| 1. |
- Alves, Luis, et al.
(författare)
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New Insights on the Role of Urea on the Dissolution and Thermally-Induced Gelation of Cellulose in Aqueous Alkali
- 2018
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Ingår i: GELS. - : MDPI AG. - 2310-2861. ; 4:4
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Tidskriftsartikel (refereegranskat)abstract
- The gelation of cellulose in alkali solutions is quite relevant, but still a poorly understood process. Moreover, the role of certain additives, such as urea, is not consensual among the community. Therefore, in this work, an unusual set of characterization methods for cellulose solutions, such as cryo-transmission electronic microscopy (cryo-TEM), polarization transfer solid-state nuclear magnetic resonance (PTssNMR) and diffusion wave spectroscopy (DWS) were employed to study the role of urea on the dissolution and gelation processes of cellulose in aqueous alkali. Cryo-TEM reveals that the addition of urea generally reduces the presence of undissolved cellulose fibrils in solution. These results are consistent with PTssNMR data, which show the reduction and in some cases the absence of crystalline portions of cellulose in solution, suggesting a pronounced positive effect of the urea on the dissolution efficiency of cellulose. Both conventional mechanical macrorheology and microrheology (DWS) indicate a significant delay of gelation induced by urea, being absent until ca. 60 degrees C for a system containing 5wt % cellulose, while a system without urea gels at a lower temperature. For higher cellulose concentrations, the samples containing urea form gels even at room temperature. It is argued that since urea facilitates cellulose dissolution, the high entanglement of the cellulose chains in solution (above the critical concentration, C*) results in a strong three-dimensional network.
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| 2. |
- Alves, Luis, et al.
(författare)
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Revisiting the dissolution of cellulose in H3PO4(aq) through cryo-TEM, PTssNMR and DWS
- 2021
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617 .- 1879-1344. ; 252
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Tidskriftsartikel (refereegranskat)abstract
- Cellulose can be dissolved in concentrated acidic aqueous solvents forming extremely viscous solutions, and, in some cases, liquid crystalline phases. In this work, the concentrated phosphoric acid aqueous solvent is revisited implementing a set of advanced techniques, such as cryo-transmission electronic microscopy (cryo-TEM), polarization transfer solid-state nuclear magnetic resonance (PTssNMR), and diffusing wave spectroscopy (DWS). Cryo-TEM images confirm that this solvent system is capable to efficiently dissolve cellulose. No cellulose particles, fibrils, or aggregates are visible. Conversely, PTssNMR revealed a dominant CP signal at 25 °C, characteristic of C-H bond reorientation with correlation time longer than 100 ns and/or order parameter above 0.5, which was ascribed to a transient gel-like network or an anisotropic liquid crystalline phase. Increasing the temperature leads to a gradual transition from CP to INEPT-dominant signal and a loss of birefringence in optical microscopy, suggesting an anisotropic-to-isotropic phase transition. Finally, an excellent agreement between optical microrheology and conventional mechanical rheometry was also obtained.
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| 3. |
- Biffi, Stefania, et al.
(författare)
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Cubosomes for in vivo fluorescence lifetime imaging
- 2017
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 28:5
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Tidskriftsartikel (refereegranskat)abstract
- Herein we provided the first proof of principle for in vivo fluorescence optical imaging application using monoolein-based cubosomes in a healthy mouse animal model. This formulation, administered at a non-cytotoxic concentration, was capable of providing both exogenous contrast for NIR fluorescence imaging with very high efficiency and chemospecific information upon lifetime analysis. Time-resolved measurements of fluorescence after the intravenous injection of cubosomes revealed that the dye rapidly accumulated mainly in the liver, while lifetimes profiles obtained in vivo allowed for discriminating between free dye or dye embedded within the cubosome nanostructure after injection.
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| 4. |
- Caltagirone, Claudia, et al.
(författare)
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Solvatochromic fluorescent BODIPY derivative as imaging agent in camptothecin loaded hexosomes for possible theranostic applications
- 2015
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Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 5:30, s. 23443-23449
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Tidskriftsartikel (refereegranskat)abstract
- We here discuss the potential theranostic nanomedicine application of an innovative formulation consisting of monoolein-based nanoparticles with a two-dimensional hexagonal inner structure stabilized in water using a mixture of PEO132-PPO50-PEO132 block copolymers with and without conjugated folate for targeting. The proposed tumor-cell targeted formulation was shown to be able to simultaneously host the model anticancer drug camptothecin and a pyrene-modified BODIPY fluorophore, based on dynamic light scattering, small-angle X-ray scattering, and cryogenic transmission electron microscopy. The photophysical properties of the fluorophore were studied in solution in various solvents. A marked fluorescent solvatochromism, whose origin was explained by time-dependent density functional theory theoretical calculations, was observed. Fluorescence microscopy showed that HeLa cells readily internalize these nanoparticles, and that the fluorophore localizes within the lipid droplets. In addition, cytotoxicity test revealed that these nanoparticles are not toxic at the concentration used for the imaging analysis.
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| 5. |
- Costa, Carolina, et al.
(författare)
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Cellulose-stabilized oil-in-water emulsions : Structural features, microrheology, and stability
- 2021
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617 .- 1879-1344. ; 252
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Tidskriftsartikel (refereegranskat)abstract
- Cellulose-based oil-in-water (O/W) emulsions were studied by diffusing wave spectroscopy (DWS) regarding the effect of the cellulose concentration and mixing rate on the average droplet size, microrheological features and stability. Furthermore, the microstructure of these emulsions was imaged by cryo-scanning electron microscopy (cryo-SEM). The micrographs showed that cellulose was effectively adsorbed at the oil-water interface, resembling a film-like shell that protected the oil droplets from coalescing. The non-adsorbed cellulose that was observed in the continuous aqueous medium, contributed to the enhancement of the viscosity of the medium, leading to an improvement in the stability of the overall system. Generally, the higher the cellulose concentration and mixing rate, the smaller the emulsion droplets formed, and the higher was their stability. The combination of both techniques, DWS and cryo-SEM, revealed a very appealing and robust methodology for the characterization and design of novel emulsion-based formulations.
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| 6. |
- Danino, Dganit, et al.
(författare)
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Microstructures in the aqueous solutions of a hybrid anionic fluorocarbon/hydrocarbon surfactant
- 2003
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Ingår i: Journal of Colloid and Interface Science. ; 259:2, s. 382-90
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Tidskriftsartikel (refereegranskat)abstract
- The aqueous solutions of the anionic hybrid fluorocarbon/hydrocarbon surfactant sodium 1-oxo-1[4-(tridecafluorohexyl)phenyl]-2-hexanesulfate (FC6HC4) shows peculiar rheological behavior. At 25 °C the viscosity vs concentration curve goes successively through a maximum and a minimum, while the viscosity vs temperature curve of the 10 wt% aqueous FC6HC4 solution goes through a marked maximum at 36 °C [Tobita et al., Langmuir 13 (1997) 5054]. In an attempt to explain these properties the microstructure of aqueous solutions of FC6HC4 has been investigated by means of digital light microscopy, transmission electron microscopy at cryogenic temperature (cryo-TEM), rheology, and self-diffusion NMR. At 20 °C, the increase of the FC6HC4 concentration was found to result in a progressive change of structure of the surfactant assemblies from mainly spherical micelles at 0.5 wt% to mainly cylindrical micelles at 10 wt%. At intermediate concentrations small disklike micelles and small complete and incomplete vesicles coexisting with cylindrical micelles were visualized. The occurrence of stretched cylindrical micelles is responsible for the effect of the surfactant concentration on the solution viscosity. Cryo-TEM, rheology, and self-diffusion NMR all suggest that an increase of the temperature brings about a growth of the assemblies present in the 10 wt% solution of FC6HC4. The structure of the assemblies present at the temperature where the viscosity is a maximum could not be elucidated by cryo-TEM because of the probable occurrence of an on-the-grid phase transformation, the result of blotting during specimen preparation. Nevertheless, the results show that the observed large assemblies break up at higher temperature to give rise to a more labile bicontinuous structure that consists of multiconnected disordered lamellae, with many folds and creases, and that may well be the L3 phase.
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| 7. |
- Ferreira, Guilherme A., et al.
(författare)
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Complexes of Charged-Neutral Block Copolymers and Surfactants : Process-Dependent Features and Long-Term Stability of Their Aqueous Dispersions
- 2023
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Ingår i: Langmuir : the ACS journal of surfaces and colloids. - : American Chemical Society (ACS). - 0743-7463. ; 39:11, s. 4113-4124
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Tidskriftsartikel (refereegranskat)abstract
- Aqueous dispersions of charged-neutral block copolymers (poly(acrylamide)-b-poly(acrylate)) complexed with an oppositely charged surfactant (dodecyltrimethylammonium) have been prepared by different approaches: the simple mixing of two solutions (MS approach) containing the block copolymer and surfactant, with their respective simple counterions, and dispersion of a freeze-dried complex salt prepared in the absence of simple counterions (CS approach). The CS particles were investigated under different conditions: dispersion of a CS in salt-free water and dispersion of a CS in a dilute salt solution, the latter condition yielding dispersions with the same composition as the MS process. Additionally, aged dispersions (up to 6 months) and dispersed complexes of the polyacrylate homopolymer and dodecyltrimethylammonium surfactant were evaluated. By employing different characterization techniques, it was seen that dispersions prepared by the MS approach display nanometric spherical particles with disordered cores, and poor colloidal stability, partially caused by the absence of surface charge (ζ-potential close to zero). Oppositely, anisometric particles were formed in CS dispersions and were large enough to sustain micellar cubic cores. The CS particles presented long-time colloidal stability, partially due to a net negative surface charge, but the stability varied with the length of the neutral block composing the corona. Our results demonstrate that all dispersed particles are metastable structures, with physicochemical properties strongly dependent on the preparation procedure, thus making these particles suitable for fundamental studies and potential applications where accurate control of their properties, including size, shape, internal structure, and stability, is desired.
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| 8. |
- Meli, Valeria, et al.
(författare)
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Docetaxel-Loaded Fluorescent Liquid-Crystalline Nanoparticles for Cancer Theranostics.
- 2015
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 31:35, s. 9566-9575
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Tidskriftsartikel (refereegranskat)abstract
- Here, we describe a novel monoolein-based cubosome formulation engineered for possible theranostic applications in oncology. The Docetaxel-loaded nanoparticles were stabilized in water by a mixture of commercial Pluronic (poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer) F108 (PF108) and rhodamine- and folate-conjugated PF108 so that the nanoparticles possess targeting, therapeutic, and imaging properties. Nanoparticles were investigated by DLS, cryo-TEM, and SAXS to confirm their structural features. The fluorescent emission characterization of the proposed formulation indicated that the rhodamine conjugated to the PF108 experiences an environment less polar than water (similar to chloroform), suggesting that the fluorescent fragment is buried within the poly(ethylene oxide) corona surrounding the nanoparticle. Furthermore, these nanoparticles were successfully used to image living HeLa cells and demonstrated a significant short-term (4 h incubation) cytotoxicity effect against these cancer cells. Furthermore, given their analogy as nanocarriers for molecules of pharmaceutical interest and to better stress the singularities of these bicontinuous cubic nanoparticles, we also quantitatively evaluated the differences between cubosomes and multilamellar liposomes in terms of surface area and hydrophobic volume.
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| 9. |
- Meli, Valeri, et al.
(författare)
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Theranostic hexosomes for cancer treatments : an in vitro study
- 2017
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Ingår i: New Journal of Chemistry. - : Royal Society of Chemistry (RSC). - 1144-0546 .- 1369-9261. ; 41:4, s. 1558-1565
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Tidskriftsartikel (refereegranskat)abstract
- We have formulated and investigated innovative lipid-based nanoparticles characterized by a reverse hexagonal liquid crystalline inner structure (hexosomes). These nanoparticles were doped with a potent, highly water insoluble anticancer drug, namely docetaxel, and stabilized by a mixture of commercial and folate- and rhodamine-conjugated Pluronic F108. Thus, they simultaneously possess therapeutic, imaging, and targeting properties toward cancer cells. The morphological and structural aspects of the hexosomes were investigated at different temperatures (10, 25, 37, and 50 °C), and our results demonstrate good performance in terms of stability of these nanoparticles. The latter was furthermore confirmed by the very slow and continuous release profile of docetaxel observed in drug release experiments. Although it was not possible to assess a specific compartmentalization of the dye, this formulation allowed the successful visualization of HeLa cells. Finally, cytotoxic assays showed a 20-fold higher toxic effect of the drug-doped hexosomes against HeLa cells with respect to the free (not loaded in hexosomes) anticancer drug. On the whole, these results indicate that this formulation is a potential theranostic tool in oncology.
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| 10. |
- Miceli, Vitale, et al.
(författare)
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In vitro imaging of b-cells using fluorescent cubic bicontinuous liquid crystalline nanoparticles
- 2016
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Ingår i: RSC Advances. - 2046-2069. ; 6, s. 62119-62127
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Tidskriftsartikel (refereegranskat)abstract
- To evaluate the potential of monoolein-based cubic bicontinuous liquid crystalline nanoparticles (cubosomes) as diagnostic tools in diabetes and pancreatic β-cell transplantation, fluorescent cubosomes were formulated, entrapping within the lipid bilayer a newly synthesized, potent, hydrophobic dye. Cryo-TEM, SAXS, and DLS were performed to assess the morphological and structural aspects of this formulation. Rat pancreatic β-cells (INS-1E) readily took up the cubosome nanoparticles, as revealed by in vitro internalization tests, and flow-cytometric analyses confirmed the persistence of the fluorescence for up to 24 hours. The cytotoxicity of cubosomes at various concentrations, evaluated with a real-time analysis of proliferation, revealed that the proliferation curves relative to the less concentrated formulation (5 μM in terms of monoolein content) were comparable to the untreated cultures. INS-1E cell cycle and apoptosis supported such results. In conclusion, this formulation, with dye content in the nanomolar range, seems to be useful for β-cell imaging.
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