iRGD-mediated core-shell nanoparticles loading carmustine and O6-benzylguanine for glioma therapy

Fe3O4@Chitosan@ZIF-8@RVG29, an anti-glioma nanoplatform guided by fixed and activated by alternating magnetic field

There is considerable interest in developing anti-glioma nanoplatforms. They make the all-in-one combination of therapies possible. Here we show how the selective Glioblastoma multiforme (GBM) cell killing of the here-established nanoplatforms increased after each coating and how the here-established vibration-inducing Alternating magnetic field (AMF) decreased the treatment time from 72 h to 30 s. Thanks to their magnetite core, these nanoplatforms can be guided to the tumor's specific site by a Fixed magnetic field, they bypass the Blood-Brain Barrier (BBB) and accumulate at the tumor site thanks to the RVG29 bonding to the G-protein on the ion-gated channel receptor known as the nicotinic acetylcholine receptor (nAchR), which expresses on BBB cells and overexpresses on GBM cells, and thanks to the positive charge gained by both chitosan and RVG29's peptide. Both ZIF-8 and its mediate adherence, Chitosan increases the drug loading capacity that stimuli response to the tumor's acidic environment. The Zn2+ ions generated from ZIF-8 sustained degradation in such an environment kill the GBM cells. Dynamic Light Scattering (DLS) evaluated these nanoplatform's mean size 155 nm indicating their almost optimum size for brain applications. Based on their elements' intrinsic properties, these nanoplatforms can enhance and combine other adjuvant therapies.

Cancer therapy with iRGD as a tumor-penetrating peptide

One of the primary threats in tumor treatment revolves around the limited ability to penetrate tumor sites, leading to reduced therapeutic effectiveness, which remains a critical concern. Recently gaining importance are novel peptides, namely CRGDK/RGPD/EC (iRGD), that possess enhanced tumor-penetrating and inhibitory properties. These peptides specifically target and penetrate tumors by binding to αvβ integrins, namely αvβ3 and αvβ5, as well as NRP-1 receptors. Remarkably abundant on both the vasculature and tumor cell surfaces, these peptides show promising potential for improving tumor treatment outcomes. As a result, iRGD penetrated deep into the tumor tissues with biological products, contrast agents (imaging agents), antitumor drugs, and immune modulators after co-injecting them with peptides or chemically linked to peptides. The synthesis of iRGD peptides is a relatively straightforward process compared to the synthesis of other traditional peptides, and they significantly improved tumor tissue penetration inhibiting tumor metastasis effectively. Recent studies demonstrate the effectiveness of iRGD-driven dual-targeting chemotherapeutics on cancer cells, and the nanocarriers were modified with iRGD, serving as a favorable delivery strategy of payloads for deeper tumor regions. This review aims to provide an overview to emphasize the recent advancements and advantages of iRGD in treating and imaging various cancers.

Molecular View on the iRGD Peptide Binding Mechanism: Implications for Integrin Activity and Selectivity Profiles

Receptor-selective peptides are widely used as smart carriers for specific tumor-targeted delivery. A remarkable example is the cyclic nonapeptide iRGD (CRGDKPGDC, 1) that couples intrinsic cytotoxic effects with striking tumor-homing properties. These peculiar features are based on a rather complex multistep mechanism of action, where the primary event is the recognition of RGD integrins. Despite the high number of preclinical studies and the recent success of a phase I trial for the treatment of pancreatic ductal adenocarcinoma (PDAC), there is little information available about the iRGD three-dimensional (3D) structure and integrin binding properties. Here, we re-evaluate the peptide's affinity for cancer-related integrins including not only the previously known targets αvβ3 and αvβ5 but also the αvβ6 isoform, which is known to drive cell growth, migration, and invasion in many malignancies including PDAC. Furthermore, we use parallel tempering in the well-tempered ensemble (PT-WTE) metadynamics simulations to characterize the in-solution conformation of iRGD and extensive molecular dynamics calculations to fully investigate its binding mechanism to integrin partners. Finally, we provide clues for fine-tuning the peptide's potency and selectivity profile, which, in turn, may further improve its tumor-homing properties.

Curcumin combining temozolomide formed localized nanogel for inhibition of postsurgical chemoresistant glioblastoma

Aim: To investigate the use of nanoparticle (NP)-encapsulated injectable thermosensitive hydrogel-formed nanogel for inhibition of postsurgical residual temozolomide (TMZ)-resistant glioblastoma (GBM) recurrence. Materials & methods: Curcumin (Cur) was coloaded with TMZ into PEG-PLGA NPs, then NPs were further encapsulated into a thermosensitive hydrogel to form a nanogel, which was injected into the resection cavity of the GBM postsurgery. Results: The prepared nanogel displayed excellent drug-loading capacity and long-term drug release. Estimated survival characteristics demonstrated that the nanogel could play a significant role in TMZ-resistant tumor inhibition with low drug-induced toxicity. The originally designed ratio of Cur/TMZ was sustained, making it an effective therapeutic outcome. Conclusion: Cur-combined TMZ-formed nanogels can be a promising candidate for the local inhibition of GBM recurrence.

Advances in Preclinical/Clinical Glioblastoma Treatment: Can Nanoparticles Be of Help?

Glioblastoma multiforme (GB) is the most aggressive and frequent primary malignant tumor in the central nervous system (CNS), with unsatisfactory and challenging treatment nowadays. Current standard of care includes surgical resection followed by chemotherapy and radiotherapy. However, these treatments do not much improve the overall survival of GB patients, which is still below two years (the 5-year survival rate is below 7%). Despite various approaches having been followed to increase the release of anticancer drugs into the brain, few of them demonstrated a significant success, as the blood brain barrier (BBB) still restricts its uptake, thus limiting the therapeutic options. Therefore, enormous efforts are being devoted to the development of novel nanomedicines with the ability to cross the BBB and specifically target the cancer cells. In this context, the use of nanoparticles represents a promising non-invasive route, allowing to evade BBB and reducing systemic concentration of drugs and, hence, side effects. In this review, we revise with a critical view the different families of nanoparticles and approaches followed so far with this aim.

Deeply Infiltrating iRGD-Graphene Oxide for the Intensive Treatment of Metastatic Tumors through PTT-Mediated Chemosensitization and Strengthened Integrin Targeting-Based Antimigration

A limited infiltration and the subsequent low effective drug concentration result in poor chemotherapeutic outcomes against tumors, and even further promote tumor resistance and metastatic. Herein, iRGD-modified graphene oxide (GO) nanosheets (IPHG) are developed for the intensive treatment of metastatic tumors using focus-specific penetrated delivery together with photothermal therapy-mediated chemosensitization and photothermal therapy-strengthened integrin targeting-based antimigration. In vitro and in vivo data verified the mechanism of the tumor-selective infiltration of IPHG is based on a rigid 2D structure-associated advantage regarding hemodynamics and endothelial contact, followed by iRGD-endowed transendothelial and intratumoral transport. Once IPHG-DOX-penetrated 4T1 tumors are exposed to near-infrared irradiation, hyperthermia stress and photothermal therapy-elevated effective drug concentrations result in chemosensitization and prominent tumor suppression. Meanwhile, the specific binding of iRGD to integrins and photothermal therapy leads to the synergistic perturbation of cytoskeleton remodeling and subsequent impairment of cell motility and metastasis. The tailored design of IPHG validates a promising paradigm for drug delivery to combat tumor resistance and metastasis resulting from poor target access for single chemotherapy.

Theranostic Nanomedicine for Synergistic Chemodynamic Therapy and Chemotherapy of Orthotopic Glioma

Glioma is a common primary brain malignancy with a poor prognosis. Chemotherapy is the first-line treatment for brain tumors but low efficiency of drugs in crossing the blood-brain barrier (BBB) and drug resistance related to tumor hypoxia thwart its efficacy. Herein, a theranostic nanodrug (iRPPA@TMZ/MnO) is developed by incorporating oleic acid-modified manganese oxide (MnO) and temozolomide (TMZ) into a polyethylene glycol-poly(2-(diisopropylamino)ethyl methacrylate-based polymeric micelle containing internalizing arginine-glycine-aspartic acid (iRGD). The presence of iRGD provides the nanodrug with a high capacity of crossing the BBB and penetrating the tumor tissue. After accumulation in glioma, the nanodrug responds to the tumor microenvironment to simultaneously release TMZ, Mn2+, and O2. The released TMZ induces tumor cell apoptosis and the released Mn2+ causes intracellular oxidative stress that kill tumor cells via a Fenton-like reaction. The O2 produced in situ alleviates tumor hypoxia and enhances the chemotherapy/chemodynamic therapeutic effects against glioma. The Mn2+ can also serve as a magnetic resonance imaging (MRI) contrast agent for tumor imaging during therapy. The study demonstrates the great potential of this multifunctional nanodrug for MRI-visible therapy of brain glioma.

Polyamidoamine-based nanovector for the efficient delivery of methotrexate to U87 glioma cells

The purpose of this study was to design a polyamidoamine (PAMAM)-based nanovector for the efficient delivery of methotrexate to U87 glioma cells. To this end, 0-100% acetylated PAMAM dendrimers of the fourth generation were synthesized and evaluated using drug encapsulation measurements, molecular dynamics simulations, neurotoxicity assays and neuronal internalization experiments. The best system was tested as a nanovector for methotrexate delivery to U87 glioma cells. The authors found that 25% acetylated PAMAM dendrimers of the fourth-generation combine low intrinsic toxicity, large drug complexation capacity and efficient internalization into hippocampal neurons. Nanovector complexation enhances the cytotoxic response of methotrexate against U87 glioma cells compared with free drug solutions. In conclusion, 25% acetylated PAMAM dendrimers of the fourth-generation increase drug uptake by glioma cells and thereby act as efficient nanovectors for methotrexate delivery.

iRGD Peptide as a Tumor-Penetrating Enhancer for Tumor-Targeted Drug Delivery

The unique structure and physiology of a tumor microenvironment impede intra-tumoral penetration of chemotherapeutic agents. A novel iRGD peptide that exploits the tumor microenvironment can activate integrin-dependent binding to tumor vasculatures and neuropilin-1 (NRP-1)-dependent transport to tumor tissues. Recent studies have focused on its dual-targeting ability to achieve enhanced penetration of chemotherapeutics for the efficient eradication of cancer cells. Both the covalent conjugation and the co-administration of iRGD with chemotherapeutic agents and engineered delivery vehicles have been explored. Interestingly, the iRGD-mediated drug delivery also enhances penetration through the blood-brain barrier (BBB). Recent studies have shown its synergistic effect with BBB disruptive techniques. The efficacy of immunotherapy involving immune checkpoint blockades has also been amplified by using iRGD as a targeting moiety. In this review, we presented the recent advances in iRGD technology, focusing on cancer treatment modalities, including the current clinical trials using iRGD. The iRGD-mediated nano-carrier system could serve as a promising strategy in drug delivery to the deeper tumor regions, and be combined with various therapeutic interventions due to its novel targeting ability.

Nanoparticle Drug Delivery System for Glioma and Its Efficacy Improvement Strategies: A Comprehensive Review

Gliomas are the most common tumor of the central nervous system. However, the presence of the brain barrier blocks the effective delivery of drugs and leads to the treatment failure of various drugs. The development of a nanoparticle drug delivery system (NDDS) can solve this problem. In this review, we summarized the brain barrier (including blood-brain barrier (BBB), blood-brain tumor barriers (BBTB), brain-cerebrospinal fluid barrier (BCB), and nose-to-brain barrier), NDDS of glioma (such as passive targeting systems, active targeting systems, and environmental responsive targeting systems), and NDDS efficacy improvement strategies and deficiencies. The research prospect of drug-targeted delivery systems for glioma is also discussed.

Cell-penetrating corosolic acid liposome as a functional carrier for delivering chemotherapeutic drugs

Corosolic acid (CA), a natural pentacyclic triterpenoid, exhibits antitumor and synergistic therapy effect with chemotherapeutic drugs mainly through inhibiting STAT3 activation. In this study, it is found that CA possesses cholesterol-like properties in liposome by regulating membrane phase behavior to form stable cholesterol-free CA liposomes (CALP). Compared with traditional cholesterol liposomes (CHOLP), CALP exhibit stronger membrane fusion and higher cellular uptake, and other functions including inhibition of STAT3 activation and suppression of the recruitment of macrophages to tumor microenvironment. Therefore, CALP is used as a functional carrier, and doxorubicin-loaded CALP (DOX/CALP) based on PEGylated liposomal doxorubicin (DOXIL^Ⓡ) are prepared by replacing its cholesterol with CA. The physicochemical properties and biological activities are compared with those of doxorubicin-loaded cholesterol liposomes (DOX/LP). Both DOX/CALP and DOX/LP possess approximately similar physical properties and exhibit high stability and low drug leakage as shown by the published data of DOXIL^Ⓡ. Nevertheless, it is noteworthy that DOX/CALP displays higher in vitro cellular uptake and tumor spheroid permeation along with stronger cytotoxicity against tumor cells than DOX/LP. Despite DOX/CALP has the same PK parameters, normal tissue biodistribution, and safety profile as DOX/LP, the results of an in vivo study in 4T1-bearing mice indicate that the DOX/CALP treatment group exhibit higher tumor accumulation, more significant tumor growth inhibition, and longer life span than the DOX/LP group. Overall, DOX/CALP is a representative example of CA-doped liposomes, suggesting that CALP as a functional drug carrier for solving low efficacy of present liposomal drugs might have promising application potential. STATEMENT OF SIGNIFICANCE: An original drug delivery nanocarrier, corosolic acid liposome (CALP), was developed in this study. It was found that CA possesses cholesterol-like function to regulate phospholipid membrane phase behavior. By replacing the cholesterol with CA, the liposomes were converted into high cellular uptake carriers, possessing anti-inflammatory activity and synergism with chemotherapeutic drugs. The variability of CALP formulations enabled to deliver therapeutic agents. The use of CALP to deliver doxorubicin not only significantly enhanced the therapeutic efficacy compared with the classic PEGylated liposomal doxorubicin, but also maintained the improved safety. Because CALP can be obtained by conventional liposome preparation methods, its use as functional drug carriers for solving low efficacy of present liposomal drugs would have promising application potential.

Nose-to-Brain Delivery of Cancer-Targeting Paclitaxel-Loaded Nanoparticles Potentiates Antitumor Effects in Malignant Glioblastoma

Glioblastoma multiforme (GBM) is an aggressive tumor with no curative treatment. The tumor recurrence after resection often requires chemotherapy or radiation to delay the infiltration of tumor remnants. Intracerebral chemotherapies are preferentially being used to prevent tumor regrowth, but treatments remain unsuccessful because of the poor drug distribution in the brain. In this study, we investigated the therapeutic efficacy of cancer-targeting arginyl-glycyl-aspartic tripeptide (RGD) conjugated paclitaxel (PTX)-loaded nanoparticles (NPs) against GBM by nose-to-brain delivery. Our results demonstrated that RGD-modified PTX-loaded NPs showed cancer-specific delivery and enhanced anticancer effects in vivo. The intranasal (IN) inoculation of RGD-PTX-loaded NPs effectively controls the tumor burden (75 ± 12% reduction) by inducing apoptosis and/or inhibiting cancer cell proliferation without affecting the G₀ stage of normal brain cells. Our data provide therapeutic evidence supporting the use of intranasally delivered cancer-targeted PTX-loaded NPs for GBM therapy.

Co-Administration Of iRGD Enhances Tumor-Targeted Delivery And Anti-Tumor Effects Of Paclitaxel-Loaded PLGA Nanoparticles For Colorectal Cancer Treatment

BACKGROUND

Nanoparticles exhibit great promise for improving the solubility and tissue-specific distribution of chemotherapeutic agents; however, the passive and highly variable enhanced permeability and retention (EPR) effects observed in tumors frequently leads to insufficient delivery of nanodrugs into tumors. The tumor-penetrating peptide iRGD can actively enhance tumor-selective delivery of nanoparticles into tumors by binding to integrin and interacting with tissue-penetrating receptor neuropilin-1.

MATERIALS AND METHODS

To improve colorectal cancer treatment, in this study, we prepared a paclitaxel (PTX)-loaded PLGA nanoparticle (PLGA-PTX) and evaluated its tumor-targeting and antitumor activity by co-administration with iRGD.

RESULTS

Compared to free PTX, encapsulated PTX retained preferential cytotoxicity toward various colorectal cancer cells while effectively sparing healthy cells. PLGA-PTX treatment resulted in cell cycle arrest at the G2/M phase and apoptosis, leading to inhibition of cancer cell migration and invasion. PLGA-PTX combined with iRGD displayed little enhancement of cytotoxicity in vitro. Despite this, iRGD receptors integrin and neuropilin-1 were found to be primarily overexpressed on abundant tumor vessels in mice bearing colorectal tumors. Consequently, co-administration of nanoparticles with iRGD promoted the selective delivery of nanoparticles into tumor tissues in vivo. Additionally, the combined regimen enhanced the antitumor effects compared to those of each individual reagent.

CONCLUSION

Our findings suggest that PLGA nanoparticles combined with the iRGD peptide provide a promising drug delivery strategy for facilitating active drug accumulation into tumors, given that iRGD receptors are overexpressed on tumor vessels. This co-administration system lacking covalent conjugation provides a more convenient means to combine various therapeutic agents with iRGD to achieve personalized nanotherapy.

iRGD: A Promising Peptide for Cancer Imaging and a Potential Therapeutic Agent for Various Cancers

Poor penetration into the tumor parenchyma and the reduced therapeutic efficacy of anticancer drugs and other medications are the major problems in tumor treatment. A new tumor-homing and penetrating peptide, iRGD (CRGDK/RGPD/EC), can be effectively used to combine and deliver imaging agents or anticancer drugs into tumors. The different “vascular zip codes” expressed in different tissues can serve as targets for docking-based (synaptic) delivery of diagnostic and therapeutic molecules. αv-Integrins are abundantly expressed in the tumor vasculature, where they are recognized by peptides containing the RGD integrin recognition motif. The iRGD peptide follows a multistep tumor-targeting process: First, it is proteolytically cleaved to generate the CRGDK fragment by binding to the surface of cells expressing αv integrins (αvβ3 and αvβ5). Then, the fragment binds to neuropilin-1 and penetrates the tumor parenchyma more deeply. Compared with conventional RGD peptides, the affinity of iRGD for αv integrins is in the mid to low nanomolar range, and the CRGDK fragment has a stronger affinity for neuropilin-1 than that for αv integrins because of the C-terminal exposure of a conditional C-end Rule (CendR) motif (R/KXXR/K), whose receptor proved to be neuropilin-1. Consequently, these advantages facilitate the transfer of CRGDK fragments from integrins to neuropilin-1 and consequently deeper penetration into the tumor. Due to its specific binding and strong affinity, the iRGD peptide can deliver imaging agents and anticancer drugs into tumors effectively and deeply, which is useful in detecting the tumor, blocking tumor growth, and inhibiting tumor metastasis. This review aims to focus on the role of iRGD in the imaging and treatment of various cancers.

Cell Permeable NBD Peptide-Modified Liposomes by Hyaluronic Acid Coating for the Synergistic Targeted Therapy of Metastatic Inflammatory Breast Cancer

Chronic inflammation is closely related to the development, deterioration, and metastasis of tumors. Recently, many studies have shown that down-regulating the expression of inflammation by blocking nuclear factor-κB (NF-κB) and signal transducer and activator of transcription 3 (STAT3) pathways could significantly inhibit tumor growth and metastasis. The combined application of curcumin (CUR) and celecoxib (CXB) has been proven to exert a synergistic antitumor effect via inhibiting the activation of NF-κB and STAT3. TAT-NBD (TN) peptide, a fusion peptide of NF-κB essential modulator (NEMO)-binding domain peptide (NBD) and cell-penetrating peptide (TAT), can selectively block NF-κB activating pathway resulting in tumor growth inhibition. In the present study, a novel TN-modified liposome coloading both CXB and CUR (TN-CCLP) at a synergistic ratio was first constructed with the property of synchronous release, then hyaluronic acid (HA) as CD44 targeting moiety was coated on the surface of the cationic liposome via electrostatic interaction to prepare the anionic HA/TN-CCLP. In vitro results of cytotoxicity, macrophage migration inhibition, and anti-inflammation efficacy revealed that TN-CCLP and HA/TN-CCLP were significantly superior to TN-LP and CCLP, while TN-CCLP exhibited better effects than HA/TN-CCLP due to higher cellular uptake ability. Different from in vitro data, after systematically treating 4T1 breast tumor-bearing mice, HA/TN-CCLP exerted the most striking effects on anti-inflammation, inhibition of macrophage recruitment, and antitumor because of the longest circulation time and maximum tumor accumulation. In particular, HA/TN-CCLP could availably block the lung metastasis of breast cancer. Taken together, the novel CD44 targeted TN-CCLP exhibited the potential for inhibiting tumor development and metastasis through improving inflammatory infiltration of tumor tissue.

Evaluation of anti-EGFR-iRGD recombinant protein with GOLD nanoparticles: synergistic effect on antitumor efficiency using optimized deep neural networks

NP screening through a deep learning approach against Anti-EGFR and validation through docking with AuNP. Biochemical pathway and simulation of AuNP with Anti-EGFR and further implementation in biological circuits.

Design of an Amphiphilic iRGD Peptide and Self-Assembling Nanovesicles for Improving Tumor Accumulation and Penetration and the Photodynamic Efficacy of the Photosensitizer

Photodynamic therapy (PDT) is a minimally invasive treatment for many diseases, including infections and tumors. Nevertheless, clinical utilization of PDT is severely restricted due to the shortcomings of the photosensitizers, especially their low water solubility and poor tumor selectivity. iRGD (internalizing RGD, CRGDKGPDC), a nine-unit cyclic peptide, was applied as an active ligand to realize tumor homing and tissue penetration. Herein, we innovatively fabricated a novel OFF-ON mode iRGD-based peptide amphiphile (PA) to self-assemble into spherical nanovesicles to enhance the tumor-targeting and tumor-penetrating efficacy of PDT. To introduce the self-assembling feature into iRGD, a hydrophilic arginine-rich sequence and hydrophobic alkyl chains were sequentially linked to the iRGD motif. A short proline sequence was selected to control the morphology of the self-assembled aggregates. Next, the photosensitizer hypocrellin B (HB) was encapsulated into PA vesicles with a high loading efficiency. The aggregation-caused quenching effect inactivated HB in the PA vesicles; however, the iRGD-peptide-based material was able to be selectively degraded in tumor cells. Thus, the HB fluorescence was recovered to achieve tumor-targeted imaging. This approach endows HB-loaded PA vesicles (HB-PA) with tumor-targeted activation, preferable tumor accumulation, and deep tumor penetration, thus leading to an excellent fluorescence-imaging-guided photodynamic efficacy both in vitro and in vivo. These amphiphilic iRGD aggregates provide a novel strategy for improving the accumulation, penetration, and imaging-guided photodynamic efficacy of photosensitizers.

Targeting experimental orthotopic glioblastoma with chitosan-based superparamagnetic iron oxide nanoparticles (CS-DX-SPIONs)

Background

Glioblastoma is the most devastating primary brain tumor of the central nervous system in adults. Magnetic nanocarriers may help not only for a targeted delivery of chemotherapeutic agents into the tumor site but also provide contrast enhancing properties for diagnostics using magnetic resonance imaging (MRI).

Methods

Synthesized hybrid chitosan-dextran superparamagnetic nanoparticles (CS-DX-SPIONs) were characterized using transmission electron microscopy (TEM) and relaxometry studies. Nonlinear magnetic response measurements were employed for confirming the superparamagnetic state of particles. Following in vitro analysis of nanoparticles cellular uptake tumor targeting was assessed in the model of the orthotopic glioma in rodents.

Results

CS-DX-SPIONs nanoparticles showed a uniform diameter of 55 nm under TEM and superparamagentic characteristics as determined by T₁ (spin-lattice relaxation time) and T₂ (spin-spin relaxation time) proton relaxation times. Application of the chitosan increased the charge from +8.9 to +19.3 mV of the dextran-based SPIONs. The nonlinear magnetic response at second harmonic of CS-DX-SPIONs following the slow change of stationary magnetic fields with very low hysteresis evidenced superparamagnetic state of particles at ambient temperatures. Confocal microscopy and flow cytometry studies showed an enhanced internalization of the chitosan-based nanoparticles in U87, C6 glioma and HeLa cells as compared to dextran-coated particles. Cytotoxicity assay demonstrated acceptable toxicity profile of the synthesized nanoparticles up to a concentration of 10 μg/ml. Intravenously administered CS-DX-SPIONs in orthotopic C6 gliomas in rats accumulated in the tumor site as shown by high-resolution MRI (11.0 T). Retention of nanoparticles resulted in a significant contrast enhancement of the tumor image that was accompanied with a dramatic drop in T₂ values (P<0.001). Subsequent histological studies proved the accumulation of the nanoparticles inside glioblastoma cells.

Conclusion

Hybrid chitosan-dextran magnetic particles demonstrated high MR contrast enhancing properties for the delineation of the brain tumor. Due to a significant retention of the particles in the tumor an application of the CS-DX-SPIONs could not only improve the tumor imaging but also could allow a targeted delivery of chemotherapeutic agents.

Multicellular Tumor Spheroids (MCTS) as a 3D In Vitro Evaluation Tool of Nanoparticles

Multicellular tumor spheroid models (MCTS) are often coined as 3D in vitro models that can mimic the microenvironment of tissues. MCTS have gained increasing interest in the nano-biotechnology field as they can provide easily accessible information on the performance of nanoparticles without using animal models. Considering that many countries have put restrictions on animals testing, which will only tighten in the future as seen by the recent developments in the Netherlands, 3D models will become an even more valuable tool. Here, an overview on MCTS is provided, focusing on their use in cancer research as most nanoparticles are tested in MCTS for treatment of primary tumors. Thereafter, various types of nanoparticles-from self-assembled block copolymers to inorganic nanoparticles, are discussed. A range of physicochemical parameters including the size, shape, surface chemistry, ligands attachment, stability, and stiffness are found to influence nanoparticles in MCTS. Some of these studies are complemented by animal studies confirming that lessons from MCTS can in part predict the behaviour in vivo. In summary, MCTS are suitable models to gain additional information on nanoparticles. While not being able to replace in vivo studies, they can bridge the gap between traditional 2D in vitro studies and in vivo models.

Contributions of immune cell populations in the maintenance, progression, and therapeutic modalities of glioma

Immunotherapies are becoming a promising strategy for malignant disease. Selectively directing host immune responses to target cancerous tissue is a milestone of human health care. The roles of the innate and adaptive immune systems in both cancer progression and elimination are now being realized. Defining the immune cell environment and identifying the contributions of each sub-population of these cells has lead to an understanding of the immunotherapeutic processes, and demonstrated the potential of the immune system to drive cancer shrinkage and sustained immunity against disease. Poorly treated diseases, such as high-grade glioma, suffer from lack of therapeutic efficacy and rapid progression. Immunotherapeutic success in other solid malignancies, such as melanoma, now provides the principals for which this treatment paradigm can be adapted for primary brain cancers. The central nervous system is complex, and relative contributions of immune sub-populations to high grade glioma progression are not fully characterized. Here, we summarize recent research in both animal and humans which add to the knowledge base of how innate and adaptive immune cells contribute to glioma progression, and outline work which has demonstrated their potential to elicit anti-tumorigenic responses. Additionally, we highlight Neuropilin 1, a cell surface receptor protein, describe its signaling functions in the context of immunity, and point to its potential to slow glioma progression.

Targeting Malignant Brain Tumors with Antibodies

Antibodies have been shown to be a potent therapeutic tool. However, their use for targeting brain diseases, including neurodegenerative diseases and brain cancers, has been limited, particularly because the blood–brain barrier (BBB) makes brain tissue hard to access by conventional antibody-targeting strategies. In this review, we summarize new antibody therapeutic approaches to target brain tumors, especially malignant gliomas, as well as their potential drawbacks. Many different brain delivery platforms for antibodies have been studied such as liposomes, nanoparticle-based systems, cell-penetrating peptides (CPPs), and cell-based approaches. We have already shown the successful delivery of single-chain fragment variable (scFv) with CPP as a linker between two variable domains in the brain. Antibodies normally face poor penetration through the BBB, with some variants sufficiently passing the barrier on their own. A “Trojan horse” method allows passage of biomolecules, such as antibodies, through the BBB by receptor-mediated transcytosis (RMT). Such examples of therapeutic antibodies are the bispecific antibodies where one binding specificity recognizes and binds a BBB receptor, enabling RMT and where a second binding specificity recognizes an antigen as a therapeutic target. On the other hand, cell-based systems such as stem cells (SCs) are a promising delivery system because of their tumor tropism and ability to cross the BBB. Genetically engineered SCs can be used in gene therapy, where they express anti-tumor drugs, including antibodies. Different types and sources of SCs have been studied for the delivery of therapeutics to the brain; both mesenchymal stem cells (MSCs) and neural stem cells (NSCs) show great potential. Following the success in treatment of leukemias and lymphomas, the adoptive T-cell therapies, especially the chimeric antigen receptor-T cells (CAR-Ts), are making their way into glioma treatment as another type of cell-based therapy using the antibody to bind to the specific target(s). Finally, the current clinical trials are reviewed, showing the most recent progress of attractive approaches to deliver therapeutic antibodies across the BBB aiming at the specific antigen.

Mimicking Tumors: Toward More Predictive In Vitro Models for Peptide- and Protein-Conjugated Drugs

Macromolecular drug candidates and nanoparticles are typically tested in 2D cancer cell culture models, which are often directly followed by in vivo animal studies. The majority of these drug candidates, however, fail in vivo. In contrast to classical small-molecule drugs, multiple barriers exist for these larger molecules that two-dimensional approaches do not recapitulate. In order to provide better mechanistic insights into the parameters controlling success and failure and due to changing ethical perspectives on animal studies, there is a growing need for in vitro models with higher physiological relevance. This need is reflected by an increased interest in 3D tumor models, which during the past decade have evolved from relatively simple tumor cell aggregates to more complex models that incorporate additional tumor characteristics as well as patient-derived material. This review will address tissue culture models that implement critical features of the physiological tumor context such as 3D structure, extracellular matrix, interstitial flow, vascular extravasation, and the use of patient material. We will focus on specific examples, relating to peptide-and protein-conjugated drugs and other nanoparticles, and discuss the added value and limitations of the respective approaches.