Oligonucleotides and polynucleotides condensation onto liposome surface: effects of the base and of the nucleotide length

Oral delivery of all-trans retinoic acid mediated by liposome carriers

All-trans retinoic acid (ATRA) is a molecule that finds wide applications in medicine. Connection between cancer cell proliferation and ATRA is a well-established item. Driven by the potential applications of liposomes in stabilizing and protecting therapeutic compounds thus enabling effective delivery of encapsulated compounds, recent research efforts have been directed to understanding mechanisms of oral delivery through the gastrointestinal tract. The surface charge of the liposome bilayers can modify the interactions between the aggregates and the gastrointestinal fluids. Here, we investigated the ability of cationic and anionic liposomes to encapsulate, protect and deliver ATRA in an in-vitro digestion process as a different oral administration route. Stability and encapsulation efficiency of ATRA in negatively and positively charged liposomes enriched with α-tocopherol were investigated by means of UV-vis spectroscopy, dynamic light scattering and ζ-potential. The applicability of the carriers was tested by means of an in-vitro digestion procedure allowing for the measurement of the bioavailability of ATRA. From this study evidence was provided that the water insoluble molecules, ATRA and α-tocopherol are intercalated in liposome membranes regardless of the surface charge of the vesicle bilayers. Comparisons between cationic and anionic liposomes incorporating retinoic acid show differences in bioavailability. The cationic vesicles are preferable for a larger amount of ATRA bioavailability, which can be understood from electrostatic interactions. Thus ATRA is ionized in a wide range of pHs but protonated in anionic vesicles.

Polymer Capsules for Enzymatic Catalysis in Confined Environments

Catalysis is at the base of a series of biological and technological application processes. In recent years, the tendency has developed to carry out catalyzed reactions within confined structures, thus forming systems called micro or nanoreactors. Compartmentalized structures are cavities delimited by a wall where specific functions are introduced with a defined concentration and in the desired sites. These containers are generally referred to as nano or microcapsules, assuming the function of reactors in the presence of chemical reactions. Among the various types of existing structures, one of the most interesting is represented by systems made with polymers. This review aims to highlight some of the current advances in the use of functionalized structures that are useful for catalysis reactions, paying particular attention to polymer capsules and enzymes. The built-up methods used for the production of polymer capsules, as well as the aspects that influence membrane permeability and reactivity to environmental conditions, are discussed. Recent advances on biocatalysis confined in polymeric capsules are illustrated, and the strengths and weaknesses of the principal nanoreactors are considered.

Liposomal drug delivery systems for targeted cancer therapy: is active targeting the best choice?

Liposomes are biodegradable and biocompatible self-forming spherical lipid bilayer vesicles. They can encapsulate and deliver one or more hydrophobic and hydrophilic therapeutic agents with poor therapeutic indices to tumor sites. Properties such as lipid bilayer fluidity, charge, size and surface hydration can be modified to extend liposome circulation time in the bloodstream and enhance efficacy. The focus of this review is on ligand-conjugated liposomes and their potential application in tumor-targeted delivery. Ligand-conjugated liposomes are designed to target receptors which are overexpressed on tumor cells to decrease drugs side effects by enhancing their selective delivery to tumor site. Despite the extensive research in this area, no small molecule ligand-conjugated liposome has been approved up to date for cancer therapy.

On the role of a coumarin derivative for sensing applications: Nucleotide identification using a micellar system

The recognition of nucleotides is of crucial importance because they are the basic constituents of nucleic acids. The present study is focused on the selective interaction between a novel amphiphilic fluorophore containing coumarin and imidazole, CI (1-methyl-3-(12-((2-oxo-2H-chromen-7-yl)oxy)dodecyl)-1H-imidazol-3-ium bromide), and different nucleotide-monophosphates (NMPs). It was supposed that the solubilization of the low water soluble CI in a micelle system of hexadecyltrimethylammonium chloride (CTAC) would make the coumarin moiety of CI available to the interaction with the water-soluble NMPs. Changes in CTAC critical micelle concentration suggested that CI strongly interacted with the host cationic surfactant, thus forming a positively charged interface enriched with coumarin able to interact with the anionic NMPs. Steady-state fluorescence quenching revealed that CI/CTAC system was capable of distinguish between purine- and pyrimidine-based nucleotides. A modified Stern-Volmer equation permitted the use of a quenching model that accounted for the possible interactions between the micelles and the nucleotides. The data analysis allowed calculating selective parameters that differentiated according to the type of nucleotide either at 25 or 50°C. Our results established the utility of the novel coumarin derivative fluorophore, supported by the simple and suitable micellar systems, as a tool for DNA sensing applications.

From self-assembly fundamental knowledge to nanomedicine developments

This review highlights the key role of NMR techniques in demonstrating the molecular aspects of the self-assembly of surfactant molecules that nowadays constitute the basic knowledge which modern nanoscience relies on. The aim is to provide a tutorial overview. The story of a rigorous scientific approach to understand self-assembly in surfactant systems and biological membranes starts in the early seventies when the progresses of SAXRD and NMR technological facilities allowed to demonstrate the existence of ordered soft matter, and the validity of Tanford approach concerning self-assembly at a molecular level. Particularly, NMR quadrupolar splittings, NMR chemical shift anisotropy, and NMR relaxation of dipolar and quadrupolar nuclei in micellar solutions, microemulsions, and liquid crystals proved the existence of an ordered polar-apolar interface, on the NMR time scale. NMR data, rationalized in terms of the two-step model of relaxation, allowed to quantify the dynamic aspects of the supramolecular aggregates in different soft matter systems. In addition, NMR techniques allowed to obtain important information on counterion binding as well as on size of the aggregate through molecular self-diffusion. Indeed NMR self-diffusion proved without any doubt the existence of bicontinuous microemulsions and bicontinuous cubic liquid crystals, suggested by pioneering and brilliant interpretation of SAXRD investigations. Moreover, NMR self-diffusion played a fundamental role in the understanding of microemulsion and emulsion nanostructures, phase transitions in phase diagrams, and particularly percolation phenomena in microemulsions. Since the nineties, globalization of the knowledge along with many other technical facilities such as electron microscopy, particularly cryo-EM, produced huge progresses in surfactant and colloid science. Actually we refer to nanoscience: bottom up/top down strategies allow to build nanodevices with applications spanning from ICT to food technology. Developments in the applied fields have also been addressed by important progresses in theoretical skills aimed to understand intermolecular forces, and specific ion interactions. Nevertheless, this is still an open question. Our predictive ability has however increased, hence more ambitious targets can be planned. Nanomedicine represents a major challenging field with its main aims: targeted drug delivery, diagnostic, theranostics, tissue engineering, and personalized medicine. Few recent examples will be mentioned. Although the real applications of these systems still need major work, nevertheless new challenges are open, and perspectives based on integrated multidisciplinary approaches would enable both a deeper basic knowledge and the expected advances in biomedical field.

Templated globules--applications and perspectives

Polyelectrolyte capsules represent a class of particles composed of an internal core and an external polymer matrix shell. In recent years, it has become clear that the manufacture of polyelectrolyte capsule is likely to have a significant role in several areas including medicine and biology. Many distinct methodologies for the fabrications of templated globules have been reported. Despite the huge availability of knowledge used to obtain such globules, the choice of the appropriate technology for the desired applications demands a deeper appreciation of this issue. Furthermore, the extent to which the applications of polyelectrolyte capsule may be actively involved in the practical biomedical field is still a fascinating challenge. Here, we review the recipes for the globule assembly with their own benefits and limitations and how different templates could affect the final globule features, with a particular focus on the Layer by Layer (LbL) procedure. The latest applications in biological, therapeutical and diagnostic areas are also discussed and some outlooks for the strategic development of polymer globule are highlighted.

Evidence for the role of hydrophobic forces on the interactions of nucleotide-monophosphates with cationic liposomes

In this work, the interaction of nucleotide-monophosphates (NMPs) with unilamellar liposomes made of 1,2-Dioleoyl-3-Trimethylammonium-Propane (DOTAP) and 1,2-Dioleoyl-sn-Glycero-3-Phosphoethanolamine (DOPE) was investigated. Here, we demonstrate how adsorption is affected by the type of nucleotide-monophosphate. Dynamic light scattering (DLS) results revealed, for each NMP, that a distinguishable concentration exists at which a significant growth of the aggregates occurs. Adenosine 5'-monophosphate (AMP) and guanosine 5'-monophosphate (GMP) have shown a higher propensity to induce liposome aggregation process and in particular GMP appears to be the most effective. From ζ-potential experiments we found that liposomes loaded with purine based nucleotides (AMP and GMP) are able to decrease the ζ-potential values to a greater extent in comparison with the pyrimidine based nucleotides thimydine 5'-monophosphate (TMP) and uridine 5'-monophosphate (UMP). Moreover, a careful analysis of nucleotide-liposome interactions revealed that nucleotides have different capacity to induce the formation of nucleotide-liposome complexes, and purine based nucleotides have higher affinities with lipid membranes. On the whole, the data emphasize that the mechanisms driving the interactions between liposomes and NMPs are also influenced by the existence of hydrophobic forces.

Oxidation-proof microemulsions: Microstructure and reactivity in the presence of dioxiranes

Dioxiranes are used as reagents in a myriad of synthetically useful oxidations performed in aqueous medium. To extend such an approach also to substrates that are highly hydrophobic, we propose here the use of microemulsions based on the surfactant hexadecyltrimethylammonium hydrogen sulphate (CTAHS) because of its high stability against peroxide species. In this paper, we examine the dioxirane (isolated or generated in situ) reactivity in different CTAHS microemulsions. Yield and selectivity of the oxidation of β-methylstyrene by dimethyldioxirane (DDO) generate "in situ" and of laurolactam by isolated methyl(trifluorometyl)dioxirane (TFDO) were studied. For each microemulsion, the aggregate size and the localization of the components were determined by a combination of NMR and light scattering techniques. The hydrodynamic radius of the micelles is close to the length of the surfactant and this suggests they are spherical in shape. When acetone (the precursor of DDO) is present in the formulation, it partitions itself between the aqueous bulk and the micellar palisade so that the dioxirane eventually formed is readily available to oxidize substrates secluded in the micelle. Apolar substrates, confined within the micelles, are protected from uncontrolled oxidations, leading to an astonishing high selectivity of oxidation of laurolactam to 12-nitro-lauric acid by TFDO. This opens the way to an easy procedure (performed in water under mild conditions) to synthetize ω-nitroacids.