Agnese Bisazza

Nanosponge formulations as oxygen delivery systems

Three types of cyclodextrin nanosponges were synthetized cross-linking α, β or γ cyclodextrin with carbonyldiimidazole as cross-linker. Nanosponges are solid nanoparticles previously used as drug carriers. In this studies cyclodextrin nanosponges were developed as oxygen delivery system. For this purpose the three types of nanosponges suspended in water were saturated with oxygen and in vitro characterized. The nanosponge safety was tested on Vero cells. Their ability to release oxygen in the presence and in the absence of ultrasound (US) was determined over time. Oxygen permeation through a silicone membrane was obtained using a β-cyclodextrin nanosponge/hydrogel combination system. Nanosponge formulations might be potential gas delivery systems showing the ability to store and to release oxygen slowly over time.

Preparation and characterization of dextran nanobubbles for oxygen delivery

Dextran nanobubbles were prepared with a dextran shell and a perfluoropentan core in which oxygen was stored. To increase the stability polyvinylpirrolidone was also added to the formulation as stabilizing agent. Rhodamine B was used as fluorescent marker to obtain fluorescent nanobubbles. The nanobubble formulations showed sizes of about 500nm, a negative surface charge and a good capacity of loading oxygen, no hemolytic activity or toxic effect on cell lines. The fluorescent labelled nanobubbles could be internalized in Vero cells. Oxygen-filled nanobubbles were able to release oxygen in different hypoxic solutions at different time after their preparation in in vitro experiments. The oxygen release kinetics could be enhanced after nanobubble insonation with ultrasound at 2.5MHz. The oxygen-filled nanobubble formulations might be proposed for therapeutic applications in various diseases.

New chitosan nanobubbles for ultrasound-mediated gene delivery: preparation and in vitro characterization.

Background The development of nonviral gene delivery systems is one of the most intriguing topics in nanomedicine. However, despite the advances made in recent years, several key issues remain unsettled. One of the main problems relates to the difficulty in designing nanodevices for targeted delivery of genes and other drugs to specific anatomic sites. In this study, we describe the development of a novel chitosan nanobubble-based gene delivery system for ultrasound-triggered release. Methods and results Chitosan was selected for the nanobubble shell because of its low toxicity, low immunogenicity, and excellent biocompatibility, while the core consisted of perfluoropentane. DNA-loaded chitosan nanobubbles were formed with a mean diameter of less than 300 nm and a positive surface charge. Transmission electron microscopic analysis confirmed composition of the core-shell structure. The ability of the chitosan nanobubbles to complex with and protect DNA was confirmed by agarose gel assay. Chitosan nanobubbles were found to be stable following insonation (2.5 MHz) for up to 3 minutes at 37°C. DNA release was evaluated in vitro in both the presence and absence of ultrasound. The release of chitosan nanobubble-bound plasmid DNA occurred after just one minute of insonation. In vitro transfection experiments were performed by exposing adherent COS7 cells to ultrasound in the presence of different concentrations of plasmid DNA-loaded nanobubbles. In the absence of ultrasound, nanobubbles failed to trigger transfection at all concentrations tested. In contrast, 30 seconds of ultrasound promoted a moderate degree of transfection. Cell viability experiments demonstrated that neither ultrasound nor the nanobubbles affected cell viability under these experimental conditions. Conclusion Based on these results, chitosan nanobubbles have the potential to be promising tools for ultrasound-mediated DNA delivery.

Ultrasound-mediated oxygen delivery from chitosan nanobubbles

Ultrasound (US) energy combined with gas-filled microbubbles has been used for several years in medical imaging. This study investigated the ability of oxygen-loaded chitosan bubbles to exchange oxygen in the presence or in the absence of US. Oxygen delivery is enhanced by sonication and both frequency and time duration of US affected the exchange kinetics.

Amphoteric Agmatine Containing Polyamidoamines as Carriers for Plasmid DNA in Vitro and in Vivo Delivery

In this paper we report on the investigation, as DNA nonviral carriers, of three samples of an amphoteric polyamidoamine bearing 4-aminobutylguanidine deriving units, AGMA5, AGMA10, and AGMA20, characterized by different molecular weights (M(w) 5100, 10100, and 20500, respectively). All samples condensed DNA in spherical, positively charged nanoparticles and protected it against enzymatic degradation. AGMA10 and AGMA20 polyplexes had average diameters lower than 100 nm. AGMA5 polyplexes were larger. All polyplexes showed negligible cytotoxicity and were internalized in cells. AGMA10 and AGMA20 performed differently from AGMA5 as nucleic acid carriers in vitro. AGMA10 and AGMA20 effectively promoted transfection, whereas AGMA5 was ineffective. FITC-labeled AGMA10 was prepared and the intracellular trafficking of its DNA polyplex was studied. DNA/AGMA10 polyplex was largely localized inside the nucleus, while AGMA10 concentrated in the perinuclear region. DNA/AGMA10 polyplex intravenously administered to mice promoted gene expression in liver but not in other organs without detectable toxic side effects.

Tricarbonyl−Rhenium Complexes of a Thiol-Functionalized Amphoteric Poly(amidoamine)

An amphoteric thiol-functionalized poly(amidoamine) nicknamed ISA23SH(10%) was synthesized. Rhenium complexes 1 and 2, containing 0.5 and 0.8 equiv of rhenium, respectively, were easily obtained by reacting ISA23SH(10%) with [Re(CO)(3)(H(2)O)(3)](CF(3)SO(3)) in aqueous solution at pH 5.5. Both ISA23SH(10%), and its rhenium complexes were soluble in water under physiological conditions. The resultant solutions were stable, even in the presence of cysteine. Rhenium chelation occurred through the S and N atoms of the cysteamine moiety, as demonstrated by (1)H, (13)C, and (15)N NMR spectroscopy. The diffusion coefficients and the hydrodynamic radii of ISA23SH(10%) and complex 1 were determined by pulsed gradient spin echo (PGSE) NMR experiments. The radius of the rhenium complexes 1 and 2 was always slightly larger than that of the parent polymer. TEM analysis showed that both complexes form spherical nanoparticles with narrow size distributions. Consistent results were obtained by dynamic light scattering. The observed sizes were in good agreement with those evaluated by PGSE. Preliminary in vitro and in vivo biological studies have been performed on complexes 1 and 2 as well as on the parent ISA23SH(10%). Neither hemolytic activity of the two rhenium complexes and the parent polymer, up to a concentration of 5 mg/mL, nor cytotoxic effects were observed on Hela cell after 48 h at a concentration of 100 ng/mL. In vivo toxicological tests showed that ISA23SH(10%) is highly biocompatible, with a maximum tolerated dose (MTD) of 500 mg/kg. No toxic side effects were apparent after the intravenous injection in mice of the two rhenium complexes in doses up to 20 mg/kg.

Microbubble-mediated oxygen delivery to hypoxic tissues as a new therapeutic device

Chitosan-coated oxygen microbubbles of average diameter 2.5 μm, narrow size distribution and spherical shape were prepared. A core-shell structure was evidenced by fluorescence microscopy using fluorescent microbubbles. Such microbubbles can be a therapeutic device for vehiculating oxygen to hypoxic tissues, provided they show proper permeability and diffusivity properties and are non-toxic. Our study proves that oxygen is efficiently delivered both in ‘in vitro’ and ‘in vivo’ preparations, and can be conveniently metabolized reversing the cellular hypoxic response. Moreover, toxic effects were investigated in human blood and in cultured cells and no evidence for them was found.

Enhanced antiviral activity of acyclovir loaded into nanoparticles.

The activity of antivirals can be enhanced by their incorporation in nanoparticulate delivery systems. Peculiar polymeric nanoparticles, based on a β-cyclodextrin-poly(4-acryloylmorpholine) monoconjugate (β-CD-PACM), are proposed as acyclovir carriers. The experimental procedure necessary to obtain the acyclovir-loaded nanoparticles using the solvent displacement preparation method will be described in this chapter. Fluorescent labeled nanoparticles are prepared using the same method for cellular trafficking studies. The biocompatibility assays necessary to obtain safe nanoparticles are reported. Section 4 of this chapter describes the assessment of the antiviral activity of the acyclovir-loaded nanoparticles.

The in vitro characterization of dextran-based nanobubbles as possible DNA transfection agents

Nanobubbles consisting of a diethylaminoethyl-dextran (DEAE) shell and a perfluoropentane core were prepared as a novel DNA transfection agent. Nanobubble diameters were less than 500 nm, they possessed positive surface charge, and the ability to complex with and transfect DNA. DEAE nanobubbles present a novel platform for DNA delivery into cells that may be combined with ultrasound for imaging and targeting purposes.

The inclusion complex of 4-hydroxynonenal with a polymeric derivative of β-cyclodextrin enhances the antitumoral efficacy of the aldehyde in several tumor cell lines and in a three-dimensional human melanoma model

4-Hydroxynonenal (HNE) is the most studied end product of the lipoperoxidation process, by virtue of its relevant biological activity. The antiproliferative and proapoptotic effects of HNE have been widely demonstrated in a great variety of tumor cell types in vitro. Thus, it might represent a promising new molecule in anticancer therapy strategies. However, the extreme reactivity of this aldehyde, as well as its insolubility in water, a limiting factor for drug bioavailability, and its rapid degradation by specific enzymes represent major obstacles to its possible in vivo application. Various strategies can used to overcome these problems. One of the most attractive strategies is the use of nanovehicles, because loading drugs into nanosized structures enhances their stability and solubility, thus improving their bioavailability and their antitumoral effectiveness. Several natural or synthetic polymers have been used to synthesize nanosized structures and, among them, β-cyclodextrin (βCD) polymers are playing a very important role in drug formulation by virtue of the ability of βCD to form inclusion compounds with a wide range of solid and liquid molecules by molecular complexation. Moreover, several βCD derivatives have been designed to improve their physicochemical properties and inclusion capacities. Here we report that the inclusion complex of HNE with a derivative of βCD, the βCD-poly(4-acryloylmorpholine) conjugate (PACM-βCD), enhances the aldehyde stability. Moreover, the inclusion of HNE in PACM-βCD potentiates its antitumor effects in several tumor cell lines and in a more complex system, such as a human reconstructed skin carrying melanoma tumor cells.