Chitosan nanoemulsions of cold-pressed orange essential oil to preserve fruit juices.

Sweet orange essential oil is obtained from the peels of Citrus sinensis (CSEO) by cold pressing, and used as a valuable product by the food industry. Nanoencapsulation is known as a valid strategy to improve chemical stability, organoleptic properties, and delivery of EO-based products. In the present study we encapsulated CSEO using chitosan nanoemulsions (cn) as nanocarrier, and evaluated its antimicrobial activity in combination with mild heat, as well as its sensorial acceptability in orange and apple juices. CSEO composition was analyzed by GC-MS, and 19 components were identified, with limonene as the predominant constituent (95.1%). cn-CSEO was prepared under low shear conditions and characterized according to droplet size (<60 nm) and polydispersity index (<0.260 nm). Nanoemulsions were stable for at least 3 months at 4 ± 2 °C. cn-CSEO were compared with suspensions of CSEO (s-CSEO) (0.2 µL of CSEO/mL) in terms of antibacterial activity in combination with mild heat (52 °C) against Escherichia coli O157:H7 Sakai. cn-CSEO displayed a greater bactericidal activity than s-CSEO at pH 7.0 and pH 4.0. The validation in fruit juices showed an improved bactericidal effect of cn-CSEO in comparison with s-CSEO when combined with mild heat in apple juice, but not in orange juice. In both juices, the combination of CSEO and mild heat exerted synergistic lethal effects, reducing the treatment time to cause the inactivation of up to 5 Log10 cycles of E. coli O157:H7 Sakai cells. Finally, the sensory characteristics of both juices were acceptable either when using s-CSEO or CSEO nanoemulsified with chitosan. Therefore, as a promising carrier for lipophilic substances, the encapsulation of EOs with chitosan nanoemulsions might represent an advantageous alternative when combined with mild heat to preserve fruit juices.

Design of a nanoprobe for high field magnetic resonance imaging, dual energy X-ray computed tomography and luminescent imaging.

The combination of different bioimaging techniques, mainly in the field of oncology, allows circumventing the defects associated with the individual imaging modalities, thus providing a more reliable diagnosis. The development of multimodal endogenous probes that are simultaneously suitable for various imaging modalities, such as magnetic resonance imaging (MRI), X-ray computed tomography (CT) and luminescent imaging (LI) is, therefore, highly recommended. Such probes should operate in the conditions imposed by the newest imaging equipment, such as MRI operating at high magnetic fields and dual-energy CT. They should show, as well, high photoluminescence emission intensity for their use in optical imaging and present good biocompatibility. In this context, we have designed a single nanoprobe, based on a core-shell architecture, composed of a luminescent Eu3+:Ba0.3Lu0.7F2.7 core surrounded by an external HoF3 shell that confers the probe with very high magnetic transverse relaxivity at high field. An intermediate, optically inert Ba0.3Lu0.7F2.7 layer was interposed between the core and the shell to hinder Eu3+-Ho3+ cross-relaxation and avoid luminescence quenching. The presence of Ba and Lu, with different K-edges, allows for good X-ray attenuation at high and low voltages. The core-shell nanoparticles synthesized are good potential candidates as trimodal bioprobes for MRI at high field, dual-energy CT and luminescent imaging.

Effective in Vitro Photokilling by Cell-Adhesive Gold Nanorods.

Upon excitation of their localized surface plasmon resonance (LSPR) band, gold nanorods (AuNRs) show a characteristic light-to-heat transduction, a useful and versatile property for a range of biomedical applications such as photothermal therapy, drug delivery, optoacoustic imaging and biosensing, among others. Nanoparticle (NP)-mediated photothermal therapy (PTT) rests on the ability of nanomaterials to convert light energy into heat and can currently be considered as a promising method for selectively destroying tumor cells by (photo)-thermoablation. One inherent limitation to NP-mediated PTT is that the nanoparticles must arrive at the site of action to exert their function and this typically involves cellular internalization. Here we report the use of the Keggin-type polyoxometalate (POM) phosphotungstic acid (PTA) as an inorganic gelling agent for the encapsulation of plasmonic gold nanorods (AuNRs) inside a biocompatible and cell-adhesive chitosan hydrogel matrix. These functional sub-micrometric containers are non-cytotoxic and present the ability to adhere to the cytoplasmic membranes of cells avoiding any need for cellular internalization, rendering them as highly efficient thermoablating agents of eukaryotic cells in vitro.

Targeted Nanoparticles for the Treatment of Alzheimer's Disease.

BACKGROUND: Alzheimer's disease (AD) has a dramatic impact on society. The therapeutic targets are located in the central nervous system (CNS), which limits the efficacy of drugs systemically administered: the blood-brain barrier (BBB) selectively allows the permeation of just a few kinds of molecules from the systemic circulation to the CNS. On the other hand, local administration routes to CNS are highly invasive. METHODS: In this article, we have reviewed therapeutic approaches against AD, which are based on nanoparticles targeted to the brain and to the pathological hallmarks of the disease. The existing literature has been classified according to the AD feature that is addressed. RESULTS: Nanoparticles have been used for the targeted delivery of drugs aiming to reduce the AD symptoms or to reverse the course of the disease. For this task the multivalency of nanoparticles has allowed their functionalization with several kinds of targeting groups, to cross the BBB and to target the place of treatment. With this approach an increased drug bioavailability has been achieved in the CNS using intravenous administration in place of more invasive administration routes. Additionally, nanoparticles have also been used in the development of vaccines and therapeutic formulations for intranasal administration. CONCLUSION: Targeted nanoparticles have been proved useful to enhance the performance of therapies against AD in animal models. A better understanding of AD mechanisms will help the successful application of targeted nanoparticles for combined therapies.

Controlling Properties and Cytotoxicity of Chitosan Nanocapsules by Chemical Grafting.

The tunability of the properties of chitosan-based carriers opens new ways for the application of drugs with low water-stability or high adverse effects. In this work, the combination of a nanoemulsion with a chitosan hydrogel coating and the following poly (ethylene glycol) (PEG) grafting is proven to be a promising strategy to obtain a flexible and versatile nanocarrier with an improved stability. Thanks to chitosan amino groups, a new easy and reproducible method to obtain nanocapsule grafting with PEG has been developed in this work, allowing a very good control and tunability of the properties of nanocapsule surface. Two different PEG densities of coverage are studied and the nanocapsule systems obtained are characterized at all steps of the optimization in terms of diameter, Z potential and surface charge (amino group analysis). Results obtained are compatible with a conformation of PEG molecules laying adsorbed on nanoparticle surface after covalent linking through their amino terminal moiety. An improvement in nanocapsule stability in physiological medium is observed with the highest PEG coverage density obtained. Cytotoxicity tests also demonstrate that grafting with PEG is an effective strategy to modulate the cytotoxicity of developed nanocapsules. Such results indicate the suitability of chitosan as protective coating for future studies oriented toward drug delivery.