UPA-sensitive ACPP-conjugated nanoparticles for multi-targeting therapy of brain glioma

Aptamers: ushering in new hopes in targeted glioblastoma therapy

Glioblastoma, a formidable brain cancer, has remained a therapeutic challenge due to its aggressive nature and resistance to conventional treatments. Recent data indicate that aptamers, short synthetic DNA or RNA molecules can be used in anti-cancer therapy due to their better tumour penetration, specific binding affinity, longer retention in tumour sites and their ability to cross the blood-brain barrier. With the ability to modify these oligonucleotides through the selection process, and using rational design to modify them, post-SELEX aptamers offer several advantages in glioblastoma treatment, including precise targeting of cancer cells while sparing healthy tissue. This review discusses the pivotal role of aptamers in glioblastoma therapy and diagnosis, emphasising their potential to enhance treatment efficacy and also highlights recent advancements in aptamer-based therapies which can transform the landscape of glioblastoma treatment, offering renewed hope to patients and clinicians alike.

Cell-Penetrating Peptides: Promising Therapeutics and Drug-Delivery Systems for Neurodegenerative Diseases

Currently, one of the most significant and rapidly growing unmet medical challenges is the treatment of neurodegenerative diseases such as Alzheimer's disease (AD) and Parkinson's disease (PD). This challenge encompasses the imperative development of efficacious therapeutic agents and overcoming the intricacies of the blood-brain barrier for successful drug delivery. Here we focus on the delivery aspect with particular emphasis on cell-penetrating peptides (CPPs), widely used in basic and translational research as they enhance drug delivery to challenging targets such as tissue and cellular compartments and thus increase therapeutic efficacy. The combination of CPPs with nanomaterials such as nanoparticles (NPs) improves the performance, accuracy, and stability of drug delivery and enables higher drug loads. Our review presents and discusses research that utilizes CPPs, either alone or in conjugation with NPs, to mitigate the pathogenic effects of neurodegenerative diseases with particular reference to AD and PD.

Current advances in nanoformulations of therapeutic agents targeting tumor microenvironment to overcome drug resistance

The tumor microenvironment (TME) plays a pivotal role in cancer development and progression. In this line, revealing the precise mechanisms of the TME and associated signaling pathways of tumor resistance could pave the road for cancer prevention and efficient treatment. The use of nanomedicine could be a step forward in overcoming the barriers in tumor-targeted therapy. Novel delivery systems benefit from enhanced permeability and retention effect, decreasing tumor resistance, reducing tumor hypoxia, and targeting tumor-associated factors, including immune cells, endothelial cells, and fibroblasts. Emerging evidence also indicates the engagement of multiple dysregulated mediators in the TME, such as matrix metalloproteinase, vascular endothelial growth factor, cytokines/chemokines, Wnt/β-catenin, Notch, Hedgehog, and related inflammatory and apoptotic pathways. Hence, investigating novel multitargeted agents using a novel delivery system could be a promising strategy for regulating TME and drug resistance. In recent years, small molecules from natural sources have shown favorable anticancer responses by targeting TME components. Nanoformulations of natural compounds are promising therapeutic agents in simultaneously targeting multiple dysregulated factors and mediators of TME, reducing tumor resistance mechanisms, overcoming interstitial fluid pressure and pericyte coverage, and involvement of basement membrane. The novel nanoformulations employ a vascular normalization strategy, stromal/matrix normalization, and stress alleviation mechanisms to exert higher efficacy and lower side effects. Accordingly, the nanoformulations of anticancer monoclonal antibodies and conventional chemotherapeutic agents also improved their efficacy and lessened the pharmacokinetic limitations. Additionally, the coadministration of nanoformulations of natural compounds along with conventional chemotherapeutic agents, monoclonal antibodies, and nanomedicine-based radiotherapy exhibits encouraging results. This critical review evaluates the current body of knowledge in targeting TME components by nanoformulation-based delivery systems of natural small molecules, monoclonal antibodies, conventional chemotherapeutic agents, and combination therapies in both preclinical and clinical settings. Current challenges, pitfalls, limitations, and future perspectives are also discussed.

Recent Advances in Targeting the Urokinase Plasminogen Activator with Nanotherapeutics

The aberrant proteolytic landscape of the tumor microenvironment is a key contributor of cancer progression. Overexpression of urokinase plasminogen activator (uPA) and/or its associated cell-surface receptor (uPAR) in tumor versus normal tissue is significantly associated with worse clinicopathological features and poorer patient survival across multiple cancer types. This is linked to mechanisms that facilitate tumor cell invasion and migration, via direct and downstream activation of various proteolytic processes that degrade the extracellular matrix─ultimately leading to metastasis. Targeting uPA has thus long been considered an attractive anticancer strategy. However, poor bioavailability of several uPA-selective small-molecule inhibitors has limited early clinical progress. Nanodelivery systems have emerged as an exciting method to enhance the pharmacokinetic (PK) profile of existing chemotherapeutics, allowing increased circulation time, improved bioavailability, and targeted delivery to tumor tissue. Combining uPA inhibitors with nanoparticle-based delivery systems thus offers a remarkable opportunity to overcome existing PK challenges associated with conventional uPA inhibitors, while leveraging potent candidates into novel targeted nanotherapeutics for an improved anticancer response in uPA positive tumors.

The Role of Nanotechnologies in Brain Tumors

The treatment of glioma remains one of the most interesting topics in neurooncology. Glioblastoma multiforme is the most aggressive and prevalent malignant brain tumor. Nowadays, technologies and new tools are helping the neurosurgeons to define a tailored surgery. However, there are few pharmaceutical strategies in operated and nonoperated patients. There are still few anticancer drugs approved by FDA and EMA. Moreover, these drugs are not so effective and have a lot of side effects due to their toxicity. Nanoparticles are a new strategy which could help to create and carry new drugs. In fact, NPs improve the pharmacokinetic properties of anticancer drugs, reduce side-effects, and increase drug half-life and its selectivity. Nanoparticle drug delivery system has been studied for targeting different molecular biomarkers and signaling pathways. Furthermore, the first problem of anticancer drugs in the treatment of gliomas is penetrating the blood brain barrier which represents an insurmountable wall for most of synthetic and natural particles. In the last 15 years, a lot of researches tried to design a perfect nanoparticle both able to cross blood-brain barrier and to selectively target glioma cells, unfortunately, without great results. In vivo human trials are still ongoing and many of them have already failed. In this chapter we evaluate the effectiveness of nanotechnologies in the treatment of brain tumors. There is not yet, currently, a nanoparticle drug designed for the treatment of gliomas approved by FDA and EMA. Advancements in discovery of molecular characteristics of tumors lead to the development of targeted nanoparticles that are tested in numerous in vitro and in vivo studies on gliomas. Novel and repurposed drugs, as well as novel drug combinations, have also been already studied but those are not included in this chapter because the carried drugs (active substances) are not included among the approved anticancer drug used in the treatment of gliomas.

Targeting Options of Tumor-Associated Macrophages (TAM) Activity in Gliomas

Tumor-associated macrophages (TAMs), the most plastic cells of the hematopoietic system, exhibit increased tumor-infiltrating properties and functional heterogeneity depending on tumor type and associated microenvironment. TAMs constitute a major cell type of cancer-related inflammation, commonly enhancing tumor growth. They are profoundly involved in glioma pathogenesis, contributing to many cancer hallmarks such as angiogenesis, survival, metastasis, and immunosuppression. Efficient targeting of TAMs presents a promising approach to tackle glioma progression. Several targeting options involve chemokine signaling axes inhibitors and antibodies, antiangiogenic factors, immunomodulatory molecules, surface immunoglobulins blockers, receptor and transcription factor inhibitors, as well as microRNAs (miRNAs), administered either as standalone or in combination with other conventional therapies. Herein, we provide a critical overview of current therapeutic approaches targeting TAMs in gliomas with the promising outcome.

Polymer nanocarriers for targeted local delivery of agents in treating brain tumors

Glioblastoma (GBM), the deadliest brain cancer, presents a multitude of challenges to the development of new therapies. The standard of care has only changed marginally in the past 17 years, and few new chemotherapies have emerged to supplant or effectively combine with temozolomide. Concurrently, new technologies and techniques are being investigated to overcome the pharmacokinetic challenges associated with brain delivery, such as the blood brain barrier (BBB), tissue penetration, diffusion, and clearance in order to allow for potent agents to successful engage in tumor killing. Alternative delivery modalities such as focused ultrasound and convection enhanced delivery allow for the local disruption of the BBB, and the latter in particular has shown promise in achieving broad distribution of agents in the brain. Furthermore, the development of polymeric nanocarriers to encapsulate a variety of cargo, including small molecules, proteins, and nucleic acids, have allowed for formulations that protect and control the release of said cargo to extend its half-life. The combination of local delivery and nanocarriers presents an exciting opportunity to address the limitations of current chemotherapies for GBM toward the goal of improving safety and efficacy of treatment. However, much work remains to establish standard criteria for selection and implementation of these modalities before they can be widely implemented in the clinic. Ultimately, engineering principles and nanotechnology have opened the door to a new wave of research that may soon advance the stagnant state of GBM treatment development.

Advances in the study of spheroids as versatile models to evaluate biological interactions of inorganic nanoparticles

Spheroids are in vitro three-dimensional multicellular microstructures able to mimic the biological microenvironment, including the complexity of tumor architecture. Therefore, results closer to those expected for in vivo organisms can be reached using spheroids compared to the cell culture monolayer model. Inorganic nanoparticles (NPs) have also been playing relevant roles in the comprehension of biological processes. Moreover, they have been probed as novel diagnostic and therapeutical nanosystems. In this context, in this review, we present applications, published in the last five years, which show that spheroids can be versatile models to study and evaluate biological interactions involving inorganic NPs. Applications of spheroids associated with (i) basic studies to assess the penetration profile of nanostructures, (ii) the evaluation of NP toxicity, and (iii) NP-based therapeutical approaches are described. Fundamentals of spheroids and their formation methods are also included. We hope that this review can be a reference and guide future investigations related to this interesting three-dimensional biological model, favoring advances to Nanobiotechnology.

Combination of cell-penetrating peptides with nanomaterials for the potential therapeutics of central nervous system disorders: a review

Although nanomedicine have greatly developed and human life span has been extended, we have witnessed the soared incidence of central nervous system (CNS) diseases including neurodegenerative diseases (Alzheimer's disease, Parkinson's disease), ischemic stroke, and brain tumors, which have severely damaged the quality of life and greatly increased the economic and social burdens. Moreover, partial small molecule drugs and almost all large molecule drugs (such as recombinant protein, therapeutic antibody, and nucleic acid) cannot cross the blood-brain barrier. Therefore, it is especially important to develop a drug delivery system that can effectively deliver therapeutic drugs to the central nervous system for the treatment of central nervous system diseases. Cell penetrating peptides (CPPs) provide a potential strategy for the transport of macromolecules through the blood-brain barrier. This study analyzed and summarized the progress of CPPs in CNS diseases from three aspects: CPPs, the conjugates of CPPs and drug, and CPPs modified nanoparticles to provide scientific basis for the application of CPPs for CNS diseases.

Tumor-targeted Drug Delivery by Nanocomposites

BACKGROUND

Tumor-targeted delivery by nanoparticles is a great achievement towards the use of highly effective drug at very low doses. The conventional development of tumor-targeted delivery by nanoparticles is based on enhanced permeability and retention (EPR) effect and endocytosis based on receptor-mediated are very demanding due to the biological and natural complications of tumors as well as the restrictions on the design of the accurate nanoparticle delivery systems.

METHODS

Different tumor environment stimuli are responsible for triggered multistage drug delivery systems (MSDDS) for tumor therapy and imaging. Physicochemical properties, such as size, hydrophobicity and potential transform by MSDDS because of the physiological blood circulation different, intracellular tumor environment. This system accomplishes tumor penetration, cellular uptake improved, discharge of drugs on accurate time, and endosomal discharge.

RESULTS

Maximum drug delivery by MSDDS mechanism to target therapeutic cells and also tumor tissues and sub cellular organism. Poorly soluble compounds and bioavailability issues have been faced by pharmaceutical industries, which are resolved by nanoparticle formulation.

CONCLUSION

In our review, we illustrate different types of triggered moods and stimuli of the tumor environment, which help in smart multistage drug delivery systems by nanoparticles, basically a multi-stimuli sensitive delivery system, and elaborate their function, effects, and diagnosis.

Construction of nanomaterials as contrast agents or probes for glioma imaging

Malignant glioma remains incurable largely due to the aggressive and infiltrative nature, as well as the existence of blood-brain-barrier (BBB). Precise diagnosis of glioma, which aims to accurately delineate the tumor boundary for guiding surgical resection and provide reliable feedback of the therapeutic outcomes, is the critical step for successful treatment. Numerous imaging modalities have been developed for the efficient diagnosis of tumors from structural or functional aspects. However, the presence of BBB largely hampers the entrance of contrast agents (Cas) or probes into the brain, rendering the imaging performance highly compromised. The development of nanomaterials provides promising strategies for constructing nano-sized Cas or probes for accurate imaging of glioma owing to the BBB crossing ability and other unique advantages of nanomaterials, such as high loading capacity and stimuli-responsive properties. In this review, the recent progress of nanomaterials applied in single modal imaging modality and multimodal imaging for a comprehensive diagnosis is thoroughly summarized. Finally, the prospects and challenges are offered with the hope for its better development.

Dual-triggered biomimetic vehicles enable treatment of glioblastoma through a cancer stem cell therapeutic strategy

Glioma stem cells (GSCs) and their complex microenvironment play a crucial role in the high invasion of cancer and therapeutic resistance and are considered to be the most likely cause of cancer relapse. We constructed a biomimetic vehicle (LDL-SAL-Ang) based on a low density lipoprotein triggered by Angiopep-2 peptide and ApoB protein, to improve the transport of an anti-GSC therapeutic agent into the brain. The LDL-SAL-Ang showed significant inhabitation for GSC microsphere formation and induced the highest apoptotic rate in two types of GSCs. LDL-SAL-Ang reduced the number of GSC-derived endothelial tubules at a lower drug concentration and inhibited endothelial cell migration and angiogenesis. The pharmacokinetic analysis showed that the brain tissue uptake rate (% ID g^-1) for LDL-SAL-Ang was significantly enhanced at 0.45. For anti-glioblastoma activity in vivo, the median survival time of LDL-SAL-Ang plus temozolomide group was 47 days, which were significantly increased compared with the control or temozolomide only groups. The endogenous biomimetic nanomedicine that we designed provides a potential approach to improve treatments for intracranial tumors and reduced neurotoxicity of nanomedicine.

Nanoparticles Dual Targeting Both Myeloma Cells and Cancer-Associated Fibroblasts Simultaneously to Improve Multiple Myeloma Treatment

Cancer-associated fibroblasts (CAFs) and myeloma cells could mutually drive myeloma progression, indicating that drug delivery to kill both CAFs and myeloma cells simultaneously could achieve better therapeutic benefits than to kill each cell type alone. Here, we designed a dual-targeting drug delivery system by conjugating paclitaxel (PTX)-loaded poly(ethylene glycol)-poly(lactic acid) nanoparticles (NPs) with a cyclic peptide (CNPs-PTX) with a special affinity with platelet-derived growth factor/platelet-derived growth factor receptor (PDGFR-β) overexpressed on both CAFs and myeloma cells. Cellular uptake experiments revealed that the cyclic peptide modification on CNPs could significantly enhance CNPs uptake by both CAFs and myeloma cells compared with unmodified NPs. Cytotoxicity tests showed that CNPs-PTX was more toxic to both CAFs and myeloma cells compared with its counterpart PTX-loaded conventional NPs (NPs-PTX). In vivo imaging and biodistribution experiments showed that CNPs could abundantly accumulate in tumors and were highly co-localized with CAFs and myeloma cells. The in vivo anti-tumor experiments confirmed that the anti-myeloma efficacy of CNPs-PTX was significantly stronger than that of NPs-PTX and free drugs. In summary, it is the first time that a dual-targeting strategy was utilized in the field of myeloma treatment through targeting both CAFs and myeloma cells simultaneously, which harbors a high potential of clinical translation for myeloma treatment.

Current Status and Perspectives of Protease Inhibitors and Their Combination with Nanosized Drug Delivery Systems for Targeted Cancer Therapy

In cancer treatments, many natural and synthetic products have been examined; among them, protease inhibitors are promising candidates for anti-cancer agents. Since dysregulated proteolytic activities can contribute to tumor development and metastasis, antagonization of proteases with tailored inhibitors is an encouraging approach. Although adverse effects of early designs of these inhibitors disappeared after the introduction of next-generation agents, most of the proposed inhibitors did not pass the early stages of clinical trials due to their nonspecific toxicity and lack of pharmacological effects. Therefore, new applications that modulate proteases more specifically and serve their programmed way of administration are highly appreciated. In this context, nanosized drug delivery systems have attracted much attention because preliminary studies have demonstrated that the therapeutic capacity of inhibitors has been improved significantly with encapsulated formulation as compared to their free forms. Here, we address this issue and discuss the current application and future clinical prospects of this potential combination towards targeted protease-based cancer therapy.

Thrombin-responsive engineered nanoexcavator with full-thickness infiltration capability for pharmaceutical-free deep venous thrombosis theranostics

Although nanotechnology has shown great promise for treating multiple vascular diseases in recent years, simultaneous noninvasive detection and efficient dissolution of deep venous thrombosis (DVT) still remains challenging. In particular, long blockage areas and large thrombus thicknesses in DVT cause enormous difficulties for site-specific deep-seated thrombus theranostics. Therefore, based on the unique components of DVT, the novel concept of a thrombin-responsive full-thickness infiltration nonpharmaceutical nanoplatform for DVT theranostics is proposed here. The penetration depth is innovatively enhanced with efficient targeting and accumulation in the whole thrombi. Herein, we report a thrombin-responsive phase-transition liposome incorporating a liquid perfluoropentane (PFP) core and modified with two binding peptides, activatable cell-penetrating peptide (ACPP) and fibrin-binding ligand (FTP), which contribute to efficient liposome targeting and accumulation within the thrombi. This targeted nanoplatform is constructed to dig out the thrombus with the assistance of low-intensity focused ultrasound (LIFU), performing the destructive function of an excavator via an acoustic droplet vaporization effect (acting as a "nanoexcavator" system), which can activate and vaporize into microbubbles to enhance LIFU efficacy. The resulting microbubbles enable real-time monitoring of the therapeutic process with ultrasound imaging and high performance photoacoustic imaging after loading DIR. This non-invasive nonpharmaceutical thrombolytic strategy is an improvement over existing clinical methods without systemic side effects.

Tumor microenvironment-induced structure changing drug/gene delivery system for overcoming delivery-associated challenges

Nano-drug/gene delivery systems (DDS) are powerful weapons for the targeted delivery of various therapeutic molecules in treatment of tumors. Nano systems are being extensively investigated for drug and gene delivery applications because of their exceptional ability to protect the payload from degradation in vivo, prolong circulation of the nanoparticles (NPs), realize controlled release of the contents, reduce side effects, and enhance targeted delivery among others. However, the specific properties required for a DDS vary at different phase of the complex delivery process, and these requirements are often conflicting, including the surface charge, particle size, and stability of DDS, which severely reduces the efficiency of the drug/gene delivery. Therefore, researchers have attempted to fabricate structure, size, or charge changeable DDS by introducing various tumor microenvironment (TME) stimuli-responsive elements into the DDS to meet the varying requirements at different phases of the delivery process, thus improving drug/gene delivery efficiency. This paper summarizes the most recent developments in TME stimuli-responsive DDS and addresses the aforementioned challenges.

Targeting hemostasis-related moieties for tumor treatment

Under normal conditions, the hemostatic system, that includes the involvement of the coagulation response and platelets, is anatomically and functionally inseparable from the vasculature. However, the hemostatic response always occurs in a wide range of tumors because of the high expression of coagulation initiator tissue factor (TF) in many tumor tissues, and due to the leakage of coagulation factors and platelets from the circulation system into the tumor interstitium through abnormal tumor vessels. Therefore, in addition to TF, these coagulation factors, platelets, the central moiety thrombin, the final product fibrin, and fibronectin, which is capable of stabilizing coagulation clots, are also abundant in tumors. These hemostasis-related moieties (HRMs), including TF, thrombin, fibrin, fibronectin, and platelets, are also closely associated with tumor progression, e.g., primary tumor growth and distal metastasis. The hemostatic response only occurs under pathological conditions, such as tumors, thrombosis, and atherosclerosis other than in normal tissues. The HRMs within tumors are also highly specific, establishing functional and therapeutic targets for tumor treatment. Therefore, strategies including active targeting to these moieties, modulation of HRMs deposited in the tumor microenvironment to improve tumor drug delivery, activation of prodrug by the coagulation complex formed during coagulation response, and direct inhibition of the tumor-promoting activity of HRMs could be designed for tumor therapy. In this review, we summarize various strategies that target HRMs for tumor treatment.

Stimuli-Sensitive Cell Penetrating Peptide-Modified Nanocarriers

The integration of drugs into nanocarriers favorably altered their pharmacodynamics and pharmacokinetics compared to free drugs, and increased their therapeutic index. However, selective cellular internalization in diseased tissues rather than normal tissues still presents a formidable challenge. In this chapter I will cover solutions involving environment-responsive cell-penetrating peptides (CPPs). I will discuss properties of CPPs as universal cellular uptake enhancers, and the modifications imparted to CPP-modified nanocarriers to confine CPP activation to diseased tissues.

Engineered superparamagnetic iron oxide nanoparticles (SPIONs) for dual-modality imaging of intracranial glioblastoma via EGFRvIII targeting

In this work, a peptide-modified, biodegradable, nontoxic, brain-tumor-targeting nanoprobe based on superparamagnetic iron oxide nanoparticles (SPIONs) (which have been commonly used as T ₂-weighted magnetic resonance (MR) contrast agents) was successfully synthesized and applied for accurate molecular MR imaging and sensitive optical imaging. PEPHC1, a short peptide which can specifically bind to epidermal growth factor receptor variant III (EGFRvIII) that is overexpressed in glioblastoma, was conjugated with SPIONs to construct the nanoprobe. Both in vitro and in vivo MR and optical imaging demonstrated that the as-constructed nanoprobe was effective and sensitive for tumor targeting with desirable biosafety. Given its desirable properties such as a 100 nm diameter (capable of penetration of the blood-brain barrier) and bimodal imaging capability, this novel and versatile multimodal nanoprobe could bring a new perspective for elucidating intracranial glioblastoma preoperative diagnosis and the accuracy of tumor resection.

Lower Tubulin Expression in Glioblastoma Stem Cells Attenuates Efficacy of Microtubule-Targeting Agents

Sensitivity to microtubule-targeting agents (MTAs) varies among cancers and predicting the response of individual cancer patients to MTAs remains challenging. As microtubules possess vast molecular heterogeneity generated by tubulin isotypes and their post-translational modifications, we questioned whether this heterogeneity can impact MTA sensitivity. We investigated microtubule heterogeneity in 15 glioblastoma cell lines and measured sensitivity of orthogonal MTAs using a per-division growth rate inhibition method that corrects for the confounding effects of variable cell proliferation rates. We found that the tubulin profile is unique for each glioblastoma cell line and that the total α- and β-tubulin levels impact on MTA sensitivity. The baseline levels of α- and β-tubulin were up to 20% lower in cells that were not effectively killed by MTAs. We report that lower α/β-tubulin expression is associated with lack of cell differentiation and increased expression of stemness markers. The dedifferentiated stem-like cells with low α/β-tubulin levels survive MTAs treatment via reversible nonmutational dormancy. Our findings provide novel insights into the relationships between microtubules and MTAs and lay a foundation for better understanding of the sensitivity of cancer cells to MTAs.

Application of nanotechnology to target and exploit tumour associated proteases

Proteases are hydrolytic enzymes fundamental for a variety of physiological processes, but the loss of their regulation leads to aberrant functions that promote onset and progression of many diseases including cancer. Proteases have been implicated in almost every hallmark of cancer and whilst widely investigated for tumour therapy, clinical adoption of protease inhibitors as drugs remains a challenge due to issues such as off-target toxicity and inability to achieve therapeutic doses at the disease site. Now, nanotechnology-based solutions and strategies are emerging to circumvent these issues. In this review, preclinical advances in approaches to enhance the delivery of protease drugs and the exploitation of tumour-derived protease activities to promote targeting of nanomedicine formulations is examined. Whilst this field is still in its infancy, innovations to date suggest that nanomedicine approaches to protease targeting or inhibition may hold much therapeutic and diagnostic potential.

Vinorelbine cationic liposomes modified with wheat germ agglutinin for inhibiting tumor metastasis in treatment of brain glioma

Glioma is the most common primary malignant brain tumor with a poor prognosis. The application of chemotherapeutic drugs is limited due to the existence of blood-brain barrier and serious side effects. Liposomes have been proven to be a stable and useful drug delivery system for tumors. In this paper, WGA (wheat germ agglutinin) modified vinorelbine cationic liposomes had been successfully constructed for treating glioma. In the liposomes, WGA was modified on the liposomal surface for crossing the blood-brain barrier and increasing the targeting effects, 3-(N-(N', N'-dimethylaminoethane) carbamoyl) cholesterol (DC-Chol) was used as cationic material and vinorelbine was encapsulated in the aqueous core of liposomes to inhibit tumor metastasis and kill tumor cells. Studies were performed on C6 cells in vitro and were verified in brain glioma-bearing mice in vivo. Results in vitro demonstrated that the targeting liposomes could induce C6 cells apoptosis, promote drugs across the blood-brain barrier, inhibit the metastasis of tumor cells and increase targeting effects to tumor cells. Meanwhile, action mechanism studies showed that the targeting liposomes could down-regulate PI3K, MMP-2, MMP-9 and FAK to inhibit tumor metastasis. Results in vivo exhibited that the targeting liposomes displayed an obvious antitumor efficacy by accumulating selectively in tumor site and exhibited low toxicity to blood system and major organs. Hence, WGA modified vinorelbine cationic liposomes might provide a safe and efficient therapy strategy for glioma.

Etoposide loaded layered double hydroxide nanoparticles reversing chemoresistance and eradicating human glioma stem cells in vitro and in vivo

Glioblastoma (GBM) is the most malignant and lethal glioma in human brain tumors and contains self-renewing, tumorigenic glioma stem cells (GSCs) that contribute to tumor initiation, therapeutic resistance and further recurrence. In this study, we combined in vitro cellular efficacy with in vivo antitumor performance to evaluate the outcome of an etoposide (VP16) loaded layered double hydroxide (LDH) nanocomposite (L-V) on human GSCs. The effects on GSC proliferation and apoptosis showed that loading with LDH could significantly sensitize GSCs to VP16 and enhance the GSC elimination. Further qPCR and western blot assays demonstrated that L-V could effectively attenuate GSC related pluripotency gene expression and reduce the cancer stemness. An in vivo GSC xenograft mice model showed that L-V can overcome drug resistance, eradicate GSCs, sharply decrease the stemness and reverse the epithelial-mesenchymal transition (EMT). RNA-seq analysis elucidated that L-V plays a vital role by down-regulating the PI3K/AKt/mTOR expression and activating the Wnt/GSK3β/β-catenin signaling pathway, hence leading to GSC stemness loss and greatly enhancing the GSC targeting effect. Taken together, this study demonstrated the outstanding performance of L-V reversing the drug resistance of GSCs, thus providing a novel strategy for clinical translation application of nanomedicine in malignant glioma chemotherapy.

Methotrexate-Loaded Extracellular Vesicles Functionalized with Therapeutic and Targeted Peptides for the Treatment of Glioblastoma Multiforme

Despite promising in vitro evidence for effective glioblastoma treatment, most drugs are hindered from entering the central nervous system because of the presence of the blood-brain barrier (BBB). Thus, successful modification of drug delivery and novel therapeutic strategies are needed to overcome this obstacle. Extracellular vesicles (EVs), cell-derived membrane-encapsulated structures with diameters ranging from 50 to 1000 nm, have been explored as the drug delivery system to deliver their cargo to the brain tissue. Moreover, tumor targeting and selective drug delivery has been facilitated by engineering their parent cells to secrete modified EVs. However, the method suffers from many shortcomings including poor repeatability and complex and time-consuming operations. In this context, we present an easy-to-adapt and highly versatile methodology to modify EVs with an engineered peptide capable of recognition and eradication of glioma. On the basis of molecular recognition between phospholipids on EV lipid bilayer membranes and ApoA-I mimetic peptides, we have developed methotrexate (MTX)-loaded EVs functionalized with therapeutic [Lys-Leu-Ala (KLA)] and targeted [low-density lipoprotein (LDL)] peptides. In vitro experiments demonstrated that EVs decorated with LDL or KLA-LDL could obviously ameliorate their uptake by human primary glioma cell line U87 and permeation into three-dimensional glioma spheroids in contrast to blank EVs, and consequently, the treatment outcome of the payload is improved. Both ex vivo and in vivo imaging experiments revealed that peptide LDL could obviously promote EV extravasation across the BBB and distribution in the glioma site. Furthermore, compared with the mice administrated with MTX and MTX@EVs, MTX@EVs-KLA-LDL-treated mice showed the longest median survival period. In conclusion, functionalizing with the peptide onto EV surfaces may provide a substantial advancement in the application of EVs for selective target binding as well as therapeutic effects for brain tumor treatment.

Modulating the Tumor Microenvironment to Enhance Tumor Nanomedicine Delivery

Nanomedicines including liposomes, micelles, and nanoparticles based on the enhanced permeability and retention (EPR) effect have become the mainstream for tumor treatment owing to their superiority over conventional anticancer agents. Advanced design of nanomedicine including active targeting nanomedicine, tumor-responsive nanomedicine, and optimization of physicochemical properties to enable highly effective delivery of nanomedicine to tumors has further improved their therapeutic benefits. However, these strategies still could not conquer the delivery barriers of a tumor microenvironment such as heterogeneous blood flow, dense extracellular matrix, abundant stroma cells, and high interstitial fluid pressure, which severely impaired vascular transport of nanomedicines, hindered their effective extravasation, and impeded their interstitial transport to realize uniform distribution inside tumors. Therefore, modulation of tumor microenvironment has now emerged as an important strategy to improve nanomedicine delivery to tumors. Here, we review the existing strategies and approaches for tumor microenvironment modulation to improve tumor perfusion for helping more nanomedicines to reach the tumor site, to facilitate nanomedicine extravasation for enhancing transvascular transport, and to improve interstitial transport for optimizing the distribution of nanomedicines. These strategies may provide an avenue for the development of new combination chemotherapeutic regimens and reassessment of previously suboptimal agents.

On-Demand Drug Release from Dual-Targeting Small Nanoparticles Triggered by High-Intensity Focused Ultrasound Enhanced Glioblastoma-Targeting Therapy

Glioblastoma is one of the most challenging and intractable tumors with the difficult treatment and poor prognosis. Unsatisfactory traditional systemic chemotherapies for glioblastoma are mainly attributed to the insufficient and nonspecific drug delivery into the brain tumors as well as the incomplete drug release at the tumor sites. Inspired by the facts that angiopep-2 peptide is an acknowledged dual-targeting moiety for brain tumor-targeting delivery and high-intensity focused ultrasound (HIFU) is an ideal trigger for drug release with an ultrahigh energy and millimeter-sized focus ability, in the present study, a novel HIFU-responsive angiopep-2-modified small poly(lactic-co-glycolic acid) (PLGA) hybrid nanoparticle (NP) drug delivery system holding doxorubicin/perfluorooctyl bromide (ANP-D/P) was designed to increase the intratumoral drug accumulation, further trigger on-demand drug release at the glioblastoma sites, and enhance glioblastoma therapy. It was shown that the ANP-D/P was stable and had a small size of 41 nm. The angiopep-2 modification endowed the ANP-D/P with improved blood-brain barrier transportation and specific accumulation in glioblastoma tissues by 17 folds and 13.4 folds compared with unmodified NPs, respectively. Under HIFU irradiation, the ANP-D/P could release 47% of the drug within 2 min and induce the apoptosis of most tumor cells. HIFU-triggered instantaneous drug release at the glioblastoma sites eventually enabled the ANP-D/P to achieve the strongest antiglioblastoma efficacy with the longest median survival time (56 days) of glioblastoma-bearing mice and the minimum vestiges of tumor cells in the pathological slices among all groups. In conclusion, the HIFU-responsive ANP-D/P in this study provided a new way for glioblastoma therapy with a great potential for clinical applications.

Celecoxib normalizes the tumor microenvironment and enhances small nanotherapeutics delivery to A549 tumors in nude mice

Barriers presented by the tumor microenvironment including the abnormal tumor vasculature and interstitial matrix invariably lead to heterogeneous distribution of nanotherapeutics. Inspired by the close association between cyclooxygenase-2 (COX-2) and tumor-associated angiogenesis, as well as tumor matrix formation, we proposed that tumor microenvironment normalization by COX-2 inhibitors might improve the distribution and efficacy of nanotherapeutics for solid tumors. The present study represents the first time that celecoxib, a special COX-2 inhibitor widely used in clinics, was explored to normalize the tumor microenvironment and to improve tumor nanotherapeutics delivery using a human-derived A549 tumor xenograft as the solid tumor model. Immunofluorescence staining of tumor slices demonstrated that oral celecoxib treatment at a dose of 200 mg/kg for two weeks successfully normalized the tumor microenvironment, including tumor-associated fibroblast reduction, fibronectin bundle disruption, tumor vessel normalization, and tumor perfusion improvement. Furthermore, it also significantly enhanced the in vivo accumulation and deep penetration of 22-nm micelles rather than 100-nm nanoparticles in tumor tissues by in vivo imaging and distribution experiments and improved the therapeutic efficacy of paclitaxel-loaded micelles in tumor xenograft-bearing mouse models in the pharmacodynamics experiment. As celecoxib is widely and safely used in clinics, our findings may have great potential in clinics to improve solid tumor treatment.

Thermosensitive Liposomal Codelivery of HSA-Paclitaxel and HSA-Ellagic Acid Complexes for Enhanced Drug Perfusion and Efficacy Against Pancreatic Cancer

Fibrotic stroma and tumor-promoting pancreatic stellate cells (PSCs), critical characters in the pancreatic ductal adenocarcinoma (PDA) microenvironment, promote a tumor-facilitating environment that simultaneously prevents drug penetration into tumor foci and stimulates tumor growth. Nab-PTX, a human serum albumin (HSA) nanoparticle of paclitaxel (PTX), indicates enhanced matrix penetration in PDA probably due to its small size in vivo and high affinity of HSA with secreted protein acidic and rich in cysteine (SPARC), overexpressed in the PDA stroma. However, this HSA nanoparticle shows poor drug blood retention because of its weak colloidal stability in vivo, thus resulting in insufficient drug accumulation within tumor. Encapsulating HSA nanoparticles into the internal aqueous phase of ordinary liposomes improves their blood retention and the following tumor accumulation, but the large 200 nm size and shielding of HSA in the interior might make it difficult for this hybrid nanomedicine to penetrate the fibrotic PDA matrix and promote bioavailability of the payload. In our current work, we prepared ∼9 nm HSA complexes with an antitumor drug (PTX) and an anti-PSC drug (ellagic acid, EA), and these two HSA-drug complexes were further coencapsulated into thermosensitive liposomes (TSLs). This nanomedicine was named TSL/HSA-PE. The use of TSL/HSA-PE could improve drug blood retention, and upon reaching locally heated tumors, these TSLs can rapidly release their payloads (HSA-drug complexes) to facilitate their further tumor accumulation and matrix penetration. With superior tumor accumulation, impressive matrix penetration, and simultaneous action upon tumor cells and PSCs to disrupt PSCs-PDA interaction, TSL/HSA-PE treatment combined with heat exhibited strong tumor growth inhibition and apoptosis in vivo.

Investigating the Cellular Specificity in Tumors of a Surface-Converting Nanoparticle by Multimodal Imaging

Active targeting of nanoparticles through surface functionalization is a common strategy to enhance tumor delivery specificity. However, active targeting strategies tend to work against long polyethylene glycol's shielding effectiveness and associated favorable pharmacokinetics. To overcome these limitations, we developed a matrix metalloproteinase-2 sensitive surface-converting polyethylene glycol coating. This coating prevents nanoparticle-cell interaction in the bloodstream, but, once exposed to matrix metalloproteinase-2, i.e., when the nanoparticles accumulate within the tumor interstitium, the converting polyethylene glycol coating is cleaved, and targeting ligands become available for binding to tumor cells. In this study, we applied a comprehensive multimodal imaging strategy involving optical, nuclear, and magnetic resonance imaging methods to evaluate this coating approach in a breast tumor mouse model. The data obtained revealed that this surface-converting coating enhances the nanoparticle's blood half-life and tumor accumulation and ultimately results in improved tumor-cell targeting. Our results show that this enzyme-specific surface-converting coating ensures a high cell-targeting specificity without compromising favorable nanoparticle pharmacokinetics.

ACPI Conjugated Gold Nanorods as Nanoplatform for Dual Image Guided Activatable Photodynamic and Photothermal Combined Therapy In Vivo

The nanoplatform GNR-ACPP-PpIX (designated as GNR-ACPI) is designed for dual image guided combined activatable photodynamic therapy (PDT) and photothermal therapy (PTT). In GNR-ACPI, gold nanorods (GNRs) are modified with a protoporphyrin (PpIX, a PDT agent) conjugated activatable cell penetrating peptide (ACPP), which consists of the matrix metalloproteinases-2 (MMP-2) sensitive peptide sequence GPLGLAG. First, the photoactivity of PpIX is effectively quenched by GNRs due to the strong near infrared region light absorption of GNR and the special "U type" structure of ACPP induced close contact between PpIX and GNR. However, once arriving at the tumor site, the GPLGLAG sequence is hydrolyzed by the MMP-2 overexpressed by tumor cells, resulting in the release of the residual cell membrane penetrating peptide (CPP) attached PpIX (CPP-PpIX) with the recovery of photoactivity of PpIX. In addition, with the help of CPP, more efficient cellular uptake of PpIX by tumor cells can be achieved, which will greatly improve the PDT efficacy. Moreover, the GNR can also be utilized for photothermic imaging as well as PTT for tumors. It is found that the combination of PTT and PDT under the guidance of dual-mode imaging greatly enhances the antitumor effects, while possessing negligible systematic toxicity.

Development and Biological Evaluation of a Photoactivatable Small Molecule Microtubule-Targeting Agent

Photoremovable protecting groups added to bioactive molecules provide spatial and temporal control of the biological effects. We present synthesis and characterization of the first photoactivatable small-molecule tubulin inhibitor. By blocking the pharmacophoric OH group on compound 1 with photoremovable 4,5-dimethoxy-2-nitrobenzyl moiety we developed the photocaged prodrug 2 that had no effect in biological assays. Short UV light exposure of the derivative 2 or UV-irradiation of cells treated with 2 resulted in fast and potent inhibition of tubulin polymerization, attenuation of cell viability, and apoptotic cell death, implicating release of the parent active compound. This study validates for the first time the photoactivatable prodrug concept in the field of small molecule tubulin inhibitors. The caged derivative 2 represents a novel tool in antitubulin approaches.

Enhancing siRNA-based cancer therapy using a new pH-responsive activatable cell-penetrating peptide-modified liposomal system

As a potent therapeutic agent, small interfering RNA (siRNA) has been exploited to silence critical genes involved in tumor initiation and progression. However, development of a desirable delivery system is required to overcome the unfavorable properties of siRNA such as its high degradability, molecular size, and negative charge to help increase its accumulation in tumor tissues and promote efficient cellular uptake and endosomal/lysosomal escape of the nucleic acids. In this study, we developed a new activatable cell-penetrating peptide (ACPP) that is responsive to an acidic tumor microenvironment, which was then used to modify the surfaces of siRNA-loaded liposomes. The ACPP is composed of a cell-penetrating peptide (CPP), an acid-labile linker (hydrazone), and a polyanionic domain, including glutamic acid and histidine. In the systemic circulation (pH 7.4), the surface polycationic moieties of the CPP (polyarginine) are "shielded" by the intramolecular electrostatic interaction of the inhibitory domain. When exposed to a lower pH, a common property of solid tumors, the ACPP undergoes acid-catalyzed breakage at the hydrazone site, and the consequent protonation of histidine residues promotes detachment of the inhibitory peptide. Subsequently, the unshielded CPP would facilitate the cellular membrane penetration and efficient endosomal/lysosomal evasion of liposomal siRNA. A series of investigations demonstrated that once exposed to an acidic pH, the ACPP-modified liposomes showed elevated cellular uptake, downregulated expression of polo-like kinase 1, and augmented cell apoptosis. In addition, favorable siRNA avoidance of the endosome/lysosome was observed in both MCF-7 and A549 cells, followed by effective cytoplasmic release. In view of its acid sensitivity and therapeutic potency, this newly developed pH-responsive and ACPP-mediated liposome system represents a potential platform for siRNA-based cancer treatment.

Current Multistage Drug Delivery Systems Based on the Tumor Microenvironment

The development of traditional tumor-targeted drug delivery systems based on EPR effect and receptor-mediated endocytosis is very challenging probably because of the biological complexity of tumors as well as the limitations in the design of the functional nano-sized delivery systems. Recently, multistage drug delivery systems (Ms-DDS) triggered by various specific tumor microenvironment stimuli have emerged for tumor therapy and imaging. In response to the differences in the physiological blood circulation, tumor microenvironment, and intracellular environment, Ms-DDS can change their physicochemical properties (such as size, hydrophobicity, or zeta potential) to achieve deeper tumor penetration, enhanced cellular uptake, timely drug release, as well as effective endosomal escape. Based on these mechanisms, Ms-DDS could deliver maximum quantity of drugs to the therapeutic targets including tumor tissues, cells, and subcellular organelles and eventually exhibit the highest therapeutic efficacy. In this review, we expatiate on various responsive modes triggered by the tumor microenvironment stimuli, introduce recent advances in multistage nanoparticle systems, especially the multi-stimuli responsive delivery systems, and discuss their functions, effects, and prospects.

Size changeable nanosystems for precise drug controlled release and efficient overcoming of cancer multidrug resistance

Herein we demonstrate the rational design of a size changeable nanosystem for precise drug controlled release and efficient overcoming of cancer multidrug resistance in cancer cells by enhancing the cellular uptake and inhibiting the expression of ABC family proteins.

Precise glioblastoma targeting by AS1411 aptamer-functionalized poly (l-γ-glutamylglutamine)-paclitaxel nanoconjugates

Chemotherapy is still the main adjuvant strategy after surgery in glioblastoma therapy. As the main obstacles of chemotherapeutic drugs for glioblastoma treatment, the blood brain barrier (BBB) and non-specific delivery to non-tumor tissues greatly limit the accumulation of drugs into tumor tissues and simultaneously cause serious toxicity to nearby normal tissues which altogether compromised the chemotherapeutic effect. In the present study, we established an aptamer AS1411-functionalized poly (l-γ-glutamyl-glutamine)-paclitaxel (PGG-PTX) nanoconjugates drug delivery system (AS1411-PGG-PTX), providing an advantageous solution of combining the precisely active targeting and the optimized solubilization of paclitaxel. The receptor nucleolin, highly expressed in glioblastoma U87 MG cells as well as neo-vascular endothelial cells, mediated the binding and endocytosis of AS1411-PGG-PTX nanoconjugates, leading to significantly enhanced uptake of AS1411-PGG-PTX nanoconjugates by tumor cells and three-dimension tumor spheroids, and intensive pro-apoptosis effect of AS1411-PGG-PTX nanoconjugates. In vivo fluorescence imaging and tissue distribution further demonstrated the higher tumor distribution of AS1411-PGG-PTX as compared with PGG-PTX. As a result, the AS1411-PGG-PTX nanoconjugates presented the best anti-glioblastoma effect with prolonged median survival time and most tumor cell apoptosis in vivo as compared with other groups. In conclusion, the AS1411-PGG-PTX nanoconjugates exhibited a promising targeting delivery strategy for glioblastoma therapy.

Peptides as a therapeutic avenue for nanocarrier-aided targeting of glioma

INTRODUCTION

Very few successful interventions have been possible in glioma therapy owing to its aggressive nature as well as its hindrance of targeted therapy together with the limited access afforded by the blood-brain barrier (BBB). With the advent of nanotechnology based delivery vehicles such as micelles, dendrimers, polymer-based nanoparticles and nanogels, the breach of the BBB has been facilitated. However, there remains the issue of targeted therapy for glioma cells. Peptide-mediated surface modification of nanocarriers serves this purpose, extending the ability to target glioma further than the enhanced permeability and retention effect. Areas covered: Here we have tried to re-establish the significance of peptides that could be used in various ways for treating glioma. Peptide-embellished nanocarriers used to deliver anticancer drugs; nucleic acids (siRNA, miRNA); micelles or dendrimers grafted with immunogenic glioma-derived peptides used for stimulating active immunity in vaccine therapy, glioma targets for cell penetrating peptides and homing to specific receptors are reviewed. Expert opinion: Peptides have multifunctional potential in targeting, BBB and cell penetration, and can serve as antagonists of various ligands and agonists of particular over-expressed receptors as discussed in this review. Using peptides in targeted personalized therapy would be one step forward and may offer new avenues for glioma therapeutics.

Glioma-targeted superparamagnetic iron oxide nanoparticles as drug-carrying vehicles for theranostic effects

Multifunctional nanoparticles capable of the specific delivery of therapeutics to diseased cells and the real-time imaging of these sites have the potential to improve cancer treatment through personalized therapy. In this study, we have proposed a multifunctional nanoparticle that integrate magnetic targeting, drug-carrier functionality and real-time MRI imaging capabilities in one platform for the theranostic treatment of tumors. The multifunctional nanoparticle was designed with a superparamagnetic iron oxide core and a multifunctional shell composed of PEG/PEI/polysorbate 80 (Ps 80) and was used to encapsulate DOX. DOX-loaded multifunctional nanoparticles (DOX@Ps 80-SPIONs) with a Dh of 58.0 nm, a zeta potential of 28.0 mV, and a drug loading content of 29.3% presented superior superparamagnetic properties with a saturation magnetization (Ms) of 24.1 emu g(-1). The cellular uptake of DOX@Ps 80-SPIONs by C6 cells under a magnetic field was significantly enhanced over that of free DOX in solution, resulting in stronger in vitro cytotoxicity. The real-time therapeutic outcome of DOX@Ps 80-SPIONs was easily monitored by MRI. Furthermore, the negative contrast enhancement effect of the nanoparticles was confirmed in glioma-bearing rats. Prussian blue staining and ex vivo DOX fluorescence assays showed that the magnetic Ps 80-SPIONs and encapsulated DOX were delivered to gliomas by imposing external magnetic fields, indicating effective magnetic targeting. Due to magnetic targeting and Ps 80-mediated endocytosis, DOX@Ps 80-SPIONs in the presence of a magnetic field led to the complete suppression of glioma growth in vivo at 28 days after treatment. The therapeutic mechanism of DOX@Ps 80-SPIONs acted by inducing apoptosis through the caspase-3 pathway. Finally, DOX@Ps 80-SPIONs' safety at therapeutic dosage was verified using pathological HE assays of the heart, liver, spleen, lung and kidney. Multifunctional SPIONs could be used as potential carriers for the theranostic treatment of CNS diseases.

Tumor-Homing and Penetrating Peptide-Functionalized Photosensitizer-Conjugated PEG-PLA Nanoparticles for Chemo-Photodynamic Combination Therapy of Drug-Resistant Cancer

The combination of photodynamic therapy (PDT) and chemotherapy holds great potential in combating drug-resistant cancers. However, the major challenge that lies ahead is how to achieve high coloading capacity for both photosensitizer and chemo-drugs and how to gain efficient delivery of drugs to the drug-resistant tumors. In this study, we prepared a nanovehicle for codelivery of photosensitizer (pyropheophorbide-a, PPa) and chemo-drugs (paclitaxel, PTX) based on the synthesis of PPa-conjugated amphiphilic copolymer PPa-PLA-PEG-PLA-PPa. The obtained nanoparticles (PP NP) exhibited a satisfactory high drug-loading capacity for both drugs. To achieve effective tumor-targeting therapy, the surface of PP NP was decorated with a tumor-homing and penetrating peptide F3. In vitro cellular experiments showed that F3-functionalized PP NP (F3-PP NP) exhibited higher cellular association than PP NP and resulted in the strongest antiproliferation effect. In addition, compared with the unmodified nanoparticles, F3-PP NP exhibited a more preferential enrichment at the tumor site. Pharmacodynamics evaluation in vivo demonstrated that a longer survival time was achieved by the tumor-bearing mice treated with PP NP (+laser) than those treated with chemotherapy only or PDT only. Such antitumor efficacy of combination therapy was further improved following the F3 peptide functionalization. Collectively, these results suggested that targeted combination therapy may pave a promising way for the therapy of drug-resistant tumor.

Cyclopamine disrupts tumor extracellular matrix and improves the distribution and efficacy of nanotherapeutics in pancreatic cancer

The dense extracellular matrix in pancreatic ductal adenocarcinoma dramatically reduces the penetration and efficacy of nanotherapeutics. Disruption of the tumor extracellular matrix may help improve the distribution and efficacy of nanotherapeutics in pancreatic cancer. In this study, we tested whether cyclopamine, a special inhibitor of the hedgehog signaling pathway with powerful anti-fibrotic activity, could promote the penetration and efficacy of nanotherapeutics in pancreatic cancer. It was shown that cyclopamine disrupted tumor extracellular fibronectins, decompressed tumor blood vessels, and improved tumor perfusion. Furthermore, cyclopamine improved the accumulation and intratumoral distribution of i.v.-administered fluorescence indicator-labeled nanoparticles. Finally, cyclopamine also significantly improved the tumor growth inhibition effect of i.v.-injected nanotherapeutics in pancreatic tumor xenograft mouse models. Thus, cyclopamine may have great potential to improve the therapeutic effects of nanomedicine in patients with pancreatic cancer.

Size-Shifting Micelle Nanoclusters Based on a Cross-Linked and pH-Sensitive Framework for Enhanced Tumor Targeting and Deep Penetration Features

The antitumor effect of chemotherapeutics loaded micelles mainly depends on two aspects: the accumulation in the tumor region and the penetration into the tumor interior. These two processes have different demands on particle size. The optimal particle size for enhanced permeability and retention (EPR) is commonly believed to be around 100 nm, while much smaller size is desired for deeper penetration into the tumor interior. To address these two different requirements, we constructed size-shifting micelle nanoclusters (MNC) based on a cross-linked framework interspersed with micelles. The particle size of the micelles was 14.6 ± 0.8 nm and increased to 104.2 ± 8.1 nm after the MNC were formed, leading to an effective utilization of the EPR effect. MNC were shifted to independent micelles in lysosomes, so that a more favorable particle size for penetration could be realized. The results of antitumor growth in vivo demonstrated that size-shifting MNC were more beneficial for tumor therapy than micelles.

Nanoparticle-mediated drug delivery to high-grade gliomas

High grade gliomas (HGGs) are fatal brain tumors due to their infiltration capacity and the presence of resistant cell populations. Further, the brain is naturally protected from many exogenous molecules by the brain blood barrier (BBB), which limits or cancels passage of cytotoxic drugs to the tumor sites. In order to cope with the latter problem, nanoparticle (NP)-based carriers are intensively investigated, due to multiple possibilities to drive them across the BBB to the tumor sites and drop cytotoxic molecules there. The current status of research on NP for drug delivery to HGGs has been analyzed. The results indicate gold, lipids and proteins as three main materials featuring NP formulations for HGG treatment. Albeit specific drug targeting to HGG cells may have not been so far significantly improved, NP may help drugs crossing the BBB and enter the brain thus potentially fixing at least one part of the problem.

FROM THE CLINICAL EDITOR

High grade gliomas (HGG) are very aggressive tumours and current therapy remains unsatisfactory. The advance in nanomedicine has allowed the development of novel treatment modalities. In this review article, the authors outlined the current status in using nanoparticle (NP)-based carriers for drug delivery to HGG. This should help readers to understand and develop ideas for further drug carrier designs.