Dual-targeting superparamagnetic iron oxide nanoprobes with high and low target density for brain glioma imaging

Functionalized nanoparticles crossing the brain-blood barrier to target glioma cells

Glioma is the most common tumor of the central nervous system (CNS), with a 5-year survival rate of <35%. Drug therapy, such as chemotherapeutic and immunotherapeutic agents, remains one of the main treatment modalities for glioma, including temozolomide, doxorubicin, bortezomib, cabazitaxel, dihydroartemisinin, immune checkpoint inhibitors, as well as other approaches such as siRNA, ferroptosis induction, etc. However, the filter function of the blood-brain barrier (BBB) reduces the amount of drugs needed to effectively target CNS tumors, making it one of the main reasons for poor drug efficacies in glioma. Thus, finding a suitable drug delivery platform that can cross the BBB, increase drug aggregation and retainment in tumoral areas and avoid accumulation in non-targeted areas remains an unsolved challenge in glioma drug therapy. An ideal drug delivery system for glioma therapy should have the following features: (1) prolonged drug life in circulation and effective penetration through the BBB; (2) adequate accumulation within the tumor (3) controlled-drug release modulation; (4) good clearance from the body without significant toxicity and immunogenicity, etc. In this regard, due to their unique structural features, nanocarriers can effectively span the BBB and target glioma cells through surface functionalization, providing a new and effective strategy for drug delivery. In this article, we discuss the characteristics and pathways of different nanocarriers for crossing the BBB and targeting glioma by listing different materials for drug delivery platforms, including lipid materials, polymers, nanocrystals, inorganic nanomaterials, etc.

Biocompatible Iron Oxide Nanoparticles for Targeted Cancer Gene Therapy: A Review

In recent years, gene therapy has made remarkable achievements in tumor treatment. In a successfully cancer gene therapy, a smart gene delivery system is necessary for both protecting the therapeutic genes in circulation and enabling high gene expression in tumor sites. Magnetic iron oxide nanoparticles (IONPs) have demonstrated their bright promise for highly efficient gene delivery target to tumor tissues, partly due to their good biocompatibility, magnetic responsiveness, and extensive functional surface modification. In this review, the latest progress in targeting cancer gene therapy is introduced, and the unique properties of IONPs contributing to the efficient delivery of therapeutic genes are summarized with detailed examples. Furthermore, the diagnosis potentials and synergistic tumor treatment capacity of IONPs are highlighted. In addition, aiming at potential risks during the gene delivery process, several strategies to improve the efficiency or reduce the potential risks of using IONPs for cancer gene therapy are introduced and addressed. The strategies and applications summarized in this review provide a general understanding for the potential applications of IONPs in cancer gene therapy.

An update on dual targeting strategy for cancer treatment

The key issue in the treatment of solid tumors is the lack of efficient strategies for the targeted delivery and accumulation of therapeutic cargoes in the tumor microenvironment (TME). Targeting approaches are designed for more efficient delivery of therapeutic agents to cancer cells while minimizing drug toxicity to normal cells and off-targeting effects, while maximizing the eradication of cancer cells. The highly complicated interrelationship between the physicochemical properties of nanoparticles, and the physiological and pathological barriers that are required to cross, dictates the need for the success of targeting strategies. Dual targeting is an approach that uses both purely biological strategies and physicochemical responsive smart delivery strategies to increase the accumulation of nanoparticles within the TME and improve targeting efficiency towards cancer cells. In both approaches, either one single ligand is used for targeting a single receptor on different cells, or two different ligands for targeting two different receptors on the same or different cells. Smart delivery strategies are able to respond to triggers that are typical of specific disease sites, such as pH, certain specific enzymes, or redox conditions. These strategies are expected to lead to more precise targeting and better accumulation of nano-therapeutics. This review describes the classification and principles of dual targeting approaches and critically reviews the efficiency of dual targeting strategies, and the rationale behind the choice of ligands. We focus on new approaches for smart drug delivery in which synthetic and/or biological moieties are attached to nanoparticles by TME-specific responsive linkers and advanced camouflaged nanoparticles.

Advances in magnetic resonance imaging contrast agents for glioblastoma-targeting theranostics

Glioblastoma (GBM) is the most aggressive malignant brain tumour, with a median survival of 3 months without treatment and 15 months with treatment. Early GBM diagnosis can significantly improve patient survival due to early treatment and management procedures. Magnetic resonance imaging (MRI) using contrast agents is the preferred method for the preoperative detection of GBM tumours. However, commercially available clinical contrast agents do not accurately distinguish between GBM, surrounding normal tissue and other cancer types due to their limited ability to cross the blood–brain barrier, their low relaxivity and their potential toxicity. New GBM-specific contrast agents are urgently needed to overcome the limitations of current contrast agents. Recent advances in nanotechnology have produced alternative GBM-targeting contrast agents. The surfaces of nanoparticles (NPs) can be modified with multimodal contrast imaging agents and ligands that can specifically enhance the accumulation of NPs at GBM sites. Using advanced imaging technology, multimodal NP-based contrast agents have been used to obtain accurate GBM diagnoses in addition to an increased amount of clinical diagnostic information. NPs can also serve as drug delivery systems for GBM treatments. This review focuses on the research progress for GBM-targeting MRI contrast agents as well as MRI-guided GBM therapy.

Trastuzumab and folic acid functionalized gold nanoclusters as a dual-targeted radiosensitizer for megavoltage radiation therapy of human breast cancer

In the present study, the effect of functionalized gold nanoclusters (AuNCs) with trastuzumab (Herceptin®) and/or folic acid (FA) as a single and dual-targeted radiosensitizers for the enhancement of megavoltage radiation therapy efficacy was investigated. SK-BR3 breast cancer cells as human epidermal growth factor 2 (HER2) and folate overexpressing cell line and the murine fibroblast (L929) as a control cell line were selected. The cellular uptake was followed using inductively coupled plasma optical emission spectrometry (ICP-OES) that showed AuNCs-FA-HER uptake by SK-BR3 cells was 3 times more than the non-targeted AuNCs after 12 h incubation. MTT and clonogenic assays revealed that the viability and surviving fraction of cancer cells were significantly inhibited by treating with all AuNCs under radiation compared to treating with radiation alone. However, these effects in the dual-targeted AuNCs group (AuNCs-FA-HER) was significantly greater than non-targeted and single-targeted AuNCs groups. Also, apoptosis was evaluated using an Annexin V-FITC/propidium iodide (PI) kit in flow cytometry. All AuNCs, in combination with 4 Gy of photon beam, induced more apoptosis. By fitting the survival fraction data on the linear-quadratic model, the sensitization enhancement factor (SER) of AuNCs, AuNCs-FA, AuNCs-HER, and AuNCs-FA-HER, were obtained 1.17, 1.32, 1.48 and 1.77, respectively. SER for AuNCs-FA-HER was significantly higher than that non-targeted and single-targeted AuNCs (p-value < 0.05) that can be attributed to more internalization in the cancer cells. It was concluded that functionalized AuNCs with both folic acid and Herceptin could represent a promising strategy for increased cellular internalization that improved radiation therapy efficiency in SK-BR3 breast cancer cells.

Ligand-Installed Nanocarriers toward Precision Therapy

Development of drug-delivery systems that selectively target neoplastic cells has been a major goal of nanomedicine. One major strategy for achieving this milestone is to install ligands on the surface of nanocarriers to enhance delivery to target tissues, as well as to enhance internalization of nanocarriers by target cells, which improves accuracy, efficacy, and ultimately enhances patient outcomes. Herein, recent advances regarding the development of ligand-installed nanocarriers are introduced and the effect of their design on biological performance is discussed. Besides academic achievements, progress on ligand-installed nanocarriers in clinical trials is presented, along with the challenges faced by these formulations. Lastly, the future perspectives of ligand-installed nanocarriers are discussed, with particular emphasis on their potential for emerging precision therapies.

Preparation and anti-cancer activity of transferrin/folic acid double-targeted graphene oxide drug delivery system

In this study, a transferrin/folic acid double-targeting graphene oxide drug delivery system loaded with doxorubicin was designed. Graphene oxide was prepared by ultrasound improved Hummers method and was modified with Pluronic F68, folic acid, and transferrin to decrease its toxicity and to allow dual-targeting. The results show that the double target drug delivery system (TFGP*DOX) has good and controllable drug delivery performance with no toxicity. Moreover, TFGP*DOX has a better inhibitory effect on SMMC-7721 cells than does a single target drug delivery system (FGP*DOX). The results of drug release analysis and cell inhibition studies showed that TFGP*DOX has a good sustained release function that can reduce the drug release rate in blood circulation over time and improve the local drug concentration in or near a targeted tumor. Therefore, the drug loading system (TFGP*DOX) has potential application value in the treatment of hepatocellular carcinoma.

Dual and multi-targeted nanoparticles for site-specific brain drug delivery

In recent years, nanomedicines have emerged as a promising method for central nervous system drug delivery, enabling the drugs to overcome the blood-brain barrier and accumulate preferentially in the brain. Despite the current success of brain-targeted nanomedicines, limitations still exist in terms of the targeting specificity. Based on the molecular mechanism, the exact cell populations and subcellular organelles where the injury occurs and the drugs take effect have been increasingly accepted as a more specific target for the next generation of nanomedicines. Dual and multi-targeted nanoparticles integrate different targeting functionalities and have provided a paradigm for precisely delivering the drug to the pathological site inside the brain. The targeting process often involves the sequential or synchronized navigation of the targeting moieties, which allows highly controlled drug delivery compared to conventional targeting strategies. Herein, we focus on the up-to-date design of pathological site-specific nanoparticles for brain drug delivery, highlighting the dual and multi-targeting strategies that were employed and their impact on improving targeting specificity and therapeutic effects. Furthermore, the background discussion of the basic properties of a brain-targeted nanoparticle and the common lesion features classified by neurological pathology are systematically summarized.

Targeted Theranostic Nanoparticles for Brain Tumor Treatment

The poor prognosis and rapid recurrence of glioblastoma (GB) are associated to its fast-growing process and invasive nature, which make difficult the complete removal of the cancer infiltrated tissues. Additionally, GB heterogeneity within and between patients demands a patient-focused method of treatment. Thus, the implementation of nanotechnology is an attractive approach considering all anatomic issues of GB, since it will potentially improve brain drug distribution, due to the interaction between the blood⁻brain barrier and nanoparticles (NPs). In recent years, theranostic techniques have also been proposed and regarded as promising. NPs are advantageous for this application, due to their respective size, easy surface modification and versatility to integrate multiple functional components in one system. The design of nanoparticles focused on therapeutic and diagnostic applications has increased exponentially for the treatment of cancer. This dual approach helps to understand the location of the tumor tissue, the biodistribution of nanoparticles, the progress and efficacy of the treatment, and is highly useful for personalized medicine-based therapeutic interventions. To improve theranostic approaches, different active strategies can be used to modulate the surface of the nanotheranostic particle, including surface markers, proteins, drugs or genes, and take advantage of the characteristics of the microenvironment using stimuli responsive triggers. This review focuses on the different strategies to improve the GB treatment, describing some cell surface markers and their ligands, and reports some strategies, and their efficacy, used in the current research.

Aminopeptidase N (CD13) targeted MR and NIRF dual-modal imaging of ovarian tumor xenograft

The development of tumor-specific imaging nanoprobes with the potential to improve the accuracy of cancer diagnosis has become an area of intense research. Aminopeptidase N (CD13) predominantly expresses on the surface of ovarian tumor cells and can be specifically recognized by Asn-Gly-Arg (NGR) peptide. The applicability of CD13 as a target for specific ovarian tumor imaging, however, remains unexploited so far. In this study, Cy5.5-labeled, NGR-conjugated iron oxide nanoparticles (Cy5.5-NGR-Fe₃O₄ NPs) were prepared as an ovarian tumor specific bimodal imaging nanoprobe. It is demonstrated that the conjugation of NGR targeting moiety leads to a higher cellular uptake toward ES-2 cells, the human ovarian carcinoma cells that highly express CD13. Moreover, magnetic resonance imaging of ovarian tumor xenograft reveals that the Fe₃O₄-Cy5.5-NGR NPs results in a significant T₂* signal reduction in the tumor. Meanwhile, near infrared fluorescence imaging indicates a higher accumulation of Fe₃O₄-Cy5.5-NGR NPs in the tumor xenograft. Therefore, CD13 could be applied as a novel and efficient target for constructing ovarian tumor specific nanoprobes with improved accuracy for ovarian tumor diagnosis.

MnO nanoparticles with unique excitation-dependent fluorescence for multicolor cellular imaging and MR imaging of brain glioma

The authors describe MnO nanoparticles (NPs) with unique excitation-dependent fluorescence across the entire visible spectrum. These NPs are shown to be efficient optical nanoprobe for multicolor cellular imaging. Synthesis of the NPs is accomplished by a thermal decomposition method. The MnO NPs exhibit a high r₁ relaxivity of 4.68 mM^-1 s^-1 and therefore give an enhanced contrast effect in magnetic resonance (MR) studies of brain glioma. The cytotoxicity assay, hemolysis analysis, and hematoxylin and eosin (H&E) staining tests verify that the MnO NPs are biocompatible. In the authors' perception, the simultaneous attributes of multicolor fluorescence and excellent MR functionality make this material a promising dual-modal nanoprobe for use in bio-imaging. Graphical abstract A direct method to synthesize fluorescent MnO NPs is reported. The NPs are biocompatible and have been successfully applied for multicolor cellular imaging and MR detection of brain glioma.

Comparative toxicity and contrast enhancing assessments of Gd2O3@BSA and MnO2@BSA nanoparticles for MR imaging of brain glioma

The albumin-templated Gd₂O₃ and MnO₂ nanoparticles (NPs) have been developed as a new type of magnetic resonance (MR) T₁ contrast agents. However, their potential toxicity and applicability for MR imaging of brain gliomas has not been fully explored so far. In this study, we prepared Gd₂O₃@BSA and MnO₂@BSA nanoparticles (NPs) and investigated their toxicity comprehensively and comparatively by H&E staining, blood biochemical analysis, and adverse outcome pathways testing. It is revealed that both Gd₂O₃@BSA and MnO₂@BSA NPs are biocompatible at a rational dose level. Although the relaxivity of MnO₂@BSA NPs is less than that of Gd₂O₃@BSA NPs, the MnO₂@BSA NPs lead to a greater contrast enhancement in the brain glioma due to the controlled release of Mn ions under the acidic tumor microenvironmental conditions. These comparative toxicity and contrast enhancement data are of fundamental importance for the clinical translation of Gd₂O₃@BSA and MnO₂@BSA NPs as MR contrast agents for brain glioma diagnosis.

Modulating angiogenesis with integrin-targeted nanomedicines

Targeting angiogenesis-related pathologies, which include tumorigenesis and metastatic processes, has become an attractive strategy for the development of efficient guided nanomedicines. In this respect, integrins are cell-adhesion molecules involved in angiogenesis signaling pathways and are overexpressed in many angiogenic processes. Therefore, they represent specific biomarkers not only to monitor disease progression but also to rationally design targeted nanomedicines. Arginine-glycine-aspartic (RGD) containing peptides that bind to specific integrins have been widely utilized to provide ligand-mediated targeting capabilities to small molecules, peptides, proteins, and antibodies, as well as to drug/imaging agent-containing nanomedicines, with the final aim of maximizing their therapeutic index. Within this review, we aim to cover recent and relevant examples of different integrin-assisted nanosystems including polymeric nanoconstructs, liposomes, and inorganic nanoparticles applied in drug/gene therapy as well as imaging and theranostics. We will also critically address the overall benefits of integrin-targeting.

Multifunctional targeted liposomal drug delivery for efficient glioblastoma treatment

Glioblastoma multiforme (GBM) has been considered to be the most malignant brain tumors. Due to the existence of various barriers including the blood–brain barrier (BBB) and blood–brain tumor barrier (BBTB) greatly hinder the accumulation and deep penetration of chemotherapeutics, the treatment of glioma remains to be the most challenging task in clinic. In order to circumvent these hurdles, we developed a multifunctional liposomal glioma-targeted drug delivery system (c(RGDyK)/pHA-LS) modified with cyclic RGD (c(RGDyK)) and p-hydroxybenzoic acid (pHA) in which c(RGDyK) could target integrin α_vβ₃ overexpressed on the BBTB and glioma cells and pHA could target dopamine receptors on the BBB. In vitro, c(RGDyK)/pHA-LS could target glioblastoma cells (U87), brain capillary endothelial cells (bEnd.3) and umbilical vein endothelial cells (HUVECs) through a comprehensive pathway. Besides, c(RGDyK)/pHA-LS could also increase the cytotoxicity of doxorubicin encapsulated in liposomes on glioblastoma cells, and was able to penetrate inside the glioma spheroids after traversing the in vitro BBB and BBTB. In vivo, we demonstrated the targeting ability of c(RGDyK)/pHA-LS to intracranial glioma. As expected, c(RGDyK)/pHA-LS/DOX showed a median survival time of 35 days, which was 2.31-, 1.76- and 1.5-fold higher than that of LS/DOX, c(RGDyK)-LS/DOX, and pHA-LS/DOX, respectively. The findings here suggested that the multifunctional glioma-targeted drug delivery system modified with both c(RGDyK) and pHA displayed strong antiglioma efficiency in vitro and in vivo, representing a promising platform for glioma therapy.

A Smart Responsive Dual Aptamers-Targeted Bubble-Generating Nanosystem for Cancer Triplex Therapy and Ultrasound Imaging

The absence of targeted, single treatment methods produces low therapeutic value for treating cancers. To increase the accumulation of drugs in tumors and improve the treatment effectiveness, near-infrared 808 nm photothermal responsive dual aptamers-targeted docetaxel (DTX)-containing nanoparticles is proposed. In this system, DTX and NH₄ HCO₃ are loaded in thermosensitive liposomes. The surface of liposomes is coated with gold nanoshells and connected with sulfydryl (SH) modified AS1411 and S2.2 aptamers. The nanosystem has good biocompatibility and uniform size (diameter about 200 nm). The drug is rapidly released, reaching a maximum amount (84%) at 4 h under 808 nm laser irradiation. The experiments conducted in vitro and in vivo demonstrate the nanosystem can synergistically inhibit tumor growth by combination of chemotherapy, photothermal therapy, and biological therapy. Dual ligand functionalization significantly increases cellular uptake on breast cancer cell line (MCF-7) cells and achieves ultrasound imaging (USI) at tumor site. The results indicate that this drug delivery system is a promising theranostic agent involving light-thermal response at tumor sites, dual ligand targeted triplex therapy, and USI.

The relative length of dual-target conjugated on iron oxide nanoparticles plays a role in brain glioma targeting

Cy5.5-labeled, CTX/PEG-FA dual-target conjugated Fe₃O₄ NPs were prepared and the effect of dual-target relative length on glioma targeting was investigated.

Folic acid on iron oxide nanoparticles: platform with high potential for simultaneous targeting, MRI detection and hyperthermia treatment of lymph node metastases of prostate cancer

Folic acid directly bound to the surface of iron oxide nanoparticles with simultaneously high targeting, MRI relaxivity and heating efficacy.

Dual-Targeting Magnetic PLGA Nanoparticles for Codelivery of Paclitaxel and Curcumin for Brain Tumor Therapy

Chemotherapy is one of the most important strategies for glioma treatment. However, the "impermeability" of the blood-brain barrier (BBB) impedes most chemotherapeutics from entering the brain, thereby rendering very few drugs suitable for glioma therapy, letting alone application of a combination of chemotherapeutics. Thereby, there is a pressing need to overcome the obstacles. A dual-targeting strategy was developed by a combination of magnetic guidance and transferrin receptor-binding peptide T7-mediated active targeting delivery. The T7-modified magnetic PLGA nanoparticle (NP) system was prepared with co-encapsulation of the hydrophobic magnetic nanoparticles and a combination of drugs (i.e., paclitaxel and curcumin) based on a "one-pot" process. The combined drugs yielded synergistic effects on inhibition of tumor growth via the mechanisms of apoptosis induction and cell cycle arrest, displaying significantly increased efficacy relative to the single use of each drug. Dual-targeting effects yielded a >10-fold increase in cellular uptake studies and a >5-fold enhancement in brain delivery compared to the nontargeting NPs. For the in vivo studies with an orthotopic glioma model, efficient brain accumulation was observed by using fluorescence imaging, synchrotron radiation X-ray imaging, and MRI. Furthermore, the antiglioma treatment efficacy of the delivery system was evaluated. With application of a magnetic field, this system exhibited enhanced treatment efficiency and reduced adverse effects. All mice bearing orthotopic glioma survived, compared to a 62.5% survival rate for the combination group receiving free drugs. This dual-targeting, co-delivery strategy provides a potential method for improving brain drug delivery and antiglioma treatment efficacy.

Progress and perspectives on targeting nanoparticles for brain drug delivery

Due to the ability of the blood-brain barrier (BBB) to prevent the entry of drugs into the brain, it is a challenge to treat central nervous system disorders pharmacologically. The development of nanotechnology provides potential to overcome this problem. In this review, the barriers to brain-targeted drug delivery are reviewed, including the BBB, blood-brain tumor barrier (BBTB), and nose-to-brain barrier. Delivery strategies are focused on overcoming the BBB, directly targeting diseased cells in the brain, and dual-targeted delivery. The major concerns and perspectives on constructing brain-targeted delivery systems are discussed.

Perspectives on Dual Targeting Delivery Systems for Brain Tumors

Brain tumor remains one of the most serious threats to human beings. Different from peripheral tumors, drug delivery to brain tumor is largely restricted by the blood brain barrier (BBB). To fully conquer this barrier and specifically deliver drugs to brain tumor, dual targeting delivery systems were explored, which are functionalized with two active targeting ligands: one to the BBB and the other to the brain tumor. The development of dual targeting delivery system is still in its early stage, and attentions need to be paid to issues and concerns that remain unresolved in future studies.