Alice Gaudin

Squalenoyl adenosine nanoparticles provide neuroprotection after stroke and spinal cord injury.

There is an urgent need to develop new therapeutic approaches for the treatment of severe neurological trauma, such as stroke and spinal cord injuries. However, many drugs with potential neuropharmacological activity, like adenosine, are inefficient upon systemic administration because of their fast metabolisation and rapid clearance from the bloodstream. Here, we show that the conjugation of adenosine to the lipid squalene and the subsequent formation of nanoassemblies allow a prolonged circulation of this nucleoside, to provide neuroprotection in mouse stroke and rat spinal cord injury models. The animals receiving systemic administration of squalenoyl adenosine nanoassemblies showed a significant improvement of their neurologic deficit score in the case of cerebral ischaemia, and an early motor recovery of the hindlimbs in the case of spinal cord injury. Moreover, in vitro and in vivo studies demonstrated that the nanoassemblies were able to extend adenosine circulation and its interaction with the neurovascular unit. This paper shows, for the first time, that a hydrophilic and rapidly metabolised molecule like adenosine may become pharmacologically efficient owing to a single conjugation with the lipid squalene.

Distribution of polymer nanoparticles by convection-enhanced delivery to brain tumors.

Glioblastoma multiforme (GBM) is a fatal brain tumor characterized by infiltration beyond the margins of the main tumor mass and local recurrence after surgery. The blood-brain barrier (BBB) poses the most significant hurdle to brain tumor treatment. Convection-enhanced delivery (CED) allows for local administration of agents, overcoming the restrictions of the BBB. Recently, polymer nanoparticles have been demonstrated to penetrate readily through the healthy brain when delivered by CED, and size has been shown to be a critical factor for nanoparticle penetration. Because these brain-penetrating nanoparticles (BPNPs) have high potential for treatment of intracranial tumors since they offer the potential for cell targeting and controlled drug release after administration, here we investigated the intratumoral CED infusions of PLGA BPNPs in animals bearing either U87 or RG2 intracranial tumors. We demonstrate that the overall volume of distribution of these BPNPs was similar to that observed in healthy brains; however, the presence of tumors resulted in asymmetric and heterogeneous distribution patterns, with substantial leakage into the peritumoral tissue. Together, our results suggest that CED of BPNPs should be optimized by accounting for tumor geometry, in terms of location, size and presence of necrotic regions, to determine the ideal infusion site and parameters for individual tumors.

PEGylated squalenoyl-gemcitabine nanoparticles for the treatment of glioblastoma

New treatments for glioblastoma multiforme (GBM) are desperately needed, as GBM prognosis remains poor, mainly due to treatment resistance, poor distribution of therapeutics in the tumor tissue, and fast metabolism of chemotherapeutic drugs in the brain extracellular space. Convection-enhanced delivery (CED) of nanoparticles (NPs) has been shown to improve the delivery of chemotherapeutic drugs to the tumor bed, providing sustained release, and enhancing survival of animals with intracranial tumors. Here we administered gemcitabine, a nucleoside analog used as a first line treatment for a wide variety of extracranial solid tumors, within squalene-based NPs using CED, to overcome the above-mentioned challenges of GBM treatment. Small percentages of poly(ethylene) glycol (PEG) dramatically enhanced the distribution of squalene-gemcitabine nanoparticles (SQ-Gem NPs) in healthy animals and tumor-bearing animals after administration by CED. When tested in an orthotopic model of GBM, SQ-Gem-PEG NPs demonstrated significantly improved therapeutic efficacy compared to free gemcitabine, both as a chemotherapeutic drug and as a radiosensitizer. Furthermore, MR contrast agents were incorporated into the SQ-Gem-PEG NP formulation, providing a way to non-invasively track the NPs during infusion.

Application of Nanomedicine to the CNS Diseases

Drug delivery to the brain is a challenge because of the many mechanisms that protect the brain from the entry of foreign substances. Numerous molecules which could be active against brain disorders are not clinically useful due to the presence of the blood-brain barrier. Nanoparticles can be used to deliver these drugs to the brain. Encapsulation within colloidal systems can allow the passage of nontransportable drugs across this barrier by masking their physicochemical properties. It should be noted that the status of the blood-brain barrier is different depending on the brain disease. In fact, in some pathological situations such as tumors or inflammatory disorders, its permeability is increased allowing very easy translocation of carriers. This chapter gathers the promising results obtained by using nanoparticles as drug delivery systems with the aim to improve the therapy of some CNS diseases such as brain tumor, Alzheimers disease, and stroke. The data show that several approaches can be investigated: (1) carrying drug through a permeabilized barrier, (2) crossing the barrier thanks to receptor-mediated transcytosis pathway in order to deliver drug into the brain parenchyma, and also (3) targeting and treating the endothelial cells themselves to preserve locally the brain tissue. The examples given in this chapter contribute to demonstrate that delivering drugs into the brain is one of the most promising applications of nanotechnology in clinical neuroscience.

Improved threshold selection for the determination of volume of distribution of nanoparticles administered by convection-enhanced delivery

Nanotechnology, in conjunction with convection-enhanced delivery (CED), has gained traction as a promising method to treat many debilitating neurological diseases, including gliomas. One of the key parameters to evaluate the effectiveness of delivery is the volume of distribution (Vd) of nanoparticles within the brain parenchyma. Measurements of Vd are commonly made using fluorescent reporter systems. However, reported analyses lack accurate and robust methods for determining Vd. Current methods face the problems of varying background intensities between images, high intensity aggregates that can shift intensity distributions, and faint residual backgrounds that can occur as artifacts of fluorescent imaging. These problems can cause inaccurate results to be reported when a percentage of the maximum intensity is set as the threshold value. Here we show an implementation of Otsus method more reliably selects accurate threshold values than the fixed-threshold method. We also introduce a goodness of fit value η that quantifies the appropriateness of using Otsus method to calculate Vd. Adoption of Otsus method and reporting of η may help standardize fluorescent image analysis of nanoparticles administered by convection-enhanced delivery.

4.30 Nanomaterials for Drug Delivery to the Brain

Nanomaterials have emerged as important and versatile platforms for the delivery of therapeutics to the brain. This article describes the complex anatomy and physiology of the brain, which create challenges in treating diseases of the central nervous system, and current strategies using nanomedicines to address these challenges. We discuss various approaches to overcome the blood-brain barrier, examples of successful incorporation of therapeutics with nanomaterials, and strategies to achieve efficient delivery of nanomedicines into specific cells.

Abstract B33: PEGylated squalenoyl-gemcitabine nanoparticles for the treatment of glioblastoma

Abstracts: AACR Special Conference: Engineering and Physical Sciences in Oncology; June 25-28, 2016; Boston, MA Given its deadly prognosis, new treatments for glioblastoma multiforme (GBM) are desperately needed. Despite major progress in the development of new chemotherapeutic drugs and improved surgical technique, GBM prognosis remains grim, with a median survival of 15 months, mainly due to the almost invariable tumor recurrence. Convection-enhanced delivery (CED) of nanoparticles (NPs) has been proposed as an efficient way to deliver chemotherapeutic drugs locally into the tumor bed and to enhance treatment of intracranial tumors. Gemcitabine is an antimetabolite, and an effective inhibitor of DNA synthesis, that is used as a first line treatment for a wide variety of solid tumors. Gemcitabine has demonstrated efficacy against human glioma cell lines in vitro, but its clinical effectiveness is limited by its inability to cross the blood-brain barrier (BBB) after systemic delivery, its rapid deamination in the brain interstitial space to its inactive difluorodeoxyuridine metabolite, and its limited uptake by brain tumor cells. Here we propose to use CED to circumvent the BBB, and to administer the chemotherapeutic drug gemcitabine in a squalene-based nanoparticulate form, which is designed to protect the drug from metabolism, to provide a sustained release of the drug, and to enhance its cellular internalization. SQGem NPs were prepared by the nanoprecipitation technique, and presented a diameter of around 120 nm when measured by DLS, with a negative surface charge of around -20 mV. Modification of the surface of SQGem NPs using different amounts of polyethylene glycol (PEG) was performed by incorporating squalenoyl-PEG (SQPEG) to the formulation, providing SQGem/SQPEG NPs. The PEGylated NPs retained the physico-chemical properties of SQGem NPs, and the addition of PEG prevented the aggregation of the particles in aCSF. The stabilized formulations presented significantly larger volumes of distribution (Vd) in the healthy brain and the tumor-bearing brain after administration by CED. We further demonstrated that the combination of a non-distributing formulation and a distributing formulation offered the possibility of tuning the volume distribution of the nanoparticles in the brain tissue, and thus controlling the local drug concentration. To evaluate the effect of PEGylation on therapeutic efficacy, Fischer 344 rats were implanted with RG2 cells, and treated by CED using different SQGem/SQPEG formulations. Given the dual action of gemcitabine as chemotherapeutic and radiosensitizer, we also evaluated the addition of radiation to the treatment schedule. Overall, all formulations increased survival compared to free drug. Finally, as a first step toward clinical translation, we incorporated ultra-small iron particles oxide (USPIO) to the SQGem/SQPEG NPs formulation, to add the possibility of tracking the particles during CED using MRI. These NPs retained suitable characteristics to be administered by CED and were able to distribute in the brain tissue. This study demonstrates for the first time the safe administration of SQGem NPs by CED, providing significant survival improvement compared to the free drug. It also demonstrates a new method to optimize drug distribution by modulating surface properties of the nanoparticles. The administration by CED of optimized SQGem NPs formulations is expected to increase survival and could, in the future, change the way that GBM patients are treated in the US and around the world. Citation Format: Alice Gaudin, Eric Song, King Amanda, Didier Desmaele, Patrick Couvreur, Mark Saltzman. PEGylated squalenoyl-gemcitabine nanoparticles for the treatment of glioblastoma. [abstract]. In: Proceedings of the AACR Special Conference on Engineering and Physical Sciences in Oncology; 2016 Jun 25-28; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2017;77(2 Suppl):Abstract nr B33.