Catherine Passirani

Lipid nanocapsules: A new platform for nanomedicine

Nanomedicine, an emerging new field created by the fusion of nanotechnology and medicine, is one of the most promising pathways for the development of effective targeted therapies with oncology being the earlier and the most notable beneficiary to date. Indeed, drug-loaded nanoparticles provide an ideal solution to overcome the low selectivity of the anticancer drugs towards the cancer cells in regards to normal cells and the induced severe side-effects, thanks to their passive and/or active targeting to cancer tissues. Liposome-based systems encapsulating drugs are already used in some cancer therapies (e.g. Myocet, Daunoxome, Doxil). But liposomes have some important drawbacks: they have a low capacity to encapsulate lipophilic drugs (even though it exists), they are manufactured through processes involving organic solvents, and they are leaky, unstable in biological fluids and more generally in aqueous solutions for being commercialized as such. We have developed new nano-cargos, the lipid nanocapsules, with sizes below the endothelium fenestration (phi<100 nm), that solve these disadvantages. They are prepared according to a solvent-free process and they are stable for at least one year in suspension ready for injection, which should reduce considerably the cost and convenience for treatment. Moreover, these new nano-cargos have the ability to encapsulate efficiently lipophilic drugs, offering a pharmaceutical solution for their intravenous administration. The lipid nanocapsules (LNCs) have been prepared according to an original method based on a phase-inversion temperature process recently developed and patented. Their structure is a hybrid between polymeric nanocapsules and liposomes because of their oily core which is surrounded by a tensioactive rigid membrane. They have a lipoprotein-like structure. Their size can be adjusted below 100 nm with a narrow distribution. Importantly, these properties confer great stability to the structure (physical stability>18 months). Blank or drug-loaded LNCs can be prepared, with or without PEG (polyethyleneglycol)ylation that is a key parameter that affects the vascular residence time of the nano-cargos. Other hydrophilic tails can also be grafted. Different anticancer drugs (paclitaxel, docetaxel, etoposide, hydroxytamoxifen, doxorubicin, etc.) have been encapsulated. They all are released according to a sustained pattern. Preclinical studies on cell cultures and animal models of tumors have been performed, showing promising results.

Biocompatibility of implantable synthetic polymeric drug carriers: focus on brain biocompatibility

Numerous polymeric biomaterials are implanted each year in human bodies. Among them, drug delivery devices are potent novel powerful therapeutics for diseases which lack efficient treatments. Controlled release systems are in direct and sustained contact with the tissues, and some of them degrade in situ. Thus, both the material itself and its degradation products must be devoid of toxicity. The knowledge and understanding of the criteria and mechanisms determining the biocompatibility of biomaterials are therefore of great importance. The classical tissue response to a foreign material leads to the encapsulation of the implant, which may impair the drug diffusion in the surrounding tissue and/or cause implant failure. This tissue response depends on different factors, especially on the implantation site. Indeed, several organs possess a particular immunological status, which may reduce the inflammatory and immune reactions. Among them, the central nervous system is of particular interest, since many pathologies still need curative treatments. This review describes the classical foreign body reaction and exposes the particularities of the central nervous system response. The recent in vivo biocompatibility studies of implanted synthetic polymeric drug carriers are summarized in order to illustrate the behavior of different classes of polymers and the methodologies used to evaluate their tolerance.

Structure and Function of a Mitochondrial Late Embryogenesis Abundant Protein Are Revealed by Desiccation

Few organisms are able to withstand desiccation stress; however, desiccation tolerance is widespread among plant seeds. Survival without water relies on an array of mechanisms, including the accumulation of stress proteins such as the late embryogenesis abundant (LEA) proteins. These hydrophilic proteins are prominent in plant seeds but also found in desiccation-tolerant organisms. In spite of many theories and observations, LEA protein function remains unclear. Here, we show that LEAM, a mitochondrial LEA protein expressed in seeds, is a natively unfolded protein, which reversibly folds into α-helices upon desiccation. Structural modeling revealed an analogy with class A amphipathic helices of apolipoproteins that coat low-density lipoprotein particles in mammals. LEAM appears spontaneously modified by deamidation and oxidation of several residues that contribute to its structural features. LEAM interacts with membranes in the dry state and protects liposomes subjected to drying. The overall results provide strong evidence that LEAM protects the inner mitochondrial membrane during desiccation. According to sequence analyses of several homologous proteins from various desiccation-tolerant organisms, a similar protection mechanism likely acts with other types of cellular membranes.

Mesenchymal stem cells as cellular vehicles for delivery of nanoparticles to brain tumors

The prognosis of patients with malignant glioma remains extremely poor, despite surgery and improvements in radio- and chemo-therapies. Nanotechnologies represent great promise in glioma therapy as they protect therapeutic agent and allow its sustained release. However, new paradigms allowing tumor specific targeting and extensive intratumoral distribution must be developed to efficiently deliver nanoparticles (NPs). Knowing the tropism of mesenchymal stem cells (MSCs) for brain tumors, the aim of this study was to obtain the proof of concept that these cells can be used as NP delivery vehicles. Two types of NPs loaded with coumarin-6 were investigated: poly-lactic acid NPs (PLA-NPs) and lipid nanocapsules (LNCs). The results show that these NPs can be efficiently internalized into MSCs while cell viability and differentiation are not affected. Furthermore, these NP-loaded cells were able to migrate toward an experimental human glioma model. These data suggest that MSCs can serve as cellular carriers for NPs in brain tumors.

A review of the current status of siRNA nanomedicines in the treatment of cancer.

RNA interference currently offers new opportunities for gene therapy by the specific extinction of targeted gene(s) in cancer diseases. However, the main challenge for nucleic acid delivery still remains its efficacy through intravenous administration. Over the last decade, many delivery systems have been developed and optimized to encapsulate siRNA and to specifically promote their delivery into tumor cells and improve their pharmacokinetics for anti-cancer purposes. This review aims to sum up the potential targets in numerous pathways and the properties of recently optimized siRNA synthetic nanomedicines with their preclinical applications and efficacy. Future perspectives in cancer treatment are discussed including promising concomitant treatment with chemotherapies or other siRNA. The outcomes in human clinical trials are also presented.

Long-circulating DNA lipid nanocapsules as new vector for passive tumor targeting

Systemic gene delivery systems are needed for therapeutic application to organs that are inaccessible by percutaneous injection. Currently, the main objective is the development of a stable and non-toxic vector that can encapsulate and deliver foreign genetic material to target cells. To this end, DNA, complexed with cationic lipids i.e. DOTAP/DOPE, was encapsulated into lipid nanocapsules (LNCs) leading to the formation of stable nanocarriers (DNA LNCs) with a size inferior to 130 nm. Amphiphilic and flexible poly (ethylene glycol) (PEG) polymer coatings [PEG lipid derivative (DSPE-mPEG(2000)) or F108 poloxamer] at different concentrations were selected to make DNA LNCs stealthy. Some of these coated lipid nanocapsules were able to inhibit complement activation and were not phagocytized in vitro by macrophagic THP-1 cells whereas uncoated DNA LNCs accumulated in the vacuolar compartment of THP-1 cells. These results correlated with a significant increase of in vivo circulation time in mice especially for DSPE-mPEG(2000) 10 mm and an early half-life time (t(1/2) of distribution) 5-fold greater than for non-coated DNA LNCs (7.1 h vs 1.4 h). Finally, a tumor accumulation assessed by in vivo fluorescence imaging system was evidenced for these coated LNCs as a passive targeting without causing any hepatic damage.

Lipid nanocapsules loaded with an organometallic tamoxifen derivative as a novel drug-carrier system for experimental malignant gliomas

Ferrocenyl diphenol tamoxifen derivative (Fc-diOH) is one of the most active molecules of a new class of organometallic drugs, showing in vitro antiproliferative effects on both hormone-dependent and independent breast cancer cells. For the first time, Fc-diOH was tested on a 9L glioma model according to two encapsulation strategies: lipid nanocapsules (LNC) and swollen micelles. LNC showed a higher drug loading capacity because of a larger oily core in their structure and were able to be up taken by glioma cells. The large amount of PEG present at the micellar interface prevented interaction with cytoplasm membrane which led to a low level of micelle cell uptake and no biological activity. On the contrary, Fc-diOH cytostatic activity was conserved after its encapsulation in LNC and was very effective on 9L-glioma cells as the IC(50) was about 0.6 microM. Interestingly, Fc-diOH-loaded LNC showed low toxicity levels when in contact with healthy cells, conferring a functional specificity of this compound on tumour cells. Finally, Fc-diOH LNC treatment was able to lower significantly both tumour mass and volume evolution after 9L-cell implantation into rats which evidenced for the first time the in vivo efficacy of this new kind of organometallic compound.

Non-viral nanosystems for systemic siRNA delivery

To use siRNA (small interfering ribonucleic acids) for systemic administration, a delivery system is often necessary to overcome barriers between administration and the target sites. These delivery systems require different properties to be efficient. On the one hand, they have to protect siRNA from degradation and/or inactivation and, on the other hand, they have themselves to be stable in blood and possess stealth properties to avoid elimination and degradation. Active and/or passive targeting should help the delivery system to reach the desired cell type or tissue, to be internalised, and to deliver siRNA to the cytoplasm so that siRNA can act by RNA interference and inhibit protein synthesis. This review presents an overview of different non-viral delivery systems, which have been evaluated in vivo or entered in clinical trials, with a focus on their physicochemical properties in order to help the development of new and efficient siRNA delivery systems, as the therapeutic solutions of tomorrow.

Passive and active tumour targeting with nanocarriers.

Nanocarriers can penetrate the tumour vasculature through its leaky endothelium and, in this way, accumulate in several solid tumours. This is called the enhanced permeation and retention (EPR) effect. Together with nanocarriers whose surface is tailored for prolonged blood circulation times, the concept is referred to as passive targeting. Targeting ligands, which bind to specific receptors on the tumour cells and endothelium, can be attached on the nanocarrier surface. This active targeting increases the selectivity of the delivery of drugs. Passive and active drug targeting with nanocarriers to tumours reduce toxic side-effects, increase efficacy, and enhance delivery of poorly soluble or sensitive therapeutic molecules. In this review, currently studied and used passive and active targeting strategies in cancer therapy are presented.

The potential of combinations of drug-loaded nanoparticle systems and adult stem cells for glioma therapy

The prognosis of patients with malignant glioma remains extremely poor, despite surgery and improvements in radio- and chemo-therapies. Nanotechnologies hold great promise in glioma therapy as they protect the therapeutic agent and allow its sustained release. However, new paradigms permitting tumor-specific targeting and extensive intratumoral distribution must be developed to efficiently deliver nanoparticles. Modifications and functionalizations of nanoparticles have been developed to specifically track tumor cells. However, these nanoparticles have yielded few clinical results due to intra-patient heterogeneity and inter-patient variability. Stem cells with a specific tropism for brain tumors could be used as delivery vehicles for nanoparticles. Indeed, these cells have a natural tendency to migrate and distribute within the tumor mass and they can also incorporate nanoparticles. Stem cell therapy combined with nanotechnology could be a promising tool to efficiently deliver drugs to brain tumors.