Valentina Alice Cauda

Multiple Core−Shell Functionalized Colloidal Mesoporous Silica Nanoparticles

The selective functionalization of the inner and outer surfaces of colloidal mesoporous silica (CMS) nanoparticles with different trialkoxysilanes, following a newly developed delayed co-condensation approach, results in bifunctional CMS. Complementary CMS nanoparticles were prepared with two different functional groups located either on the outer shell or in the inner core of the particle. The identification and localization of the functional groups was achieved by means of different techniques including zeta potential, nitrogen sorption measurements, and fluorescence spectroscopy. This last technique was applied to fluorescein isothiocyanate (FITC)-labeled CMS featuring aminopropyl functional groups on the periphery or the internal pore surface of the particles. Fluorescence quenching experiments were carried out with dodecanethiolate-stabilized gold nanoparticles having a diameter greater than the pore size of the CMS. It could be shown that fluorescence quenching occurs only when the FITC is positioned on the outer surface of the CMS nanoparticles, whereas no quenching was observed for FITC located in the inner core of the nanoparticle. These results clearly confirm the controlled localization of the aminopropyl groups in the nanometer space of the CMS particles. Our approach thus offers the opportunity to synthesize, in a novel multistep co-condensation strategy, various bifunctional mesoporous nanoparticles with controlled localization of different functional groups in the inner core or on the outer shell of the nanoparticle.

Role of Endosomal Escape for Disulfide-Based Drug Delivery from Colloidal Mesoporous Silica Evaluated by Live-Cell Imaging

Redox-driven intracellular disulfide-cleavage is a promising strategy to achieve stimuli-responsive and controlled drug release. We synthesized colloidal mesoporous silica (CMS) nanoparticles with ATTO633-labeled cysteine linked to the inner particle core via disulfide-bridges and characterized their cysteine release behavior after internalization into HuH7 cells by high-resolution fluorescence microscopy. Our study revealed that endosomal escape is a bottleneck for disulfide-linkage based drug release. Photochemical opening of the endosome leads to successful delivery of fluorescently labeled cysteine to the cytosol.

Flexible tactile sensing based on piezoresistive composites: a review.

The large expansion of the robotic field in the last decades has created a growing interest in the research and development of tactile sensing solutions for robot hand and body integration. Piezoresistive composites are one of the most widely employed materials for this purpose, combining simple and low cost preparation with high flexibility and conformability to surfaces, low power consumption, and the use of simple read-out electronics. This work provides a review on the different type of composite materials, classified according to the conduction mechanism and analyzing the physics behind it. In particular piezoresistors, strain gauges, percolative and quantum tunnelling devices are reviewed here, with a perspective overview on the most used filler types and polymeric matrices. A description of the state-of-the-art of the tactile sensor solutions from the point of view of the architecture, the design and the performance is also reviewed, with a perspective outlook on the main promising applications.

Impact of different PEGylation patterns on the long-term bio-stability of colloidal mesoporous silica nanoparticles

Inorganic–organic core-shell mesoporous silica nanoparticles have high potential as drug delivery vehicles. They can combine high loading levels of guest molecules in the mesoporous core with an organic shell showing stimuli-responsive controlled release capabilities, high stabilization in colloidal suspension, and biocompatibility. We describe colloidal core-shell mesoporous silica (CMS) nanoparticles with an external coating of a hydrophilic polymer shell (poly(ethylene glycol), PEG). By means of a delayed co-condensation approach, different PEG-silane precursors were added to the CMS synthesis solution after certain time periods during the nanoparticle growth. Specifically, three different types of linear PEGylated CMS nanoparticles were obtained, having two different PEG-chain lengths with (i) Mw 550, (ii) Mw 5000, and (iii) a mixture of the latter two (75 mol% of Mw550 and 25 mol% of Mw5000). Samples were characterized by different techniques, showing high surface area and pore volume, an effective coating of the silica nanoparticles with the PEG layer (e.g., 12% w/w of linear PEG5000), and improved monodisperse suspension in water and biological media with respect to the unfunctionalized CMS nanoparticles. The behavior of PEG-coated CMS nanoparticles was investigated in simulated body fluid (SBF) for up to 1 month at 37 °C, with the aim of gaining new insights regarding the stability and bio-degradability of these organic-inorganic hybrid nanoparticles. Depending on the density of the coverage and the chain length of the polymer, the PEG-shell significantly reduces the rate of degradation of silica in SBF. The present study extends the PEGylation approach to develop biocompatible hybrid nanocarriers for drug delivery applications.

Optimization of 1D ZnO@TiO2 core-shell nanostructures for enhanced photoelectrochemical water splitting under solar light illumination.

A fast and low-cost sol-gel synthesis used to deposit a shell of TiO2 anatase onto an array of vertically aligned ZnO nanowires (NWs) is reported in this paper. The influence of the annealing atmosphere (air or N2) and of the NWs preannealing process, before TiO2 deposition, on both the physicochemical characteristics and photoelectrochemical (PEC) performance of the resulting heterostructure, was studied. The efficient application of the ZnO@TiO2 core-shells for the PEC water-splitting reaction, under simulated solar light illumination (AM 1.5G) solar light illumination in basic media, is here reported for the first time. This application has had a dual function: to enhance the photoactivity of pristine ZnO NWs and to increase the photodegradation stability, because of the protective role of the TiO2 shell. It was found that an air treatment induces a better charge separation and a lower carrier recombination, which in turn are responsible for an improvement in the PEC performance with respect to N2-treated core-shell materials. Finally, a photocurrent of 0.40 mA/cm(2) at 1.23 V versus RHE (2.2 times with respect to the pristine ZnO NWs) was obtained. This achievement can be regarded as a valuable result, considering similar nanostructured electrodes reported in the literature for this application.

Colchicine-Loaded Lipid Bilayer-Coated 50 nm Mesoporous Nanoparticles Efficiently Induce Microtubule Depolymerization upon Cell Uptake

We report on a one-step assembly route where supported lipid bilayers (SLB) are deposited on functionalized colloidal mesoporous silica (CMS) nanoparticles, resulting in a core-shell hybrid system (SLB@CMS). The supported membrane acts as an intact barrier against the escape of encapsulated dye molecules. These stable SLB@CMS particles loaded with the anticancer drug colchicine are readily taken up by cells and lead to the depolymerization of microtubules with remarkably enhanced efficiency as compared to the same dose of drug in solution.

Nanoconfinement: an effective way to enhance PVDF piezoelectric properties.

The dimensional confinement and oriented crystallization are both key factors in determining the piezoelectric properties of a polymeric nanostructured material. Here we prepare arrays of one-dimensional polymeric nanowires showing piezoelectric features by template-wetting two distinct polymers into anodic porous alumina (APA) membranes. In particular, poly(vinylidene fluoride), PVDF, and its copolymer poly(vinylidene fluoride-trifluoroethylene), PVTF, are obtained in commercially available APA, showing a final diameter of about 200 nm and several micrometers in length, reflecting the templating matrix features. We show that the crystallization of both polymers into a ferroelectric phase is directed by the nanotemplate confinement. Interestingly, the PVDF nanowires mainly crystallize into the β-phase in the nanoporous matrix, whereas the reference thin film of PVDF crystallizes in the α nonpolar phase. In the case of the PVTF nanowires, needle-like crystals oriented perpendicularly to the APA channel walls are observed, giving insight on the molecular orientation of the polymer within the nanowire structure. A remarkable piezoelectric behavior of both 1-D polymeric nanowires is observed, upon recording ferroelectric polarization, hysteresis, and displacement loops. In particular, an outstanding piezoelectric effect is observed for the PVDF nanowires with respect to the polymeric thin film, considering that no poling was carried out. Current versus voltage (I-V) characteristics showed a consistent switching behavior of the ferroelectric polar domains, thus revealing the importance of the confined and oriented crystallization of the polymer in monodimensional nanoarchitectures.

Heparin Coating on Ureteral Double J Stents Prevents Encrustations: An in Vivo Case Study

PURPOSE To evaluate the ability of heparin coating to inhibit Double J stent encrustation and compare it with the classic polyurethane Double J stent. PATIENTS AND METHODS The study involved five patients with bilateral obstructions, who required bilateral ureteral Double J stent placement. Every patient received a heparin-coated Double J stent and a traditional polyurethane Double J stent for 1 month. After removal, the stents were analyzed using field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), and micro-infrared spectrophotometry (Micro-IR). These same techniques were used to analyze the heparin-coated and uncoated stents before insertion. The thickness, extension, and composition of encrustation of the coated and uncoated stents were compared. Moreover, two heparin-coated stents were analyzed with the same techniques after they had been in place for 10 and 12 months. RESULTS FESEM analysis showed that the difference in encrustation thickness and extension between the two groups was significant. EDS and Micro-IR confirmed that in the heparinized stents the encrustations were not as uniform and compact as those in the uncoated stents. The stents that were left in place long-term were free of encrustations and had no changes in the heparin layer. CONCLUSIONS Heparin coating reduces stent encrustation. Moreover, as no changes were seen in the heparin layer, we concluded that covalent heparin bonding enhances its adhesion to the polyurethane surface and ensures its stability for long periods. The heparin-coated stent appears to be a useful tool for long-term urinary drainage.

Controlling the delivery kinetics from colloidal mesoporous silica nanoparticles with pH-sensitive gates

An effective pH-dependent nanoscale delivery system was synthesized, based on ionic interactions between amino functionalities and sulfonate groups that are located at the pore entrance of colloidal mesoporous silica (CMS) nanoparticles. By means of a delayed co-condensation approach, we were able to synthesize CMS nanoparticles with aminopropyl functional groups located exclusively at the outer particle surface. Sulfophenyl isothiocyanate (SULF) molecules were covalently attached to part of the amino moieties. At acidic pH, the unreacted protonated amino groups interact with the sulfonate groups, leading to a gating system. The small mesopores (3.7 nm) were effectively sealed under acidic condition (pH 2 and 4), thus preventing the release of the model drug ibuprofen from the inner volume of the modified CMS particles. In the absence of the gating system, unfunctionalized CMS nanoparticles released the drug within a short period. When the pore size was increased by about 1 nm, the sealing effect was no longer observed, implying a delicate matching of the gate size and the pore diameter. At neutral pH, the unprotonated amino groups engage in weaker interactions with the SULF moieties, thus gradually opening the mesopores. A sustained release behavior was observed for the small pore gated sample. In contrast, fast release of the drug was shown from the unfunctionalized mesopores and the large-pore gated sample. These findings show that the drug release rate can be finely controlled by changing the pH value of the release medium, as long as the size of the gating system is matched to the mesopore diameter.

Length‐Dependent Charge Generation from Vertical Arrays of High‐Aspect‐Ratio ZnO Nanowires

Aqueous chemical growth of zinc oxide nanowires is a flexible and effective approach to obtain dense arrays of vertically oriented nanostructures with high aspect ratio. Herein we present a systematic study of the different synthesis parameters that influence the ZnO seed layer and thus the resulting morphological features of the free-standing vertically oriented ZnO nanowires. We obtained a homogeneous coverage of transparent conductive substrates with high-aspect-ratio nanowire arrays (length/diameter ratio of up to 52). Such nanostructured vertical arrays were examined to assess their electric and piezoelectric properties, and showed an electric charge generation upon mechanical compressive stress. The principle of energy harvesting with these nanostructured ZnO arrays was demonstrated by connecting them to an electronic charge amplifier and storing the generated charge in a series of capacitors. We found that the generated charge and the electrical behavior of the ZnO nanowires are strictly dependent on the nanowire length. We have shown the importance of controlling the morphological properties of such ZnO nanostructures for optimizing a nanogenerator device.