Photoactive materials called photosensitizers can be used for treatment of different types of cancer in combination with light source. In this paper, we have investigated pro-oxidant and antioxidant ...potentials of four graphene based nanomaterials (graphene oxide-GO, graphene quantum dots-GQDs, carbon quantum dots-CQDs and N-doped carbon quantum dots-N-CQDs) depending on the presence/absence of visible light source. Structural and optical properties of these materials and their potentials for reactive oxygen species generation/quenching are investigated by applying different microscopy and spectroscopy techniques (transmission electron microscopy, FTIR, UV–Vis, photoluminescence, electron paramagnetic resonance). Results show that all types of quantum dots has pro-oxidant and antioxidant potentials whereas GO demonstrated only moderate antioxidant effect. The best free radical scavenger is CQDs sample in the absence of light. CQDs are the best singlet oxygen generator under blue light irradiation as well. To check photo-cytotoxicity of these materials, photo-cytotoxic concentrations of the GO, GQDs, CQDs and N-CQDs were determined for three cellular lines: human rhabdomyosarcoma (RD), cell line derived from human cervix carcinoma Hep2c (HeLa) and fibroblast cell line from murine (L2OB). Cytotoxicity test has indicated that all samples are much less photocytotoxic than cis-diamminedichloroplatinum (cis-DPP). The production method and doping of quantum dots affect the photodynamic activity of tested samples very much.
Display omitted
•Graphene oxide size and structure materials.•Crossover between pro-oxidant and antioxidant activities.•Fullerene like structure affects ROS generation/quenching.•Blue light dependent cytotoxicity toward cancer cells.
It is well known that geopolymers are a new group of binder materials of alumosilicate origin. Geopolymers are made by the reaction of precursor aluminosilicate materials with alkaline activator ...solutions. The current research relates to a low-cost and eco-friendly procedure, suitable of being implemented in two easy steps. The first step is the production of a solid phase based on fly ash (Obrenovac, Serbia) and eggshell ash as waste materials rich in calcium. The second step is alkali activating the solid phase using an alkaline activator (a mixture of NaOH and Na2SiO3) and procedures in proper laboratory conditions. Four samples with different eggshell ash content were synthesized. The concentration of used NaOH was 12 mol dm−3. The structural properties of all investigated samples were analyzed by XRD (X-ray diffraction), DRIFT (diffuse reflectance infrared Fourier transform), SEM (scanning electron microscopy) and UV/Vis spectroscopy analysis. XRD determined the amorphous halo with the presence of quartz as the crystal phase in all of the investigated samples. These results were confirmed by DRIFT analysis. The morphology of the samples was determined by SEM analysis. UV/Vis showed that the material could be a potential adsorbent.
The study of Cu(II) from aqueous solutions using the adsorption process on synthetically modified geopolymers was performed under static conditions. Three geopolymers (based on metaphase of Serbian ...clay, metaphase of German clay and metaphase of German clay plus 10% of carbon cloth) were used. The geopolymers were made by condensing a mixture of metaphases and alkali activator solution at a fixed ratio at room temperature and then at a temperature of 60 °C in a dry oven. Then, the geopolymer samples were pre-crashed to a fixed-radius size. Their properties were characterized by X-ray diffractometry (XRD), Diffuse Reflectance Infrared Fourier Transform (DRIFT) analysis and Scanning Electron Microscopy (SEM) with Energy Dispersive Spectroscopy (EDS). Adsorption experiments were carried out under batch process as a function of the dose, concentration of metal, and contact time. The uptake of Cu(II) was rapid, and it increased with increasing metal concentration. The sorption percentage decreased with increasing concentration of Cu(II). The equilibrium adsorption capacity of geopolymers was measured and extrapolated using more isotherms. The data fit very well the linear Langmuir isotherm model. The pseudo-second-order kinetic model can well describe the adsorption behavior of Cu(II) ions with geopolymers samples. These results show that used geopolymers hold great potential to remove Cu(II) from industrial wastewater.
To investigate the influence of spinel structure and sintering temperature on the functional properties of BaTiO3/NixZn1−xFe2O4 (x = 0, 0.5, 1), NiFe2O4, ZnFe2O4, and Ni0.5Zn0.5Fe2O4 were in situ ...prepared by thermal decomposition onto BaTiO3 surface from acetylacetonate precursors. As-prepared powders were additionally sintered at 1150 °C and 1300 °C. X-ray powder diffraction (XRPD) and scanning electron microscopy (SEM) coupled with electron dispersive spectroscopy (EDS) were used for the detailed examination of phase composition and morphology. The magnetic, dielectric, and ferroelectric properties were investigated. The optimal phase composition in the BaTiO3/NiFe2O4 composite, sintered at 1150 °C, resulted in a wide frequency range stability. Additionally, particular phase composition indicates favorable properties such as low conductivity and ideal-like hysteresis loop behavior. The favorable properties of BaTiO3/NiFe2O4 make this particular composite an ideal material choice for further studies on applications of multi-ferroic devices.
Objective: The purpose of this study was to evaluate the surface texture and biofilm adhesion of veneered or CAD/CAM milled zirconia (partially stabilized with yttrium) after professional oral ...hygiene procedures. The samples (4 × 4 mm, thickness 2 mm; n = 72) were separated from zirconia blanks (3Y-TZP-LA). One group was veenered with ceramics, and the other group of samples was CAD/CAM milled. Each group had two subgroups: polished and glazed. The samples were subjected to simulated strokes of professional brushing using abrasive paste and ultrasonic scaling. The parameters of surface micromorphology and receptivity to biofilm were calculated before and after simulating the given methods of the professional maintenance of oral hygiene. Scanning electron microscopy (SEM) was used to evaluate zirconia surface properties. Microbial (bacterial/fungal) species (Staphylococcus aureus, Streptococcus sanguinis and Candida albicans) were used and cultured on respective sterilized zirconia surfaces. Colony-forming unit (CFU) counts were used to quantify the amount of biofilm formation on zirconia samples surfaces. Results: The SEM analysis showed the greatest change in surface microtopography after the use of ultrasonic scaling on glazed zirconia samples. Less formation of colonies on the surfaces of CAD/CAM milled zirconia restorations was observed. Conclusion: Routine methods of oral hygiene professional maintenance can damage the surfaces of glazed zirconia restorations.
Two methods of enzyme immobilization onto silica core-shell particles were developed. The first method involved the immobilization of Candida rugosa lipase inside a previously synthesized mesoporous ...silica layer (deposited at 80°C) surrounding a dense silica core. To prevent lipase leakage from the support, an outer mesoporous silica layer was deposited at 40°C around the first silica layer containing the immobilized lipase. The deposition of the second layer was performed at a relatively lower temperature, to prevent thermal inactivation of the immobilized enzyme. The internal silica layer was obtained by assembling primary silica nanoparticles generated from highly basic sodium silicate solution at 80°C on the surface of poly (diallyldimethylammonium chloride) (PDDA) functionalized silica core particles. The average shell thickness and pore size of the internal silica layer was ∼60nm and 24nm, respectively. The effect of process parameters on generation and aggregation of silica nanoparticles prepared from highly basic sodium silicate solution was also investigated. The aggregation of silica particles generated at 40°C and 80°C took place after 840s and 570 of reactions, respectively. The immobilization efficiency of lipase on the mesoporous silica monolayer was 80%. A decline of immobilized lipase activity was approximately 6 times after 10 reaction cycles due to lipase leakage from the monolayered shell. An outer mesoporous silica layer was deposited at 40°C onto the surface of previously PDDA-functionalized monolayered silica core-shell particles containing the immobilized lipase. The average thickness and pore size of outer mesoporous silica layer was ∼60nm and 17nm, respectively. The activity of lipase immobilized inside the bilayered shell was further reduced due to diffusion resistance within the outer silica layer and PDDA layer however, it was retained for the next reaction cycles.
The pore size of mesoporous silica layer obtained at 80°C was insufficient to allow invertase immobilization. Thus, the second method for the immobilization of invertase was developed. It involved the preparation of the mesoporous silica layer simultaneously with invertase immobilization at 40°C. The immobilized invertase showed decreased activity, but it was not hampered by substrate inhibition, as in the case of the free enzyme, due to the location of the enzyme inside the mesoporous silica layer, where the mass transfer resistance for the substrate to the enzyme active site was present.
Han sido desarrollados dos métodos de inmovilización enzimática sobre las partículas de la núcleo-cubierta de sílice. El primer método implicaba la inmovilización de Candida rugosa lipasa dentro de una capa de sílice mesoporosa previamente sintetizada (depositada a 80°C), la cual rodea un núcleo denso de sílice. Para evitar fugas de la lipasa del soporte, se depositó una capa externa mesoporosa de sílice a una temperatura de 40°C sobre la superficie de las partículas de la núcleo-cubierta de sílice que contenían la lipasa inmovilizada. La deposición de la segunda capa se realizó a una temperatura relativamente más baja para evitar la inactivación térmica de la enzima inmovilizada. La capa interna de sílice se obtuvo ensamblando nanopartículas de sílice primaria generadas a partir de una solución de silicato de sodio altamente básica a 80°C en la superficie de las partículas del núcleo de sílice funcionalizadas con poli (cloruro de dialildimetilamonio) (PDDA). El grosor medio de la cubierta y el tamaño de poro de la capa interna de sílice fue de ∼60nm y 24nm, respectivamente. También se investigó el efecto de los parámetros del proceso sobre la generación y agregación de las nanopartículas de sílice preparadas a partir de una solución de silicato de sodio altamente básica. La agregación de las partículas de sílice generadas a 40°C y 80°C tuvo lugar después de 840s y 570s de reacción, respectivamente. La eficiencia de la inmovilización de la lipasa en la monocapa de sílice mesoporosa fue del 80%. La disminución de la actividad de la lipasa inmovilizada fue de aproximadamente 6 veces después de 10 ciclos de reacción debido a la fuga de la lipasa de la cubierta monocapa. Se depositó una capa de sílice mesoporosa externa a 40°C sobre la superficie de las partículas de la núcleo-cubierta de sílice monocapa previamente estratificadas de PDDA que contenían la lipasa inmovilizada. El grosor promedio y el tamaño de los poros de la capa de sílice mesoporosa externa fue de ∼60nm y 17nm, respectivamente. La actividad de la lipasa inmovilizada dentro de la cubierta bicapa se redujo aún más debido a la resistencia a la difusión dentro de la capa de sílice externa y la capa de PDDA y, sin embargo, se retuvo para los siguientes ciclos de reacción.
El tamaño de poro de la capa de sílice mesoporosa obtenida a 80°C fue insuficiente para permitir la inmovilización de la invertasa. Así, El segundo método para la inmovilización de la invertasa fue desarrollado debido a que la invertasa era mayor que el poro de la capa de sílice mesoporosa previamente sintetizada. Lo mismo implicaba la preparación de la capa de sílice mesoporosa simultáneamente con la inmovilización de la invertasa a una temperatura de 40°C. La invertasa inmovilizada mostró una actividad disminuida, pero no fue obstaculizada por la inhibición del sustrato, como en el caso de la enzima libre, debido a la ubicación de la enzima dentro de la capa de sílice mesoporosa, donde existía resistencia a la transferencia de masa del sustrato a la enzima activa.
Therapy of bacterial urinary tract infections (UTIs) and catheter associated urinary tract infections (CAUTIs) is still a great challenge because of the resistance of bacteria to nowadays used ...antibiotics and encrustation of catheters. Bacterial cellulose (BC) as a biocompatible material with a high porosity allows incorporation of different materials in its three dimensional network structure. In this work a low molecular weight chitosan (Chi) polymer is incorporated in BC with different concentrations. Different characterization techniques are used to investigate structural and optical properties of these composites. Radical scavenging activity test shows moderate antioxidant activity of these biocompatible composites whereas
in vitro
release test shows that 13.3% of chitosan is released after 72 h. Antibacterial testing of BC-Chi composites conducted on Gram-positive and Gram-negative bacteria causing UTIs and CAUTIs (
Escherichia coli
,
Pseudomonas aeruginosa
,
Klebsiella pneumoniae
) and encrustation (
Proteus mirabilis
) show bactericidal effect. The morphology analysis of bacteria after the application of BC-Chi shows that they are flattened with a rough surface, with a tendency to agglomerate and with decreased length and width. All obtained results show that BC-Chi composites might be considered as potential biomedical agents in treatment of UTIs and CAUTIs and as a urinary catheter coating in encrustation prevention.
Bacterial cellulose-chitosan composite with antibacterial and moderate antioxidant activity for potential UTI/CAUTI treatment and catheter coating in encrustation prevention.
Unsaturated fatty acid (FA)–modified nanocellulose (m‐NC) shows potential application in improving mechanical properties of unsaturated polyester/m‐NC nanocomposites (UPe/m‐NC). A polyester matrix is ...obtained by polycondensation of maleic anhydride and products of poly(ethylene terephthalate) depolymerization with propylene glycol. Two methods of NC modification are performed: direct esterification with oleic acid, linseed, or sunflower oil FAs, and esterification/amidation with maleic acid/ethylene diamine (MA/EDA) bridging group followed by amidation with methyl ester of FAs. Increases of stress at break in the ranges from 148.8% to 181.4% and from 155.8% to193.0% for UPe/m‐NC composites loaded with 1 wt% of NC modified directly or via MA/EDA cross‐linker, respectively, are obtained. Results of the modeling of tensile modulus, by using the Cox–Krenchel model, show good agreement with experimentally obtained data. The effect of FAs' cross‐linking capabilities on the dynamic‐mechanical and thermal properties of the UPe/m‐NC is studied. Cross‐linking density, modulus, and Tg of the nanocomposite show appropriate relation with the unsaturation extent/structure of NC modification.
Nanocrystalline cellulose is functionalized directly with fatty acid (FA) or via a vinyl/amino (maleic acid/ethylene diamine, MA/EDA) bridge. Vinyl reactive FA residues at NC surface copolymerize with the polyester chains. The MA/EDA bridging group forms dipole/induced dipole interaction with polyester chains. The FA and MA/EDA/FA‐modified nanocrystalline cellulose shows high reinforcement in polyester‐based composites.
PDF
