The art of attraction: applications of multifunctional magnetic nanomaterials for malignant glioma

Systemic Delivery of an Adjuvant CXCR4-CXCL12 Signaling Inhibitor Encapsulated in Synthetic Protein Nanoparticles for Glioma Immunotherapy

Glioblastoma (GBM) is an aggressive primary brain cancer, with a 5 year survival of ∼5%. Challenges that hamper GBM therapeutic efficacy include (i) tumor heterogeneity, (ii) treatment resistance, (iii) immunosuppressive tumor microenvironment (TME), and (iv) the blood-brain barrier (BBB). The C-X-C motif chemokine ligand-12/C-X-C motif chemokine receptor-4 (CXCL12/CXCR4) signaling pathway is activated in GBM and is associated with tumor progression. Although the CXCR4 antagonist (AMD3100) has been proposed as an attractive anti-GBM therapeutic target, it has poor pharmacokinetic properties, and unfavorable bioavailability has hampered its clinical implementation. Thus, we developed synthetic protein nanoparticles (SPNPs) coated with the transcytotic peptide iRGD (AMD3100-SPNPs) to target the CXCL2/CXCR4 pathway in GBM via systemic delivery. We showed that AMD3100-SPNPs block CXCL12/CXCR4 signaling in three mouse and human GBM cell cultures in vitro and in a GBM mouse model in vivo. This results in (i) inhibition of GBM proliferation, (ii) reduced infiltration of CXCR4⁺ monocytic myeloid-derived suppressor cells (M-MDSCs) into the TME, (iii) restoration of BBB integrity, and (iv) induction of immunogenic cell death (ICD), sensitizing the tumor to radiotherapy and leading to anti-GBM immunity. Additionally, we showed that combining AMD3100-SPNPs with radiation led to long-term survival, with ∼60% of GBM tumor-bearing mice remaining tumor free after rechallenging with a second GBM in the contralateral hemisphere. This was due to a sustained anti-GBM immunological memory response that prevented tumor recurrence without additional treatment. In view of the potent ICD induction and reprogrammed tumor microenvironment, this SPNP-mediated strategy has a significant clinical translation applicability.

Review of Noninvasive or Minimally Invasive Deep Brain Stimulation

Brain stimulation is a critical technique in neuroscience research and clinical application. Traditional transcranial brain stimulation techniques, such as transcranial magnetic stimulation (TMS), transcranial direct current stimulation (tDCS), and deep brain stimulation (DBS) have been widely investigated in neuroscience for decades. However, TMS and tDCS have poor spatial resolution and penetration depth, and DBS requires electrode implantation in deep brain structures. These disadvantages have limited the clinical applications of these techniques. Owing to developments in science and technology, substantial advances in noninvasive and precise deep stimulation have been achieved by neuromodulation studies. Second-generation brain stimulation techniques that mainly rely on acoustic, electronic, optical, and magnetic signals, such as focused ultrasound, temporal interference, near-infrared optogenetic, and nanomaterial-enabled magnetic stimulation, offer great prospects for neuromodulation. This review summarized the mechanisms, development, applications, and strengths of these techniques and the prospects and challenges in their development. We believe that these second-generation brain stimulation techniques pave the way for brain disorder therapy.

Nanoparticles for Stem Cell Therapy Bioengineering in Glioma

Gliomas are a dismal disease associated with poor survival and high morbidity. Current standard treatments have reached a therapeutic plateau even after combining maximal safe resection, radiation, and chemotherapy. In this setting, stem cells (SCs) have risen as a promising therapeutic armamentarium, given their intrinsic tumor homing as well as their natural or bioengineered antitumor properties. The interplay between stem cells and other therapeutic approaches such as nanoparticles holds the potential to synergize the advantages from the combined therapeutic strategies. Nanoparticles represent a broad spectrum of synthetic and natural biomaterials that have been proven effective in expanding diagnostic and therapeutic efforts, either used alone or in combination with immune, genetic, or cellular therapies. Stem cells have been bioengineered using these biomaterials to enhance their natural properties as well as to act as their vehicle when anticancer nanoparticles need to be delivered into the tumor microenvironment in a very precise manner. Here, we describe the recent developments of this new paradigm in the treatment of malignant gliomas.

Hyperthermia treatment advances for brain tumors

Hyperthermia therapy (HT) of cancer is a well-known treatment approach. With the advent of new technologies, HT approaches are now important for the treatment of brain tumors. We review current clinical applications of HT in neuro-oncology and ongoing preclinical research aiming to advance HT approaches to clinical practice. Laser interstitial thermal therapy (LITT) is currently the most widely utilized thermal ablation approach in clinical practice mainly for the treatment of recurrent or deep-seated tumors in the brain. Magnetic hyperthermia therapy (MHT), which relies on the use of magnetic nanoparticles (MNPs) and alternating magnetic fields (AMFs), is a new quite promising HT treatment approach for brain tumors. Initial MHT clinical studies in combination with fractionated radiation therapy (RT) in patients have been completed in Europe with encouraging results. Another combination treatment with HT that warrants further investigation is immunotherapy. HT approaches for brain tumors will continue to a play an important role in neuro-oncology.

Progress in neuromodulation of the brain: A role for magnetic nanoparticles?

The field of neuromodulation is developing rapidly. Current techniques, however, are still limited as they i) either depend on permanent implants, ii) require invasive procedures, iii) are not cell-type specific, iv) involve slow pharmacokinetics or v) have a restricted penetration depth making it difficult to stimulate regions deep within the brain. Refinements into the different fields of neuromodulation are thus needed. In this review, we will provide background information on the different techniques of neuromodulation discussing their latest refinements and future potentials including the implementation of nanoparticles (NPs). In particular we will highlight the usage of magnetic nanoparticles (MNPs) as transducers in advanced neuromodulation. When exposed to an alternating magnetic field (AMF), certain MNPs can generate heat through hysteresis. This MNP heating has been promising in the field of cancer therapy and has recently been introduced as a method for remote and wireless neuromodulation. This indicates that MNPs may aid in the exploration of brain functions via neuromodulation and may eventually be applied for treatment of neuropsychiatric disorders. We will address the materials chemistry of MNPs, their biomedical applications, their delivery into the brain, their mechanisms of stimulation with emphasis on MNP heating and their remote control in living tissue. The final section compares and discusses the parameters used for MNP heating in brain cancer treatment and neuromodulation. Concluding, using MNPs for nanomaterial-mediated neuromodulation seem promising in a variety of techniques and could be applied for different neuropsychiatric disorders when more extensively investigated.

High-Density Lipoprotein-Mimicking Nanodiscs for Chemo-immunotherapy against Glioblastoma Multiforme

Glioblastoma multiforme (GBM) is an aggressive primary brain tumor, for which there is no cure. Treatment effectiveness for GBM has been limited due to tumor heterogeneity, an immunosuppressive tumor microenvironment (TME), and the presence of the blood-brain barrier, which hampers the transport of chemotherapeutic compounds to the central nervous system (CNS). High-density lipoprotein (HDL)-mimicking nanodiscs hold considerable promise to achieve delivery of bioactive compounds into tumors. Herein, we tested the ability of synthetic HDL nanodiscs to deliver chemotherapeutic agents to the GBM microenvironment and elicit tumor regression. To this end, we developed chemo-immunotherapy delivery vehicles based on sHDL nanodiscs loaded with CpG, a Toll-like receptor 9 (TLR9) agonist, together with docetaxel (DTX), a chemotherapeutic agent, for targeting GBM. Our data show that delivery of DTX-sHDL-CpG nanodiscs into the tumor mass elicited tumor regression and antitumor CD8+ T cell responses in the brain TME. We did not observe any overt off-target side effects. Furthermore, the combination of DTX-sHDL-CpG treatment with radiation (IR), which is the standard of care for GBM, resulted in tumor regression and long-term survival in 80% of GBM-bearing animals. Mice remained tumor-free upon tumor cell rechallenge in the contralateral hemisphere, indicating the development of anti-GBM immunological memory. Collectively, these data indicate that sHDL nanodiscs constitute an effective drug delivery platform for the treatment of GBM, resulting in tumor regression, long-term survival, and immunological memory when used in combination with IR. The proposed delivery platform has significant potential for clinical translation.

Polyplexes of Functional PAMAM Dendrimer/Apoptin Gene Induce Apoptosis of Human Primary Glioma Cells In Vitro

Highly efficient and safe gene delivery has become an important aspect of neuronal gene therapy. We evaluated the ability of polyamidoamine (PAMAM) dendrimer grafted with phenylalanine, histidine, and arginine (PAMAM-FHR), a nonviral gene delivery vector, to deliver a therapeutic, tumor cell-specific killer gene, apoptin, into the human primary glioma cell line GBL-14 and human dermal fibroblasts. We performed a transfection assay using plasmids of luciferase and enhanced green fluorescent protein (EGFP) and assessed cell viability. Both cell lines were treated with complexes of PAMAM-FHR and apoptin after which their intracellular uptake and localization were examined by fluorescence-activated cell sorting (FACS)analysis and confocal laser scanning microscopy. Confocal microscopy showed that the PAMAM-FHR escaped from the endo-lysosome into the cytosol. Cell cycle phase distribution analysis, annexin V staining, and a tetramethylrhodamine ethyl ester (TMRE) assay established that apoptin triggered apoptosis in the GBL-14 cell line but not in normal fibroblasts. These results indicated that the PAMAM-FHR/apoptin complex is an effective gene vehicle for cancer therapy in vitro.

Ferumoxytol of ultrahigh magnetization produced by hydrocooling and magnetically internal heating co-precipitation

Ferumoxytol, which is originally intended for MRI and anemia treatment, is currently the only inorganic nanodrug approved by FDA for clinical application in vivo. Common ferumoxytol seems incapable of meeting the requirements for diverse applications. Thus, the development of a novel strategy based on co-precipitation to produce ferumoxytol with high quality is an imminent task. Herein, we proposed a physically assisted strategy, namely hydrocooling and magnetically internal heating co-precipitation, to optimize the properties of ferumoxytol and thus significantly enhance its magnetic performance. Magnetization of the newly developed ferumoxytol can reach 104-105 emu g-1 Fe, which is the highest value among the reported results. It has been found that the crystalline structures of the newly developed ferumoxytol have been greatly improved on the basis of pharmaceutical quality criteria.

An EGFRvIII targeted dual-modal gold nanoprobe for imaging-guided brain tumor surgery

Surgery is a mainstay to treat malignant brain tumors. However, due to the infiltrative nature of these tumors, it is a great challenge for surgeons to accurately identify and excise all the tumor foci. EGFRvIII, a variant of epidermal growth factor receptor (EGFR), is found in 20% of glioblastoma cases, which is the brain tumor with the highest malignancy. In this study, we developed an EGFRvIII-targeted nanoprobe to guide glioblastoma surgery by pre-operatively defining the tumor boundary via magnetic resonance imaging (MRI) and intra-operatively guiding resection by surface-enhanced resonance Raman scattering (SERRS) imaging. In vivo MRI studies show that this nanoprobe delineates an orthotopic EGFRvIII+ U87MG glioblastoma xenograft with a higher target to background ratio than the control nanoprobe without targeting specificity. With the assistance of a handheld Raman scanner, this nanoprobe successfully guided EGFRvIII+ glioblastoma resection by tracking its characteristic SERRS signal peaks. Ex vivo Raman microscopy and histological images verified that this nanoprobe precisely demarcated the glioblastoma boundary and no residual neoplastic foci were observed in the tumor bed. This dual-modal nanoprobe not only precisely guided glioblastoma resection, but also overcame the brain shift induced false-positive signal by real-timely co-registering pre-operative and intra-operative images. This nanoprobe is promising for the improvement in diagnostic accuracy and surgical outcome of EGFRvIII+ glioblastoma.

Dipeptide-functionalized polyamidoamine dendrimer-mediated apoptin gene delivery facilitates apoptosis of human primary glioma cells

Glioblastoma multiform (GBM) is the most frequent and aggressive form of brain tumors in adults. However, the development of more efficient and safe nonviral vector gene therapy represents a promising therapeutic approach, using a tumor-specific killer gene, named apoptin. In this study, we describe the efficacy of non-viral gene delivery vectors, the amino acid-conjugated PAMAM derivatives (PAMAM-H-R and PAMAM-H-K) in delivering a therapeutic gene, displaying affinity toward human primary glioma cells (GBL-14 cells) and dermal fibroblasts. We analyzed transfection efficiency, using luciferase (Luci) and a pDNA encoding for enhanced fluorescent protein (EGFP), and cytotoxicity in both cells. The results show that transfection efficiency of PAMAM-H-R improved compared to native PAMAM dendrimer, but cytotoxicity of PAMAM-H-R and PAMAM-H-K were very low. We treated both cells with a polyplex formation of PAMAM-H-R or PAMAM-H-K/apoptin, and analyzed their cellular uptake and localization by flow cytometry and confocal microscopy. Furthermore, we analyzed the endosomal escape effect using TEM images, and found that PAMAM-H-R showed very fast escape from endosome to the cytosol. Caspase 3 activity assay, cell cycle distribution, and JC-1 analysis showed apoptosis induced by apoptin in GBL-14 cells. This indicates that PAMAM-H-R can be a potential nonviral vector gene delivery carrier for brain tumor therapy. The present study demonstrates that PAMAM-H-R/apoptin gene polyplex can be used as an effective therapeutic candidate for GBM due to its selective induction of apoptosis in primary glioma cells as a potential nonviral gene delivery carrier for brain tumor therapy.

Recombinant epidermal growth factor-like domain-1 from coagulation factor VII functionalized iron oxide nanoparticles for targeted glioma magnetic resonance imaging

The highly infiltrative and invasive nature of glioma cells often leads to blurred tumor margins, resulting in incomplete tumor resection and tumor recurrence. Accurate detection and precise delineation of glioma help in preoperative delineation, surgical planning and survival prediction. In this study, recombinant epidermal growth factor-like domain-1, derived from human coagulation factor VII, was conjugated to iron oxide nanoparticles (IONPs) for targeted glioma magnetic resonance (MR) imaging. The synthesized EGF1-EGFP-IONPs exhibited excellent targeting ability toward tissue factor (TF)-positive U87MG cells and human umbilical vein endothelial cells in vitro, and demonstrated persistent and efficient MR contrast enhancement up to 12 h for preclinical glioma models with high targeting specificity in vivo. They hold great potential for clinical translation and developing targeted theranostics against brain glioma.

Magnetically guided central nervous system delivery and toxicity evaluation of magneto-electric nanocarriers

Least component-based delivery of drug-tagged-nanocarriers across blood-brain-barriers (BBB) will allow site-specific and on-demand release of therapeutics to prevent CNS diseases. We developed a non-invasive magnetically guided delivery of magneto-electric nanocarriers (MENCs), ~20 nm, 10 mg/kg, across BBB in C57Bl/J mice. Delivered MENCs were uniformly distributed inside the brain, and were non-toxic to brain and other major organs, such as kidney, lung, liver, and spleen, and did not affect hepatic, kidney and neurobehavioral functioning.

Biodistribution of negatively charged iron oxide nanoparticles (IONPs) in mice and enhanced brain delivery using lysophosphatidic acid (LPA)

Effective treatment of brain disorders requires a focus on improving drug permeability across the blood-brain barrier (BBB). Herein, we examined the pharmacokinetic properties of negatively charged iron oxide nanoparticles (IONPs) and the capability of using lysophosphatidic acid (LPA) to transiently disrupt the tight junctions and allow IONPs to enter the brain. Under normal conditions, IONPs had a plasma half-life of six minutes, with the liver and spleen being the major organs of deposition. Treatment with LPA enhanced accumulation of IONPs in the brain and spleen (approximately 4-fold vs. control). LPA and IONP treated mice revealed no sign of peripheral immune cell infiltration in the brain and no significant activation of microglia or astrocytes. These studies show improved delivery efficiency of IONPs following LPA administration. Our findings suggest transient disruption of the BBB may be a safe and effective method for increasing IONP delivery to the brain.

Rotating magnetic field induced oscillation of magnetic particles for in vivo mechanical destruction of malignant glioma

Magnetic particles that can be precisely controlled under a magnetic field and transduce energy from the applied field open the way for innovative cancer treatment. Although these particles represent an area of active development for drug delivery and magnetic hyperthermia, the in vivo anti-tumor effect under a low-frequency magnetic field using magnetic particles has not yet been demonstrated. To-date, induced cancer cell death via the oscillation of nanoparticles under a low-frequency magnetic field has only been observed in vitro. In this report, we demonstrate the successful use of spin-vortex, disk-shaped permalloy magnetic particles in a low-frequency, rotating magnetic field for the in vitro and in vivo destruction of glioma cells. The internalized nanomagnets align themselves to the plane of the rotating magnetic field, creating a strong mechanical force which damages the cancer cell structure inducing programmed cell death. In vivo, the magnetic field treatment successfully reduces brain tumor size and increases the survival rate of mice bearing intracranial glioma xenografts, without adverse side effects. This study demonstrates a novel approach of controlling magnetic particles for treating malignant glioma that should be applicable to treat a wide range of cancers.

Design, Properties, and In Vivo Behavior of Super-paramagnetic Persistent Luminescence Nanohybrids

With the fast development of noninvasive diagnosis, the design of multimodal imaging probes has become a promising challenge. If many monofunctional nanocarriers have already proven their efficiency, only few multifunctional nanoprobes have been able to combine the advantages of diverse imaging modalities. An innovative nanoprobe called mesoporous persistent luminescence magnetic nanohybrids (MPNHs) is described that shows both optical and magnetic resonance imaging (MRI) properties intended for in vivo multimodal imaging in small animals. MPNHs are based on the assembly of chromium-doped zinc gallate oxide and ultrasmall superparamagnetic iron oxide nanoparticles embedded in a mesoporous silica shell. MPNHs combine the optical advantages of persistent luminescence, such as real time imaging with highly sensitive and photostable detection, and MRI negative contrast properties that ensure in vivo imaging with rather high spatial resolution. In addition to their imaging capabilities, these MPNHs can be motioned in vitro with a magnet, which opens multiple perspectives in magnetic vectorization and cell therapy research.

Doxorubicin loaded magnetic gold nanoparticles for in vivo targeted drug delivery

Treatment of approximately 50% of human cancers includes the use of chemotherapy. The major problem associated with chemotherapy is the inability to deliver pharmaceuticals to specific site of the body without inducing normal tissue toxicity. Latterly, magnetic targeted drug delivery (MTD) has been used to improve the therapeutic performance of the chemotherapeutic agents and reduce the severe side effects associated with the conventional chemotherapy for malignant tumors. In this study, we were focused on designing biocompatible magnetic nanoparticles that can be used as a nanocarrier's candidate for MTD regimen. Magnetic gold nanoparticles (MGNPs) were prepared and functionalized with thiol-terminated polyethylene glycol (PEG), then loaded with anti-cancer drug doxorubicin (DOX). The physical properties of the prepared NPs were characterized using different techniques. Transmission electron microscopy (TEM) revealed the spherical mono-dispersed nature of the prepared MGNPs with size about 22 nm. Energy dispersive X-ray spectroscopy (EDX) assured the existence of both iron and gold elements in the prepared nanoparticles. Fourier transform infrared (FTIR) spectroscopy assessment revealed that PEG and DOX molecules were successfully loaded on the MGNPs surfaces, and the amine group of DOX is the active attachment site to MGNPs. In vivo studies proved that magnetic targeted drug delivery can provide a higher accumulation of drug throughout tumor compared with that delivered by passive targeting. This clearly appeared in tumor growth inhibition assessment, biodistribution of DOX in different body organs in addition to the histopathological examinations of treated and untreated Ehrlich carcinoma. To assess the in vivo toxic effect of the prepared formulations, several biochemical parameters such as aspartate aminotransferase (AST), alanine transaminase (ALT), lactate dehydrogenase (LDH), creatine kinase MB (CK-MB), urea, uric acid and creatinine were measured. MTD technology not only minimizes the random distribution of the chemotherapeutic agents, but also reduces their side effects to healthy tissues, which are the two primary concerns in conventional cancer therapies.