The therapeutic efficacy of conjugated linoleic acid - paclitaxel on glioma in the rat

Steady-State Delivery and Chemical Modification of Food Nutrients to Improve Cancer Intervention Ability

Cancer is a crucial global health problem, and prevention is an important strategy to reduce the burden of the disease. Daily diet is the key modifiable risk factor for cancer, and an increasing body of evidence suggests that specific nutrients in foods may have a preventive effect against cancer. This review summarizes the current evidence on the role of nutrients from foods in cancer intervention. It discusses the potential mechanisms of action of various dietary components, including phytochemicals, vitamins, minerals, and fiber. The findings of epidemiological and clinical studies on their association with cancer risk are highlighted. The foods are rich in bioactive compounds such as carotenoids, flavonoids, and ω-3 fatty acids, which have been proven to have anticancer properties. The effects of steady-state delivery and chemical modification of these food's bioactive components on anticancer and intervention are summarized. Future research should focus on identifying the specific bioactive compounds in foods responsible for their intervention effects and exploring the potential synergistic effects of combining different nutrients in foods. Dietary interventions that incorporate multiple nutrients and whole foods may hold promise for reducing the risk of cancer and improving overall health.

Progress in the Treatment of Central Nervous System Diseases Based on Nanosized Traditional Chinese Medicine

Traditional Chinese Medicine (TCM) is widely used in clinical practice to treat diseases related to central nervous system (CNS) damage. However, the blood-brain barrier (BBB) constitutes a significant impediment to the effective delivery of TCM, thus substantially diminishing its efficacy. Advances in nanotechnology and its applications in TCM (also known as nano-TCM) can deliver active ingredients or components of TCM across the BBB to the targeted brain region. This review provides an overview of the physiological and pathological mechanisms of the BBB and systematically classifies the common TCM used to treat CNS diseases and types of nanocarriers that effectively deliver TCM to the brain. Additionally, drug delivery strategies for nano-TCMs that utilize in vivo physiological properties or in vitro devices to bypass or cross the BBB are discussed. This review further focuses on the application of nano-TCMs in the treatment of various CNS diseases. Finally, this article anticipates a design strategy for nano-TCMs with higher delivery efficiency and probes their application potential in treating a wider range of CNS diseases.

Blood-brain barrier transporters: a translational consideration for CNS delivery of neurotherapeutics

INTRODUCTION

Successful neuropharmacology requires optimization of CNS drug delivery and, by extension, free drug concentrations at brain molecular targets. Detailed assessment of blood-brain barrier (BBB) physiological characteristics is necessary to achieve this goal. The 'next frontier' in CNS drug delivery is targeting BBB uptake transporters, an approach that requires evaluation of brain endothelial cell transport processes so that effective drug accumulation and improved therapeutic efficacy can occur.

AREAS COVERED

BBB permeability of drugs is governed by tight junction protein complexes (i.e., physical barrier) and transporters/enzymes (i.e., biochemical barrier). For most therapeutics, a component of blood-to-brain transport involves passive transcellular diffusion. Small molecule drugs that do not possess acceptable physicochemical characteristics for passive permeability may utilize putative membrane transporters for CNS uptake. While both uptake and efflux transport mechanisms are expressed at the brain microvascular endothelium, uptake transporters can be targeted for optimization of brain drug delivery and improved treatment of neurological disease states.

EXPERT OPINION

Uptake transporters represent a unique opportunity to optimize brain drug delivery by leveraging the endogenous biology of the BBB. A rigorous understanding of these transporters is required to improve translation from the bench to clinical trials and stimulate the development of new treatment paradigms for neurological diseases.

Oral lipid-based formulations alter delivery of cannabidiol to different anatomical regions in the brain

Delivery to the brain is a challenging task due to its protection by the blood-brain barrier (BBB). Lipids and fatty acids are reported to affect the permeability of the BBB, although this has not been reported following oral administration. Cannabidiol (CBD) has high therapeutic potential in the brain, therefore, this work investigated CBD delivery to anatomical brain regions following oral administration in lipid-based and lipid-free vehicles. All formulations resulted in a short brain T_max (1 h) and brain-plasma ratios ≥ 3.5, with retention up to 18 h post administration. The highest CBD delivery was observed in the olfactory bulb and striatum, and the medulla pons and cerebellum the lowest. The lipid-free vehicle led to the highest levels of CBD in the whole brain. However, when each anatomical region was assessed individually, the long chain triglyceride-rich rapeseed oil formulation commonly showed optimal performance. The medium chain triglyceride-rich coconut oil formulation did not result in the highest CBD concentration in any brain region. Overall, differences in CBD delivery to the whole brain and various brain regions were observed following administration in different formulations, indicating that the oral formulation selection may be important for optimal delivery to specific regions of the brain.

Exosomal miR-1304-3p promotes breast cancer progression in African Americans by activating cancer-associated adipocytes

Breast cancer displays disparities in mortality between African Americans and Caucasian Americans. However, the exact molecular mechanisms remain elusive. Here, we identify miR-1304-3p as the most upregulated microRNA in African American patients. Importantly, its expression significantly correlates with poor progression-free survival in African American patients. Ectopic expression of miR-1304 promotes tumor progression in vivo. Exosomal miR-1304-3p activates cancer-associated adipocytes that release lipids and enhance cancer cell growth. Moreover, we identify the anti-adipogenic gene GATA2 as the target of miR-1304-3p. Notably, a single nucleotide polymorphism (SNP) located in the miR-1304 stem-loop region shows a significant difference in frequencies of the G allele between African and Caucasian American groups, which promotes the maturation of miR-1304-3p. Therefore, our results reveal a mechanism of the disparity in breast cancer progression and suggest a potential utility of miR-1304-3p and the associated SNP as biomarkers for predicting the outcome of African American patients.

Amalgamation of Nanoparticles within Drug Carriers: A Synergistic Approach or a Futile Attempt?

In recent years, nanotechnology has gained much attention from scientists and significant advances in therapeutic potential. Nano-delivery systems have emerged as an effective way in order to improve the therapeutic properties of drugs including solubility, stability, prolongation of half-life as well as promoting the accumulation of drug at the target site. The nanoparticles have also been incorporated into various conventional drug delivery systems. This review study aims to introduce the amalgamation of nanoparticles into drug carriers. To overcome the limitations of single nanoparticles such as toxicity, high instability, rapid drug release as well as limited drug loading capacity, a multi-component system is developed. Liposomes, microparticles, nanofibers, dendrimers etc., are promising drug carriers, having some limitations that can be minimized, and the compilation of nanoparticles synergizes the properties. The amalgamated nanocarriers are used for the diagnostic purpose as well as treatment of various chronic diseases. It also increases the solubility of hydrophobic drugs. However, each system has its advantages and disadvantages based on its physicochemical properties, efficacy, and other parameters. This review details the past and present state of development for the fusion of nanoparticles within drug carriers and from which we identify future research works needed for the same.

Paclitaxel Drug Delivery Systems: Focus on Nanocrystals' Surface Modifications

Paclitaxel (PTX) is a chemotherapeutic agent that belongs to the taxane family and which was approved to treat various kinds of cancers including breast cancer, ovarian cancer, advanced non-small-cell lung cancer, and acquired immunodeficiency syndrome (AIDS)-related Kaposi’s sarcoma. Several delivery systems for PTX have been developed to enhance its solubility and pharmacological properties involving liposomes, nanoparticles, microparticles, micelles, cosolvent methods, and the complexation with cyclodextrins and other materials that are summarized in this article. Specifically, this review discusses deeply the developed paclitaxel nanocrystal formulations. As PTX is a hydrophobic drug with inferior water solubility properties, which are improved a lot by nanocrystal formulation. Based on that, many studies employed nano-crystallization techniques not only to improve the oral delivery of PTX, but IV, intraperitoneal (IP), and local and intertumoral delivery systems were also developed. Additionally, superior and interesting properties of PTX NCs were achieved by performing additional modifications to the NCs, such as stabilization with surfactants and coating with polymers. This review summarizes these delivery systems by shedding light on their route of administration, the methods used in the preparation and modifications, the in vitro or in vivo models used, and the advantages obtained based on the developed formulations.

Is Oral Lipid-Based Delivery for Drug Targeting to the Brain Feasible?

This review outlines the feasibility of oral lipid-based targeted delivery of drugs to the brain, including permeation of the central nervous system's (CNS) protective blood-brain barrier (BBB). The structure of the BBB and disruption caused by varying disease states highlights the need for disease-specific approaches to alter permeation. Disruption during disease state, and the effects of certain molecules on the barrier, demonstrate the possibility of exploiting such BBB disruption for drug delivery. Many administration methods can be used to target the brain, but oral administration is considered ideal for chronic, long-term illnesses. Several lipids that have been shown to facilitate drug delivery into the brain after systemic administration, but could also be delivered orally are discussed, including oleic acid, triolein, alkylglycerol, and conjugates of linoleic and myristic acids. Current data reveal the potential for the use of such lipids as part of oral formulations for delivery to the brain by reaching sufficient plasma levels after administration to increase the permeability of the BBB. However, gaps in the literature remain regarding the concentrations and form of most lipids required to produce the desired effects. The use of lipids via oral delivery for brain targeting has not been investigated thoroughly enough to determine with certainty if similar permeability-enhancing effects would be observed as for parenteral administration. In conclusion, further research to fill research gaps is needed, but the limited evidence suggests that oral lipid-based drug delivery for brain targeting is potentially feasible.

Antitumor Activity of α-Linolenic Acid-Paclitaxel Conjugate Nanoparticles: In vitro and in vivo

Purpose

Small molecule modified antitumor drug conjugate nanoparticles have the advantages of high drug loading, simple synthesis and preparation, and better biocompatibility. Due to the large demand for exogenous α-linolenic acid (ALA) by tumor cells, we synthesized α-linolenic acid-paclitaxel conjugate (ALA-PTX) and prepared α-linolenic acid-paclitaxel conjugate nanoparticles (ALA-PTX NPs), in order to obtain better tumor cellular uptake and antitumor activity in vitro and in vivo.

Methods

We synthesized and characterized ALA-PTX, and then prepared and characterized ALA-PTX NPs. The cellular uptake, uptake pathways, intracellular behavior, in vitro and in vivo antitumor activity of ALA-PTX NPs were evaluated.

Results

The size of ALA-PTX NPs was approximately 110.7±1.7 nm. The drug loading was approximately 90% (w/w) with CrEL-free and organic solvent-free characteristics. The cellular uptake of ALA-PTX NPs was significantly higher than that of PTX injection by MCF-7, MCF-7/ADR and HepG2 cells. In these three cell lines, the cellular uptake of ALA-PTX NPs at 6h was approximately 1.5-2.6 times higher than that of PTX injection. ALA-PTX NPs were ingested through clathrin-mediated endocytosis, then transferred to lysosomes, and could dissolve in cells to play an antitumor activity. The in vitro and in vivo antitumor activity of ALA-PTX NPs was confirmed in MCF-7/ADR and HepG2 cell models and tumor-bearing nude mouse models.

Conclusion

ALA-PTX NPs developed in our study could provide a new method for the preparation of nano-delivery systems suitable for antitumor therapy that could increase tumor cellular uptake and enhance antitumor activity.

Nanoparticulation of Prodrug into Medicines for Cancer Therapy

This article provides a broad spectrum about the nanoprodrug fabrication advances co-driven by prodrug and nanotechnology development to potentiate cancer treatment. The nanoprodrug inherits the features of both prodrug concept and nanomedicine know-how, attempts to solve underexploited challenge in cancer treatment cooperatively. Prodrugs can release bioactive drugs on-demand at specific sites to reduce systemic toxicity, this is done by using the special properties of the tumor microenvironment, such as pH value, glutathione concentration, and specific overexpressed enzymes; or by using exogenous stimulation, such as light, heat, and ultrasound. The nanotechnology, manipulating the matter within nanoscale, has high relevance to certain biological conditions, and has been widely utilized in cancer therapy. Together, the marriage of prodrug strategy which shield the side effects of parent drug and nanotechnology with pinpoint delivery capability has conceived highly camouflaged Trojan horse to maneuver cancerous threats.

Bioactive Heterocyclic Compounds as Potential Therapeutics in the Treatment of Gliomas: A Review

Cancer is one of the most alarming diseases, with an estimation of 9.6 million deaths in 2018. Glioma occurs in glial cells surrounding nerve cells. The majority of the patients with gliomas have a terminal prognosis, and the ailment has significant sway on patients and their families, be it physical, psychological, or economic wellbeing. As Glioma exhibits, both intra and inter tumour heterogeneity with multidrug resistance and current therapies are ineffective. So the development of safer anti gliomas agents is the need of hour. Bioactive heterocyclic compounds, eithernatural or synthetic,are of potential interest since they have been active against different targets with a wide range of biological activities, including anticancer activities. In addition, they can cross the biological barriers and thus interfere with various signalling pathways to induce cancer cell death. All these advantages make bioactive natural compounds prospective candidates in the management of glioma. In this review, we assessed various bioactive heterocyclic compounds, such as jaceosidin, hispudlin, luteolin, silibinin, cannabidiol, tetrahydrocannabinol, didemnin B, thymoquinone, paclitaxel, doxorubicin, and cucurbitacins for their potential anti-glioma activity. Also, different kinds of chemical reactions to obtain various heterocyclic derivatives, e.g. indole, indazole, benzimidazole, benzoquinone, quinoline, quinazoline, pyrimidine, and triazine, are listed.

A review on engineered magnetic nanoparticles in Non-Small-Cell lung carcinoma targeted therapy

There are growing appeals forthe design of efficacious treatment options for non-small-cell lung carcinoma (NSCLC) as it accrues to ~ 85% cases of lung cancer. Although platinum-based doublet chemotherapy has been the main therapeutic intervention in NSCLC management, this leads to myriad of problems including intolerability to the doublet regimens and detrimental side effects due to high doses. A new approach is therefore needed and warrants the design of targeted drug delivery systems that can halt tumor proliferation and metastasis by targeting key molecules, while exhibiting minimal side effects and toxicity. This review aims to explore the rational design of magnetic nanoparticles for the development of tumor-targeting systems for NSCLC. In the review, we explore the anticancer merits of conjugated linoleic acid (CLA) and provide a concise incursion into its application for the invention of functionalized magnetic nanoparticles in the targeted treatment of NSCLC. Recent nanoparticle-based targeted chemotherapies for targeting angiogenesis biomarkers in NSCLC will also be reviewed to further highlight versatility of magnetic nanoparticles. These developments through molecular tuning at the nanoscale and supported by comprehensive pre-clinical studies could lead to the establishment of precise nanosystems for tumor-homing cancer therapy.

Unsaturated fatty acids as a co-therapeutic agents in cancer treatment

Chemotherapy is standard treatments for many malignancies. However, in most cases, this method is not able to induce apoptosis and in many cases, with cancer recurrence, leads to patient death. There are several procedure to control and suppress malignant cells, but among these methods, administration of ɷ-3 fatty acids and ɷ-6 fatty due to their destructive effects on cancer cells is more prominent. Many clinical studies have shown beneficial effects of ɷ-3 and ɷ-6 fatty acids in cardiovascular disorders, asthma, rheumatoid arthritis, osteoporosis and in most cancers such as colon, breast, prostate and other malignancies. Studies showed that polyunsaturated fatty acids (PUFAs) have a toxic effect on cancer cells. However, the exact mechanism of how ɷ- fatty acids affect cancer cells is still unknown. In this review alternative issues of malignancies co-treatments agents such as PUFAs have been studied. Also, the latest known PUFAs mechanisms on malignancies have been described.

Brain metastasis models: What should we aim to achieve better treatments?

Brain metastasis is emerging as a unique entity in oncology based on its particular biology and, consequently, the pharmacological approaches that should be considered. We discuss the current state of modelling this specific progression of cancer and how these experimental models have been used to test multiple pharmacologic strategies over the years. In spite of pre-clinical evidences demonstrating brain metastasis vulnerabilities, many clinical trials have excluded patients with brain metastasis. Fortunately, this trend is getting to an end given the increasing importance of secondary brain tumors in the clinic and a better knowledge of the underlying biology. We discuss emerging trends and unsolved issues that will shape how we will study experimental brain metastasis in the years to come.

Opportunities and challenges of fatty acid conjugated therapeutics

Instability, poor cellular uptake and unfavorable pharmacokinetics and biodistribution of many therapeutic molecules require modification in their physicochemical properties. The conjugation of these APIs with fatty acids has demonstrated an enhancement in their lipophilicity and stability. The improvement in the formulations that resulted from the conjugation of a drug with a fatty acid includes increased half-life, enhanced cellular uptake and retention, targeted tumor delivery, reduced chemoresistance in cancer, and improved blood-brain-barrier (BBB) penetration. In this review, various therapeutic molecules, including small molecules, peptides and oligonucleotides, that have been conjugated with fatty acid have been thoroughly discussed along with various conjugation strategies. The application of nano-system based delivery is gaining a lot of attention due to its ability to provide controlled drug release, targeting and reducing the extent of side effects. This review also covers various nano-carriers that have been utilized for the delivery of fatty acid drug conjugates. The enhanced lipophilicity of the drug-fatty acid conjugate has shown to enhance the affinity of the drug towards these carriers, thereby increasing the entrapment efficiency and formulation performance.

Aptamer-Based In Vivo Therapeutic Targeting of Glioblastoma

Glioblastoma (GBM) is the most aggressive, infiltrative, and lethal brain tumor in humans. Despite the extensive advancement in the knowledge about tumor progression and treatment over the last few years, the prognosis of GBM is still very poor due to the difficulty of targeting drugs or anticancer molecules to GBM cells. The major challenge in improving GBM treatment implicates the development of a targeted drug delivery system, capable of crossing the blood–brain barrier (BBB) and specifically targeting GBM cells. Aptamers possess many characteristics that make them ideal novel therapeutic agents for the treatment of GBM. They are short single-stranded nucleic acids (RNA or ssDNA) able to bind to a molecular target with high affinity and specificity. Several GBM-targeting aptamers have been developed for imaging, tumor cell isolation from biopsies, and drug/anticancer molecule delivery to the tumor cells. Due to their properties (low immunogenicity, long stability, and toxicity), a large number of aptamers have been selected against GBM biomarkers and tested in GBM cell lines, while only a few of them have also been tested in in vivo models of GBM. Herein, we specifically focus on aptamers tested in GBM in vivo models that can be considered as new diagnostic and/or therapeutic tools for GBM patients’ treatment.

Emerging insights on drug delivery by fatty acid mediated synthesis of lipophilic prodrugs as novel nanomedicines

Many drug molecules that are currently in the market suffer from short half-life, poor absorption, low specificity, rapid degradation, and resistance development. The design and development of lipophilic prodrugs can provide numerous benefits to overcome these challenges. Fatty acids (FAs), which are lipophilic biomolecules constituted of essential components of the living cells, carry out many necessary functions required for the development of efficient prodrugs. Chemical conjugation of FAs to drug molecules may change their pharmacodynamics/pharmacokinetics in vivo and even their toxicity profile. Well-designed FA-based prodrugs can also present other benefits, such as improved oral bioavailability, promoted tumor targeting efficiency, controlled drug release, and enhanced cellular penetration, leading to improved therapeutic efficacy. In this review, we discuss diverse drug molecules conjugated to various unsaturated FAs. Furthermore, various drug-FA conjugates loaded into various nanostructure delivery systems, including liposomes, solid lipid nanoparticles, emulsions, nano-assemblies, micelles, and polymeric nanoparticles, are reviewed. The present review aims to inspire readers to explore new avenues in prodrug design based on the various FAs with or without nanostructured delivery systems.

Oleic Acid Copolymer as A Novel Upconversion Nanomaterial to Make Doxorubicin-Loaded Nanomicelles with Dual Responsiveness to pH and NIR

Oleic acid (OA) as main component of plant oil is an important solvent but seldom used in the nanocarrier of anticancer drugs because of strong hydrophobicity and little drug release. In order to develop a new type of OA nanomaterial with dual responses to pH and near infrared light (NIR) to achieve the intelligent delivery of anticancer drugs. The novel OA copolymer (mPEG-PEI-(NBS, OA)) was synthesized by grafting OA and o-nitrobenzyl succinate (NBS) onto mPEGylated polyethyleneimine (mPEG-PEI) by amidation reaction. It was further conjugated with NaYF₄:Yb³⁺/Er³⁺ nanoparticles, and encapsulated doxorubicin (DOX) through self-assembly to make upconversion nanomicelles with dual response to pH and NIR. Drug release behavior of DOX, physicochemical characteristics of the nanomicelles were evaluated, along with its cytotoxic profile, as well as the degree of cellular uptake in A549 cells. The encapsulation efficiency and drug loading capacity of DOX in the nanomicelles were 73.84% ± 0.58% and 4.62% ± 0.28%, respectively, and the encapsulated DOX was quickly released in an acidic environment exposed to irradiation at 980 nm. The blank nanomicelles exhibited low cytotoxicity and excellent biocompatibility by MTT assay against A549 cells. The DOX-loaded nanomicelles showed remarkable cytotoxicity to A549 cells under NIR, and promoted the cellular uptake of DOX into the cytoplasm and nucleus of cancer cells. OA copolymer can effectively deliver DOX to cancer cells and achieve tumor targeting through a dual response to pH and NIR.

Overcoming the Blood-Brain Barrier: Successes and Challenges in Developing Nanoparticle-Mediated Drug Delivery Systems for the Treatment of Brain Tumours

High-grade gliomas are still characterized by a poor prognosis, despite recent advances in surgical treatment. Chemotherapy is currently practiced after surgery, but its efficacy is limited by aspecific toxicity on healthy cells, tumour cell chemoresistance, poor selectivity, and especially by the blood–brain barrier (BBB). Thus, despite the large number of potential drug candidates, the choice of effective chemotherapeutics is still limited to few compounds. Malignant gliomas are characterized by high infiltration and neovascularization, and leaky BBB (the so-called blood–brain tumour barrier); surgical resection is often incomplete, leaving residual cells that are able to migrate and proliferate. Nanocarriers can favour delivery of chemotherapeutics to brain tumours owing to different strategies, including chemical stabilization of the drug in the bloodstream; passive targeting (because of the leaky vascularization at the tumour site); inhibition of drug efflux mechanisms in endothelial and cancer cells; and active targeting by exploiting carriers and receptors overexpressed at the blood–brain tumour barrier. Within this concern, a suitable nanomedicine-based therapy for gliomas should not be limited to cytotoxic agents, but also target the most important pathogenetic mechanisms, including cell differentiation pathways and angiogenesis. Moreover, the combinatorial approach of cell therapy plus nanomedicine strategies can open new therapeutical opportunities. The major part of attempted preclinical approaches on animal models involves active targeting with protein ligands, but, despite encouraging results, a few number of nanomedicines reached clinical trials, and most of them include drug-loaded nanocarriers free of targeting ligands, also because of safety and scalability concerns.

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

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

Anticancer activities of fatty acids and their heterocyclic derivatives

Traditional chemotherapy relies on the premise that rapidly proliferating cancer cells are more likely to be killed by a cytotoxic agent, but in reality, the long-standing problem of chemotherapy is the lack of tumor-specific treatments. Apart from the impact on tumor cells, the drugs' major limitation is their severe adverse side effects on normal cells and tissues. Nutritional and epidemiological studies have indicated that cancer progression is correlated with the consumption of fatty acids, but the exact mechanisms still remain unknown. In the first part of our review, we discussed the beneficial effects of free fatty acids (saturated and unsaturated) on the progress of carcinogenesis in different tumor cell lines. We presented various mechanisms proposed in the literature, which explain the possible impact on the cells metabolism. The second part describes modifications of different fatty acids with existing anticancer drugs and heterocyclic moieties by condensation reactions. Such conjugations increased the tissue selectivity and made chemotherapy potentially more effective and less toxic in in vivo and in vitro studies. This fatty acid modifications, which change the activity of compounds, their uptake selectivity and alter drug delivery methods, may be the key to unlocking true medical potential of fatty acids.

Lipase Catalyzed Acidolysis for Efficient Synthesis of Phospholipids Enriched with Isomerically Pure cis-9,trans-11 and trans-10,cis-12 Conjugated Linoleic Acid

The production of phospholipid (PL) conjugates with biologically active compounds is nowadays an extensively employed approach. This type of phospholipids conjugates could improve bioavailability of many poorly absorbed active compounds such as isomers of conjugated linoleic acid (CLA), which exhibit versatile biological effects. The studies were carried out to elaborate an efficient enzymatic method for the synthesis of phospholipids with pure (>90%) cis-9,trans-11 and trans-10,cis-12 CLA isomers. For this purpose, three commercially available immobilized lipases were examined in respect to specificity towards CLA isomers in acidolysis of egg-yolk phosphatidylcholine (PC). Different incorporation rates were observed for the individual CLA isomers. Under optimal conditions: PC/CLA molar ratio 1:6; Rhizomucor miehei lipase loading 24% wt. based on substrates; heptane; DMF, 5% (v/v); water activity (aw), 0.11; 45 °C; magnetic stirring, 300 rpm; 48 h., effective incorporation (EINC) of CLA isomers into PC reached ca. 50%. The EINC of CLA isomers was elevated for 25–30% only by adding a water mimic (DMF) and reducing aw to 0.11 comparing to the reaction system performed at aw = 0.23. The developed method of phosphatidylcholine acidolysis is the first described in the literature dealing with isometrically pure CLA and allow to obtain very high effective incorporation.

PEGylation of lipophilic SN38 prodrug with DSPE-mPEG2000 versus cremophor EL: comparative study for intravenous chemotherapy

The lipophilic prodrug of hydrophobic drugs with well-designed molecular structures can form stable pure prodrug nanoparticles (NPs), but rapid NPs aggregation in plasma greatly restricted their direct use for intravenous chemotherapy. To address this, DSPE-mPEG2000 and Cremophor EL are two of the most widely used lipophilic PEG derivatives to enhance their colloidal stability in plasma. However, their drug delivery performances have never been comparatively studied. Here, a redox-responsive lipophilic prodrug of SN38 was chosen as the model drug for such comparative investigations. We found that Cremophor EL/NPs having a small diameter (∼15 nm) and poor kinetic stability displayed an enhanced cell internalization, higher cytotoxicity and prolonged circulation time as compared with DSPE-mPEG2000/NPs. Most importantly, these superiorities further resulted in a much more potent antitumor activity in CT26 colorectal cancer xenograft, but the increased loss of body weight was also noted. These results suggested that Cremophor EL could be more advantageous than DSPE-mPEG2000 in terms of the improvement of antitumor activity, but the enhanced toxicity warranted further attention in the future study.

Hydrophilic Fluorescent Nanoprodrug of Paclitaxel for Glioblastoma Chemotherapy

Highly water-soluble, nontoxic organic nanoparticles on which paclitaxel (PTX), a hydrophobic anticancer drug, has been covalently bound via an ester linkage (4.5% of total weight) have been prepared for the treatment of glioblastoma. These soft fluorescent organic nanoparticles (FONPs), obtained from citric acid and diethylenetriamine by microwave-assisted condensation, show suitable size (Ø = 17-30 nm), remarkable solubility in water, softness as well as strong blue fluorescence in an aqueous environment that are fully retained in cell culture medium. Moreover, these FONPs were demonstrated to show in vitro safety and preferential internalization in glioblastoma cells through caveolin/lipid raft-mediated endocytosis. The PTX-conjugated FONPs retain excellent solubility in water and remain stable in water (no leaching), while they showed anticancer activity against glioblastoma cells in two-dimensional and three-dimensional culture. PTX-specific effects on microtubules reveal that PTX is intracellularly released from the nanocarriers in its active form, in relation with an intracellular-promoted lysis of the ester linkage. As such, these hydrophilic prodrug formulations hold major promise as biocompatible nanotools for drug delivery.

Herceptin-conjugated paclitaxel loaded PCL-PEG worm-like nanocrystal micelles for the combinatorial treatment of HER2-positive breast cancer

We have constructed Herceptin-conjugated, paclitaxel (PTX) loaded, PCL-PEG worm-like nanocrystal micelles (PTX@PCL-PEG-Herceptin) for the combinatorial therapy of HER2-positive breast cancer that exploit the specific targeting of Herceptin to HER2-positive breast cancer cells. Firstly, amphiphilic PCL₂₀₀₀-MPEG₂₀₀₀ and PCL₅₀₀₀-PEG₂₀₀₀-CHO were selected as the optimized matrix to wrap PTX that self-assembled into worm-like micelles with internal nanocrystal structures (PTX@PCL-PEG). Then the aldehydes of PCL₅₀₀₀-PEG₂₀₀₀-CHO exposed on the outside surface of PTX@PCL-PEG were utilized to react with the primary amines of Herceptin and formed stable, carbon-nitrogen single linkers (-C-N-) between the antibodies and nanoparticles. This study shows PTX@PCL-PEG-Herceptin remained relatively stable in the circulation and in the tumor microenvironment, and rapidly targeted and entered into the HER2-overexpressing tumor cells while sparing normal tissues from the toxic effects. PTX@PCL-PEG-Herceptin shrank the tumors and prolonged survival time in a SKBR-3-tumor-xenograft, nude mice model more effectively than TAXOL®, PTX@PCL-PEG, Herceptin+TAXOL® and Herceptin+PTX@PCL-PEG. Mechanistic studies showed that PTX@PCL-PEG-Herceptin entered into the HER2-positive tumor cells through the caveolin-mediated pathway. The conjugated Herceptin greatly enhanced the binding ability of the nanoparticle to the targeted SKBR-3 cells. This novel strategy provides a rational and simple antibody-conjugated-nanoparticle platform for the clinical application of combinatorial anticancer treatment.

Poly(ethylene glycol)-block-poly(d,l-lactic acid) micelles containing oligo(lactic acid)8-paclitaxel prodrug: In Vivo conversion and antitumor efficacy

Poly(ethylene glycol)-block-poly(d,l-lactic acid) (PEG-b-PLA) micelles affect drug solubilization, and a paclitaxel (PTX) loaded-PEG-b-PLA micelle (PTX-PM) is approved for cancer treatment due to injection safety and dose escalation (Genexol-PM®) compared to Taxol®. However, PTX-PM is unstable in blood, has rapid clearance, and causes dose-limiting toxicity. We have synthesized a prodrug for PTX (7-OH), using oligo(lactic acid) as a novel pro-moiety (o(LA)₈-PTX) specifically for PEG-b-PLA micelles, gaining higher loading and slower release of o(LA)₈-PTX over PTX. Notably, o(LA)₈-PTX prodrug converts into PTX by a backbiting reaction in vitro, without requiring esterases. We hypothesize that o(LA)₈-PTX-loaded PEG-b-PLA micelles (o(LA)₈-PTX-PM) has a lower C_max and higher plasma AUC than PTX-PM for improved therapeutic effectiveness. In Sprague-Dawley rats at 10 mg/kg, compared to o(LA)₈-PTX-PM (10% w/w loading) and PTX-PM (10%), o(LA)₈-PTX-PM (50% w/w loading) produces a 2- and 3-fold higher plasma AUC_0-24 of PTX, lactic acid-PTX, and o(LA)₂-PTX (o(LA)_0-2-PTX), respectively. For o(LA)₈-PTX-PM at 10 and 50% w/w loading, PTX and lactic acid-PTX are major bioactive metabolites, respectively. Fast prodrug conversion of o(LA)₈-PTX in vivo versus in vitro (by backbiting) suggests that o(LA)₈ is a good substrate for esterases. At 60 mg/kg (qwx3), o(LA)₈-PTX-PM (50%) has higher antitumor activity than o(LA)₈-PTX-PM (10%) and PTX-PM (10%) in a syngeneic 4T1-luc breast tumor model based on measurements of tumor volume, 4T1-luc breast tumor bioluminescence, and survival. Importantly, intravenous administration of o(LA)₈-PTX-PM is well tolerated by BALB/c mice. In summary, oligo(lactic acid)₈-PTX is more compatible than PTX with PEG-b-PLA micelles, more stable, and may expand the role of PEG-b-PLA micelles from "solubilizer" into "nanocarrier" for PTX as a next-generation taxane for cancer.

Anti-tumour activity of low molecular weight heparin doxorubicin nanoparticles for histone H1 high-expressive prostate cancer PC-3M cells

Nucleus-targeting drug delivery systems (NTDDs) deliver chemotherapeutic agents to nuclei in order to improve the efficacy of anti-tumour therapy. Histone H1 (H1) plays a key role in establishing and maintaining higher order chromatin structures and could bind to cell membranes. In the present study, we selected H1 as a target to prepare a novel H1-mediated NTDD. Low molecular weight heparin (LMHP) and doxorubicin (DOX) were combined to form LMHP-DOX. Then, a novel NTDD consisting of LMHP-DOX nanoparticles (LMHP-DOX NPs) was prepared by self-assembly. The characteristics of LMHP-DOX and LMHP-DOX NPs were investigated. Histone H1 high-expressive prostate cancer PC-3M cell line was selected as the cell model. Cellular uptake, and the in vitro and in vivo anti-tumour activity of LMHP-DOX NPs were evaluated on H1 high-expressive human prostate cancer PC-3M cells. Our results indicated that intact LMHP-DOX NPs mediated by H1 could be absorbed by H1 high-expressive PC-3M cells, escape from the lysosomes to the cytoplasm, and localize in the perinuclear region via H1-mediated, whereby DOX could directly enter the cell nucleus and quickly increase the concentration of DOX in the nuclei of H1 high-expressive PC-3M cells to enhance the apoptotic activity of cancer cells. The anti-coagulant activity of LMHP-DOX NPs was almost completely diminished in rat blood compared with that of LMHP, indicating the safety of LMHP-DOX NPs. Compared to traditional NTDD strategies, LMHP-DOX NPs avoid the complicated modification of nucleus-targeting ligands and provide a compelling solution for the substantially enhanced nuclear uptake of chemotherapeutic agents for the development of more intelligent NTDDs.

Pygopus2 inhibits the efficacy of paclitaxel-induced apoptosis and induces multidrug resistance in human glioma cells

Anti-microtubule drugs, such as paclitaxel (PTX), are extensively used for the treatment of numerous cancers. However, growing evidence has shown that PTX resistance, either intrinsic or acquired, frequently occurs in patients and results in the failure of treatment, contributing to the high cancer mortality rate. Therefore, it is necessary to identify the genes or pathways involved in anti-microtubule drug resistance for future successful treatment of cancers. Pygopus2 (Pygo2), which contains a Zn-coordinated plant homeodomain (PHD) finger domain, is critical for β-catenin-dependent transcriptional switches in normal and malignant tissues and is over-expressed in various cancers, including human brain glioma. In this study, we report that over-expression of Pygo2 inhibited the efficacy of PTX and contributed to cell multidrug resistance in two different ways. First, over-expression of Pygo2 inhibited the PTX-induced phosphorylation of B-cell lymphoma 2 (Bcl-2), suppressing the proteolytic cleavage of procaspase-8/9 and further inhibiting the activation of caspase-3, which also inhibits the activation of the JNK/SAPK pathway, ultimately inhibiting cell apoptosis. Second, over-expression of Pygo2 facilitated the expression of P-glycoprotein, which acts as a drug efflux pump, by promoting the transcription of Multi-drug resistance 1 (MDR1) at the MDR1 promoter loci, resulting in acceleration of the efflux of PTX.

Effect of XlogP and Hansen Solubility Parameters on Small Molecule Modified Paclitaxel Anticancer Drug Conjugates Self-Assembled into Nanoparticles

Small molecule modified anticancer drug conjugates (SMMDCs) can self-assemble into nanoparticles (NPs) as therapeutic NP platforms for cancer treatment. Here we demonstrate that the XlogP and Hansen solubility parameters of paclitaxel (PTX) SMMDCs is essential for SMMDCs self-assembling into NPs. The amorphous state of PTX SMMDCs will also affect SMMDCs self-assembling into NPs. However, the antitumor activity of these PTX SMMDCs NPs decreased along with their XlogP values, indicating that a suitable XlogP value for designing the SMMDCs is important for self-assembling into NPs and for possessing antitumor activity. For higher level XlogP SMMDCs, a degradable linker should be considered in the design of SMMDCs to overcome the problem of lower antitumor activity. It is preferable that the hydrophilic groups in the SMMDCs should be present on the surface of self-assembling NPs.

The anti-tumor efficacy of 3-(2-Nitrophenyl) propionic acid-paclitaxel (NPPA-PTX): a novel paclitaxel bioreductive prodrug

Hypoxia is an important microenvironmental pressure present in the majority of solid tumors and, so, tumor hypoxia might be considered an attractive target for tumor therapy. One strategy for targeting hypoxia is to develop bioreductive prodrugs. In the present research, we synthesized a bioreductive paclitaxel prodrug, 3-(2-Nitrophenyl) propionic acid-paclitaxel (NPPA-PTX). The stability of NPPA-PTX in PBS and rat plasma was investigated. The anti-tumor activity of NPPA-PTX was also evaluated in vitro and in vivo. The results of our stability study indicated that NPPA-PTX was stable in PBS and rat plasma as well as in the blood circulation. The in vitro and in vivo anti-tumor activity of NPPA-PTX was confirmed in both KB cells and MDA-MB-231 cells. Our results also indicated that NPPA-PTX could completely convert to active PTX in tumor tissues and produced the anti-tumor activity in both KB and MDA-MB-231 tumor-bearing nude mice. We suggest that the dissociated PTX which converted from NPPA-PTX in tumor tissues played a key role in producing anti-tumor activity. Considering all our results, we suggest that NPPA-PTX is a novel bioreductive PTX prodrug which could undergo further evaluation.

Light-activatable dual-source ROS-responsive prodrug nanoplatform for synergistic chemo-photodynamic therapy

In the context of prodrug nanomedicines for cancer therapy, one of the great challenges is the slow and variable release of the parent drug in tumors.

Preclinical development of drug delivery systems for paclitaxel-based cancer chemotherapy

Paclitaxel (PTX) is one of the most successful drugs ever used in cancer chemotherapy, acting against a variety of cancer types. Formulating PTX with Cremophor EL and ethanol (Taxol®) realized its clinical potential, but the formulation falls short of expectations due to side effects such as peripheral neuropathy, hypotension, and hypersensitivity. Abraxane®, the albumin bound PTX, represents a superior replacement of Taxol® that mitigates the side effects associated with Cremophor EL. While Abraxane® is now considered a gold standard in chemotherapy, its 21% response rate leaves much room for further improvement. The quest for safer and more effective cancer treatments has led to the development of a plethora of innovative PTX formulations, many of which are currently undergoing clinical trials. In this context, we review recent development of PTX drug delivery systems and analyze the design principles underpinning each delivery strategy. We chose several representative examples to highlight the opportunities and challenges of polymeric systems, lipid-based formulations, as well as prodrug strategies.

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.

Enzyme-Sensitive and Amphiphilic PEGylated Dendrimer-Paclitaxel Prodrug-Based Nanoparticles for Enhanced Stability and Anticancer Efficacy

In this study, we prepared a smart polymeric vehicle for the hydrophobic drug paclitaxel (PTX) that allowed a maximum steady-state circulation and a fast intracellular release in tumors. PTX was linked to the Janus PEGylated (PEG = poly(ethylene glycol)) peptide dendrimer via an enzyme-sensitive linker glycylphenylalanylleucylglycine tetrapeptide by efficient click reaction, resulting in Janus dendritic prodrug with 20.9% PTX content. The prodrug self-assembled into nanoscale particles with appropriate nanosizes, compact morphology, and negative surface charge. In addition to high stability during circulation, as demonstrated by protein adsorption assays and drug release studies in the cancer's intracellular environment, the nanoparticles were able to quickly release the drug intact in its original molecular structure, as verified via high-performance liquid chromatography and mass spectrometry analyses. Compared to free PTX, the enzyme-responsive feature of nanoparticles promoted higher cytotoxicity against 4T1 cancer cells and much lower cytotoxicity against normal cells. The nanoparticles accumulated in the tumor and were retained for an extended period of time, as confirmed by fluorescence imaging. Therefore, these nanoparticles exhibited significantly enhanced antitumor efficiency in the 4T1 breast cancer model as indicated by the observed inhibition of angiogenesis and proliferation as well as induction of apoptosis. Moreover, the nanoparticles reduced the occurrence of side effects, particularly dose-limited toxicities, as monitored by body weight and hematological features. Hence, our Janus PEGylated dendrimer-PTX prodrug-based nanoparticles may potentially serve as nanoscale vehicles for breast cancer therapy.

Pluronic F68-Linoleic Acid Nano-spheres Mediated Delivery of Gambogic Acid for Cancer Therapy

Gambogic acid (GA), a natural compound from gamboge resin, has been introduced as a promising antitumor drug contributing to its broad spectrum of antitumor activity. However, the poor aqueous solubility and short half-life hinder its clinical application. Pluronic F68 (F68) is a well-known amphiphilic block copolymer consisting of hydrophobic propylene oxide units and hydrophilic ethylene oxide. Although F68 has an amphiphilic structure, its short propylene oxide segment limits its dilution stability and drug-loading capacity. To overcome this limitation, we modified F68 by conjugating linoleic acid, a hydrophobic fatty acid, to increase the hydrophilic-hydrophobic interaction and thus improve the stability of F68 nano-spheres. This F68-linoleic acid (F68-LA) conjugate was synthesized and was used to load GA to improve its anticancer effects. GA-loaded F68-LA nano-spheres were stable for 6 days, with a mean diameter of 159.3 nm and zeta potential of -23.2 mV. The entrapment efficiency of GA in F68-LA nano-spheres was as high as 92.0%. Furthermore, F68-LA/GA nano-spheres exhibited an enhanced cytotoxic activity and proapoptotic effect against human ovarian cancer A2780 cells, compared with free GA. Our results showed that the F68-LA/GA nano-spheres might be a promising cancer-targeted drug delivery system in ovarian cancer therapy.

Facile Fabrication of Tumor Redox-Sensitive Nanoassemblies of Small-Molecule Oleate Prodrug as Potent Chemotherapeutic Nanomedicine

The conjugate of paclitaxel (PTX) and docosahexaenoic acid has entered into clinical trials. However, the most recent clinical outcomes fell short of expectations, due to the extremely slow drug release from the hydrophobic conjugates. Herein, a novel prodrug-based nanoplatform self-assembled by the disulfide bond linked conjugates of PTX and oleic acid for rapid and differential release of PTX in tumor cells is reported. This redox-responsive prodrug-nanosystem demonstrates multiple therapeutic advantages, including one-step facile fabrication, high drug-loading efficiency (56%, w/w), on-demand drug release responding to redox stimuli, as well as favorable cellular uptake and biodistribution. These advantages result in significantly enhanced antitumor efficacy in vivo, with the tumor almost completely disappearing in mice. Such a uniquely engineered prodrug-nanosystem has great potential to be used as potent chemotherapeutic nanomedicine in clinical cancer therapy.

A self-assembling nanomedicine of conjugated linoleic acid-paclitaxel conjugate (CLA-PTX) with higher drug loading and carrier-free characteristic

The main objective of this study was to demonstrate the proof-of-principle for the hypothesis that conjugated linoleic acid-paclitaxel conjugate (CLA-PTX), a novel fatty acid modified anti-cancer drug conjugate, could self-assemble forming nanoparticles. The results indicated that a novel self-assembling nanomedicine, CLA-PTX@PEG NPs (about 105 nm), with Cremophor EL (CrEL)-free and organic solvent-free characteristics, was prepared by a simple precipitation method. Being the ratio of CLA-PTX:DSPE-PEG was only 1:0.1 (w/w), the higher drug loading CLA-PTX@PEG NPs (about 90%) possessed carrier-free characteristic. The stability results indicated that CLA-PTX@PEG NPs could be stored for at least 9 months. The safety of CLA-PTX@PEG NPs was demonstrated by the MTD results. The anti-tumor activity and cellular uptake were also confirmed in the in vitro experiments. The lower crystallinity, polarity and solubility of CLA-PTX compared with that of paclitaxel (PTX) might be the possible reason for CLA-PTX self-assembling forming nanoparticles, indicating a relationship between PTX modification and nanoparticles self-assembly. Overall, the data presented here confirm that this drug self-delivery strategy based on self-assembly of a CLA-PTX conjugate may offer a new way to prepare nanomedicine products for cancer therapy involving the relationship between anticancer drug modification and self-assembly into nanoparticles.

Self-Assembled Redox Dual-Responsive Prodrug-Nanosystem Formed by Single Thioether-Bridged Paclitaxel-Fatty Acid Conjugate for Cancer Chemotherapy

Chemotherapeutic efficacy can be greatly improved by developing nanoparticulate drug delivery systems (nano-DDS) with high drug loading capacity and smart stimulus-triggered drug release in tumor cells. Herein, we report a novel redox dual-responsive prodrug-nanosystem self-assembled by hydrophobic small-molecule conjugates of paclitaxel (PTX) and oleic acid (OA). Thioether linked conjugates (PTX-S-OA) and dithioether inserted conjugates (PTX-2S-OA) are designed to respond to the redox-heterogeneity in tumor. Dithioether has been reported to show redox dual-responsiveness, but we find that PTX-S-OA exhibits superior redox sensitivity over PTX-2S-OA, achieving more rapid and selective release of free PTX from the prodrug nanoassemblies triggered by redox stimuli. PEGylated PTX-S-OA nanoassemblies, with impressively high drug loading (57.4%), exhibit potent antitumor activity in a human epidermoid carcinoma xenograft. This novel prodrug-nanosystem addresses concerns related to the low drug loading and inefficient drug release from hydrophobic prodrugs of PTX, and provides possibilities for the development of redox dual-sensitive conjugates or polymers for efficient anticancer drug delivery.

Molecular-matched materials for anticancer drug delivery and imaging

AIM

In this study, we aim to construct nanoformulation with high-cargo loading and controlled serum kinetics.

MATERIALS & METHODS

Molecular-matched materials (MMMs) are established through the conjugation of the functional moiety to a molecule representative of the nanoparticle's core. Molecular-matched nanoemulsions and liposomes were prepared using MMMs.

RESULTS

This technique based on MMMs even allows us to efficiently load either hydrophobic or hydrophilic moieties into a hydrophobic core of the nanoparticles. MMMs-based nanoparticles showed marked improvement in serum pharmacokinetics and anticancer effect.

CONCLUSION

The desired performance can be achieved when the hydrophobic anchor of the PEG derivatives and the moiety conjugated to the therapeutic (or imaging) agents are molecularly identical to the core.

Programmed Hydrolysis in Designing Paclitaxel Prodrug for Nanocarrier Assembly

Nanocarriers delivering prodrugs are a way of improving in vivo effectiveness and efficiency. For therapeutic efficacy, the prodrug must hydrolyze to its parent drug after administration. Based on the fact that the hydrolysis is impeded by steric hindrance and improved by sufficient polarity, in this study, we proposed the PTX-S-S-VE, the conjugation of paclitaxel (PTX) to vitamin E (VE) through a disulfide bridge. This conjugate possessed the following advantages: first, it can be encapsulated in the VE/VE₂-PEG₂₀₀₀/water nanoemulsions because of favorable hydrophobic interactions; second, the nanoemulsions had a long blood circulation time; finally, the concentrated glutathione in the tumor microenvironment could cleave the disulfide bond to weaken the steric hindrance and increase the polarity, promoting the hydrolysis to PTX and increasing the anticancer activity. It was demonstrated in vitro that the hydrolysis of PTX-S-S-VE was enhanced and the cytotoxicity was increased. In addition, PTX-S-S-VE had greater anticancer activity against the KB-3-1 cell line tumor xenograft and the tumor size was smaller after the 4^th injection. The present result suggests a new way, use of reduction, to improve the in vivo anticancer activity of a prodrug for nanocarrier delivery by unshielding the ester bond and taking off the steric block.

Antitumor effect of iRGD-modified liposomes containing conjugated linoleic acid-paclitaxel (CLA-PTX) on B16-F10 melanoma

In the present study, we prepared a novel delivery system of iRGD (CRGDK/RGPD/EC)-modified sterically stabilized liposomes (SSLs) containing conjugated linoleic acid–paclitaxel (CLA-PTX). The anti-tumor effect of iRGD-SSL-CLA-PTX was investigated on B16-F10 melanoma in vitro and in vivo. The in vitro targeting effect of iRGD-modified SSLs was investigated in a real-time confocal microscopic analysis experiment. An endocytosis-inhibition assay was used to evaluate the endocytosis pathways of the iRGD-modified SSLs. In addition, the in vitro cellular uptake and in vitro cytotoxicity of iRGD-SSL-CLA-PTX were evaluated in B16-F10 melanoma cells. In vivo biodistribution and in vivo antitumor effects of iRGD-SSL-CLA-PTX were investigated in B16-F10 tumor-bearing mice. The induction of apoptosis by iRGD-SSL-CLA-PTX was evaluated in tumor-tissue sections. Real-time confocal microscopic analysis results indicated that the iRGD-modified SSLs internalized into B16-F10 cells faster than SSLs. The identified endocytosis pathway of iRGD-modified SSLs indicated that energy- and lipid raft-mediated endocytosis played a key role in the liposomes’ cellular uptake. The results of the cellular uptake experiment indicated that the increased cellular uptake of CLA-PTX in the iRGD-SSL-CLA-PTX-treated group was 1.9-, 2.4-, or 2.1-fold compared with that in the CLA-PTX group after a 2-, 4-, or 6-hour incubation, respectively. In the biodistribution test, the CLA-PTX level in tumor tissues from iRGD-SSL-CLA-PTX-treated mice at 1 hour (1.84±0.17 μg/g) and 4 hours (1.17±0.28 μg/g) was 2.3- and 2.0-fold higher than that of CLA-PTX solution at 1 hour (0.79±0.06 μg/g) and 4 hours (0.58±0.04 μg/g). The value of the area under the curve for the first 24 hours in the tumors of iRGD-SSL-CLA-PTX-treated mice was significantly higher than that in the SSL-CLA-PTX and CLA-PTX solution-treated groups (P<0.01). The in vivo antitumor results indicated that iRGD-SSL-CLA-PTX significantly inhibited the growth of B16-F10 tumors compared with the SSL-CLA-PTX or CLA-PTX solution-treatment groups (P<0.01). The results of tumor-cell apoptosis showed that tumors from the iRGD-SSL-CLA-PTX-treated group exhibited more advanced cell apoptosis compared with the control, CLA-PTX solution-, and SSL-CLA-PTX-treated groups. In conclusion, the antitumor effect of iRGD-SSL-CLA-PTX was confirmed on B16-F10 melanoma in vitro and in vivo.

Novel isoprenoyl nanoassembled prodrug for paclitaxel delivery

A new paclitaxel (Ptx) prodrug was designed by coupling a single terpene unit (MIP) to the hydroxyl group in position 2' of the drug molecule. Using a squalene derivative of polyethylene glycol (SQ-PEG) as surface active agent, the resulting bioconjugate (PtxMIP) self-assembled in water leading to the formation of stable nanoparticles (PtxMIP_SQ-PEG NPs) with an impressively high drug loading (82%). In vivo, the anticancer activity of this novel Ptx nanoassembled prodrug was compared to the conventional Cremophor-containing formulation (Taxol) on a murine model of breast cancer lung metastasis induced by intravenous injection of 4T1 tumor cells, genetically modified to stably express firefly luciferase. Cell growth was assessed noninvasively by bioluminescence imaging (BLI) which enabled monitoring tumor metastatic burden in the same animals. PtxMIP_SQ-PEG nanoparticles slowed metastatic spread and were better tolerated than the Cremophor-containing formulation (i.e., free drug), thus demonstrating the potential of terpene-based nanoassembled prodrugs in the improvement of the therapeutic index of Ptx in balb/c mice.