Biana Godin

Nanomedicine – challenge and perspectives

The application of nanotechnology concepts to medicine joins two large cross-disciplinary fields with an unprecedented societal and economical potential arising from the natural combination of specific achievements in the respective fields. The common basis evolves from the molecular-scale properties relevant to the two fields. Local probes and molecular imaging techniques allow surface and interface properties to be characterized on a nanometer scale at predefined locations, while chemical approaches offer the opportunity to elaborate and address surfaces, for example, for targeted drug delivery, enhanced biocompatibility, and neuroprosthetic purposes. However, concerns arise in this cross-disciplinary area about toxicological aspects and ethical implications. This Review gives an overview of selected recent developments and applications of nanomedicine.

Ethosomes — novel vesicular carriers for enhanced delivery: characterization and skin penetration properties

This work describes a novel carrier for enhanced skin delivery, the ethosomal system, which is composed of phospholipid, ethanol and water. Ethosomal systems were much more efficient at delivering a fluorescent probe to the skin in terms of quantity and depth, than either liposomes or hydroalcoholic solution. The ethosomal system dramatically enhanced the skin permeation of minoxidil in vitro compared with either ethanolic or hydroethanolic solution or phospholipid ethanolic micellar solution of minoxidil. In addition, the transdermal delivery of testosterone from an ethosomal patch was greater both in vitro and in vivo than from commercially available patches. Skin permeation of ethosomal components, ethanol and phospholipid, was demonstrated in diffusion-cell experiments. Ethosomal systems composed of soy phosphatidylcholine 2%, ethanol 30% and water were shown by electron microscopy to contain multilamellar vesicles. 31P-NMR studies confirmed the bilayer configuration of the lipids. Calorimetry and fluorescence measurements suggested that the vesicular bilayers are flexible, having a relatively low T(m) and fluorescence anisotropy compared with liposomes obtained in the absence of ethanol. Dynamic light scattering measurements indicated that ethanol imparted a negative charge to the vesicles. The average vesicle size, as measured by dynamic light scattering, was modulated by altering the ethosome composition. Experiments using fluorescent probes and ultracentrifugation showed that the ethosomes had a high entrapment capacity for molecules of various lyophilicities.

Size and shape effects in the biodistribution of intravascularly injected particles

Understanding how size and shape can affect the biodistribution of intravascularly injected particles is of fundamental importance both for the rational design of delivery systems and from a standardization and regulatory view point. In this work, uncoated silica spherical beads, with a diameter ranging from 700 nm to 3 microm, and uncoated non-spherical silicon-based particles, with quasi-hemispherical, cylindrical and discoidal shapes, have been injected into tumor bearing mice. The number of particles accumulating in the major organs and within the tumor mass has been measured through elemental silicon (Si) analysis. For the spherical beads, it has been found that the number of particles accumulating in the non-RES organs reduces monotonically as the diameter d increases, suggesting the use of smaller particles to provide a more uniform tissue distribution. However, discoidal particles have been observed to accumulate more than others in most of the organs but the liver, where cylindrical particles are deposited at a larger extent. These preliminary results support the notion of using sub-micrometer discoidal particles as intravascular carriers to maximize accumulation in the target organ whilst reducing sequestration by the liver.

Geometrical confinement of gadolinium-based contrast agents in nanoporous particles enhances T1 contrast

Magnetic resonance imaging contrast agents are currently designed by modifying their structural and physiochemical properties in order to improve relaxivity and to enhance image contrast. Here we show a general method for increasing relaxivity by confining contrast agents inside the nanoporous structure of silicon particles. Magnevist, gadofullerenes and gadonanotubes were loaded inside the pores of quasi-hemispherical and discoidal particles. For all combinations of nanoconstructs, a boost in longitudinal proton relaxivity r1 was observed: for Magnevist, r1~14 mM-1s-1/Gd3+ion (~8.15×10+7 mM-1s-1/construct); for gadofullerenes, r1~200 mM-1s-1/Gd3+ion (~7×10+9 mM-1s-1/construct); for gadonanotubes, r1~150 mM-1s-1/Gd3+ion (~2×10+9 mM-1s-1/construct). These relaxivity values are about 4 to 50 times larger than that of clinically-available gadolinium-based agents (~4 mM-1s-1 /Gd3+ion). The enhancement in contrast is attributed to the geometrical confinement of the agents, which influences the paramagnetic behavior of the Gd3+ions. Thus, nanoscale confinement offers a new and general strategy for enhancing the contrast of gadolinium-based contrast agents.

Sustained Small Interfering RNA Delivery by Mesoporous Silicon Particles

RNA interference (RNAi) is a powerful approach for silencing genes associated with a variety of pathologic conditions; however, in vivo RNAi delivery has remained a major challenge due to lack of safe, efficient, and sustained systemic delivery. Here, we report on a novel approach to overcome these limitations using a multistage vector composed of mesoporous silicon particles (stage 1 microparticles, S1MP) loaded with neutral nanoliposomes (dioleoyl phosphatidylcholine, DOPC) containing small interfering RNA (siRNA) targeted against the EphA2 oncoprotein, which is overexpressed in most cancers, including ovarian. Our delivery methods resulted in sustained EphA2 gene silencing for at least 3 weeks in two independent orthotopic mouse models of ovarian cancer following a single i.v. administration of S1MP loaded with EphA2-siRNA-DOPC. Furthermore, a single administration of S1MP loaded with-EphA2-siRNA-DOPC substantially reduced tumor burden, angiogenesis, and cell proliferation compared with a noncoding control siRNA alone (SKOV3ip1, 54%; HeyA8, 57%), with no significant changes in serum chemistries or in proinflammatory cytokines. In summary, we have provided the first in vivo therapeutic validation of a novel, multistage siRNA delivery system for sustained gene silencing with broad applicability to pathologies beyond ovarian neoplasms.

Intracellular delivery mediated by an ethosomal carrier

The goal of this work was to investigate the efficiency of transcellular delivery into Swiss albino mice 3T3 fibroblasts of molecules with various physico-chemical characteristics from ethosomes, phospholipid vesicular carriers containing ethanol. The probes chosen were: 4-(4-diethylamino) styryl-N-methylpyridinium iodide (D-289), rhodamine red dihexadecanoylglycerophosphoethanolamine (RR) and fluorescent phosphatidylcholine (PC*). The penetration of these fluorescent probes into fibroblasts and nude mice skin was examined by CLSM and FACS. CLSM micrographs showed that ethosomes facilitated the penetration of all probes into the cells, as evident from the high-intensity fluorescence. In comparison, when incorporated in hydroethanolic solution or classic liposomes, almost no fluorescence was detected. The intracellular presence of each of the three probes tested, was evident after 3 min of incubation. Furthermore, with ethosomal D-289, fluorescence was also seen in the fibroblast nucleus. Enhanced delivery of molecules from the ethosomal carrier was also observed in permeation experiments with the hydrophilic calcein and lypophilic RR to whole nude mouse skin. Calcein penetrated the skin to a depth of 160, 80 and 60 microm from ethosomes, hydroethanolic solution and liposomes, respectively. Maximum fluorescence intensities measured for RR delivered from ethosomes, hydroethanolic solution and liposomes were 150, 40 and 20 AU, respectively. Fibroblast viability tests showed that the ethosomal carrier is not toxic to the cultured cells.

Emerging applications of nanomedicine for the diagnosis and treatment of cardiovascular diseases

Nanomedicine is an emerging field that utilizes nanotechnology concepts for advanced therapy and diagnostics. This convergent discipline merges research areas such as chemistry, biology, physics, mathematics and engineering. It therefore bridges the gap between molecular and cellular interactions, and has the potential to revolutionize medicine. This review presents recent developments in nanomedicine research poised to have an important impact on the treatment of cardiovascular disease. This will occur through improvement of the diagnosis and therapy of cardiovascular disorders as atherosclerosis, restenosis and myocardial infarction. Specifically, we discuss the use of nanoparticles for molecular imaging and advanced therapeutics, specially designed drug eluting stents and in vivo/ex vivo early detection techniques.

Biocompatibility Assessment of Si-based Nano- and Micro-particles

Silicon is one of the most abundant chemical elements found on the Earth. Due to its unique chemical and physical properties, silicon based materials and their oxides (e.g. silica) have been used in several industries such as building and construction, electronics, food industry, consumer products and biomedical engineering/medicine. This review summarizes studies on effects of silicon and silica nano- and micro-particles on cells and organs following four main exposure routes, namely, intravenous, pulmonary, dermal and oral. Further, possible genotoxic effects of silica based nanoparticles are discussed. The review concludes with an outlook on improving and standardizing biocompatibility assessment for nano- and micro-particles.

Enhanced delivery of drugs into and across the skin by ethosomal carriers

In dermal and transdermal delivery, the skin is used as a portal of entry for drugs, for localized and systemic treatment. Because of the barrier properties of the outer layer of the skin, in many cases, permeation‐enhancing agents are needed to achieve therapeutic levels of drug. Classic liposomal systems were found to be effective at forming drug reservoir in the upper layers of the skin, for local skin therapy. Recently, it was found that ethosomal carriers, phospholipid vesicular systems containing relatively high concentrations of alcohol, were very effective at enhancing dermal and transdermal delivery of both lipophilic and hydrophilic molecules. Fluorescent probes delivered from ethosomal systems reached the deep strata of the skin. Delivery of minoxidil to the pilosebaceous units from ethosomes was much greater compared to delivery from classic liposomes. In addition, clinical studies with aciclovir showed that ethosomal formulations were superior to the currently available topical therapy at treating recurrent herpes labialis. Ethosomal systems were also highly effective at transdermal delivery of drugs. In vivo skin permeation of testosterone from patches containing ethosomal drug were more effective at delivering testosterone through rabbit pinna skin than commercially available Testoderm patches. Results using trihexyphenidyl hydrochloride ethosomes indicated that this system has the potential to be further developed into an antiparkinsonian patch. Lastly, the transdermal delivery of insulin from an ethosomal carrier resulted in lower blood glucose levels in normal and diabetic rats in vivo, with a plateau effect lasting for at least 8 h. Drug Dev. Res. 50:406–415, 2000.

Multi-stage delivery nano-particle systems for therapeutic applications

BACKGROUND The daunting task for drug molecules to reach pathological lesions has fueled rapid advances in Nanomedicine. The progressive evolution of nanovectors has led to the development of multi-stage delivery systems aimed at overcoming the numerous obstacles encountered by nanovectors on their journey to the target site. SCOPE OF REVIEW This review summarizes major findings with respect to silicon-based drug delivery vectors for cancer therapeutics and imaging. Based on rational design, well-established silicon technologies have been adapted for the fabrication of nanovectors with specific shapes, sizes, and porosities. These vectors are part of a multi-stage delivery system that contains multiple nano-components, each designed to achieve a specific task with the common goal of site-directed delivery of therapeutics. MAJOR CONCLUSIONS Quasi-hemispherical and discoidal silicon microparticles are superior to spherical particles with respect to margination in the blood, with particles of different shapes and sizes having unique distributions in vivo. Cellular adhesion and internalization of silicon microparticles is influenced by microparticle shape and surface charge, with the latter dictating binding of serum opsonins. Based on in vitro cell studies, the internalization of porous silicon microparticles by endothelial cells and macrophages is compatible with cellular morphology, intracellular trafficking, mitosis, cell cycle progression, cytokine release, and cell viability. In vivo studies support superior therapeutic efficacy of liposomal encapsulated siRNA when delivered in multi-stage systems compared to free nanoparticles. This article is part of a Special Issue entitled Nanotechnologies - Emerging Applications in Biomedicine.