanosheets and CS-PVA. The obtained composites are mechanically strong and exhibit improved thermal stability. By addition of 6 wt.% GO within CS-PVA blend, the elastic modulus increased over 200%. The cell viability and proliferation results showed that MC3T3-E1 mouse osteoblastic cells can adhere and developed on the CS-PVA/GO composite films. A significant proliferation potential was displayed by the cells in contact with CS-PVA/GO 6 wt.%. Graphene oxide reinforced CS-PVA with high mechanical and bioactive properties are potential candidates for tissue engineering.

In vitro cytocompatibility evaluation of chitosan/graphene oxide 3D scaffold composites designed for bone tissue engineering

Extensively studied nowadays, graphene oxide (GO) has a benefic effect on cell proliferation and differentiation, thus holding promise for bone tissue engineering (BTE) approaches. The aim of this study was not only to design a chitosan 3D scaffold improved with GO for optimal BTE, but also to analyze its physicochemical properties and to evaluate its cytocompatibility and ability to support cell metabolic activity and proliferation. Overall results show that the addition of GO in the scaffolds composition improved mechanical properties and pore formation and enhanced the bioactivity of the scaffold material for tissue engineering. The new developed CHT/GO 3 wt% scaffold could be a potential candidate for further in vitro and in vivo osteogenesis studies and BTE approaches.

Epoxy-Based Nanocomposites Reinforced with New Amino Functionalized Multi-Walled Carbon Nanotubes

The aim of the work was to synthesize epoxy-based nanocomposites reinforced with multi-walled carbon nanotubes (MWNT). MWNTs were first functionalized in order to increase the dispersion degree within the polymer matrix and thus to ensure good adhesion between the two components. The functionalization process consists of two steps: first, MWNT were oxidized, and then an amidation reaction occurred with various amines using carbondiimide and succinimide as activators. Thus, new modified MWNT with benzylamine (BA) and nonylphenoxy polypropyleneoxyamine (B100) were synthesized. The nanocomposites obtained were based on diglycidyl ether of bisphenol A (DGEBA) and modified MWNT and were fully characterized by TGA, DMA, XPS, SEM, TEM, and FTIR.

Preparation and characterization of polysulfone/ammonia-functionalized graphene oxide composite membrane material

The study highlights the first use of ammonia-functionalized graphene oxide (GO-NH2) as an additive to enhance the features of polysulfone (PSF) matrix. Composite membrane materials with different ratios of GO-NH2 (0.25, 0.5, 1, and 1.5 wt%) were obtained by phase inversion method. Subsequently structural and morphological characteristics were investigated by Raman spectroscopy, X-ray diffraction (XRD), scanning, and transmission electron microscopy (TEM). Lastly, mechanical and thermogravimetric studies were performed in order to establish whether GO-NH2 addition influenced PSF/GO-NH2 composite material performance. Raman spectroscopy, XRD, and TEM revealed evenly dispersed GO-NH2 within PSF/GO-NH2 composite membrane material forming exfoliated structures for lower concentration of GO-NH2. An enhancement in both mechanical and thermal characteristics was attained. The decomposition temperature at which the mass loss is 3%, of the composite membrane material with 1 wt% GO-NH2 was increased with 7°C. Conversely, an increase in Young’s modulus from 246 MPa to 285 MPa was achieved with the addition of 1 wt% GO-NH2 within the PSF matrix.

Characterization and In Vitro and In Vivo Assessment of a Novel Cellulose Acetate-Coated Mg-Based Alloy for Orthopedic Applications

Despite their good biocompatibility and adequate mechanical behavior, the main limitation of Mg alloys might be their high degradation rates in a physiological environment. In this study, a novel Mg-based alloy exhibiting an elastic modulus E = 42 GPa, Mg-1Ca-0.2Mn-0.6Zr, was synthesized and thermo-mechanically processed. In order to improve its performance as a temporary bone implant, a coating based on cellulose acetate (CA) was realized by using the dipping method. The formation of the polymer coating was demonstrated by FT-IR, XPS, SEM and corrosion behavior comparative analyses of both uncoated and CA-coated alloys. The potentiodynamic polarization test revealed that the CA coating significantly improved the corrosion resistance of the Mg alloy. Using a series of in vitro and in vivo experiments, the biocompatibility of both groups of biomaterials was assessed. In vitro experiments demonstrated that the media containing their extracts showed good cytocompatibility on MC3T3-E1 pre-osteoblasts in terms of cell adhesion and spreading, viability, proliferation and osteogenic differentiation. In vivo studies conducted in rats revealed that the intramedullary coated implant for fixation of femur fracture was more efficient in inducing bone regeneration than the uncoated one. In this manner, the present study suggests that the CA-coated Mg-based alloy holds promise for orthopedic aplications.

Schiff base-functionalized mesoporous silicas (MCM-41, HMS) as Pb( ii ) adsorbents

Three Schiff base-functionalized mesoporous silicas: MCM-41@salen, HMS-C12@salen and HMS-C16@salen have been synthesized by a post-synthetic grafting strategy and their sorption capacities toward Pb(II) from synthetic aqueous solutions have been assessed. FTIR spectra, TG/DSC analyses, X-ray powder diffraction, X-ray photoelectron spectroscopy (XPS), N2 adsorption isotherms and HRTEM micrographs were used to characterize the novel functionalized mesoporous silicas. The novel adsorbents have been tested for their capability in the remediation of synthetic aqueous systems containing Pb(II). The Langmuir maximum values of sorption capacities of these adsorbents toward Pb(II) are: 138.88 mg Pb(II) per g MCM-41@salen, 144.92 mg Pb(II) per g HMS-C12@salen, and 181.81 mg Pb(II) per g HMS-C16@salen, therefore, the functionalized silicas (MCM-41@salen, HMS-C12@salen, HMS-C16@salen) could be used as effective adsorbents of Pb(II) ions from wastewater.

Epoxy-based nanocomposites with amine modified single walled carbon nanotubes

Abstract Carboxylated Single Walled Carbon Nanotubes (SWNT-COOH) were functionalized using different types of amines as modifier agents to improve the compatibility with the epoxy matrix. Covalent attachment was proved by XPS and Raman spectroscopy. TGA showed that only long chain modifier agents improved the thermal stability of modified SWNTs. Epoxy-based composites were synthesized using diglycidyl ether of bisphenol A (DGEBA) as polymer matrix and modified SWNTs as reinforcing agent.