Folate-functionalized polymeric micelles for tumor targeted delivery of a potent multidrug-resistance modulator FG020326

Advances in active targeting of ligand-directed polymeric nanomicelles via exploiting overexpressed cellular receptors for precise nanomedicine

Many of the utilized drugs which already exist in the pharmaceutical sector are hydrophobic in nature. These drugs are characterized by being poorly absorbed and difficult to formulate in aqueous environments with low bioavailability, which could result in consuming high and frequent doses in order to fulfil the required therapeutic effect. As a result, there is a decisive demand to find modern alternatives to overcome all these drawbacks. Self-assembling polymeric nanomicelles (PMs) with their unique structure appear to be a fascinating choice as a pharmaceutical carrier system for improving the solubility & bioavailability of many drugs. PMs as drug carriers have many advantages including suitable size, high stability, prolonged circulation time, elevated cargo capacity and controlled therapeutic release. Otherwise, the pathological features of some diseased cells, like cancer, allow PMs with particle size <200 nm to be passively uptaken via enhanced permeability and retention phenomenon (EPR). However, the passive targeting approach was proven to be insufficient in many cases. Consequently, the therapeutic efficiency of these PMs can be further reinforced by enhancing their cellular internalization via incorporating targeting ligands. These targeting ligands can enhance the assemblage of loaded cargos in the intended tissues via receptor-mediated endocytosis through exploiting receptors robustly expressed on the exterior of the intended tissue while minimizing their toxic effects. In this review, the up-to-date approaches of harnessing active targeting ligands to exploit certain overexpressed receptors will be summarized concerning the functionalization of the exterior of PMs for ameliorating their targeting potential in the scope of nanomedicine.

The role of peptides in reversing chemoresistance of breast cancer: current facts and future prospects

Breast cancer is the first malignant tumor in women, and its incidence is also increasing year by year. Chemotherapy is one of the standard therapies for breast cancer, but the resistance of breast cancer cells to chemotherapy drugs is a huge challenge for the effective treatment of breast cancer. At present, in the study of reversing the drug resistance of solid tumors such as breast cancer, peptides have the advantages of high selectivity, high tissue penetration, and good biocompatibility. Some of the peptides that have been studied can overcome the resistance of tumor cells to chemotherapeutic drugs in the experiment, and effectively control the growth and metastasis of breast cancer cells. Here, we describe the mechanism of different peptides in reversing breast cancer resistance, including promoting cancer cell apoptosis; promoting non-apoptotic regulatory cell death of cancer cells; inhibiting the DNA repair mechanism of cancer cells; improving the tumor microenvironment; inhibiting drug efflux mechanism; and enhancing drug uptake. This review focuses on the different mechanisms of peptides in reversing breast cancer drug resistance, and these peptides are also expected to create clinical breakthroughs in promoting the therapeutic effect of chemotherapy drugs in breast cancer patients and improving the survival rate of patients.

Design and application of hybrid cyclic-linear peptide-doxorubicin conjugates as a strategy to overcome doxorubicin resistance and toxicity

Doxorubicin (Dox) is used for breast cancer, leukemia, and lymphoma treatment as an effective chemotherapeutic agent. However, Dox use is restricted due to inherent and acquired resistance and an 8-fold increase in the risk of potentially fatal cardiotoxicity. Hybrid cyclic-linear peptide [R₅K]W₇A and linear peptide R₅KW₇A were conjugated with Dox through a glutarate linker to afford [R₅K]W₇A-Dox and R₅KW₇A-Dox conjugates to generate Dox derivatives. Alternatively, [R₅K]W₇C was conjugated with Dox via a disulfide linker to generate [R₅K]W₇C-S-S-Dox conjugate, where S-S is a disulfide bond. Comparative antiproliferative assays between conjugates [R₅K]W₇A-Dox, [R₅K]W₇C-S-S-Dox, linear R₅KW₇A-Dox, the corresponding physical mixtures of the peptides, and Dox were performed in normal and cancer cells. [R₅K]W₇A-Dox conjugate was 2-fold more efficient than R₅KW₇A-Dox, and [R₅K]W₇C-S-S-Dox conjugates in inhibiting the cell proliferation of human leukemia cells (CCRF-CEM). Therefore, hybrid cyclic-linear [R₅K]W₇A-Dox conjugate was selected for further studies and inhibited the cell viability of CCRF-CEM (84%), ovarian adenocarcinoma (SK-OV-3, 39%), and gastric carcinoma (AGS, 73%) at a concentration of 5 μM after 72 h of incubation, which was comparable to Dox (5 μM) efficacy (CCRF-CEM (85%), SK-OV-3 (33%), and AGS (87%)). While [R₅K]W₇A-Dox had a significant effect on the viability of cancer cells, it exhibited minimal cytotoxicity to normal kidney (LLC-PK1, 5-7%) and heart cells (H9C2, <9%) at concentrations of 5-10 μM (compared to free Dox at 5 μM that reduced the viability of kidney and heart cells by 85% and 44%, respectively). The fluorescence microscopy images were consistent with the cytotoxicity studies, indicating minimal uptake of the cyclic-linear [R₅K]W₇A-Dox (5 μM) in H9C2 cells. In comparison, Dox (5 μM) showed significant uptake, reduced cell viability, and changed the morphology of the cells after 24 h. [R₅K]W₇A-Dox showed 16-fold and 9.5-fold higher activity against Dox-resistant cells MDA231R and MES-SA/MX2 (lethal dose for 50% cell death or LC₅₀ of 2.3 and 4.3 μM, respectively) compared to free Dox (LC₅₀ of 36-41 μM, respectively). These data, along with the results obtained from the cell viability tests, indicate comparable efficiency of [R₅K]W₇A-Dox to free Dox in leukemia, ovarian, and gastric cancer cells, significantly reduced toxicity in normal kidney LLC-PK1 and heart H9C2 cells, and significantly higher efficiency in Dox-resistant cells. A number of endocytosis inhibitors did not affect the cellular uptake of [R₅K]W₇A-Dox.

A pretargeting nanoplatform for imaging and enhancing anti-inflammatory drug delivery

This work details a newly developed “sandwich” nanoplatform via neutravidin-biotin system for the detection and treatment of inflammation. First, biotinylated- and folate-conjugated optical imaging micelles targeted activated macrophages via folate/folate receptor interactions. Second, multivalent neutravidin proteins in an optimal concentration accumulated on the biotinylated macrophages. Finally, biotinylated anti-inflammatory drug-loaded micelles delivered drugs effectively at the inflammatory sites via a highly specific neutravidin-biotin affinity. Both in vitro and in vivo studies have shown that the “sandwich” pretargeting platform was able to diagnose inflammation by targeting activated macrophages as well as improve the therapeutic efficacy by amplifying the drug delivery to the inflamed tissue. The overall results support that our new pretargeting platform has the potential for inflammatory disease diagnosis and treatment.

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A “sandwich” nanoplatform system is developed for the improved detection and treatment of inflammation.

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Biotinylated- and folate-conjugated optical imaging micelles are designed to pre-target activated macrophages.

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Multivalent neutravidins accumulate on the biotinylated macrophages via neutravidin-biotin reactions.

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Biotinylated micelles can deliver drugs effectively at the inflammatory sites via specific neutravidin/biotin affinity.

Membrane Trafficking and Subcellular Drug Targeting Pathways

The movement of micro and macro molecules into and within a cell significantly governs several of their pharmacokinetic and pharmacodynamic parameters, thus regulating the cellular response to exogenous and endogenous stimuli. Trafficking of various pharmacological agents and other bioactive molecules throughout and within the cell is necessary for the fidelity of the cells but has been poorly investigated. Novel strategies against cancer and microbial infections need a deeper understanding of membrane as well as subcellular trafficking pathways and essentially regulate several aspects of the initiation and spread of anti-microbial and anti-cancer drug resistance. Furthermore, in order to avail the maximum possible bioavailability and therapeutic efficacy and to restrict the unwanted toxicity of pharmacological bioactives, these sometimes need to be functionalized with targeting ligands to regulate the subcellular trafficking and to enhance the localization. In the recent past the scenario drug targeting has primarily focused on targeting tissue components and cell vicinities, however, it is the membranous and subcellular trafficking system that directs the molecules to plausible locations. The effectiveness of the delivery platforms largely depends on their physicochemical nature, intracellular barriers, and biodistribution of the drugs, pharmacokinetics and pharmacodynamic paradigms. Most subcellular organelles possess some peculiar characteristics by which membranous and subcellular targeting can be manipulated, such as negative transmembrane potential in mitochondria, intraluminal delta pH in a lysosome, and many others. Many specialized methods, which positively promote the subcellular targeting and restrict the off-targeting of the bioactive molecules, exist. Recent advancements in designing the carrier molecules enable the handling of membrane trafficking to facilitate the delivery of active compounds to subcellular localizations. This review aims to cover membrane trafficking pathways which promote the delivery of the active molecule in to the subcellular locations, the associated pathways of the subcellular drug delivery system, and the role of the carrier system in drug delivery techniques.

Study of biodistribution and systemic toxicity of glucose functionalized SPIO/DOX micelles

The present study examined the cytotoxicity and magnetic resonance imaging (MRI) distribution of cancer-targeted, MRI-visible polymeric micelles that encapsulate doxorubicin (DOX) and superparamagnetic iron oxide (SPIO) and are conjugated with glucose as a targeting ligand. In this study, the micelles were investigated the clinical potential of glucose-micelles, in vitro cytotoxicity assays of nonencapsulating or SPIO-and-DOX-coencapsulating micelles were performed on L929 mouse fibroblasts, and we found that glucose-micelles did not exert in vitro cytotoxic effects. Next, in vitro MRI detectability of glucose SPIO micelles was evaluated at the loaded SPIO content of 2.5% and 50%, and it was found that glucose-micelles can increase MRI relaxivity (r₂*) at high SPIO loading. Furthermore, 50% SPIO micelles persisted in the blood circulation for up to 5 days (slow liver clearance) as determined by in vivo MRI. For in vivo toxicity evaluation, 50% SPIO/DOX micelles at a dose up to 18 (mg DOX)/(kg body weight) showed no impact on animal health according to clinical chemistry and clinical hematology laboratory testing. Altogether, these results indicate that glucose-micelles can serve as an effective and safe drug delivery system.

Synthesis and in vitro experiments of carcinoma vascular endothelial targeting polymeric nano-micelles combining small particle size and supermagnetic sensitivity

Objective: To construct carcinoma vascular endothelial-targeted polymeric nanomicelles with high magnetic resonance imaging (MRI) sensitivity and to evaluate their biological safety and in vitro tumor-targeting effect, and to monitor their feasibility using clinical MRI scanner. Method: Amphiphilic block copolymer, poly(ethylene glycol)-b-poly(ε-caprolactone) (PEG-PCL) was synthesized via the ring-opening polymerization of ε-caprolactone (CL) initiated by poly(ethylene glycol) (PEG), in which cyclic pentapeptide Arg-Gly-Asp (cRGD) was conjugated with the terminal of hydrophilic PEG block. During the self-assembly of PEG-PCL micelles, superparamagnetic γ-Fe₂O₃ nanoparticles (11 nm) was loaded into the hydrophobic core. The cRGD-terminated γ-Fe₂O₃-loaded polymeric micelles targeting to carcinoma vascular endothelial cells, were characterized in particle size, morphology, loading efficiency and so on, especially high MRI sensitivity in vitro. Normal hepatic vascular endothelial cells (ED25) were incubated with the resulting micelles for assessing their safety. Human hepatic carcinoma vascular endothelial cells (T3A) were cultured with the resulting micelles to assess the micelle uptake using Prussian blue staining and the cell signal intensity using MRI. Results: All the polymeric micelles exhibited ultra-small particle sizes with approximately 50 nm, high relaxation rate, and low toxicity even at high iron concentrations. More blue-stained iron particles were present in the targeting group than the non-targeting and competitive inhibition groups. In vitro MRI showed T₂WI and T₂ relaxation times were significantly lower in the targeting group than in the other two groups. Conclusion: γ-Fe₂O₃-loaded PEG-PCL micelles not only possess ultra-small size and high superparamagnetic sensitivity, also can be actively targeted to carcinoma vascular endothelial cells by tumor-targeted cRGD. It appears to be a promising contrast agent for tumor-targeted imaging.

Folate‑targeted polymeric micelles loaded with superparamagnetic iron oxide as a contrast agent for magnetic resonance imaging of a human tongue cancer cell line

The aim of the present study was to investigate the feasibility of using folate‑targeted superparamagnetic iron oxide nanoparticles (SPIO) as a magnetic resonance (MR) contrast agent that targets human tongue cancer cells. Folate‑targeted and folate‑free bilayer micelles composed of a diblock copolymer of polyethylene glycol (PEG) and poly‑caprolactone (PCL) that encapsulated SPIO in their hydrophobic core (SPIO‑PEG‑PCL micelles) were synthesized. The cytotoxicity of each set of micelles towards Tca‑8113 cells was examined using methyl thiazolyl tetrazolium (MTT) assays. Tca‑8113 cells were incubated with folate‑free SPIO‑PEG‑PCL micelles and folate‑targeted SPIO‑PEG‑PCL micelles at an Fe concentration of 80 µg/ml for 0.5, 1 and 2 h. MR imaging was subsequently performed and relative T2 relaxation time was recorded. Endocytosis of each micelle type was observed using Prussian blue staining. The MTT assays demonstrated that varying concentrations of folate‑targeted SPIO‑PEG‑PCL micelles did not result in statistically significant differences in Tca‑8113 cell viability when compared with folate‑free SPIO‑PEG‑PCL micelles (F=0.698; P=0.676). In the MR images obtained, decreased T2‑weighted signal intensity was observed for the folate‑targeted SPIO‑PEG‑PCL and folate‑free SPIO‑PEG‑PCL micelle treatments, particularly after the 2‑h incubation period. However, the folate‑targeted micelles exhibited a significantly greater decrease in signal intensity and a higher relative T2 relaxation time at each time point (P=0.002). In addition, blue intracellular particles were observed in the cells that were incubated with each type of micelle and stained with Prussian blue. However, a greater number of blue particles underwent endocytosis in the folate‑targeted group. Thus, folate‑targeted SPIO‑PEG‑PCL micelles exhibited preferential targeting of Tca‑8113 cells when compared with folate‑free SPIO‑PEG‑PCL micelles, and these results support the potential for these micelles to be used for the early diagnosis of tongue cancer.

Synthesis and cellular characterization of various nano-assemblies of cell penetrating peptide-epirubicin-polyglutamate conjugates for the enhancement of antitumor activity

A new class of cell penetrating peptides (CPPs) named peptide amphiphile was designed to improve the intracellular uptake and the antitumor activity of epirubicin (EPR). Various amphiphilic CPPs were synthesized by solid phase peptide synthesis method and were chemically conjugated to EPR. Their corresponding nanoparticles (CPPs-E4 and CPPs-E8) were prepared via non-covalent binding of the peptides and polyanions. Cytotoxicity and anti-proliferative activity were evaluated by MTT assay. Cellular uptake was examined by flow cytometry and fluorescence microscopy. The CPPs exhibited slight cytotoxicity. Binding of polyglutamate to CPPs (CPPs-E4 and CPPs-E8 nanoparticles) decreased their cytotoxicity. CPPs-E8 nanoparticles showed lower cytotoxicity than CPPs-E4 nanoparticles. Cellular uptake of K3W4K3-E8, K2W4K2-E8 and W3K4W3-E8 reached 100% with no difference between each of the mentioned CPPs and its nanoparticles at 50 µM. The anti-proliferative activity of EPR was enhanced following conjugation to peptides and nanoparticles at 25 µM. CPPs-EPR-E4 and CPPs-E8-EPR nanoparticles displayed higher anti-proliferative activity than CPPs-EPR at 25 µM. CPPs-E8-EPR nanoparticles showed higher anti-proliferative activity than CPPs-E4-EPR. K3W4K3-E8-EPR nanoparticles exhibited the highest anti-proliferative activity at 25 µM. The synthesized peptide nanoparticles are proposed as suitable carriers for improving the intracellular delivery of EPR into tumor cells with low cytotoxicity and high antitumor activity.

PEG-PCL-based nanomedicines: A biodegradable drug delivery system and its application

The lack of efficient therapeutic options for many severe disorders including cancer spurs demand for improved drug delivery technologies. Nanoscale drug delivery systems based on poly(ethylene glycol)-poly(ε-caprolactone) copolymers (PEG-PCL) represent a strategy to implement therapies with enhanced drug accumulation at the site of action and decreased off-target effects. In this review, we discuss state-of-the-art nanomedicines based on PEG-PCL that have been investigated in a preclinical setting. We summarize the various synthesis routes and different preparation methods used for the production of PEG-PCL nanoparticles. Additionally, we review physico-chemical properties including biodegradability, biocompatibility, and drug loading. Finally, we highlight recent therapeutic applications investigated in vitro and in vivo using advanced systems such as triggered release, multi-component therapies, theranostics, or gene delivery systems.

Solubility enhancement and targeted delivery of a potent anticancer flavonoid analogue to cancer cells using ligand decorated dendrimer nano-architectures

Conventional chemotherapy using small molecule drugs is marred by several challenges such as short half-life, low therapeutic index and adverse systemic side effects. In this regard, targeted therapies using ligand directed polyamidoamine (PAMAM) dendrimers could be a promising strategy to specifically deliver anticancer drugs to cancer cells overexpressing complementary receptor binding domains. The aim of this study was to utilize folate decorated PAMAM to enhance the aqueous solubility of a highly hydrophobic but very potent anticancer flavonoid analogue, 3,4-difluorobenzylidene diferuloylmethane (CDF) and to deliver it specifically to folate receptor overexpressing cervical cancer cells (HeLa) and ovarian cancer cells (SKOV3). As compared to the non-targeted formulation, the targeted formulation exhibited significant anticancer activity with higher accumulation in folate receptor overexpressing cells, larger population of apoptotic cancer cells, elevated expression of tumor suppressor phosphatase and tensin homolog (PTEN), and inhibition of nuclear factor kappa B (NFκB) which further confirmed the targeting ability and the promising anticancer activity of the folate based nanoformulation.

Tuning the Selectivity of Dendron Micelles Through Variations of the Poly(ethylene glycol) Corona

Engineering controllable cellular interactions into nanoscale drug delivery systems is key to enable their full potential. Here, using folic acid (FA) as a model targeting ligand and dendron micelles (DM) as a nanoparticle (NP) platform, we present a comprehensive experimental and modeling investigation of the structural properties of DMs that govern the formation of controllable, FA-mediated cellular interactions. Our experimental results demonstrate that a high level of control over the specific cell interactions of FA-targeted DMs can be achieved through modulation of the PEG corona length and the FA content. Using various molecular weight PEGs (0.6K, 1K, and 2K g/mol) and contents of dendron-FA conjugate incorporated into DMs (0, 5, 10, 25 wt %), the cell interactions of the targeted DMs could be controlled to exhibit minimal to >25-fold enhancement over nontargeted DMs. Molecular dynamics simulations indicated that structural characteristics, such as solvent accessible surface area of FA, local PEG density near FA, and FA mobility, account in part for the experimental differences in cellular interactions. The molecular structure that allows FA to depart from the surface of DMs to facilitate the initial cell surface binding was revealed to be the most important contributor for determining FA-mediated cellular interactions of DMs. The modular properties of DMs in controlling their specific cell interactions support the potential of DMs as a delivery platform and offer design cues for future development of targeted NPs.

Combining Stimulus-Triggered Release and Active Targeting Strategies Improves Cytotoxicity of Cytochrome c Nanoparticles in Tumor Cells

Proteins often possess highly specific biological activities that make them potential therapeutics, but their physical and chemical instabilities during formulation, storage, and delivery have limited their medical use. Therefore, engineering of nanosized vehicles to stabilize protein therapeutics and to allow for targeted treatment of complex diseases, such as cancer, is of considerable interest. A micelle-like nanoparticle (NP) was designed for both, tumor targeting and stimulus-triggered release of the apoptotic protein cytochrome c (Cyt c). This system is composed of a Cyt c NP stabilized by a folate-receptor targeting amphiphilic copolymer (FA-PEG-PLGA) attached to Cyt c through a redox-sensitive bond. FA-PEG-PLGA-S-S-Cyt c NPs exhibited excellent stability under extracellular physiological conditions, whereas once in the intracellular reducing environment, Cyt c was released from the conjugate. Under the same conditions, the folate-decorated NP reduced folate receptor positive HeLa cell viability to 20%, while the same complex without FA only reduced it to 80%. Confocal microscopy showed that the FA-PEG-PLGA-S-S-Cyt c NPs were internalized by HeLa cells and were capable of endosomal escape. The specificity of the folate receptor-mediated internalization was confirmed by the lack of uptake by two folate receptor deficient cell lines: A549 and NIH-3T3. Finally, the potential as antitumor therapy of our folate-decorated Cyt c-based NPs was confirmed with an in vivo brain tumor model. In conclusion, we were able to create a stable, selective, and smart nanosized Cyt c delivery system.

Engineered Nanoparticles Against MDR in Cancer: The State of the Art and its Prospective

Cancer is a highly heterogeneous disease at intra/inter patient levels and known as the leading cause of death worldwide. A variety of mono and combinational therapies including chemotherapy have been evolved over the years for its effective treatment. However, advent of chemotherapeutic resistance or multidrug resistance (MDR) in cancer is a major challenge researchers are facing in cancer chemotherapy. MDR is a complex process having multifaceted non-cellular or cellular-based mechanisms. Research in the area of cancer nanotechnology over the past two decade has now proven that the smartly designed nanoparticles help in successful chemotherapy by overcoming the MDR and preferentially accumulate in the tumor region by means of active and passive targeting therefore reducing the offtarget accumulation of payload. Many of such nanoparticles are in different stages of clinical trials as nanomedicines showing promising result in cancer therapy including the resistant cases. Nanoparticles as chemotherapeutics carriers offer the opportunity to have multiple payload of drug and or imaging agents for combinational and theranostics therapy. Moreover, nanotechnology further bring in notice the new treatment strategies such as combining the NIR, MRI and HIFU in cancer chemotherapy and imaging. Here, we discussed the cellular/non-cellular factors constituting the MDR in cancer and the role of nanomedicines in effective chemotherapy of MDR cases of cancers. Moreover, recent advancements like combinational payload delivery and combined physical approach with nanotechnology in cancer therapy have also been discussed.

Folate Receptor-Targeted Polymeric Micellar Nanocarriers for Delivery of Orlistat as a Repurposed Drug against Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is a recalcitrant malignancy with no available targeted therapy. Off-target effects and poor bioavailability of the FDA-approved antiobesity drug orlistat hinder its clinical translation as a repurposed new drug against TNBC. Here, we demonstrate a newly engineered drug formulation for packaging orlistat tailored to TNBC treatment. We synthesized TNBC-specific folate receptor-targeted micellar nanoparticles (NP) carrying orlistat, which improved the solubility (70-80 μg/mL) of this water-insoluble drug. The targeted NPs also improved the delivery and bioavailability of orlistat to MDA-MB-231 cells in culture and to tumor xenografts in a nude mouse model. We prepared HEA-EHA copolymer micellar NPs by copolymerization of 2-hydroxyethylacrylate (HEA) and 2-ethylhexylacrylate (EHA), and functionalized them with folic acid and an imaging dye. Fluorescence-activated cell sorting (FACS) analysis of TNBC cells indicated a dose-dependent increase in apoptotic populations in cells treated with free orlistat, orlistat NPs, and folate-receptor-targeted Fol-HEA-EHA-orlistat NPs in which Fol-HEA-EHA-orlistat NPs showed significantly higher cytotoxicity than free orlistat. In vitro analysis data demonstrated significant apoptosis at nanomolar concentrations in cells activated through caspase-3 and PARP inhibition. In vivo analysis demonstrated significant antitumor effects in living mice after targeted treatment of tumors, and confirmed by fluorescence imaging. Moreover, folate receptor-targeted Fol-DyLight747-orlistat NP-treated mice exhibited significantly higher reduction in tumor volume compared to control group. Taken together, these results indicate that orlistat packaged in HEA-b-EHA micellar NPs is a highly promising new drug formulation for TNBC therapy. Mol Cancer Ther; 15(2); 221-31. ©2015 AACR.

Thermosensitive tribrachia star-shaped s-P(NIPAM-co-DMAM) random copolymer micelle aggregates: Preparation, characterization, and drug release applications

Tribrachia star-shaped random copolymers with tunable thermosensitive phase transition temperature were designed and synthesized via a simple one-pot ammonolysis reaction approach with trimesic acid as cores. The self-assembly micellization behavior of the copolymers in aqueous solution was examined by surface tension, UV-vis transmittance, transmission electron microscope, and dynamic light scattering measurements, etc. The results indicated that the resultant copolymers formed thermosensitive micelle aggregates through hydrophobic interactions among the isopropyl groups of poly(N-isopropylacrylamide) PNIPAM chains and inter-star association at a polymer concentration above critical aggregation concentrations from 4.06 to 6.55 mg L(-1), with a cloud point range from 36.6℃ to 52.1℃, and homogeneously distributed micelle size below 200 nm. The arm length and the compositional ratios of the two comonomers had effect on physicochemical properties of the polymer micelle aggregates. Particularly, the cloud point values were enhanced as the (N,N-dimethylacrylamide) DMAM monomer was introduced and reached to 36.6℃ and 41.0℃-44.7℃ when the mass ratio of NIPAM to DMAM was 90:10 and 80:20, respectively. The thermo-triggered drug release and cytotoxicity were evaluated to confirm the applicability of the random copolymer micelle aggregates as novel drug targeted release carriers.

PEG-PLGA copolymers: their structure and structure-influenced drug delivery applications

In the paper, we begin by describing polyethylene glycol-poly lactic acid-co-glycolic acid (PEG-PLGA) which was chosen as a typical model copolymer for the construction of nano-sized drug delivery systems and also the types of PEG-PLGA copolymers that were eluted. Following this we examine the structure-influenced drug delivery applications including nanoparticles, micelles and hydrogels. After that, the preparation methods for nano-sized delivery systems are presented. In addition, the drug loading mode of PEG-PLGA micelles is divided into three aspects. Finally, the drug release profiles of PEG-PLGA micelles, both in terms of their in vitro and in vivo characteristics, are represented. PEG-PLGA copolymers are very suitable for the construction of micelles as carriers for insoluble drugs. This article reviews the structure and the different structure-influenced applications of PEG-PLGA copolymers, concentrating on the application of PEG-PLGA micelles.

Use of magnetic folate-dextran-retinoic acid micelles for dual targeting of doxorubicin in breast cancer

Amphiphilic copolymer of folate-conjugated dextran/retinoic acid (FA/DEX-RA) was self-assembled into micelles by direct dissolution method. Magnetic iron oxide nanoparticles (MNPs) coated with oleic acid (OA) were prepared by hydrothermal method and encapsulated within the micelles. Doxorubicin HCl was loaded in the magnetic micelles. The characteristics of the magnetic micelles were determined by Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA), transmission electron microscopy (TEM), and vibrating sample magnetometer (VSM). The crystalline state of OA-coated MNPs and their heat capacity were analyzed by X-ray diffraction (XRD) and differential scanning calorimetry (DSC) methods, respectively. The iron content of magnetic micelles was determined using inductively coupled plasma optical emission spectrometry (ICP-OES). Bovine serum albumin (BSA) was used to test the protein binding of magnetic micelles. The cytotoxicity of doxorubicin loaded magnetic micelles was studied on MCF-7 and MDA-MB-468 cells using MTT assay and their quantitative cellular uptake by fluorimetry method. TEM results showed the MNPs in the hydrophobic core of the micelles. TGA results confirmed the presence of OA and FA/DEX-RA copolymer on the surface of MNPs and micelles, respectively. The magnetic micelles showed no significant protein bonding and reduced the IC₅₀ of the drug to about 10 times lower than the free drug.

Effect of PEG-PDLLA polymeric nanovesicles loaded with doxorubicin and hematoporphyrin monomethyl ether on human hepatocellular carcinoma HepG2 cells in vitro

Objective

To evaluate the cytotoxicity of poly(ethylene glycol)-block-poly(D,L-lactic acid) (PEG-PDLLA) nanovesicles loaded with doxorubicin (DOX) and the photosensitizer hematoporphyrin monomethyl ether (HMME) on human hepatocellular carcinoma HepG2 cells and to investigate potential apoptotic mechanisms.

Methods

PEG-PDLLA nanovesicles were simultaneously loaded with DOX and HMME (PEG-PDLLA-DOX-HMME), and PEG-PDLLA nanovesicles were loaded with DOX (PEG-PDLLA-DOX), HMME (PEG-PDLLA-HMME), or the PEG-PDLLA nanovesicle alone as controls. The cytotoxicity of PEG-PDLLA-DOX-HMME, PEG-PDLLA-DOX, PEG-PDLLA-HMME, and PEG-PDLLA against HepG2 cells was measured, and the cellular reactive oxygen species, percentage of cells with mitochondrial membrane potential depolarization, and apoptotic rate following treatment were determined.

Results

Four nanovesicles (PEG-PDLLA-DOX-HMME, PEG-PDLLA-DOX, PEG-PDLLA-HMME, and PEG-PDLLA) were synthesized, and mean particle sizes were 175±18 nm, 154±3 nm, 196±2 nm, and 147±15 nm, respectively. PEG-PDLLA-DOX-HMME was more cytotoxic than PEG-PDLLA-DOX, PEG-PDLLA-HMME, and PEG-PDLLA. PEG-PDLLA-HMME-treated cells had the highest mean fluorescence intensity, followed by PEG-PDLLA-DOX-HMME-treated cells, whereas PEG-PDLLA-DOX- and PEG-PDLLA-treated cells had a similar fluorescence intensity. Mitochondrial membrane potential depolarization was observed in 54.2%, 59.4%, 13.8%, and 14.8% of the cells treated with PEG-PDLLA-DOX-HMME, PEG-PDLLA-HMME, PEG-PDLLA-DOX, and PEG-PDLLA, respectively. The apoptotic rate was significantly higher in PEG-PDLLA-DOX-HMME-treated cells compared with PEG-PDLLA-DOX- and PEG-PDLLA-HMME-treated cells.

Conclusion

The PEG-PDLLA nanovesicle, a drug delivery carrier, can be simultaneously loaded with two anticancer drugs (hydrophilic DOX and hydrophobic HMME). PEG-PDLLA-DOX-HMME cytotoxicity to HepG2 cells is significantly higher than the PEG-PDLLA nanovesicle loaded with DOX or HMME alone, and DOX and HMME have a synergistic effect against human hepatocellular carcinoma HepG2 cells.

Acid-triggered core cross-linked nanomicelles for targeted drug delivery and magnetic resonance imaging in liver cancer cells

Purpose

To research the acid-triggered core cross-linked folate-poly(ethylene glycol)-b-poly[N-(N′,N′-diisopropylaminoethyl) glutamine] (folated-PEG-P[GA-DIP]) amphiphilic block copolymer for targeted drug delivery and magnetic resonance imaging (MRI) in liver cancer cells.

Methods

As an appropriate receptor of protons, the N,N-diisopropyl tertiary amine group (DIP) was chosen to conjugate with the side carboxyl groups of poly(ethylene glycol)-b-poly (L-glutamic acid) to obtain PEG-P(GA-DIP) amphiphilic block copolymers. By ultrasonic emulsification, PEG-P(GA-DIP) could be self-assembled to form nanosized micelles loading doxorubicin (DOX) and superparamagnetic iron oxide nanoparticles (SPIONs) in aqueous solution. When PEG-P(GA-DIP) nanomicelles were combined with folic acid, the targeted effect of folated-PEG-P(GA-DIP) nanomicelles was evident in the fluorescence and MRI results.

Results

To further increase the loading efficiency and the cell-uptake of encapsulated drugs (DOX and SPIONs), DIP (pK_a≈6.3) groups were linked with ~50% of the side carboxyl groups of poly(L-glutamic acid) (PGA), to generate the core cross-linking under neutral or weakly acidic conditions. Under the acidic condition (eg, endosome/lysosome), the carboxyl groups were neutralized to facilitate disassembly of the P(GA-DIP) blocks’ cross-linking, for duly accelerating the encapsulated drug release. Combined with the tumor-targeting effect of folic acid, specific drug delivery to the liver cancer cells and MRI diagnosis of these cells were greatly enhanced.

Conclusion

Acid-triggered and folate-decorated nanomicelles encapsulating SPIONs and DOX, facilitate the targeted MRI diagnosis and therapeutic effects in tumors.

The effect of N/P ratio on the in vitro and in vivo interaction properties of PEGylated poly[2-(dimethylamino)ethyl methacrylate]-based siRNA complexes

PEG-PnBA-PDMAEMA triblock and PEG-PDMAEMA diblock copolymers are used as model systems for studying the role of N/P ratio on the in vivo behavior of PEGylated siRNA carriers in mice. The presence of a free/uncomplexed polymer population coexisting with siRNA complexes is established. A change in the N/P ratio exerts no significant influence on the in vivo biodistribution and ex vivo blood chemistry properties of the respective systems. Histological analysis of major organs indicates that the presence of uncomplexed polymer elicits toxicity to the organ that is associated with the clearance of the siRNA complexes from the circulation system. This effect can be eliminated by working at N/P ratios near the charge-neutralization point of the complexes.

Folate-targeted polymeric micelles loaded with ultrasmall superparamagnetic iron oxide: combined small size and high MRI sensitivity

Targeted delivery of contrast agents is a highly desirable strategy for enhancing diagnostic efficiency and reducing side effects and toxicity. Water-soluble and tumor-targeting superparamagnetic iron oxide nanoparticles (SPIONs) were synthesized by loading hydrophobic SPIONs into micelles assembled from an amphiphilic block copolymer poly(ethylene glycol)- poly(ε-caprolactone) (PEG-PCL) bearing folate in the distal ends of PEG chains. Compared to the water-soluble SPIONs obtained by small molecular surfactant coating, ultrasmall SPION encapsulation with PEG-PCL micelles (PEG-PCL-SPIONs) simultaneously increases transverse (r(2)) and decreases longitudinal (r(1)) magnetic resonance (MR) relaxivities of water proton in micelle solution, leading to a notably high r(2)/r(1) ratio up to 78, which makes the PEG-PCL-SPIONs a highly sensitive MR imaging (MRI) T(2) contrast agent. The mean size of folate-attached SPION micelles (Fa-PEG-PCL-SPIONs) is 44 ± 3 nm on average, ideal for in vivo MRI applications in which long circulation is greatly determined by small particle size and is highly desirable. Prussian blue staining of BEL-7402 cells over-expressing folate receptors, after incubation with micelle-containing medium, demonstrated that folate functionalization of the magnetic particles significantly enhanced their cell uptake. The potential of Fa-PEG-PCL-SPIONs as a potent MRI probe for in vivo tumor detection was assessed. At 3 hours after intravenous injection of the Fa-PEG-PCL-SPION solution into mice bearing subcutaneous xenografts of human BEL-7402 hepatoma, a 41.2% signal intensity decrease was detected in the T(2)-weighted MR images of the tumor, indicating the efficient accumulation of Fa-PEG-PCL-SPIONs in the tumor tissue.

EILDV-conjugated, etoposide-loaded biodegradable polymeric micelles directing to tumor metastatic cells overexpressing α4β1 integrin

In the present study, poly(ethylene glycol)-b-poly(ε-caprolactone) micelles loaded with etoposide (ETO) were formulated and further conjugated with pentapeptide Glu-Ile-Leu-Asp-Val (EILDV) to target α4β1 integrin receptor overexpressed on metastatic tumor cell. Using a distinct ratio of carboxyl-terminated poly(ethylene glycol)-block-poly(ε-caprolactone) (HOOC-PEG-b-PCL) to methoxy-poly(ethylene glycol)-block-poly(ε-caprolactone (CH₃O-PEG-b-PCL) polymers, we formulated a series of micellar formulations having different surface densities of EILDV and observed optimum cellular uptake of micelles with 10% EILDV surface density by B16F10 cells. The cytotoxicity of EILDV-conjugated micelles was observed close to 1.5-fold higher than plain ETO after 72 h of drug incubation, demonstrating controlled release of drug inside the cell after enhanced intracellular uptake with the ability to selectively target cancer cells. In addition, EILDV-conjugated micelles inhibited the migration of B16F10 cells effectively compared with plain ETO and non-conjugated micellar formulations when cells were treated with equivalent cytotoxic concentration of the drug, i.e., IC₂₅. B16F10 cells treated with EILDV-conjugated micelles showed a significant reduction in the attachment of cells to the substrate-coated plate compared with non-conjugated micellar formulations, implying retention of the biological activity of EILDV after coupling to micelles. Furthermore, the in vivo experimental metastasis assay conducted on C57BL/6 mice demonstrated significant activity of EIDLV-conjugated micelles in the reduction of pulmonary metastatic nodule formation in both pretreatment and post-treatment methods. In conclusion, EIDLV-conjugated micelles showed higher efficacy in the treatment of metastasis and would be a promising approach in the treatment of metastasis.

Nanomedicine for targeted cancer therapy: towards the overcoming of drug resistance

Anticancer drug resistance almost invariably emerges and poses major obstacles towards curative therapy of various human malignancies. In the current review we will distinguish between mechanisms of chemoresistance that are predominantly mediated by ATP-driven multidrug resistance (MDR) efflux transporters, typically of the ATP-binding cassette (ABC) superfamily, and those that are independent of such drug efflux pumps. In recent years, multiple nanoparticle (NP)-based therapeutic systems have been developed that were rationally designed to overcome drug resistance by neutralizing, evading or exploiting various drug efflux pumps and other resistance mechanisms. NPs are being exploited for selective drug delivery to tumor cells, to cancer stem/tumor initiating cells and/or to the supportive cancer cell microenvironment, i.e. stroma or tumor vasculature. Some of these NPs are currently undergoing preclinical in vivo studies as well as advanced stages of clinical evaluation with promising results. Nanovehicles harboring a payload of therapeutic drug combinations for the selective targeting and elimination of tumor cells as well as the simultaneous overcoming of mechanisms of drug resistance are a subject of intense research efforts, some of which are expected to enter clinical trials in the near future. In the present review we highlight novel approaches to selectively target cancer cells and overcome drug resistance phenomena, through the use of various nanometric drug delivery systems. In the near future, it is anticipated that innovative theragnostic nanovehicles will be developed which will harbor four major components: (1) a selective targeting moiety, (2) a diagnostic imaging aid for the localization of the malignant tumor and its micro- or macrometastases, (3) a cytotoxic, small molecule drug(s) or novel therapeutic biological(s), and (4) a chemosensitizing agent aimed at neutralizing a resistance mechanism, or exploiting a molecular "Achilles hill" of drug resistant cells. We propose to name these envisioned four element-containing nanovehicle platform, "quadrugnostic" nanomedicine. This targeted strategy holds promise in paving the way for the introduction of highly effective nanoscopic vehicles for cancer therapeutics while overcoming drug resistance.

Amphiphilic block co-polyesters bearing pendant cyclic ketal groups as nanocarriers for controlled release of camptothecin

Amphiphilic block co-polymers consisting of hydrophilic poly(ethylene glycol) and hydrophobic polyester bearing pendent cyclic ketals were synthesized by ring-opening co-polymerization of ε-caprolactone (CL) and 1,4,8-trioxaspiro-[4,6]-9-undecanone (TSU) using α-hydroxyl, ω-methoxy, poly(ethylene glycol) as the initiator and stannous octoate as the catalyst. Compositional analyses indicate that TSU was randomly distributed in the hydrophobic blocks. When the TSU content in the co-polymers increased, the polymer crystallinity decreased progressively and the glass transition temperature increased accordingly. The hydrophobic, anticancer drug, camptothecin (CPT), was successfully encapsulated in the block copolymer nanoparticles. The CPT encapsulation efficiency and release kinetics were strongly dependent on the co-polymer composition and crystallinity. CPT release from nanoparticles constructed from co-polymers containing 0, 39 and 100 mol% TSU in the hydrophobic block followed the same trend, with an initial burst of approx. 40% within one day followed by a moderate and slow release lasting up to 7 days. At a TSU content of 14 mol%, CPT was released in a continuous and controlled fashion with a reduced initial burst and a 73% cumulative release by day 7. The in vitro cytoxicity assay showed that the blank nanoparticles were not toxic to the cultured bone metastatic prostate cancer cells (C4-2B). Compared to the free drug, the encapsulated CPT was more effective in inducing apoptotic responses in C4-2B cells. Modulating the physical characteristics of the amphiphilic co-polymers via co-polymerization offers a facile method for controlling the bioavailability of anticancer drugs, ultimately increasing effectiveness and minimizing toxicity.