To control floating drug delivery system in a simulated gastric environment by adjusting the Shell layer formulation

Background Gastroretentive drug delivery system (GDDS) are novel systems that have been recently developed for treating stomach diseases. The key function of all GDDS systems is to control the retention time in the stomach. However, research into the bulk density or entanglement of polymers, especially regarding their effects on drug float and release times, is scarce. Methods In this research, we prepared the floating core-shell beads carrying tetracycline. The ratio of chitosan and xanthan gum in the shell layer was changed to modify polymer compactness. Tetracycline was encapsulated in the alginate core. Results Using scanning electron microscopy (SEM) techniques, we observed that the shell formulation did not change the bead morphology. The cross-sectional images showed that the beads were highly porous. The interaction between anionic xanthan gum and cationic chitosan made the shell layer dense, resisting to the mass transfer in the shell layer. Due to the high mass transfer resistance to water penetration, the longer float and delivery time were caused by the dense surface of the beads. The cell culture demonstrated that floating core-shell beads were biocompatible. Importantly, the beads with tetracycline showed a significant prolonged anti-bacterial effect. Conclusion Research results proved that the floating and releasing progress of core-shell beads can be well controlled by adjusting the shell layer formulation that could promote the function of gastroretentive drugs.

A non-lethal method to assess element content in the endangered Pinna nobilis

The fan shell Pinna nobilis is the largest bivalve endemic to the Mediterranean and is actually a strongly endangered species. Due to the biological, ecological, and historical relevance of this species, the research of a non-lethal method to relate the element content in organism’s tissues and environment can provide information potentially useful to evaluate environmental pollution and organism physiological status. In this study, a screening on element concentration in the animal growing environment (seawater and sediments) and in four soft tissues (hepatopancreas, gills, mantle, and muscle), and two acellular tissues (calcite shell layer, and byssus) was performed. The comparison among these results was used to assess whether the no-lethal acellular tissue element concentration can be used to reveal the element presence in the environment and soft tissues. Elements, such as B, Ag, As, Mn, Mo, Pb, or Se, showed a possible relationship between their presence in the byssus and soft tissues. In the byssus Cr, Sb, Sn, and V have shown to be mostly related to the environment, more than the soft tissues, and might be used to draw a historical record of the exposure of the organism. The element concentration in the calcite shell layer did not relate with environmental element concentrations. Essential elements, like Cu, Fe, Ni, and Zn, were present in calcite shell layer and byssus and are likely related to their biological activity in the organism. The research also gave an overview on the presence of pollution and on the preferential intake route of the element. In summary, this study, performed on a limited number of specimens of this protected species, indicated that element concentration in the byssus can be applied as non-lethal method to monitor this endangered species and its interaction with the elements in the growing environment.

Improved Photoresponse Characteristics of a ZnO-Based UV Photodetector by the Formation of an Amorphous SnO2 Shell Layer

Although ZnO nanostructure-based photodetectors feature a well-established system, they still present difficulties when being used in practical situations due to their slow response time. In this study, we report on how forming an amorphous SnO2 (a-SnO2) shell layer on ZnO nanorods (NRs) enhances the photoresponse speed of a ZnO-based UV photodetector (UV PD). Our suggested UV PD, consisting of a ZnO/a-SnO2 NRs core–shell structure, shows a rise time that is 26 times faster than a UV PD with bare ZnO NRs under 365 nm UV irradiation. In addition, the light responsivity of the ZnO/SnO2 NRs PD simultaneously increases by 3.1 times, which can be attributed to the passivation effects of the coated a-SnO2 shell layer. With a wide bandgap (~4.5 eV), the a-SnO2 shell layer can successfully suppress the oxygen-mediated process on the ZnO NRs surface, improving the photoresponse properties. Therefore, with a fast photoresponse speed and a low fabrication temperature, our as-synthesized, a-SnO2-coated ZnO core–shell structure qualifies as a candidate for ZnO-based PDs.

Evolution of Structural and Magnetic Properties of Fe-Co Wire-like Nanochains Caused by Annealing Atmosphere

Thermal treatment is a post-synthesis treatment that aims to improve the crystallinity and interrelated physical properties of as-prepared materials. This process may also cause some unwanted changes in materials like their oxidation or contamination. In this work, we present the post-synthesis annealing treatments of the amorphous Fe1−xCox (x = 0.25; 0.50; 0.75) Wire-like nanochains performed at 400 °C in two different atmospheres, i.e., a mixture of 80% nitrogen and 20% hydrogen and argon. These processes caused significantly different changes of structural and magnetic properties of the initially-formed Fe-Co nanostructures. All of them crystallized and their cores were composed of body-centered cubic Fe-Co phase, whereas their oxide shells comprised of a mixture of CoFe2O4 and Fe3O4 phases. However, the annealing carried out in hydrogen-containing atmosphere caused a decomposition of the initial oxide shell layer, whereas a similar process in argon led to its slight thickening. Moreover, it was found that the cores of thermally-treated Fe0.25Co0.75 nanochains contained the hexagonal closest packed (hcp) Co phase and were covered by the nanosheet-like shell layer in the case of annealing performed in argon. Considering the evolution of magnetic properties induced by structural changes, it was observed that the coercivities of annealed Fe-Co nanochains increased in comparison with their non-annealed counterparts. The saturation magnetization (MS) of the Fe0.25Co0.75 nanomaterial annealed in both atmospheres was higher than that for the non-annealed sample. In turn, the MS of the Fe0.75Co0.25 and Fe0.50Co0.50 nanochains annealed in argon were lower than those recorded for non-annealed samples due to their partial oxidation during thermal processing.

Scaffolds Designing from Protein-loadable Coaxial Electrospun Fibermats of poly(acrylamide)-co-poly(diacetone acrylamide) and Gelatin

Background: A core-shell fiber mat is one of the attractive platforms for this purpose. However, very few details the importance of choosing the suitable material for the shell units that can endow efficient release properties. The tailored design of cytokine-releasing scaffolds aiming at in situ regenerative therapy is still one of the crucial issues to be studied. Objective: In this study, we characterized the effectiveness of core-shell fiber mats that possess cross-linked gelatin (CLG) as the shell layer of constituent nanofibers, as a protein-releasing cell-incubation scaffold. Methods: We utilized a crosslinked copolymer of poly (acrylamide)-co-poly (diacetone acrylamide) (poly (AM/DAAM)) and adipic acid dihydrazide (ADH), poly (AM/DAAM)/ADH for the core nanofibers in the core-shell fiber mats. By coaxial electrospinning and the subsequent crosslinking of the gelatin layer, we successfully constructed core-shell fiber mats consisting of double-layered nanofibers of poly (AM/DAAM)/ADH and CLG. Using fluorescein isothiocyanate-labeled lysozyme (FITC-Lys) as a dummy guest protein, we characterized the release behavior of the core-shell fiber mats containing a CLG layer. Upon loading essential fibroblast growth factor (bFGF) as cargo in our fiber mats, we also characterized the impacts of the released bFGF on the proliferation of the incubated cells. Results: Although the single-layered poly (AM/DAAM)/ADH nanofiber fiber mats did not adhere to the mammalian cells, the core-shell fiber mat with the CLG shell layer exhibited good adherence and subsequent proliferation. A sustained release of the preloaded FITC-Lys over 24 days without any burst release was observed, and the cumulative amount of released protein reached over 65% after 24 days. Upon loading bFGF in our fiber mats, we succeeded in promoting cell proliferation and highlighting its potential for therapeutic applications. Conclusion: We successfully confirmed that core-shell fiber mats with a CLG shell layer around the constituent nanofibers were practical as protein-releasing cell-incubation scaffolds.

SnO2 -SiO2 1D Core-Shell Nanowires Heterostructures for Selective Hydrogen Sensing

SnO2 is one of the most employed n-type semiconducting metal oxide (SMOX) in chemo-resistive gas-sensing although it presents serious limitations due to a low selectivity. Herein, we introduce one-dimensional (1D) SnO2-SiO2 core-shell nanowires (CSNWs). SnO2 nanowires (NWs) are synthesized by vapor–liquid–solid deposition and the amorphous SiO2-shell layer with varying thicknesses (1.8-10.5 nm) was grown by atomic layer deposition (ALD). SiO2-coated SnO2 CSNWs show lower baseline conductance as compared to the Pristine SnO2 NWs, due to an enhancement of the electron depletion layer. The SnO2-SiO2/N CSNWs (N representing the number of SiO 2 ALD cycles) sensors show a dramatic improvement of the selectivity towards hydrogen. Moreover, the sensing-response markedly depends on the thickness of the SiO2-shell layer and the working temperature. The SnO2-SiO2/60 CSNWs sensor (ca. 4.8 nm SiO2 shell thickness) was the best performing sensor in terms of selectivity and sensitivity exhibiting a response of 160 (ca. 7-folds higher than the pristine SnO2 NWs) towards 500 ppm of hydrogen at 500 °C with a lower detection limit at ppb-level (0.082 ppm). The selectivity and enhanced sensing-response are related to the masking effect of the SiO2 shell and an increased in the width of the electron depletion layer due to the strong electronic coupling between the SnO2 core and SiO2-shell layer, respectively. The remarkable sensing performances of the SnO2-SiO2/N CSNWs can be attributed to the homogeneous and conformal SiO2 shell layer by ALD,<br>electronic coupling between the core and the shell, the optimized shell thickness and high surface area provided by the 1D SnO2 NWs network.<br>