Development of a magnetic nano-graphene oxide carrier for improved glioma-targeted drug delivery and imaging: In vitro and in vivo evaluations

Highlights

• IUdR-loaded magnetic NGO + MF indicated the strongest anticancer effects in rat gliomas.

• Magnetic NGO induces thermosensitising effects in alternative magnetic field.

• Magnetic NGO under external magnetic field could overcome the BBB.

• Magnetic NGO could enhance the MRI sensitivity.

• Magnetic NGO modified with PLGA showed sustained release of IUdR.

Abstract

To overcome the obstacles inflicted by the BBB in Glioblastoma multiforme (GBM) we investigated the use of Multifunctional nanoparticles that designed with a Nano-graphene oxide (NGO) sheet functionalized with magnetic poly (lactic-co-glycolic acid) (PLGA) and was used for glioma targeting delivery of radiosensitizing 5-iodo-2-deoxyuridine (IUdR). In vitro biocompatibility of nanocomposite has been studied by the MTT assay. In vivo efficacy of magnetic targeting on the amount and selectivity of magnetic nanoparticles accumulation in glioma-bearing rats under an external magnetic field (EMF) density of 0.5 T was easily monitored with MRI. IUdR-loaded magnetic NGO/PLGA with a diameter of 71.8 nm, a zeta potential of −33.07 ± 0.07 mV, and a drug loading content of 3.04 ± 0.46% presented superior superparamagnetic properties with a saturation magnetization (Ms) of 15.98 emu/g. Furthermore, Prussian blue staining showed effective magnetic targeting, leading to remarkably improved tumor inhibitory efficiency of IUdR. The tumor volume of rats after treatment with IUdR/NGO/SPION/PLGA + MF was decreased significantly compared to the rats treated with buffer saline, IUdR and SPION/IUdR/NGO/PLGA. Most importantly, our data demonstrate that IUdR/NGO/SPION/PLGA at the present magnetic field prolongs the median survival time of animals bearing gliomas (38 days, p < 0.01). Nanoparticles also had high thermal sensitivities under the alternating magnetic field. In conclusion, we developed magnetic IUdR/NGO/PLGA, which not only achieved to high accumulation at the targeted tumor site by magnetic targeting but also indicated significantly enhanced therapeutic efficiency and toxicity for glioma both in vitro and in vivo. This innovation increases the possibility of improving clinical efficiency of IUdR as a radiosensitizer, or lowering the total drug dose to decrease systemic toxicity.

Introduction

Glioblastoma is the most common malignant primary brain tumor, with invasive nature and high proliferation rate, characterized by diffusely infiltrate neighboring brain tissue and tremendous biological heterogeneity [1,2]. Despite the development of conventional therapies that include invasive surgery, radiation therapy and chemotherapy, because of high recurrence rates, the prognosis remains very poor [3]. In most cases, it is impossible to completely eradicate malignant glioma by surgery even when combined with radiotherapy and chemotherapy due to major challenges in tumor such as infiltration rate, resistant cancer stem cells, drug delivery through the BBB and the difficulty retaining a therapeutically drug concentration at the tumor lesions [4,5]. BBB is formed by the endothelial layer with tight junctions that prevents effective targeting of diagnostic and therapeutic agents to tumor areas [6]. Most of the current anticancer agents such as radiosensitizers have short half-life time, poor hydrolytic stability and suffer from inefficiency to penetrate the BBB. Over the past decade, nanotechnology has represented an innovative approach as nanoparticle-based drug delivery systems to overcome the BBB transport [7]. Multifunctional nanoparticles (NPs) are powerful tools for current clinical diagnostics and therapeutic procedures. Nanoparticles could protect the drugs from metabolic degradation, increase circulation lifetime and decrease the rate of clearance from the blood, increase tumor drug delivery, control release and decrease unwanted side effects [8,9]. Actually, Poly (lactic-co-glycolic acid) (PLGA) due to their adjustable characteristics such as biocompatibility, biodegradability and nontoxicity are considered as useful nanocarriers for the delivery of drugs and agents [10,11].

Graphene is a two-dimensional sp² carbon networking nanomaterial that offers excellent potential in the drug delivery field because of its hexagonal carbon ring structure which allowed hydrophobic interactions, electrostatic interaction and π–π stacking with anticancer drugs with aromatic ring structures [12,13]. Graphene oxide (GO) sheets are important derivatives of graphene that have high drug-loading efficiency (both sides of a graphene oxide sheets can be used for drug loading), excellent biocompatibility and unclear toxicity. GO sheets modified with biocompatible polymers such as PLGA showed increased stability in physiological solutions for delivery of aromatic anticancer drugs and also did not indicate any significant acute toxicity on intravenous (i.v.) injection into mice [14,15]. Halogenated pyrimidines such as, 5-iodo-2-deoxyuridine are an important family of radiosensitizers [16]. Enhanced cell killing after radiotherapy is a desirable effect observed in cells treated with IUdR, which is due to the Auger emissions from the high-Z iodine [17]. It is a halogenated thymidine analogue, which is incorporated into DNA instead of thymine for phosphorylation, during the S phase of mitotic cells [18]. Due to the differential effects of IUdR, glioma tumor cells gradually become more sensitive to radiation damage. Though, IUdR is widely used to improve radiation efficacy but it has a short metabolic half-life in the circulation and can hardly cross through blood-brain barrier, which limits its clinical utility on glioma malignant [19]. In order to overcome these problems, we commonly use the Superparamagnetic iron oxide nanoparticles (SPIONs) [20,21].

SPIONs have attracted attention in the past decades due to their unique capability in noninvasive brain tumors diagnostics and therapeutics in one multifunctional platform. Since nanoparticles pass the BBB, they could be useful in the development of novel therapeutic procedures [5,22]. SPIONs can be used simultaneously for drug delivery and as magnetic resonance imaging (MRI) contrast agents, because they can be properly modified to carry anticancer agents, be magnetically guided to the targeted areas and retained at tumor areas by applying an external magnetic field as a local. Since SPIONs are powerful enhancers of proton spin–spin (T2/T2*) relaxation, MRI imaging is a suitable method for non-invasive real-time detection of such NPs, thus improving the differentiation of malignancy from normal brain tissue [6,23].

In the present study, we synthesized and tested a multifunctional nanoparticle as magnetic graphene oxide-based nanocarrier (NGO/SPION/PLGA) structure incorporating therapeutic agent (IUdR). These multifunctional magnetic nanoparticles were designed to not only target gliomas by applying external magnetic fields (magnetic NdFeB), induce BBB-opening and therapeutic drug delivery, but also serve as MRI contrast agent for real-time monitoring of nanoparticles inside tumor sites. Finally, the antitumor efficiency and safety of the IUdR-loaded multifunctional nanoparticles for loading and glioma magnetic targeting delivery of anticancer agent IUdR (IUdR/NGO/SPION/PLGA) was evaluated using by C6 glioma cell line and glioblastoma-bearing rats via systemic administration.