Choline Derivate-Modified Doxorubicin Loaded Micelle for Glioma Therapy

l-Type amino acid transporter 1-targeting nanoparticles for antisense oligonucleotide delivery to the CNS

l-Type amino acid transporter 1 (LAT1)-specific ligands and polyion complexes are used as brain-specific targets to deliver RNA-based drugs across the blood-brain barrier. We characterized an LAT1-targeting antisense oligonucleotide (ASO)-encapsulated nanoparticle, Phe-NPs/ASO. A 25% density of phenylalanine effectively binds to the surface of LAT1-targeting NPs in the GL261-Luc cells, and Phe-NPs/ASO shows higher binding affinity compared to that without phenylalanine by cellular binding assay. To further characterize the blood-brain barrier-targeting effect and tissue distribution following a single-dose intravenous injection in mice, we performed in vivo biodistribution studies using fluorescence imaging. The Phe-NPs/ASOs were detected in the brain tissue 1 h post-intravenous injection at an approximately 64-fold higher ratio than that of the same ASOs administered in the absence of any NP carrier. The brain tissue delivery of ASO-loaded Phe-NPs was also confirmed in a fluorescence imaging study performed in non-human primates. These results demonstrate that Phe-NPs may successfully deliver an ASO to the brain tissue across brain regions. Phe-NPs loaded with RNA-based drugs have the potential to treat diseases of the CNS, including all forms of neurodegenerative diseases.

Sub-50 nm core-shell nanoparticles with the pH-responsive squeezing release effect for targeting therapy of hepatocellular carcinoma

The development of drug delivery systems with high drug loading capacity, low leakage at physiological pH, and rapid release at the lesion sites remains an ongoing challenge. In this work, core-shell poly(6-O-methacryloyl-D-galactose)@poly(tert-butyl methacrylate) (PMADGal@PtBMA) nanoparticles (NPs) of sub-50 nm are facilely synthesized by reversible addition-fragmentation chain transfer (RAFT) soap-free emulsion polymerization with the assistance of 12-crown-4. A hydrophilic poly(methacrylic acid) (PMAA) core can then be revealed after deprotection of the tert-butyl groups, which is negatively charged and can adsorb nearly 100% of incubated doxorubicin (DOX) from a solution at pH 7.4. The physical shrinkage of PMAA chains below pH 6.0 endows the core with the squeezing effect, therefore realizing rapid drug release. It is demonstrated that the DOX release rate of PMADGal@PMAA NPs at pH 5 was 4 times that at pH 7.4. Cellular uptake experiments confirm the high targeting ability of the galactose modified PMADGal shell to human hepatocellular carcinoma (HepG2) cells. The fluorescence intensity of DOX in HepG2 cells is 4.86 times that of HeLa cells after 3 h incubation. Moreover, 20% cross-linked NPs show the highest uptake efficiency by HepG2 cells due to their moderate surface charge, size and hardness. In summary, both the core and the shell of PMADGal@PMAA NPs promise the rapid site-specific release of DOX in HepG2 cells. This work provides a facile and an effective strategy to synthesize core-shell NPs for hepatocellular carcinoma targeting therapy.

Transporter-Mediated Drug Delivery

Transmembrane transport of small organic and inorganic molecules is one of the cornerstones of cellular metabolism. Among transmembrane transporters, solute carrier (SLC) proteins form the largest, albeit very diverse, superfamily with over 400 members. It was recognized early on that xenobiotics can directly interact with SLCs and that this interaction can fundamentally determine their efficacy, including bioavailability and intertissue distribution. Apart from the well-established prodrug strategy, the chemical ligation of transporter substrates to nanoparticles of various chemical compositions has recently been used as a means to enhance their targeting and absorption. In this review, we summarize efforts in drug design exploiting interactions with specific SLC transporters to optimize their therapeutic effects. Furthermore, we describe current and future challenges as well as new directions for the advanced development of therapeutics that target SLC transporters.

Enhanced anti-glioma efficacy of doxorubicin with BRD4 PROTAC degrader using targeted nanoparticles

Current treatment of glioma is hampered due to the physical blood-brain barrier (BBB) and the resistance to traditional chemotherapeutic agents. Herein, we proposed a combined treatment strategy based on Cyclo (Arg-Gly-Asp-d-Phe-Lys) (cRGDfk) peptides-modified nanoparticle named cRGD-P in a self-assembly method for the co-delivery of doxorubicin (DOX) and BRD4 PROTAC degrader ARV-825 (ARV). Molecular dynamics simulations showed that cRGD-P could change its conformation to provide interaction sites for perfectly co-loading DOX and ARV. The cRGD-P/ARV-DOX exhibited an average size of 39.95 ​nm and a zeta potential of −0.25 ​mV. Increased expression of BRD4 in glioma cells was observed after being stimulated by cRGD-P/DOX, confirming one of the possible mechanisms of DOX resistance and the synergistic tumor inhibition effect of BRD4 degrading ARV combined with DOX. In the study, the combination of DOX and ARV in the cRGD-P nanoparticle system exhibited synergistic suppression of tumor growth in glioma cells on account of cell cycle arrest in the G2/M phase and the activation of tumor cells apoptosis-related pathways including triggering caspase cascade and downregulating Bcl-2 as well as upregulating Bax. The cRGD-P/ARV-DOX system could effectively suppress the heterotopic and orthotopic growth of glioma by increasing tumor apoptosis, inhibiting tumor proliferation, and decreasing tumor angiogenesis in vivo. Therefore, the cRGD-modified nanoparticle to co-deliver DOX and ARV provides a potential platform for exploiting a more effective and safer combination therapy for glioma.

A Historical Review of Brain Drug Delivery

The history of brain drug delivery is reviewed beginning with the first demonstration, in 1914, that a drug for syphilis, salvarsan, did not enter the brain, due to the presence of a blood-brain barrier (BBB). Owing to restricted transport across the BBB, FDA-approved drugs for the CNS have been generally limited to lipid-soluble small molecules. Drugs that do not cross the BBB can be re-engineered for transport on endogenous BBB carrier-mediated transport and receptor-mediated transport systems, which were identified during the 1970s-1980s. By the 1990s, a multitude of brain drug delivery technologies emerged, including trans-cranial delivery, CSF delivery, BBB disruption, lipid carriers, prodrugs, stem cells, exosomes, nanoparticles, gene therapy, and biologics. The advantages and limitations of each of these brain drug delivery technologies are critically reviewed.

Brain drug delivery and neurodegenerative diseases: Polymeric PLGA-based nanoparticles as a forefront platform

The discovery of effective drugs for the treatment of neurodegenerative disorders (NDs) is a deadlock. Due to their complex etiology and high heterogeneity, progresses in the development of novel NDs therapies have been slow, raising social/economic and medical concerns. Nanotechnology and nanomedicine evolved exponentially in recent years and presented a panoply of tools projected to improve diagnosis and treatment. Drug-loaded nanosystems, particularly nanoparticles (NPs), were successfully used to address numerous drug glitches, such as efficacy, bioavailability and safety. Polymeric nanoparticles (PNPs), mainly based on polylactic-co-glycolic acid (PLGA), have been already validated and approved for the treatment of cancer, neurologic dysfunctions and hormonal-related diseases. Despite promising no PNPs-based therapy for neurodegenerative disorders is available up to date. To stimulate the research in the area the studies performed so far with polylactic-co-glycolic acid (PLGA) nanoparticles as well as the techniques aimed to improve PNPs BBB permeability and drug targeting were revised. Bearing in mind NDs pharmacological therapy landscape huge efforts must be done in finding new therapeutic solutions along with the translation of the most promising results to the clinic, which hopefully will converge in the development of effective drugs in a foreseeable future.

RVG-functionalized reduction sensitive micelles for the effective accumulation of doxorubicin in brain

BACKGROUND

Glioblastoma is a lethal neoplasm with few effective therapy options. As a mainstay in the current treatment of glioma at present, chemotherapeutic agents usually show inadequate therapeutic efficiency due to their low blood brain barrier traversal and brain targeting, together with tumor multidrug resistance. Novel treatment strategies are thus urgently needed to improve chemotherapy outcomes.

RESULTS

Here, we report that nanomedicines developed by functionalizing the neurotropic rabies virus-derived polypeptide, RVG, and loading reduction-sensitive nanomicelles (polymer and doxorubicin) enable a highly specific and efficacious drug accumulation in the brain. Interestingly, curcumin serves as the hydrophobic core of the polymer, while suppressing the major efflux proteins in doxorubicin-resistant glioma cells. Studies on doxorubicin-resistant rat glioma cells demonstrate that the RVG-modified micelles exhibit superior cell entry and antitumor activity. In vivo research further showed that RVG modified nanomicelles significantly enhanced brain accumulation and tumor inhibition rate in mice, leading to a higher survival rate with negligible systemic toxicity. Moreover, effective suppression of recurrence and pulmonary metastatic nodules were also determined after the RVG-modified nanomicelles treatment.

CONCLUSIONS

The potential of RVG-modified nanomicelles for glioma was demonstrated. Brain accumulation was markedly enhanced after intravenous administration. This unique drug delivery nanoplatform to the brain provides a novel and powerful therapeutic strategy for the treatment of central nervous system disorders including glioma.

Disulfiram-loaded copper sulfide nanoparticles for potential anti-glioma therapy

Disulfiram (DSF) is an effective copper (Cu²⁺)-dependent antitumor agent. In the present study, we explored use of transferrin (Tf)-modified DSF/copper sulfide (CuS) nanocomplex (Tf-DSF/CuS) for glioma therapy. Tf was used as glioma targeting motifs, DSF as an anticancer agent, and CuS as a source of Cu²⁺ ions and a photothermal agent. DSF was loaded on CuS by metal-chelation, and released from the nanocomplex under acidic condition. The Tf-DSF/CuS complex exhibited high cytotoxic effect in vitro. Notably, cytotoxic activity was correlated with pH triggered release of Cu²⁺ which initiated non-toxicity to toxicity switch of DSF. Ultrasound-targeted microbubble destruction (UTMD) technique was used for highly selective accumulation of intravenous injected Tf-DSF/CuS in the glioma orthotopic tumor as compared with the free drugs and non-targeted DSF/CuS groups. Magnetic resonance imaging and pathological examinations showed that Tf-DSF/CuS effectively suppressed tumor growth, with an inhibition ratio of ~85%. Additionally, DSF load did not compromise photothermal conversion ability of CuS nanoparticles. Efficacy of the photothermal ablation therapy of Tf-DSF/CuS was evaluated under 808 nm laser irradiation both in vitro and in vivo. These findings show that copper-sulfide based disulfiram nanoparticles are effective agents for anti-glioma therapy.

New Perspectives of Gene Therapy on Polyglutamine Spinocerebellar Ataxias: From Molecular Targets to Novel Nanovectors

Seven of the most frequent spinocerebellar ataxias (SCAs) are caused by a pathological expansion of a cytosine, adenine and guanine (CAG) trinucleotide repeat located in exonic regions of unrelated genes, which in turn leads to the synthesis of polyglutamine (polyQ) proteins. PolyQ proteins are prone to aggregate and form intracellular inclusions, which alter diverse cellular pathways, including transcriptional regulation, protein clearance, calcium homeostasis and apoptosis, ultimately leading to neurodegeneration. At present, treatment for SCAs is limited to symptomatic intervention, and there is no therapeutic approach to prevent or reverse disease progression. This review provides a compilation of the experimental advances obtained in cell-based and animal models toward the development of gene therapy strategies against polyQ SCAs, providing a discussion of their potential application in clinical trials. In the second part, we describe the promising potential of nanotechnology developments to treat polyQ SCA diseases. We describe, in detail, how the design of nanoparticle (NP) systems with different physicochemical and functionalization characteristics has been approached, in order to determine their ability to evade the immune system response and to enhance brain delivery of molecular tools. In the final part of this review, the imminent application of NP-based strategies in clinical trials for the treatment of polyQ SCA diseases is discussed.

Biomimetic Dendrimer-Peptide Conjugates for Early Multi-Target Therapy of Alzheimer's Disease by Inflammatory Microenvironment Modulation

Current therapeutic strategies for Alzheimer's disease (AD) treatments mainly focus on β-amyloid (Aβ) targeting. However, such therapeutic strategies have limited clinical outcomes due to the chronic and irreversible impairment of the nervous system in the late stage of AD. Recently, inflammatory responses, manifested in oxidative stress and glial cell activation, have been reported as hallmarks in the early stages of AD. Based on the crosstalk between inflammatory response and brain cells, a reactive oxygen species (ROS)-responsive dendrimer-peptide conjugate (APBP) is devised to target the AD microenvironment and inhibit inflammatory responses at an early stage. With the modification of the targeting peptide, this nanoconjugate can efficiently deliver peptides to the infected regions and restore the antioxidant ability of neurons by activating the nuclear factor (erythroid-derived 2)-like 2 signaling pathway. Moreover, this multi-target strategy exhibits a synergistic function of ROS scavenging, promoting Aβ phagocytosis, and normalizing the glial cell phenotype. As a result, the nanoconjugate can reduce ROS level, decrease Aβ burden, alleviate glial cell activation, and eventually enhance cognitive functions in APPswe/PSEN1dE9 model mice. These results indicate that APBP can be a promising candidate for the multi-target treatment of AD.

Phenylboronic ester-modified anionic micelles for ROS-stimuli response in HeLa cell

Smart polymers as ideal drug nanocarriers have attracted much attention due to the effective drug delivery, internalization and release once triggered by intracellular stimuli, as well as reduced cytotoxicity. We here reported the anionic micelle consisting of copolymer (PEG-b-PAsp) and a PBE (Phenylboronic Ester) group grafted, which can achieve fast response to intracellular ROS and enhanced anti-tumor activity. With this, PEG-b-PAsp-g-PBE/DOX system showed better tumor growth inhibition when studied on HeLa cell lines with high level of intracellular ROS and its subcutaneous tumor models. Additionally, the administration of PEG-b-PAsp-g-PBE/DOX did cause significantly lower systemic toxicity in comparison with free DOX. Hence, PEG-b-PAsp-g-PBE could be a highly efficient and safe nanocarrier to improve the efficacy of chemotherapeutic.

Transporter-Targeted Nano-Sized Vehicles for Enhanced and Site-Specific Drug Delivery

Nano-devices are recognized as increasingly attractive to deliver therapeutics to target cells. The specificity of this approach can be improved by modifying the surface of the delivery vehicles such that they are recognized by the target cells. In the past, cell-surface receptors were exploited for this purpose, but plasma membrane transporters also hold similar potential. Selective transporters are often highly expressed in biological barriers (e.g., intestinal barrier, blood-brain barrier, and blood-retinal barrier) in a site-specific manner, and play a key role in the vectorial transfer of nutrients. Similarly, selective transporters are also overexpressed in the plasma membrane of specific cell types under pathological states to meet the biological needs demanded by such conditions. Nano-drug delivery systems could be strategically modified to make them recognizable by these transporters to enhance the transfer of drugs across the biological barriers or to selectively expose specific cell types to therapeutic drugs. Here, we provide a comprehensive review and detailed evaluation of the recent advances in the field of transporter-targeted nano-drug delivery systems. We specifically focus on areas related to intestinal absorption, transfer across blood-brain barrier, tumor-cell selective targeting, ocular drug delivery, identification of the transporters appropriate for this purpose, and details of the rationale for the approach.

6-Aminocaproic acid as a linker to improve near-infrared fluorescence imaging and photothermal cancer therapy of PEGylated indocyanine green

Clinical extensive application of indocyanine green (ICG) is limited by several drawbacks such as poor bioenvironmental stability, aggregate propensity, and rapid elimination from the body, etc. In this study, we construct a novel amphiphilic mPEG-ACA-ICG conjugate by modifying synthetic heptamethine cyanine derivative ICG-COOH with a hydrophobic linker 6-aminocaproic acid (ACA) and amino-terminal poly(ethylene glycol) (mPEG-NH₂). The as-prepared mPEG-ACA-ICG conjugate has the ability to self-assemble into micellar aggregates in an aqueous solution with a lower CMC value than mPEG-ICG conjugate without ACA linker. More importantly, compared with free ICG and mPEG-ICG conjugate, mPEG-ACA-ICG nanomicelles exhibited better stability and higher photothermal conversion efficiency upon near-infrared light irradiation due to the intramolecular introduction of a hydrophobic ACA segment. In our in vivo experiment, mPEG-ACA-ICG nanomicelles ensured the formidable effect on tumor photothermal therapy (PTT) and the maximum tumor inhibition rate reached 72.6 %. In addition, real-time determination ability for fluorescence image-guided surgery (FIGS) of mPEG-ACA-ICG nanomicelles was also confirmed on tumor xenograft mice model. Taken together, mPEG-ACA-ICG conjugate may hold great promise for non-invasive cancer theranostics.

Donepezil promotes neurogenesis via Src signaling pathway in a rat model of chronic cerebral hypoperfusion

Donepezil, a selective acetylcholinesterase (AchE) inhibitor, enhances stroke-induced neurogenesis within subventricular zone (SVZ). Src/Pyk-2 is one of the downstream pathways of acetylcholine receptors (AchRs), and has been shown to participate in the activation of fibroblast growth factor receptor (FGFR)/epidermal growth factor receptor (EGFR) signaling in cancer cells. In this study, we investigated whether donepezil could promote SVZ neurogenesis in chronic cerebral hypoperfusion (CCH) injury via Src signaling pathway. In the bilateral carotid artery occlusion (2VO) rat model, we observed more nestin/5-bromo-2'-deoxyuridine (BrdU)-positive cells and doublecortin (DCX)/BrdU-positive cells in the SVZ than that in the sham group. Further, donepezil obviously improved neurologic function after 2VO, induced the greater number of SVZ proliferative NSCs and neuroblasts, and elevated levels of Src, p-FGFR1, p-EGFR, p-Akt and p-Raf in ipsilateral SVZ. Lastly, Src inhibitor KX-01 abolished the beneficial effects of donepezil in 2VO rats. These results suggest that donepezil could upregulate Src signaling pathway to enhance CCH-induced SVZ neurogenesis.

Ligand Conjugated Targeted Nanotherapeutics for Treatment of Neurological Disorders

BACKGROUND

Human brain is amongst the most complex organs in human body, and delivery of therapeutic agents across the brain is a tedious task. Existence of blood brain barrier (BBB) protects the brain from invasion of undesirable substances; therefore it hinders the transport of various drugs used for the treatment of different neurological diseases including glioma, Parkinson's disease, Alzheimer's disease, etc. To surmount this barrier, various approaches have been used such as the use of carrier mediated drug delivery; use of intranasal route, to avoid first pass metabolism; and use of ligands (lactoferrin, apolipoprotein) to transport the drug across the BBB. Ligands bind with proteins present on the cell and facilitate the transport of drug across the cell membrane via. receptor mediated, transporter mediated or adsorptive mediated transcytosis.

OBJECTIVE

The main focus of this review article is to illustrate various studies performed using ligands for delivering drug across BBB; it also describes the procedure used by various researchers for conjugating the ligands to the formulation to achieve targeted action.

METHODS

Research articles that focused on the used of ligand conjugation for brain delivery and compared the outcome with unconjugated formulation were collected from various search engines like PubMed, Science Direct and Google Scholar, using keywords like ligands, neurological disorders, conjugation, etc. Results and Conclusion: Ligands have shown great potential in delivering drug across BBB for treatment of various diseases, yet extensive research is required so that the ligands can be used clinically for treating neurological diseases.

Multifunctional Polyethylene Glycol (PEG)-Poly (Lactic-Co-Glycolic Acid) (PLGA)-Based Nanoparticles Loading Doxorubicin and Tetrahydrocurcumin for Combined Chemoradiotherapy of Glioma

Background

This study aimed to prepare doxorubicin- and tetrahydrocurcumin-loaded and transferrin-modified PEG-PLGA nanoparticles (Tf-NPs-DOX-THC) for enhanced and synergistic chemoradiotherapy.

Material/Methods

Tf-NPs-DOX-THC were prepared via the double-emulsion method. The morphologies and particle sizes of the prepared nanoparticles were examined by TEM and DLS, respectively. The in vitro MTT, apoptosis, and clone formation assays were performed to detect the proliferation and radiosensitivity of cells with various treatments. Cellular uptake assay was also conducted. The tissue distribution of Tf-NPs was investigated by ex vivo DOX fluorescence imaging. The in vivo tumor growth inhibition efficiency of various treatments was evaluated in orthotopic C6 mouse models and C6 subcutaneously grafted mouse models.

Results

Tf-NPs-DOX-THC exhibited high drug-loading efficiency (6.56±0.32%) and desirable particle size (under 250 nm). MTT, apoptosis, and clone formation assays revealed the enhanced anti-cancer activity and favorable radiosensitizing effect of Tf-NPs-DOX-THC. Strong fluorescence was observed in the brains of mice treated with Tf-NPs-DOX. The in vitro release of drug from nanoparticles was in a pH-sensitive manner. Tf-NPs-DOX-THC in combination with radiation also achieved favorable anti-tumor efficacy in vivo.

Conclusions

All results suggest that a combination of Tf-NPs-DOX-THC and radiation is a promising strategy for synergistic and sensitizing chemoradiotherapy of glioma.

Enhanced blood-brain-barrier penetrability and tumor-targeting efficiency by peptide-functionalized poly(amidoamine) dendrimer for the therapy of gliomas

Glioblastoma is one of the most common primary tumor types of central nervous system (CNS) with high malignance and lethality. Although many treatment options are currently available, the therapy of brain cancers remains challenging because of blood-brain-barrier (BBB) which prevents most of the chemotherapeutics into the CNS. In this work, a poly(amidoamine) dendrimer-based carrier was fabricated and modified with angiopep-2 (Ang2) peptide that has been demonstrated to bind to low density lipoprotein receptor-relative protein-1 (LRP1) on the endothelial cells of BBB and could therefore induce BBB penetration of the carrier. To improve tumor-targeting effect towards the glioma sites, the dendrimer was simultaneously functionalized with an epidermal growth factor receptor (EGFR)-targeting peptide (EP-1) which was screened from a "one-bead one-compound" (OBOC) combinatorial library. EP-1 peptide was demonstrated to have high affinity and specificity to EGFR at both the molecular and cellular levels. The dual-targeting dendrimer exhibited outstanding BBB penetrability and glioma targeting efficiency both in vitro and in vivo, which strikingly enhanced the anti-gliomas effect of the drugs and prolonged the survival of gliomas-bearing mice. These results show the potential of the dual-targeting dendrimer-based carrier in the therapy of gliomas through enhancing BBB penetrability and tumor targeting.

Nanoformulations for glioblastoma multiforme: a new hope for treatment

Glioblastoma multiforme (GBM) is the most common primary malignant brain tumor in adults, associated with a high mortality rate and a survival of between 12 and 15 months after diagnosis. Due to current treatment limitations involving surgery, radiotherapy and chemotherapy with temozolamide, there is a high rate of treatment failure and recurrence. To try to overcome these limitations nanotechnology has emerged as a novel alternative. Lipid, polymeric, silica and magnetic nanoparticles, among others, are being developed to improve GBM treatment and diagnosis. These nanoformulations have many advantages, including lower toxicity, biocompatibility and the ability to be directed toward the tumor. This article reviews the progress that have been made and the large variety of nanoparticles currently under study for GBM.

Emerging transporter-targeted nanoparticulate drug delivery systems

Transporter-targeted nanoparticulate drug delivery systems (nano-DDS) have emerged as promising nanoplatforms for efficient drug delivery. Recently, great progress in transporter-targeted strategies has been made, especially with the rapid developments in nanotherapeutics. In this review, we outline the recent advances in transporter-targeted nano-DDS. First, the emerging transporter-targeted nano-DDS developed to facilitate oral drug delivery are reviewed. These include improvements in the oral absorption of protein and peptide drugs, facilitating the intravenous-to-oral switch in cancer chemotherapy. Secondly, the recent advances in transporter-assisted brain-targeting nano-DDS are discussed, focusing on the specific transporter-based targeting strategies. Recent developments in transporter-mediated tumor-targeting drug delivery are also discussed. Finally, the possible transport mechanisms involved in transporter-mediated endocytosis are highlighted, with special attention to the latest findings of the interactions between membrane transporters and nano-DDS.

Peptide decorated glycolipid nanomicelles for drug delivery across the blood–brain barrier (BBB)

Schematic summary of the development of peptide decorated glycolipid nanomicelles for brain delivery by crossing Blood Brain Barrier (BBB).

Enhanced bioreduction-responsive diselenide-based dimeric prodrug nanoparticles for triple negative breast cancer therapy

Efficient drug accumulation in tumor is essential for chemotherapy. We developed redox-responsive diselenide-based high-loading prodrug nanoparticles (NPs) for targeted triple negative breast cancer (TNBC) treatment. Method: Redox-responsive diselenide bond (Se-Se) containing dimeric prodrug (PTXD-Se) was synthesized and co-precipitated with TNBC-targeting amphiphilic copolymers to form ultra-stable NPs (uPA-PTXD NPs). The drug loading capacity and redox-responsive drug release behavior were studied. TNBC targeting effect and anti-tumor effect were also evaluated in vitro and in vivo.Results: On-demand designed paclitaxel dimeric prodrug could co-precipitate with amphiphilic copolymers to form ultra-stable uPA-PTXD NPs with high drug loading capacity. Diselenide bond (Se-Se) in uPA-PTXD NPs could be selectively cleaved by abnormally high reduced potential in tumor microenvironment, releasing prototype drug, thus contributing to improved anti-cancer efficacy. Endowed with TNBC-targeting ligand uPA peptide, uPA-PTXD NPs exhibited reduced systemic toxicity and enhanced drug accumulation in TNBC lesions, thus showed significant anti-tumor efficacy both in vitro and in vivo. Conclusion: The comprehensive advantage of high drug loading, redox-controlled drug release and targeted tumor accumulation suggests uPA-PTXD NPs as a highly promising strategy for effective TNBC treatment.

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.

Fabrication of BSA@AuNC-Based Nanostructures for Cell Fluoresce Imaging and Target Drug Delivery

Drug delivery which can offer efficient and localized drug transportation together with imaging capabilities is highly demanded in the development of cancer theranostic approaches. Herein, we report the construction of bovine serum albumin (BSA) gold nanoclusters (BSA@AuNCs) for cell fluoresce imaging and target drug delivery. BSA@AuNCs were modified with cyclic arginine-glycine-aspartate with the product RGD-BSA@AuNCs to enhance cell internalization of the nanoclusters. Furthermore, doxorubicin hydrochloride or doxorubicin (DOX), a widely used chemotherapy drug, was also used to modify RGD-BSA@AuNCs. The final design of the DOX/RGD-BSA@AuNC system was constructed through the disulfide bond. The physical microstructure and biological characterization of the BSA@AuNCs were realized through high-resolution transmission electron microscopy and confocal laser fluorescence microscopy. As the disulfide bonds were cleaved by glutathione in cancer cells, DOX-SH molecules were released from the nanosystem to inhibit the growth of cancer cells. The as-prepared DOX/RGD-BSA@AuNC system can be used not only to deliver drug but also to achieve the antitumor effect by in vivo imaging, demonstrating its promising applications in cancer treatment.

Folate-Conjugated Polyphosphoester with Reversible Cross-Linkage and Reduction Sensitivity for Drug Delivery

To improve the therapeutic efficacy and circulation stability in vivo, we synthesized a new kind of drug delivery carrier based on folic acid conjugated polyphosphoester via the combined reactions of Michael addition polymerization and esterification. The produced amphiphilic polymer, abbreviated as P(EAEP-AP)-LA-FA, could self-assemble into nanoparticles (NPs) with core-shell structure in water and reversible core cross-linked by lipoyl groups. Using the core cross-linked FA-conjugated nanoparticles (CCL-FA NPs) to encapsulate hydrophobic anticancer drug doxorubicin (DOX), we studied the stability of NPs, in vitro drug release, cellular uptake, and targeting intracellular release compared with both un-cross-linked FA-conjugated nanoparticles (UCL-FA NPs) and core cross-linked nanoparticles without FA conjugation (CCL NPs). The results showed that under the condition of pH 7.4, the DOX-loaded CCL-FA NPs could maintain stable over 72 h, and only a little DOX release (∼15%) was observed. However, under the reductive condition (pH 7.4 containing 10 mM GSH), the disulfide-cross-linked core would be broken up and resulted in 90% of DOX release at the same incubation period. The study of methyl thiazolyl tetrazolium (MTT) assay indicated that the DOX-loaded CCL-FA NPs exhibited higher cytotoxicity (IC₅₀: 0.33 mg L^-1) against HeLa cells than the DOX-loaded CCL NPs without FA. These results indicate that the core cross-linked FA-conjugated nanoparticles have unique stability and targetability.

Transporter-Guided Delivery of Nanoparticles to Improve Drug Permeation across Cellular Barriers and Drug Exposure to Selective Cell Types

Targeted nano-drug delivery systems conjugated with specific ligands to target selective cell-surface receptors or transporters could enhance the efficacy of drug delivery and therapy. Transporters are expressed differentially on the cell-surface of different cell types, and also specific transporters are expressed at higher than normal levels in selective cell types under pathological conditions. They also play a key role in intestinal absorption, delivery via non-oral routes (e.g., pulmonary route and nasal route), and transfer across biological barriers (e.g., blood–brain barrier and blood–retinal barrier. As such, the cell-surface transporters represent ideal targets for nano-drug delivery systems to facilitate drug delivery to selective cell types under normal or pathological conditions and also to avoid off-target adverse side effects of the drugs. There is increasing evidence in recent years supporting the utility of cell-surface transporters in the field of nano-drug delivery to increase oral bioavailability, to improve transfer across the blood–brain barrier, and to enhance delivery of therapeutics in a cell-type selective manner in disease states. Here we provide a comprehensive review of recent advancements in this interesting and important area. We also highlight certain key aspects that need to be taken into account for optimal development of transporter-assisted nano-drug delivery systems.

VEGF-mediated tight junctions pathological fenestration enhances doxorubicin-loaded glycolipid-like nanoparticles traversing BBB for glioblastoma-targeting therapy

The existence of blood-brain barrier (BBB) greatly hindered the penetration and accumulation of chemotherapeutics into glioblastoma (GBM), accompany with poor therapeutic effects. The growth of GBM supervene the impairment of tight junctions (TJs); however, the pathogenesis of BBB breakdown in GBM is essentially poorly understood. This study found that vascular endothelial growth factor (VEGF) secreted by GBM cells plays an important role in increasing the permeability of BBB by disrupting endothelial tight junction proteins claudin-5 and thus gave doxorubicin (DOX)-loaded glycolipid-like nanoparticles (Ap-CSSA/DOX), an effective entrance to brain tumor region for GBM-targeting therapy. In addition, VEGF downregulates the expression of claudin-5 with a dose-dependent mode, and interfering with the VEGF/VEGFR pathway using its inhibitor axitinib could reduce the permeability of BBB and enhance the integrity of the barrier. Ap-CSSA/DOX nanoparticles showed high affinity to expressed low-density lipoprotein receptor-related proteins 1 (LRP1) in both BBB and GBM. And BBB pathological fenestration in GBM further exposed more LRP1 binding sites for Ap-CSSA/DOX nanoparticles targeting to brain tumor, resulting in a higher transmembrane transport ratio in vitro and a stronger brain tumor biodistribution in vivo, and finally realizing a considerable antitumor effect. Overall, taking advantage of BBB pathological features to design an appropriate nanodrug delivery system (NDDS) might provide new insights into other central nervous system (CNS) diseases treatment.

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.

An MSN-PEG-IP drug delivery system and IL13Rα2 as targeted therapy for glioma

A combination of gene therapy and chemotherapy has recently received interest as a targeted therapy for glioma. A mesoporous silica nanoparticle (MSN)-based vehicle coated with IL13Rα2-targeted peptide (IP) using polyethylene glycol (PEG), MSN-PEG-IP (MPI), was constructed and confirmed as a potential glioma-targeted drug delivery system in vitro. In this work, tissue microarray (TMA) results revealed that IL13Rα2 was over-expressed in human glioma tissues and that high expression of IL13Rα2 in patients was associated with poor survival. Doxorubicin (DOX)-loaded MPI (MPI/D) crossed the blood-brain barrier, specifically targeting glioma cells and significantly enhancing the cellular uptake of DOX in glioma cells compared with MSN/DOX (M/D) and MSN-PEG/DOX (MP/D), whereas the normal brain was not affected. Magnetic Resonance Imaging (MRI) examinations showed that the tumour size of glioma-bearing rats in the MPI/D-treated group was much smaller than those in the M/D and MP/D treated groups. Immunofluorescence results demonstrated that MPI/D treatment induced more apoptosis and much less proliferation than the other two treatments. However, the therapeutic effect was weak when IL13Rα2 was knocked down. Furthermore, U87 cells treated with IL-13 and MPI together could increase both STAT6 and P63 expression, which attenuated glioma cell proliferation, invasion and migration compared with cells treated with IL-13 alone. The results of the subcutaneous tumour model also revealed that IL13Rα2 knockdown could hinder cell proliferation and induce more apoptosis. The promising results suggested that MPI can not only deliver DOX to glioma in a targeted manner but also occupy IL13Rα2, which can promote IL-13 binding to IL13Rα1 and activation of the JAK-STAT pathway to induce an anti-glioma effect.

Self-assembled amphiphilic core-shell nanocarriers in line with the modern strategies for brain delivery

Disorders of the central nervous system (CNS) represent increasing social and economic problems all over the world which makes the effective transport of drugs to the brain a crucial need. In the last decade, many strategies were introduced to deliver drugs to the brain trying to overcome the challenge of the blood brain barrier (BBB) using both invasive and non-invasive methods. Non-invasive strategy represented in the application of nanocarriers became very common. One of the most hopeful nanoscopic carriers for brain delivery is core-shell nanocarriers or polymeric micelles (PMs). They are more advantageous than other nanocarriers. They offer small size, ease of preparation, ease of sterilization and the possibility of surface modification with various ligands. Hence, the aim of this review is to discuss modern strategies for brain delivery, micelles as a successful delivery system for the brain and how micelles could be modified to act as "magic bullets" for brain delivery.

Telodendrimers for Physical Encapsulation and Covalent Linking of Individual or Combined Therapeutics

New therapeutics for glioblastoma multiforme and our ability to deliver them using efficient nanocarriers constitute topical areas of research. We report a comparative study of temozolomide and quercetin in the treatment of glioblastoma (GBM) in three-dimensions, and their incorporation into micelles obtained from synthetically articulated architectural copolymers, and a commercially available linear polymer poly(ethylene glycol)-poly(lactic-co-glycolic acid) (PEG-PLGA). A versatile synthetic methodology to telodendrimers, which can be easily adapted to the needs of other therapeutic interventions, is presented. These dendritic block copolymers self-assemble into micelles and offer a platform for single or combination drug therapy. Telodendrimer micelles loaded with quercetin did not exhibit superior cell killing effect over the free drug, but acetazolamide, an inhibitor carbonic anhydrase IX, significantly reduced GBM cell viability in 3D spheroids. Results from these studies show that high loading of drugs into telodendrimer micelles requires a physical fit between the biologically active agent and telodendrimer nanocarrier, and points toward new possibilities for incorporation of chemotherapeutic and other agents to enhance their effectiveness.

Swollen Micelles for the Preparation of Gated, Squeezable, pH-Responsive Drug Carriers

Natural variations in pH levels of tissues in the body make it an attractive stimuli to trigger drug release from a delivery vehicle. A number of such carriers have been developed but achieving high drug loading combined with low leakage at physiological pH and tunable controlled release at the site of action is an ongoing challenge. Here we report a novel strategy for the synthesis of entirely hydrophilic stimuli-responsive nanocarriers with high passive loading efficiency of doxorubicin (DOX), which show good stability at pH 7 and rapid tunable drug release at intracellular pH. The particles (D_h = 120-150 nm), are prepared by cross-linking the core of swollen micelles of the triblock copolymer poly[poly(ethylene glycol) methyl ether methacrylate-b-N,N'-di(methylamino)ethyl methacrylate-b-tert-butyl methacrylate] (poly(PEGMEM A)-b- PDMAEMA-b-PtBMA)). After subsequent deprotection of the tert-butyl groups a hydrophilic poly(methacrylic acid) (PMAA) core is revealed. Due to the negative charge in the acidic core the particles absorb 100% of the DOX from solution at pH 7 at up to 50 wt % DOX/polymer, making them extremely simple to load. Unlike other systems, the DMAEMA "gating" shell ensures low drug leakage at pH 7, whereas physical shrinkage of the MAA core allows rapid release below pH 6. The particles deliver DOX with high efficiency to human pancreatic cancer AsPC-1 cell lines, even lowering the IC50 of DOX. As the particles are stable as a dry powder and can be loaded with any mixture of positively charged drugs without complex synthetic or purification steps, we propose they will find use in a range of delivery applications.

Cyclo(RGD)-Decorated Reduction-Responsive Nanogels Mediate Targeted Chemotherapy of Integrin Overexpressing Human Glioblastoma In Vivo

Cyclo(Arg-Gly-Asp) peptide (cRGD) decorated disulfide (SS) containing poly(vinyl alcohol) nanogels (cRGD-SS-NGs) with an average diameter of 142 nm prepared by inverse nanoprecipitation, "click" reaction, and cRGD conjugation are developed for targeted treatment of integrin overexpressing human glioblastoma in vivo. Doxorubicin (DOX) release from cRGD-SS-NGs is highly inhibited under physiological conditions, while accelerated at endosomal pH and in response to cytoplasmic concentration of glutathione. Confocal microscopy shows that cRGD-SS-NGs facilitate the cellular uptake and intracellular DOX release in α_v β₃ integrin overexpressing human glioblastoma U87-MG cells. DOX-loaded cRGD-SS-NGs present much better killing activity toward U87-MG cells than that for nontargeted nanogels determined by MTT assay. The in vivo imaging and biodistribution studies reveal that DOX-loaded cRGD-SS-NGs have a much better tumor targetability toward human U87-MG glioblastoma xenograft in nude mice. Also the tumor growth is effectively inhibited by treatment with DOX-loaded cRGD-SS-NGs, while continuous tumor growth is observed for mice treated with nondecorated nanogels as well as free DOX. Furthermore, the treatment with DOX-loaded cRGD-SS-NGs has much fewer side effects, rendering these nanogels as a new platform for cancer chemotherapy in vivo.

Development of a hypoxia-triggered and hypoxic radiosensitized liposome as a doxorubicin carrier to promote synergetic chemo-/radio-therapy for glioma

The treatment of malignant primary brain tumors is challenging. Concomitant radiochemotherapy has become the standard clinical treatment for malignant glioma, but there are two critical challenges to overcome in order to increase efficacy. First, glioma is known to have increased resistant to radiation due to its intra-tumoral hypoxia. In addition, the blood-brain barrier (BBB) restricts the distribution of the chemotherapeutic agent to the brain. Therefore, we developed a hypoxic radiosensitizer-prodrug liposome (MLP), in order to deliver DOX to the tumor and to overcome the above challenges, achieving a synergistic chemo-/radiotherapy treatment of malignant glioma. In this study, hypoxic radiosensitizer nitroimidazoles were conjugated with lipid molecules with a hydrolysable ester bond to form MDH. MDH was mixed together with DSPE-PEG2000 and cholesterol to make MLP liposomes, which were found to have strong radiosensitivity and to promote cargo release under hypoxic conditions, due to the properties of nitroimidazoles under hypoxic conditions. MLP/DOX was found to have distinct advantages, including precise and stealthy pharmacokinetics and efficient passive uptake by the tumor. Furthermore, the combination of MLP/DOX and radiotherapy (RT) significantly inhibited glioma growth as assessed by in vivo bioluminescence imaging. These findings suggest that MLP is a promising candidate as a DOX delivery system to enhance the antitumor treatment effects on glioma, owing to synergistic chemo-/radiotherapy.

Charge-reversible and pH-responsive biodegradable micelles and vesicles from linear-dendritic supramolecular amphiphiles for anticancer drug delivery

The linear-dendritic supramolecular amphiphiles could assemble into charge-reversible and pH-responsive biodegradable micelles and vesicles.

Amino Acid Metabolism Abnormity and Microenvironment Variation Mediated Targeting and Controlled Glioma Chemotherapy

Energy metabolism abnormity is one of the most significant hallmarks of cancer. As a result, large amino acid transporter 1 (LAT1) is remarkably overexpressed in both blood-brain-barrier and glioma tumor cells, leading a rapid and sufficient substrate transportation. 3CDIT and 4CDIT are originally synthesized by modifying the existing most potent LAT1 substrate. 3CDIT is selected as its higher glioma-targeting ability. Since the microenvironment variation in tumor cells is another important feature of cancer, a great disparity in adenosine-5'-triphosphate (ATP) and glutathione (GSH) levels between extracellular and intracellular milieu can provide good possibilities for dual-responsive drug release in tumor cells. Doxorubicin (DOX) is successfully intercalated into the ATP aptamer DNA scaffolds, compressed by GSH-responsive polymer pOEI, and modified with 3CDIT to obtain 3CDIT-targeting pOEI/DOX/ATP aptamer nanoparticles (NPs). Enhanced NP accumulation and rapid GSH & ATP dual-responsive DOX release in glioma are demonstrated both in vitro and in vivo. More efficient therapeutic effects are shown with 3CDIT-targeting pOEI/DOX/ATP aptamer NPs than free DOX and no systemic toxicity is observed. Therefore, glioma-targeting delivery and GSH & ATP dual-responsive release guarantee an adequate DOX accumulation within tumor cells and ensure a safe and efficient chemotherapy for glioma.

Doxorubicin-Loaded Nanobubbles Combined with Extracorporeal Shock Waves: Basis for a New Drug Delivery Tool in Anaplastic Thyroid Cancer

BACKGROUND

No standard chemotherapy is available for anaplastic thyroid cancer (ATC). Drug-loaded nanobubbles (NBs) are a promising innovative anticancer drug formulation, and combining them with an externally applied trigger may further control drug release at the target region. Extracorporeal shock waves (ESWs) are acoustic waves widely used in urology and orthopedics, with no side effects. The aim of the present work was to combine ESWs and new doxorubicin-loaded glycol chitosan NBs in order to target doxorubicin and enhance its antitumor effect in ATC cell lines.

METHODS

CAL-62 and 8305C cells were treated with empty NBs, fluorescent NBs, free doxorubicin, and doxorubicin-loaded NBs in the presence or in the absence of ESWs. NB entrance was evaluated by fluorescence microscopy and flow cytofluorimetry. Cell viability was assessed by Trypan Blue exclusion and WST-1 proliferation assays. Doxorubicin intracellular content was measured by high-performance liquid chromatography.

RESULTS

Treatment with empty NBs and ESWs, even in combination, was safe, as cell viability and growth were not affected. Loading NBs with doxorubicin and combining them with ESWs generated the highest cytotoxic effect, resulting in drug GI50 reduction of about 40%. Mechanistically, ESWs triggered intracellular drug release from NBs, resulting in the highest nuclear drug content.

CONCLUSIONS

Combined treatment with doxorubicin-loaded NBs and ESWs is a promising drug delivery tool for ATC treatment with the possibility of using lower doxorubicin doses and thus limiting its systemic side effects.