Epidermal Growth Factor \u2013 based adhesion substrates elicit myoblast scattering, proliferation, differentiation and promote satellite cell myogenic activation

The biochemical properties of muscle extracellular matrix are essential for stem cell adhesion, motility, proliferation and myogenic development. Recombinant elastin-like polypeptides are synthetic polypeptides that, besides maintaining some properties of the native protein, can be tailored by fusing bioactive sequences to their C-terminal. Our laboratory synthesized several Human Elastin-Like Polypeptides (HELP) derived from the sequence of human tropoelastin. Here, we developed a novel HELP family member by fusing the elastin-like backbone to the sequence of human Epidermal Growth Factor. We employed this synthetic protein, named HEGF, either alone or in combination with other proteins of the HELP family carrying RGD-integrin binding sites, as adhesion substrate for C2C12 myoblasts and satellite cells primary cultures. Adhesion of myoblasts to HEGF-based substrates induced scattering, decreased adhesion and cytoskeleton assembly; the concomitant presence of the RGD motifs potentiated all these effects. Recombinant substrates induced myoblasts proliferation, differentiation and the development of multinucleated myotubes, thus favoring myoblasts expansion and preserving their myogenic potential. The effects induced by adhesion substrates were inhibited by AG82 (Tyrphostin 25) and herbimycin A, indicating their dependence on the activation of both the EGF receptor and the tyrosine kinase c-src. Finally, HEGF increased the number of muscle stem cells (satellite cells) derived from isolated muscle fibers in culture, thus highlighting its potential as a novel substrate for skeletal muscle regeneration strategies

TiO2 nanotubes film/FTO glass interface: Thermal treatment effects

Pure Ti films deposited by radio-frequency magnetron sputtering on FTO glass were anodized to fabricate TiO2 nanotubes (NTs) arrays. The TiO2 NTs/FTO samples were sintered at 450, 550 and 630°C, in ambient air. The thermal treatment did not influence the crystal phase composition, preserving in all cases the anatase single phase. As expected, the crystalline anatase quality improved with the annealing temperature. Nevertheless, slight differences in nanotubular morphology, such as the appearance of grains inside the walls, were observed in the case of the sample sintered at 630°C. Chemical analysis by X-ray Photoelectron Spectroscopy of annealed samples revealed the presence of Sn inside TiO2 NTs, due to diffusion of Sn from the substrate to TiO2. For the substrate was used FTO glass whose top layer consists of SnO2 doped with F. Rutherford Backscattering Spectrometry and Time-of-Flight Elastic Recoil Detection Analysis were carried out to study the elemental depth profile of the films. It was found that the temperature of sintering controls the Sn diffusion inside TiO2 film. Sn atoms diffuse towards the TiO2 NTs surface for the samples annealed at 450 and 550°C. The diffusion is however hindered in the case of the heat treatment at 630°C. Besides, the Ti diffusion into the SnO2 underlayer was observed, together with the formation of TiO2/SnO2 interfaces. One then expected but not a great difference in absorption between samples, since all contained anatase phase, as confirmed by Diffuse Reflectance Spectroscopy. A higher amount of Sn was however detected for the sample annealed at 550°C, which accounts for a slight red absorption shift. The importance of controlling the annealing parameters of the anodized TiO2/FTO structures was highlighted through the formation of TiO2-SnO2 interfaces and the Sn insertion from FTO, which can play an essential role in increasing the photoperformances of TiO2 NTs/FTO based structures of photovoltaic cells

Inhibice růstu krystalů struvitu-K kyselinou citrónovou: Tvorba komplexů v roztoku a efekty povrchové adsorpce

Controlled precipitation of struvite-K is of interest in the treatment of kidney stones, for phosphorous and potassium recovery from wastewaters, and in the chemistry of magnesium phosphate cements. The effect of citric acid in the growth of struvite-K from solution has been studied at room temperature and pH = 9 under different conditions of energy of mixing and concentrations of the reactants. The time-evolution of pH during the precipitation reaction evidenced that the citric acid increased induction time and decreased the apparent growth rates of crystals. Chemical speciation analysis, measurements of citrate concentration, zeta potential and X-ray photoelectron spectroscopy indicated that crystallization is controlled by the formation of complexes with magnesium ions in solution and adsorption of citric acid at the growing surfaces. In analogy with Ca-carbonates and Ca-phosphates, the latter process impairs formation of nuclei of critical size. Crystal habit is dictated by supersaturation conditions and selective adsorption at crystal faces in reason of their residual charge density; consequently, alteration in the crystal shape is observed, and the average size of crystals and the amount of precipitate are reduced.Řízené srážení struvitu-K je zajímavé při léčbě ledvinových kamenů, pro získávání fosforu a draslíku z odpadních vod a v chemii hořečnatých fosfátových cementů. Vliv kyseliny citrónové na růst struvitu-K z roztoku byl studován při pokojové teplotě a pH = 9 za různých podmínek energie míchání a koncentrací reaktantů. Časový vývoj pH během srážecí reakce ukázal, že kyselina citrónová prodloužila dobu indukce a snížila zjevnou rychlost růstu krystalů. Chemická speciační analýza, měření koncentrace citrátu, zeta potenciálu a rentgenová fotoelektronová spektroskopie ukázaly, že krystalizace je řízena tvorbou komplexů s ionty hořčíku v roztoku a adsorpcí kyseliny citrónové na rostoucích površích. Podobně jako u uhličitanů vápenatých a fosforečnanů vápenatých tento druhý proces narušuje tvorbu zárodků kritické velikosti. Vzhled krystalu je dán podmínkami přesycení a selektivní adsorpcí na plochách krystalů z důvodu jejich zbytkové hustoty náboje; následně je pozorována změna tvaru krystalu a průměrná velikost krystalů a množství sraženiny jsou sníženy

Sn-doped TiO2 nanotubular thin film for photocatalytic degradation of methyl orange dye

We fabricated Sn-doped TiO2 nanotubular film via annealing of anodized TiO2 nanotubes grown on F-SnO2 (FTO) glass. Annealing was carried out at 500 degrees C in ambient air. Anatase crystal structure was achieved with no change in nanotubular morphology in respect to as-anodized amorphous TiO(2 )nanotubes. The X-ray photoelectron spectroscopy analysis revealed Sn on the surface of TiO2 film, following the thermal treatment, probably caused by the diffusion from FTO glass. Depth profile examination of the film chemical composition was conducted by elastic recoil detection analysis, which showed that in addition to the diffusion of Sn from FTO, diffusion of Ti to FTO concurrently occurred. Thus, a higher concentration of Sn was found at the bottom of the tubes, while a lower concentration was present on the tubes' surface top. This explains the improved optical response revealed by a diffuse reflectance spectroscopy. The absorption enhancement demonstrated that Sn-doped TiO2 film was efficient in the degradation of methyl orange dye under visible light.This is the peer-reviewed version of the following article: Bjelajac, A.; Petrović, R.; Vujančević, J.; Veltruska, K.; Matolin, V.; Siketić, Z.; Provatas, G.; Jakšić, M.; Stan, G. E.; Socol, G.; Mihailescu, I. N.; Janaćković, Đ. Sn-Doped TiO2 Nanotubular Thin Film for Photocatalytic Degradation of Methyl Orange Dye. Journal of Physics and Chemistry of Solids 2020, 147. [https://doi.org/10.1016/j.jpcs.2020.109609

C-doped TiO2 nanotubes with pulsed laser deposited Bi2O3 films for photovoltaic application

Anodization was used to obtain a nanotubular TiO2 photoanode on F-SnO2 glass. Subsequent annealing in the CH4 atmosphere promoted the C-doping and improved the crystallinity of the TiO2 nanotubes. The pulsed laser deposition was applied to cover the nanotubes with Bi2O3, serving as a hole transport material. X-ray photoelectron spectroscopy analyses of the doped samples reveal a shift in the valence band's maximum position towards lower binding energy as compared to those observed for the undoped samples (annealed in the air). The doping positively affects the absorption by shifting the absorption edge to 567 nm. I-V measurements under illumination show that the C-doping of TiO2 increases the current density following the absorbance results. The highest open circuit voltage was reached for the samples with the 300 degrees C-deposited Bi2O3 layer, pointing to better quality of the p-n junction, hence of the contact between Bi2O3 and TiO2. This in situ annealing provided the formation of close contact between Bi2O3 and TiO2, which enabled a faster charge transport as compared to the contact obtained with no annealing or even with post annealing