Cyclic RGD-linked polymeric micelles for targeted delivery of platinum anticancer drugs to glioblastoma through the blood-brain tumor barrier

Targeting the Notch-regulated non-coding RNA TUG1 for glioma treatment

Targeting self-renewal is an important goal in cancer therapy and recent studies have focused on Notch signalling in the maintenance of stemness of glioma stem cells (GSCs). Understanding cancer-specific Notch regulation would improve specificity of targeting this pathway. In this study, we find that Notch1 activation in GSCs specifically induces expression of the lncRNA, TUG1. TUG1 coordinately promotes self-renewal by sponging miR-145 in the cytoplasm and recruiting polycomb to repress differentiation genes by locus-specific methylation of histone H3K27 via YY1-binding activity in the nucleus. Furthermore, intravenous treatment with antisense oligonucleotides targeting TUG1 coupled with a drug delivery system induces GSC differentiation and efficiently represses GSC growth in vivo. Our results highlight the importance of the Notch-lncRNA axis in regulating self-renewal of glioma cells and provide a strong rationale for targeting TUG1 as a specific and potent therapeutic approach to eliminate the GSC population.

Self-renewal of cancer stem cells can contribute to glioma progression. Here, the authors show that Notch1 activation in glioma stem cells induces expression of the lncRNA TUG1, which promotes self-renewal through the repression of differentiation genes, and that targeting TUG1 represses glioma growth in vivo.

Natural Non-Mulberry Silk Nanoparticles for Potential-Controlled Drug Release

Natural silk protein nanoparticles are a promising biomaterial for drug delivery due to their pleiotropic properties, including biocompatibility, high bioavailability, and biodegradability. Chinese oak tasar Antheraea pernyi silk fibroin (ApF) nanoparticles are easily obtained using cations as reagents under mild conditions. The mild conditions are potentially advantageous for the encapsulation of sensitive drugs and therapeutic molecules. In the present study, silk fibroin protein nanoparticles are loaded with differently-charged small-molecule drugs, such as doxorubicin hydrochloride, ibuprofen, and ibuprofen-Na, by simple absorption based on electrostatic interactions. The structure, morphology and biocompatibility of the silk nanoparticles in vitro are investigated. In vitro release of the drugs from the nanoparticles depends on charge-charge interactions between the drugs and the nanoparticles. The release behavior of the compounds from the nanoparticles demonstrates that positively-charged molecules are released in a more prolonged or sustained manner. Cell viability studies with L929 demonstrated that the ApF nanoparticles significantly promoted cell growth. The results suggest that Chinese oak tasar Antheraea pernyi silk fibroin nanoparticles can be used as an alternative matrix for drug carrying and controlled release in diverse biomedical applications.

Graphene-based nanosheets for delivery of chemotherapeutics and biological drugs

Graphene-based nanosheets (GNS), including graphenes, graphene oxides and reduced graphene oxides, have properties suitable for delivery of various molecules. With their two-dimensional structures, GNS provide relatively high surface areas and capacity for non-covalent π-π stacking and hydrophobic interactions with various drug molecules. Currently, GNS-based delivery applications extend to chemotherapeutics as well as biological drugs, including nucleic acid drugs, proteins, and peptides. Surfaces of GNS have been modified with various polymers, such as polyethylene glycol and biopolymers, which enhance biocompatibility and increase drug loading. Anticancer drugs are prominent among chemotherapeutic agents tested, and have been loaded onto GNS with relatively high loading capacities compared with other nanocarriers. For enhanced distribution to specific tissues, GNS have been covalently or non-covalently modified with targeting ligands, including folic acid, transferrins, and others. In this review, we cover the current status of GNS for delivery of anticancer chemotherapeutics and biological drugs, with a focus on nucleic acid drugs. Remaining challenges for the application of GNS for drug-delivery systems and future perspectives are also addressed.

Near-infrared light-triggered release of small molecules for controlled differentiation and long-term tracking of stem cells in vivo using upconversion nanoparticles

Human mesenchymal stem cells (hMSCs) hold considerable potential for regenerative medicine, but their application is limited by the lack of an efficient method to control differentiation and track the migration of implanted cells in vivo. In this study, we developed a multifunctional nanocarrier based on upconversion nanoparticles (UCNPs) for controlling differentiation and long-term tracking of hMSCs. The UCNPs are conjugated with the peptide (Cys-Arg-Gly-Asp, CRGD) and the differentiation-inducing kartogenin (KGN) via a photocaged linker on the surface, and the obtained UCNP nanocarrier can be efficiently uptaken by hMSCs. Under the exposure of near-infrared (NIR) light, the upconverted UV emission from the UCNP nanocarrier leads to the photocleavage of the photocaged linker and intracellular release of KGN. The NIR-triggered release of KGN mediated by the UCNP nanocarrier efficiently induces chondrogenic differentiation of hMSCs in vitro with reduced KGN dosage compared to the conventional protocol of directly supplementing KGN in the media. Furthermore, NIR irradiation through the skin of living animals induces the chondrogenic differentiation of the subcutaneously implanted hMSCs treated with the KGN-laden UCNP nanocarrier, thereby enhancing neocartilage formation in vivo. Finally, the luminescent UCNP nanocarrier enables the long-term tracking of the labeled hMSCs in vivo. We believe that our UCNP nanocarrier is a promising tool for the remote control of triggered delivery of inductive agents to stem cells at the prescribed time points and the elucidation of the function and the fate of the transplanted stem cells in vivo.

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.

Development of polymeric micelles for targeting intractable cancers

In relation to recent advances in nanobiotechnologies, cancer-targeted therapy using nano-scaled drug carriers (nanocarriers) has been attracting enormous attention with success in clinical studies. Polymeric micelles, core-shell-type nanoparticles formed through the self-assembly of block copolymers, are one of the most promising nanocarrier, because their critical features such as size, stability, and drug incorporation efficiency and release rate can be modulated by designing the constituent block copolymers. The utilities of polymeric micelles have been reported not only in experimental tumor models in mice but also in clinical studies. In this article, we aim to explain the rationale of designing polymeric micelles for targeting intractable cancers such as pancreatic cancer, glioblastoma, and metastases. Also, we review recent progress in clinical studies on polymeric micelles incorporating anticancer drugs. In addition, we introduce the next generation of polymeric micelles as the platform integrated with smart functionalities such as targetability, environmental sensitivity, and imaging properties. Thus, polymeric micelles can realize safe and effective cancer therapy, and offer tailor-made medicines for individual patients.

Nanoparticles Effectively Target Rapamycin Delivery to Sites of Experimental Aortic Aneurysm in Rats

Several drugs targeting the pathogenesis of aortic aneurysm have shown efficacy in model systems but not in clinical trials, potentially owing to the lack of targeted drug delivery. Here, we designed a novel drug delivery system using nanoparticles to target the disrupted aortic aneurysm micro-structure. We generated poly(ethylene glycol)-shelled nanoparticles incorporating rapamycin that exhibited uniform diameter and long-term stability. When injected intravenously into a rat model in which abdominal aortic aneurysm (AAA) had been induced by infusing elastase, labeled rapamycin nanoparticles specifically accumulated in the AAA. Microscopic analysis revealed that rapamycin nanoparticles were mainly distributed in the media and adventitia where the wall structures were damaged. Co-localization of rapamycin nanoparticles with macrophages was also noted. Rapamycin nanoparticles injected during the process of AAA formation evinced significant suppression of AAA formation and mural inflammation at 7 days after elastase infusion, as compared with rapamycin treatment alone. Correspondingly, the activities of matrix metalloproteinases and the expression of inflammatory cytokines were significantly suppressed by rapamycin nanoparticle treatment. Our findings suggest that the nanoparticle-based delivery system achieves specific delivery of rapamycin to the rat AAA and might contribute to establishing a drug therapy approach targeting aortic aneurysm.

Recent Innovations in Peptide Based Targeted Drug Delivery to Cancer Cells

Targeted delivery of chemotherapeutics and diagnostic agents conjugated to carrier ligands has made significant progress in recent years, both in regards to the structural design of the conjugates and their biological effectiveness. The goal of targeting specific cell surface receptors through structural compatibility has encouraged the use of peptides as highly specific carriers as short peptides are usually non-antigenic, are structurally simple and synthetically diverse. Recent years have seen many developments in the field of peptide based drug conjugates (PDCs), particularly for cancer therapy, as their use aims to bypass off-target side-effects, reducing the morbidity common to conventional chemotherapy. However, no PDCs have as yet obtained regulatory approval. In this review, we describe the evolution of the peptide-based strategy for targeted delivery of chemotherapeutics and discuss recent innovations in the arena that should lead in the near future to their clinical application.

Nano carriers for drug transport across the blood-brain barrier

Effective therapy lies in achieving a therapeutic amount of drug to the proper site in the body and then maintaining the desired drug concentration for a sufficient time interval to be clinically effective for treatment. The blood-brain barrier (BBB) hinders most drugs from entering the central nervous system (CNS) from the blood stream, leading to the difficulty of delivering drugs to the brain via the circulatory system for the treatment, diagnosis and prevention of brain diseases. Several brain drug delivery approaches have been developed, such as intracerebral and intracerebroventricular administration, intranasal delivery and blood-to-brain delivery, as a result of transient BBB disruption induced by biological, chemical or physical stimuli such as zonula occludens toxin, mannitol, magnetic heating and ultrasound, but these approaches showed disadvantages of being dangerous, high cost and unsuitability for most brain diseases and drugs. The strategy of vector-mediated blood-to-brain delivery, which involves improving BBB permeability of the drug-carrier conjugate, can minimize side effects, such as being submicrometre objects that behave as a whole unit in terms of their transport and properties, nanomaterials, are promising carrier vehicles for direct drug transport across the intact BBB as a result of their potential to enter the brain capillary endothelial cells by means of normal endocytosis and transcytosis due to their small size, as well as their possibility of being functionalized with multiple copies of the drug molecule of interest. This review provids a concise discussion of nano carriers for drug transport across the intact BBB, various forms of nanomaterials including inorganic/solid lipid/polymeric nanoparticles, nanoemulsions, quantum dots, nanogels, liposomes, micelles, dendrimers, polymersomes and exosomes are critically evaluated, their mechanisms for drug transport across the BBB are reviewed, and the future directions of this area are fully discussed.

Dual targeting luminescent gold nanoclusters for tumor imaging and deep tissue therapy

Dual targeting towards both extracellular and intracellular receptors specific to tumor is a significant approach for cancer diagnosis and therapy. In the present study, a novel nano-platform (AuNC-cRGD-Apt) with dual targeting function was initially established by conjugating gold nanocluster (AuNC) with cyclic RGD (cRGD) that is specific to αvβ3integrins over-expressed on the surface of tumor tissues and aptamer AS1411 (Apt) that is of high affinity to nucleolin over-expressed in the cytoplasm and nucleus of tumor cells. Then, AuNC-cRGD-Apt was further functionalized with near infrared (NIR) fluorescence dye (MPA), giving a NIR fluorescent dual-targeting probe AuNC-MPA-cRGD-Apt. AuNC-MPA-cRGD-Apt displays low cytotoxicity and favorable tumor-targeting capability at both in vitro and in vivo level, suggesting its clinical potential for tumor imaging. Additionally, Doxorubicin (DOX), a widely used clinical chemotherapeutic drug that kill cancer cells by intercalating DNA in cellular nucleus, was immobilized onto AuNC-cRGD-Apt forming a pro-drug, AuNC-DOX-cRGD-Apt. The enhanced tumor affinity, deep tumor penetration and improved anti-tumor activity of this pro-drug were demonstrated in different tumor cell lines, tumor spheroid and tumor-bearing mouse models. Results in this study suggest not only the prospect of non-toxic AuNC modified with two targeting ligands for tumor targeted imaging, but also confirm the promising future of dual targeting AuNC as a core for the design of prodrug in the field of cancer therapy.

Development of bioactive materials for glioblastoma therapy

Glioblastoma is the most common and deadly human brain cancers. Unique barriers hinder the drug delivering pathway due to the individual position of glioblastoma, including blood-brain barrier and blood-brain tumor barrier. Numerous bioactive materials have been exploited and applied as the transvascular delivery carriers of therapeutic drugs. They promote site-specific accumulation and long term release of the encapsulated drugs at the tumor sites and reduce side effects with systemic delivery. And the delivery systems exhibit a certain extent of anti-glioblastoma effect and extend the median survival time. However, few of them step into the clinical trials. In this review, we will investigate the recent studies of bioactive materials for glioblastoma chemotherapy, including the inorganic materials, lipids and polymers. These bioactive materials construct diverse delivery vehicles to trigger tumor sites in brain intravenously. Herein, we exploit their functionality in drug delivery and discuss the deficiency for the featured tumors, to provide guidance for establishing optimized therapeutic drug formulation for anti-glioblastoma therapy and pave the way for clinical application.

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Numerous bioactive materials have been exploited as delivery carriers of therapeutic drugs for glioblastoma chemotherapy.

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The functionality and deficiency of the bioactive materials are discussed.

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Combing the chemo- and immunotherapy will provide a promising strategy for glioblastoma therapy and inhibiting recurrence.

c(RGDyK)-decorated Pluronic micelles for enhanced doxorubicin and paclitaxel delivery to brain glioma

Brain glioma therapy is an important challenge in oncology. Here, doxorubicin (DOX) and paclitaxel (PTX)-loaded cyclic arginine-glycine-aspartic acid peptide (c(RGDyK))-decorated Pluronic micelles (cyclic arginine-glycine-aspartic acid peptide-decorated Pluronic micelles loaded with doxorubicin and paclitaxel [RGD-PF-DP]) were designed as a potential targeted delivery system to enhance blood–brain barrier penetration and improve drug accumulation via integrin-mediated transcytosis/endocytosis and based on integrin overexpression in blood–brain barrier and glioma cells. The physicochemical characterization of RGD-PF-DP revealed a satisfactory size of 28.5±0.12 nm with uniform distribution and core-shell structure. The transport rates across the in vitro blood–brain barrier model, cellular uptake, cytotoxicity, and apoptosis of U87 malignant glioblastoma cells of RGD-PF-DP were significantly greater than those of non-c(RGDyK)-decorated Pluronic micelles. In vivo fluorescence imaging demonstrated the specificity and efficacy of intracranial tumor accumulation of RGD-PF-DP. RGD-PF-DP displayed an extended median survival time of 39 days, with no serious body weight loss during the regimen. No acute toxicity to major organs was observed in mice receiving treatment doses via intravenous administration. In conclusion, RGD-PF-DP could be a promising vehicle for enhanced doxorubicin and paclitaxel delivery in patients with brain glioma.

MRI-guided liposomes for targeted tandem chemotherapy and therapeutic response prediction

Liposomes are effective drug delivery systems that can be functionalized with imaging contrast agents, providing both diagnosis and monitoring of disease treatment. Here we describe the design of a theranostic liposomal drug delivery system whose biodistribution can be real time imaged by contrast enhanced MRI and can achieve tandem chemotherapy drug delivery. Because T1 relaxation of MRI depends upon the chemical structure of contrast agent as well as its interaction with neighbor environment, we rationally designed a functional liposome for in vivo T1 enhanced MRI. The liposome shows a 36-fold higher T1 relaxation rate over the commercial MRI contrast agent Omniscan® and a long circulation time up to 300min in vivo. Moreover, the multifunctional liposome carries both hydrophobic and hydrophilic chemotherapeutic drugs, can synergistically enhance therapeutic effects of multiple drugs and selectively deliver them to lung tumors, leading to lower doses, toxicity and sustained release. The nanoparticles, which exhibit favorable biodistributions to tumors, offer new possibilities for the simultaneous delivery of more than one drug and the evaluation of therapeutic response in vivo by T1 enhanced MRI.

STATEMENT OF SIGNIFICANCE

Cancer cells invoke different mechanisms to resist cancer therapies, particularly when delivering a single agent in a given therapy. The combination of two (or more) thermotherapy agents provides a promising way to circumvent such situations of drug resistance, due to a favorable synergistic effect that "tricks" the drug resistance mechanism. However, challenges to the simultaneous delivery of two drugs prevail, especially with regards to the simultaneous delivery of hydrophobic and hydrophobic drugs. Furthermore, non-invasive in vivo imaging of drug distribution enables the real-time monitoring and prediction of therapeutic responses to treatment. In this study, we rationally designed a theranostic liposomal drug delivery system whose biodistribution can be imaged via T1-weighted MRI in real-time and can achieve tandem chemotherapy drug delivery. This original study will be of considerable use to the wider drug delivery community.

A Nanoparticle Platform To Evaluate Bioconjugation and Receptor-Mediated Cell Uptake Using Cross-Linked Polyion Complex Micelles Bearing Antibody Fragments

Targeted nanomedicines are a promising technology for treatment of disease; however, preparation and characterization of well-defined protein-nanoparticle systems remain challenging. Here, we describe a platform technology to prepare antibody binding fragment (Fab)-bearing nanoparticles and an accompanying real-time cell-based assay to determine their cellular uptake compared to monoclonal antibodies (mAbs) and Fabs. The nanoparticle platform was composed of core-cross-linked polyion complex (PIC) micelles prepared from azide-functionalized PEG-b-poly(amino acids), that is, azido-PEG-b-poly(l-lysine) [N3-PEG-b-PLL] and azido-PEG-b-poly(aspartic acid) [N3-PEG-b-PAsp]. These PIC micelles were 30 nm in size and contained approximately 10 polymers per construct. Fabs were derived from an antibody binding the EphA2 receptor expressed on cancer cells and further engineered to contain a reactive cysteine for site-specific attachment and a cleavable His tag for purification from cell culture expression systems. Azide-functionalized micelles and thiol-containing Fab were linked using a heterobifunctional cross-linker (FPM-PEG4-DBCO) that contained a fluorophenyl-maleimide for stable conjugation to Fabs thiols and a strained alkyne (DBCO) group for coupling to micelle azide groups. Analysis of Fab-PIC micelle conjugates by fluorescence correlation spectroscopy, size exclusion chromatography, and UV-vis absorbance determined that each nanoparticle contained 2-3 Fabs. Evaluation of cellular uptake in receptor positive cancer cells by real-time fluorescence microscopy revealed that targeted Fab-PIC micelles achieved higher cell uptake than mAbs and Fabs, demonstrating the utility of this approach to identify targeted nanoparticle constructs with unique cellular internalization properties.

A nanoparticulate pre-chemosensitizer for efficacious chemotherapy of multidrug resistant breast cancer

Small-molecule chemosensitizers can reverse cancer multidrug resistance (MDR), thus significantly improving the in vitro effect of chemotherapy drugs for MDR cancer cells, however, their in vivo effects are not always very good, because they are difficult to effectively accumulate in tumor and enter the same cancer with chemotherapy drugs after systemic administration due to individual biopharmaceutical properties. To overcome these limitations, here we study a novel nanoparticular pre-chemosensitizer which can be also used as nanocarrier of chemotherapy drugs. We take an ‘all in one’ approach to develop a self-assembled nanoparticle formula of amphiphilic poly(curcumin-dithiodipropionic acid)-b-poly(ethylene glycol)-biotin. The nanoparticle is capable of tumor-targeted delivery, responsive degradation at the intracellular level of glutathione and subsequent intracellular co-release of the chemosensitizer curcumin and the encapsulated chemotherapeutic drug doxorubicin to maximize a synergistic effect of chemosensitization and chemotherapy. We demonstrate that the antitumor efficacy of nanoparticle is much superior to that of doxorubicin in the multidrug resistant MCF-7/ADR xenografted nude mice.

A peptide-lipid nanoparticle assembly platform with integrated functions for targeted cell delivery

Liposomes are extensively used as drug carriers because of their biocompatibility, low toxicity, and controlled release properties, however challenges exist in the control of their particle size, surface properties and targeting functionality. In this work, we report a peptide-lipid nanoparticle platform that can achieve nanoparticle formation, surface functionalization and hydrophobic drug loading in an integrated assembly process. A designer peptide that harbors bivalent amphipathic α-helices linked by a central loop (ALA peptide) was used to encapsulate lipid nanoparticles (LNPs). The bivalency design affords higher peptide helicity and lipid-packaging efficiency, and allows encapsulated hydrophobic molecules for more stability under long-term storage. The central loop structure displays sufficient surface exposure as demonstrated by the interaction between penta-histidine installed LNPs and Ni-NTA agarose. RGD-inserted and cytotoxic iridium complex-encapsulated LNPs showed preferential entry and selective cytotoxicity to integrin high expression cancer cells, while showing reduced toxicity to non-cancer cells. Further study indicates that a constrained cyclic conformation of RGD is required to fully exert targeting capability, suggesting an intact structural exposure on the LNP surface. In summary, we demonstrate a simple yet effective method of peptide-based LNP surface modification with potential for various targeted deliveries of hydrophobic drugs.

Recent updates in utilizing prodrugs in drug delivery (2013-2015)

INTRODUCTION

Utilizing the prodrug approach as a method to overcome various pharmaceutical and pharmacokinetic barriers to drug delivery is significantly accelerating and achieving successes. In contrast to the older traditional prodrugs which suffer from decreased bioavailability and a high profile of side effects, due to activation at undesired sites, the targeted prodrug approach utilizes delivery systems to improve delivery for a wide range of therapeutics including anti-cancer, anti-bacterial and anti-inflammatory drugs.

AREAS COVERED

Recent updates in utilization of prodrugs in drug delivery between 2013 and 2015 are discussed. Targeted prodrugs against cancer, solid tumors, microbial infections, inflammation and other diseases using advanced delivery systems such as theranostic approaches, siRNA, DOX immunoconjugate, C 60-ser carrier vector, biotinylated prodrug, human serum albumin (HSA) carrier and others are presented.

EXPERT OPINION

Recent research efforts have been directed at developing targeted prodrugs to replace the classical prodrugs. The use of this approach has accelerated following the emergence of encouraging results from several studies on targeted prodrugs that have highlighted their higher efficiency and improved safety profiles. Targeted prodrug delivery is now considered more than a chemical modification method. It is an applicable and promising approach and, in the future, better knowledge and wide application of this approach may be attained which may pave the way for more forward-thinking and creative techniques.

Advancement in integrin facilitated drug delivery

The research of integrin-targeted anticancer agents has recorded important advancements in ingenious design of delivery systems, based either on the prodrug approach, or on nanoparticle carriers, but for now, none of these has reached a clinical stage of development. Past work in this area has been extensively reviewed by us and others. Thus, the purpose and scope of the present review is to survey the advancement reported in the last 3years, with focus on innovative delivery systems that appear to afford openings for future developments. These systems exploit the labelling with conventional and novel integrin ligands for targeting the interface of cancer cells and of endothelial cells involved in cancer angiogenesis, with the proteins of the extracellular matrix, in the circulation, in tissues, and in tumour stroma, as the site of progression and metastatic evolution of the disease. Furthermore, these systems implement the expertise in the development of nanomedicines to the purpose of achieving preferential biodistribution and uptake in cancer tissues, internalisation in cancer cells, and release of the transported drugs at intracellular sites. The assessment of the value of controlling these factors, and their combination, for future developments requires support of biological testing in appropriate mechanistic models, but also imperatively demand confirmation in therapeutically relevant in vivo models for biodistribution, efficacy, and lack of off-target effects. Thus, among many studies, we have tried to point out the results supported by relevant in vivo studies, and we have emphasised in specific sections those addressing the medical needs of drug delivery to brain tumours, as well as the delivery of oligonucleotides modulating gene-dependent pathological mechanism. The latter could constitute the basis of a promising third branch in the therapeutic armamentarium against cancer, in addition to antibody-based agents and to cytotoxic agents.

Non-viral Vector Mediated RNA Interference Technology for Central Nervous System Injury

Neuronal axons damaged by traumatic injury are unable to spontaneously regenerate in the mammalian adult central nervous system (CNS), causing permanent motor, sensory, and cognitive deficits. Regenerative failure in the adult CNS results from a complex pathology presenting multiple barriers, both the presence of growth inhibitors in the extrinsic microenvironment and intrinsic deficiencies in neuronal biochemistry, to axonal regeneration and functional recovery. There are many strategies for axonal regeneration after CNS injury including antagonism of growth-inhibitory molecules and their receptors, manipulation of cyclic nucleotide levels, and delivery of growth-promoting stimuli through cell transplantation and neurotrophic factor delivery. While all of these approaches have achieved varying degrees of improvement in plasticity, regeneration, and function, there is no clinically effective therapy for CNS injury. RNA interference technology offers strategies for improving regeneration by overcoming the aspects of the injured CNS environment that inhibit neurite growth. This occurs through the knockdown of growth-inhibitory molecules and their receptors. In this review, we discuss the current state of RNAi strategies for the treatment of CNS injury based on non-viral vector mediated delivery.

RGD-conjugated solid lipid nanoparticles inhibit adhesion and invasion of αvβ3 integrin-overexpressing breast cancer cells

αvβ3 integrin receptors expressed on cancer cell surfaces play a crucial role in promoting tumor angiogenesis and cancer cell metastasis. Thus, cyclic arginyl-glycyl-aspartic acid (cRGD) peptides have been explored as a αvβ3 integrin receptor-specific targeting moiety for the targeted delivery of nanoparticle-loaded therapeutics. However, our previous study showed that cyclic RGD could act as a double-edged sword that, on one hand, extended the retention of cRGD-modified solid lipid nanoparticles (RGD-SLNs) at αvβ3 integrin receptor overexpressing breast carcinoma, and yet on the other hand, decreased the amount of tumor accumulation of RGD-SLNs attributable to the greater uptake by the mononuclear phagocyte system (MPS). Therefore, we aimed to optimize the RGD-decorated nanoparticle systems for (1) inhibiting αvβ3 integrin receptor overexpressing tumor cell metastasis and (2) increasing nanoparticle accumulation to tumor site. SLNs with cRGD content ranging from 0 to 10 % mol of total polyethyleneglycol (PEG) chains were synthesized. The binding of RGD-SLNs with αvβ3 integrin receptors increased with increasing cRGD concentration on the nanoparticles. RGD-SLNs were demonstrated to inhibit MDA-MB-231 cell adhesion to fibronectin and invasion through Matrigel. In vivo whole-body fluorescence imaging revealed that 1 % cRGD on the SLNs' surface had maximum tumor accumulation with extended tumor retention among all formulations tested in an orthotopic MDA-MB-231/EGFP breast tumor model. This work has laid a foundation for further development of anticancer drug-loaded optimized cRGD nanoparticle formulations for the treatment of breast cancer metastasis.

Biodegradable polymeric nanostructures in therapeutic applications: opportunities and challenges

Biodegradable polymeric nanostructures (BPNs) have shown great promise in different therapeutic applications such as diagnosis, imaging, drug delivery, cosmetics, organ implants, and tissue engineering.

The synthesis and comparison of poly(methacrylic acid)–poly(ε-caprolactone) block copolymers with and without symmetrical disulfide linkages in the center for enhanced cellular uptake

A self-assembled poly(methacrylic acid)–poly(ε-caprolactone) block copolymer with a disulfide linkage, PMAA-b-PCL-SS-PCL-b-PMAA, was synthesized for enhanced cellular uptake due to a reduction response to GSH and pH-sensitive characteristics.

PDEAEMA-based pH-sensitive amphiphilic pentablock copolymers for controlled anticancer drug delivery

The synthesis of a series of PDEAEMA-based pH-sensitive amphiphilic pentablock copolymers PEG-b-(PDEAEMA-b-PMMA)₂ with different compositions proceeded via the combination of a bromination reaction andARGET ATRP.

Modulating the cellular uptake of platinum drugs with glycopolymers

The therapeutic potency of platinum-based anticancer drugs can be substantially improved through the use of fructose-coated nanocarrier systems to target cancer cells efficiently.

PAMAM dendrimer based targeted nano-carrier for bio-imaging and therapeutic agents

In the last several decades, researchers have focused on developing suitable drug carriers to deliver pharmaceutical agents to treat cancer diseases.

Targeting tumor microenvironment with PEG-based amphiphilic nanoparticles to overcome chemoresistance

Multidrug resistance is one of the biggest obstacles in the treatment of cancer. Recent research studies highlight that tumor microenvironment plays a predominant role in tumor cell proliferation, metastasis, and drug resistance. Hence, targeting the tumor microenvironment provides a novel strategy for the evolution of cancer nanomedicine. The blooming knowledge about the tumor microenvironment merging with the design of PEG-based amphiphilic nanoparticles can provide an effective and promising platform to address the multidrug resistant tumor cells. This review describes the characteristic features of tumor microenvironment and their targeting mechanisms with the aid of PEG-based amphiphilic nanoparticles for the development of newer drug delivery systems to overcome multidrug resistance in cancer cells.

FROM THE CLINICAL EDITOR

Cancer is a leading cause of death worldwide. Many cancers develop multidrug resistance towards chemotherapeutic agents with time and strategies are urgently needed to combat against this. In this review article, the authors discuss the current capabilities of using nanomedicine to target the tumor microenvironments, which would provide new insight to the development of novel delivery systems for the future.

Reduction-responsive polypeptide nanogel delivers antitumor drug for improved efficacy and safety

Chemotherapy plays an irreplaceable role in the treatment of various malignant tumors today. The traditional drug formulations lack of selectivity, cause serious damage to normal tissues, and can't achieve a desired therapeutic efficacy. For this situation, a facilely prepared reduction-responsive polypeptide nanogel was employed for targeting intracellular delivery of antitumor drug in this study. Doxorubicin (DOX) as a model drug was loaded into nanogel through a sequential dispersion and dialysis approach with a drug loading efficiency (DLE) of 56.8wt.%. The loading nanogel, i.e., NG/DOX, exhibited a medium hydrodynamic radius of 56.1±3.5nm, glutathione-accelerated DOX release, and efficient cellular uptake and proliferation inhibition. Moreover, NG/DOX exhibited upregulated intratumoral accumulation and improved antitumor efficacy toward HepG2 hepatoma-xenografted BALB/c nude mouse model compared with free drug. The enhanced tumor suppression of NG/DOX was further confirmed by the histopathological and immunohistochemical analyses. Furthermore, the excellent in vivo security of NG/DOX was systematically demonstrated by the variation detection of body weight, histopathological assay, levels of bone marrow cell micronucleus rate (BMMR) and white blood cells (WBCs), and detection of clinical parameters in corresponding organs and serum. With controllable large-scale preparation and fascinating properties in vitro and in vivo, the reduction-responsive polypeptide nanogel is revealed to exhibit great potential for on-demand intracellular delivery of antitumor drugs, and shows a good prospect for clinical chemotherapy.

STATEMENT OF SIGNIFICANCE

The traditional drug formulations lack of selectivity, cause serious damage to normal tissues, and can't achieve a desired therapeutic effect. For this situation, a facilely prepared reduction-responsive polypeptide nanogel is employed for targeting intracellular delivery of antitumor drug in this study. The laden nanogel keeps structural integrity and less drug release in the circulatory system after intravenous injection, releases the payload triggered by the intracellular high concentration of GSH, and exhibits the excellent tumor inhibition and security in vivo. Furthermore, the other hydrophobic antitumor drugs can also be on-demand delivered by the smart nanogel. All of the above advantages confirm the bright prospect of reduction-responsive nanogel on the road of malignancy chemotherapy.

cRGD-installed polymeric micelles loading platinum anticancer drugs enable cooperative treatment against lymph node metastasis

Lymph node metastasis (LNM) is correlated with decreased survival, indicating high tumor malignancy and being a potential source for subsequent fatal metastases. Targeted therapies inhibiting the formation of LNM, while eliminating established metastatic foci, could provide synergistic effects by reducing the incidence and growth of metastasis. Based on the inhibitory activity of cRGD peptide against the development of metastasis, and the LNM targeting ability of systemically injected drug-loaded polymeric micelles, herein, we studied the capability of cRGD-installed polymeric micelles incorporating the platinum anticancer drug (1,2-diaminocylohexane)platinum(II) (DACHPt) for cooperatively inhibiting the formation and progression of LNM. As cRGD-installed DACHPt-loaded micelles (cRGD-DACHPt/m) presented similar size, drug loading and surface charge to non-conjugated micelles (MeO-DACHPt/m), the differences in the biological performance of the micelles were endorsed to the effect of the ligand. In a syngeneic melanoma model, both MeO-DACHPt/m and cRGD-DACHPt/m showed comparable antitumor activity against the primary tumors and the established metastatic foci in lymph nodes. However, cRGD-DACHPt/m significantly enhanced the efficacy against LNM draining from primary tumors through the effective inhibition of the spreading of cancer cells. This improved inhibition was associated with the ability of cRGD-DACHPt/m to reduce the migration of melanoma cells, which was higher than that of MeO-DACHPt/m, free cRGD and their combination. These results support our strategy of using cRGD-installed micelles for attaining cooperative therapies against LNM exploiting the inhibitory function of the peptide and the cytotoxic effect of the micelles.

Hybrid polymer micelles capable of cRGD targeting and pH-triggered surface charge conversion for tumor selective accumulation and promoted uptake

This study presents both tumor-targeting ligands (cRGD) and pH-activated surface charge-conversional moiety (imidazole) decorated micelles for Dox delivery. cRGD is expected to induce preferential tumor accumulation, while imidazole switches on positive charge in a tumor acid environment, which leads to enhanced micelle uptake by tumor cells.

Choline Derivate-Modified Doxorubicin Loaded Micelle for Glioma Therapy

Ligand-mediated polymeric micelles have enormous potential for improving the efficacy of glioma therapy. Linear-dendritic drug-polymer conjugates composed of doxorubicin (DOX) and polyethylene glycol (PEG) were synthesized with or without modification of choline derivate (CD). The resulting MeO-PEG-DOX8 and CD-PEG-DOX8 could self-assemble into polymeric micelles with a nanosized diameter around 30 nm and a high drug loading content up to 40.6 and 32.3%, respectively. The optimized formulation 20% CD-PEG-DOX8 micelles had superior cellular uptake and antitumor activity against MeO-PEG-DOX8 micelles. The subcellular distribution using confocal study revealed that 20% CD-PEG-DOX8 micelles preferentially accumulated in the mitochondria. Pharmacokinetic study showed area under the plasma concentration-time curve (AUC0-t) and Cmax for 20% CD-PEG-DOX8 micelles and DOX solution were 1336.58 ± 179.43 mg/L·h, 96.35 ± 3.32 mg/L and 1.40 ± 0.19 mg/L·h, 1.15 ± 0.25 mg/L, respectively. Biodistribution study showed the DOX concentration of 20% CD-PEG-DOX8 micelles treated group at 48 h was 2.37-fold higher than that of MeO-PEG-DOX8 micelles treated group at 48 h and was 24 fold-higher than that of DOX solution treated group at 24 h. CD-PEG-DOX8 micelles (20%) were well tolerated with reduced cardiotoxicity, as evaluated in the body weight change and HE staining studies, while they induced most significant antitumor activity with longest media survival time in an orthotopic mouse model of U87-luci glioblastoma model as displayed in the bioluminescence imaging and survival curve studies. Our findings consequently indicated that 20% CD-PEG-DOX8 micelles are promising drug delivery system for glioma chemotherapy.

Liposomes Combined an Integrin αvβ3-Specific Vector with pH-Responsible Cell-Penetrating Property for Highly Effective Antiglioma Therapy through the Blood-Brain Barrier

Glioma, one of the most common aggressive malignancies, has the highest mortality in the present world. Delivery of nanocarriers from the systemic circulation to the glioma sites would encounter multiple physiological and biological barriers, such as blood-brain barrier (BBB) and the poor penetration of nanocarriers into the tumor. To circumvent these hurdles, the paclitaxel-loaded liposomes were developed by conjugating with a TR peptide (PTX-TR-Lip), integrin αvβ3-specific vector with pH-responsible cell-penetrating property, for transporting drug across the BBB and then delivering into glioma. Surface plasmon resonance (SPR) studies confirmed the very high affinity of TR-Lip and integrin αvβ3. In vitro results showed that TR-Lip exhibited strong transport ability across BBB, killed glioma cells and brain cancer stem cells (CSCs), and destroyed the vasculogenic mimicry (VM) channels. In vivo results demonstrated that TR-Lip could better target glioma, and eliminated brain CSCs and the VM channels in tumor tissues. The median survival time of tumor-bearing mice after administering PTX-TR-Lip (45 days) was significantly longer than that after giving free PTX (25.5 days, p < 0.001) or other controls. In conclusion, PTX-TR-Lip would improve the therapeutic efficacy of brain glioma in vitro and in vivo.

Antitumor activity of a polypyridyl chelating ligand: in vitro and in vivo inhibition of glioma

Glioblastoma multiforme is an extremely aggressive and invasive form of central nervous system tumor commonly treated with the chemotherapeutic drug Temozolomide. Unfortunately, even with treatment, the median survival time is less than 12 months. 2,9-Di-sec-butyl-1,10-phenanthroline (SBP), a phenanthroline-based ligand originally developed to deliver gold-based anticancer drugs, has recently been shown to have significant antitumor activity in its own right. SBP is hypothesized to initiate tumor cell death via interaction with non-DNA targets, and considering most glioblastoma drugs kill tumors through DNA damage processes, SBP was tested as a potential novel drug candidate against glial-based tumors. In vitro studies demonstrated that SBP significantly inhibited the growth of rodent GL-26 and C6 glioma cells, as well as human U-87, and SW1088 glioblastomas/astrocytomas. Furthermore, using a syngeneic glioma model in mice, in vivo administration of SBP significantly reduced tumor volume and increased survival time. There was no significant toxicity toward nontumorigenic primary murine and human astrocytes in vitro, and limited toxicity was observed in ex vivo tissues obtained from noncancerous mice. Terminal deoxynucleotidyl transferase dUTP nick end labeling staining and recovery assays suggest that SBP induces apoptosis in gliomas. This exploratory study suggests SBP is effective in slowing the growth of tumorigenic cells in the brain while exhibiting limited toxicity to normal cells and tissues and should therefore be further investigated for its potential in glioblastoma treatment.

The challenges facing block copolymer micelles for cancer therapy: In vivo barriers and clinical translation

The application of block copolymer micelles (BCMs) in oncology has benefitted from advances in polymer chemistry, drug formulation and delivery as well as in vitro and in vivo biological models. While great strides have been made in each of these individual areas, there remains some disappointment overall, citing, in particular, the absence of more BCM formulations in clinical evaluation and practice. In this review, we aim to provide an overview of the challenges presented by in vivo systems to the effective design and development of BCMs. In particular, the barriers posed by systemic administration and tumor properties are examined. The impact of critical features, such as the size, stability and functionalization of BCMs is discussed, while key pre-clinical endpoints and models are critiqued. Given clinical considerations, we present this work as a means to stimulate a renewed focus on the unique chemical versatility bestowed by BCMs and a measured grasp of representative in vitro and in vivo models.