Nanocarriers for drug targeting and improved bioavailability

This PhD thesis debates, mostly, on two main topics: - Drug delivery to brain - Nanosuspensions for different applications The objective of the first topic was the development of liposomes to which anti-TfR-monoclonal antibodies (Ox26) or lactoferrin was bounded to transport the selective NK3 receptor agonist senktide to CNS across the BBB. NK3 receptors are widely expressed in the CNS and their stimulation by senktide (ICV) increase extracellular DA. Liposomes were prepared using the film hydration method. In vivo microdialysis studies were performed to estimate the responsiveness of NAc shell DA to senktide as a consequence of its CNS delivery. Senktide given ICV or loaded into Ox26/lactoferrin-liposome (0.5 μg/kg iv) elicited a significant increase of dialysate DA in the NAc shell of rats whilst senktide given iv (0.1 mg/kg) or loaded in control stealth liposomes did not affect NAc shell DA. Liposomes formulation here described represent an effective way of CNS delivering of senktide following intravenous administration the TfR-transport system. On the other hand, three different types of nanosuspensions were formulated and studied: - Tretinoin nanosuspensions for topical delivery - Piroxicam nanosuspensions loaded in oral disintegrating tablet (ODT) for oral delivery - Quercetin nanosuspensions loaded in fast dissolving films for oral delivery The aims of the first work were to improve cutaneous targeting and photostability of tretinoin by using nanosuspension formulation. Tretinoin is a drug widely used in the topical treatment of various dermatological diseases. The tretinoin nanosuspension was prepared by precipitation method and then characterized by photo correlation spectroscopy for mean size and size distribution, and by transmission electron microscopy for morphological studies. An oil in water tretinoin nanoemulsion was also prepared and used as a control. Dermal and transdermal delivery of both tretinoin nanosuspension and nanoemulsion were tested in vitro by using Franz diffusion cells and newborn pig skin. Photodegradation studies were carried out by UV irradiation (1 h, λ=366 nm) of the tretinoin nanosuspension in comparison with the nanoemulsion and a methanolic solution of the drug. During 8 h percutaneous experiments, no permeation of tretinoin through the whole skin thickness was detected but the drug was deposited into the skin layers, mainly in the stratum corneum, similarly to the nanoemulsion. UV irradiation of the nanosuspension showed a great improvement of tretinoin stability in comparison with both controls. Overall results show that nanosuspension might be a useful formulation for improving tretinoin dermal delivery and stability. Piroxicam (PRX) is a non-steroidal anti-inflammatory drug characterized by a poorly water solubility and consequently by a low oral bioavailability. Different nanocrystals orally disintegrating tablets (ODT) were prepared to enhance piroxicam dissolution velocity and saturation solubility. Nanosuspensions were prepared using high pressure homogenization technique. Different ODT formulations were prepared using the same nanosuspension but changing different excipients in order to optimize dissolution properties. PRX nanocrystals size and zeta potential were determined by photon correlation spectroscopy (PCS). Characterization of PRX nanocrystals ODT was carried out by infrared spectroscopy (FTIR), X-ray powder diffractometry (XRPD), differential scanning calorimetry. Dissolution study of PRX ODT was performed in distilled water (pH 5.5) and was compared with PRX coarse suspension ODT, PRX/poloxamer 188 physical mixture, bulk PRX samples and a piroxicam commercial ODT (Feldene). All PRX nanocrystals ODT formulations showed a higher drug dissolution rate than coarse PRX ODT. PRX nanocrystals ODT prepared using gelatin or croscaramellose as excipient showed a higher PRX dissolution rate compared with the commercial formulation and with ODT prepared using xanthan gum. The improvement in PRX dissolution rate is mainly caused by the increased surface-to-volume ratio due to the submicron dimension of the drug nanocrystal, however, also the presence of the correct excipients (as disgregant) seem to play an essential role. Finally, quercetin nanosuspensions loaded fast dissolving films were formulated and studied. The aim of this work was to investigate the possible use of maltodextrin IT6 (MDX) to prepare fast-dissolving films, loaded by quercetin nanocrystals. Quercetin nanosuspensions were prepared using an high pressure homogenizer, meanwhile drug loaded films were obtained drying in a siliconized polyester sheet quercetin nanosuspensions with the others compounds in a oven at 60 °C. Films were finally cut and packed within sealed aluminium pouches. Quercetin nanocrystals were characterized by photo correlation spectroscopy for mean size and size distribution and by transmission electron microscopy for morphological studies. On the other hand, quercetin nanosuspensions loaded films were characterized in term of flexibility, tensile strength and thickness. Finally, dissolution studies in distilled water were performed, comparing release profiles of quercetin loaded films, quercetin raw material and quercetin nanosuspensions

UHPLC-MS/MS Method for the Analysis of 2,6 Toluene Diisocyanate and 2,4 Toluene Diisocyanate Released from Microa-gglomerated Corks in Wine

AbstractMicro-agglomerate corks, made by agglutination of cork granulate through the addition of different adhesives, represent an important slice of the market of cork stoppers. Binder glues which are polyurethane- or butadiene-based have been used since they have strong agglomerating effect. Unfortunately, polyurethane-based glues can have isocyanide end group compounds which can migrate into the wine. 2,4-toluene diisocyanate (2,4-TDI) and 2,6 toluene diisocyanate (2,6-TDI), can be found in adhesive and could migrate into wine. A simple ultrahigh-performance liquid chromatography-mass spectrometry (UHPLC-MS/MS) method for the determination of these active ingredients (a.is.) in wine has been developed. The method has been validated under Eurachem CITAC guidelines (Cooperation on International Traceability in Analytical Chemistry). Instrument limit of detection (LOD) and to a limit of quantification (LOQ) for 2,6 TDI and 2,4 TDI were 0.42 and 0.39 μg/L, and 1.72 and 1.57 μg/L, respectively. Four different solvents applied for recoveries showed quite different rates ranging for 2,6 TDI and 2,4 TDI from 17.96 to 88.53 %, and 40.08 to 99.18 %, respectively. Real sample analysis showed low residue levels, especially of 2,6 TDI, with values always below the LOQ. The data reported on real samples allowed to establish that from a risk management purpose, no toxicology risk can be accomplished

Growing CeO2_2 Nanoparticles within the Nano-Porous Architecture of the SiO2_2 Aerogel

In this study, new CeO$_2$-SiO$_2$ aerogel nanocomposites obtained by controlled growth of CeO$_2$ nanoparticles within the highly porous matrix of a SiO$_2$ aerogel are presented. The nanocomposites have been synthesized via a sol-gel route, employing cerium (III) nitrate as the CeO$_2$ precursor and selected capping agents to control the growth of the CeO$_2$ nanoparticles, which occurs during the supercritical drying of the aerogels. Samples with different loading of the CeO$_2$ dispersed phase, ranging from 5 to 15%, were obtained. The nanocomposites showed the morphological features typical of the SiO$_2$ aerogels such as open mesoporosity with surface area values up to 430 m$^2$·g$^{-1}$. TEM and XRD characterizations show that nanocrystals of the dispersed CeO$_2$ nanophase grow within the aerogel already during the supercritical drying process, with particle sizes in the range of 3 to 5 nm. TEM in particular shows that the CeO$_2$ nanoparticles are well distributed within the aerogel matrix. We also demonstrate the stability of the nanocomposites under high temperature conditions, performing thermal treatments in air at 450 and 900°C. Interestingly, the CeO$_2$ nanoparticles undergo a very limited crystal growth, with sizes up to only 7 nm in the case of the sample subjected to a 900°C treatment

Tuning the Properties of Nanoceria by Applying Force: Stress Induced Ostwald Ripening

The ionic conductivity and activity of a material, such as ceria, is central to its exploitation in applications such as fuel cells or catalysis. Grain Boundaries (GB) influence profoundly the ionic conductivity and activity of a material. Accordingly, the ability to control GB concentrations is pivotal to these applications. Here, we show that Oswald ripening can be induced by applying uniaxial force. In particular, grain-boundaries are purged to facilitate single nanocrystals from polycrystalline precursors. Our simulations thus predict mechanisms for strain-tunable properties

Insights into the Structure of Dot@Rod and Dot@Octapod CdSe@CdS Heterostructures

CdSe@CdS dot@rods with diameter around 6 nm and length of either 20, 27, or 30 nm and dot@octapods with pod diameters of ?15 nm and lengths of ?50 nm were investigated by X-ray absorption spectroscopy. These heterostructures are prepared by seed-mediated routes, where the structure, composition, and morphology of the CdSe nanocrystals used as a seed play key roles in directing the growth of the second semiconducting domain. The local structural environment of all the elements in the CdSe@CdS heterostructures was investigated at the Cd, S, and Se K-edges by taking advantage of the selectivity of X-ray absorption spectroscopy, and was compared to pure reference compounds. We found that the structural features of dot@rods are independent of the size of the rods. These structures can be described as made of a CdSe dot and a CdS rod, both in the wurtzite phase with a high crystallinity of both the core and the rod. This result supports the effectiveness of high temperature colloidal synthesis in promoting the formation of core@shell nanocrystals with very low defectivity. On the other hand, data on the CdSe@CdS with octapod morphology suggest the occurrence of a core composed of a CdSe cubic sphalerite phase with eight pods made of CdS wurtzite phase. Our findings are compared to current models proposed for the design of functional heterostructures with controlled nanoarchitecture