ABSTRACT
Poly(L-lactide)/reduced graphene oxide (PLLA/rGO) scaffolds were studied in the present work. The scaffolds were fabricated by TIPS (thermally induced phase separation). Nonisothermal crystallization study for PLLA/rGO was investigated and revealed the nucleating effect of rGO. rGO effect on cytotoxicity, thermal properties, and hydrolysis resistance of PLLA and PLLA/rGO scaffolds were analysed. In vitro degradation in phosphate-buffered solution at 37 °C is analyzed over twelve weeks. A high crystalline behaviour reduces the speed of hydrolysis and therefore implies less variation in pH, mass loss and water up take. The rGO does not seem to accelerate the degradation process. Finally, rGO contents in PLLA up to 1 wt% dos not lead to cytotoxic effect, the scaffolds supporting cell adhesion and proliferation.
Subject(s)
Tissue Engineering , Tissue Scaffolds , Graphite , PolyestersABSTRACT
Acute CrVI water pollution due to anthropogenic activities is an increasing worldwide concern. The high toxicity and mobility of CrVI makes it necessary to develop dual adsorbent/ion-reductive materials that are able to capture CrVI and transform it efficiently into the less hazardous CrIII . An accurate description of chromium speciation at the adsorbent/ion-reductive matrix is key to assessing whether CrVI is completely reduced to CrIII , or if its incomplete transformation has led to the stabilization of highly reactive, transient CrV species within the material. With this goal in mind, a dual ultraviolet-visible and electron paramagnetic spectroscopy approach has been applied to determine the chromium speciation within zirconium-based metal-organic frameworks (MOFs). Our findings point out that the generation of defects at Zr-MOFs boosts CrVI adsorption, whilst the presence of reductive groups on the organic linkers play a key role in stabilizing it as isolated and/or clustered CrIII ions.
ABSTRACT
Metal-Organic Frameworks (MOFs) are porous coordination networks assembled through metal complexes with organic linkers. Due to their chemical versatility, these materials are being investigated for various applications including gas storage and separation, biomedicine and catalysis. The aim of this work is the encapsulation of the model ß-alanine amino-acid in the nanostructured zirconium-based MOF (UiO-66) which contains the ligand H2BDC (1,4-benzenedicaboxylic acid). Additionally, ligand functionalization (by using H2doBDC (2,5-dihydroxy-1,4-benzenedicarboxylic acid) and defect engineering have been carried out to produce UiO-66 derivatives, in order to modify the host-guest interactions, and hence study their influence on the ß-alanine loading capacity and release kinetics. The as-obtained materials have been characterized by X-ray diffraction (XRD), X-ray thermo diffraction (TDX), infrared (IR) spectroscopy, thermogravimetric analysis-differential scanning calorimetry (TG-DSC) and elemental analysis (EA). Morphology of nanoscale MOFs has been explored by transition electron microscopy (TEM). Adsorption isotherms have been constructed, and the concentration of ß-alanine in the post-adsorption solution (supernatant) has been quantified by high performance liquid chromatography coupled with mass spectroscopy (HPLC-MS) and EA. Adsorption capacity values indicate that the presence of hydroxyl groups at the organic linker H2doBDC enhances the host-guess affinity between the framework and the adsorbate ß-alanine. The influence of defect engineering, on the adsorption however, is not that obvious. On the other hand, desorption experiments show similar behaviour for H2doBDC-based derivatives. An adsorption mechanism has been proposed consisting of a combination of host-guest interaction at low concentrations, and covalent anchoring/ligand displacement by ß-alanine at the inorganic clusters.