Liposome clearance in mice: the effect of a separate and combined presence of surface charge and polymer coating

Liposomal drug delivery systems for targeted cancer therapy: is active targeting the best choice?

Liposomes are biodegradable and biocompatible self-forming spherical lipid bilayer vesicles. They can encapsulate and deliver one or more hydrophobic and hydrophilic therapeutic agents with poor therapeutic indices to tumor sites. Properties such as lipid bilayer fluidity, charge, size and surface hydration can be modified to extend liposome circulation time in the bloodstream and enhance efficacy. The focus of this review is on ligand-conjugated liposomes and their potential application in tumor-targeted delivery. Ligand-conjugated liposomes are designed to target receptors which are overexpressed on tumor cells to decrease drugs side effects by enhancing their selective delivery to tumor site. Despite the extensive research in this area, no small molecule ligand-conjugated liposome has been approved up to date for cancer therapy.

Drug-loadable Mesoporous Bioactive Glass Nanospheres: Biodistribution, Clearance, BRL Cellular Location and Systemic Risk Assessment via (45)Ca Labelling and Histological Analysis

Mesoporous bioactive glass (MBG) nanospheres with excellent drug loading property have attracted significant attention in the field of nano-medicine. However, systemic metabolism and biosafety of MBG nanospheres which are crucial issues for clinical application are yet to be fully understood. Isotope quantitative tracing combined with biochemical parameters and histopatological changes were used to analyze biodistribution, excretion path and the effect on metabolism and major organs, and then we focused on the hepatocellular location and damaging effect of MBG. The results indicated MBG possessed a longer residence time in blood. After being cleared from circulation, nanospheres were mainly distributed in the liver and were slightly internalized in the form of exogenous phagosome by hepatocyte, whereby more than 96% of nanospheres were located in the cytoplasm (nearly no nuclear involvement). A little MBG was transferred into the mitochondria, but did not cause ROS reaction. Furthermore, no abnormal metabolism and histopathological changes was observed. The accumulation of MBG nanospheres in various organs were excreted mainly through feces. This study revealed comprehensively the systemic metabolism of drug-loadable MBG nanospheres and showed nanospheres have no obvious biological risk, which provides a scientific basis for developing MBG nanospheres as a new drug delivery in clinical application.

Porous Silicon and Polymer Nanocomposites for Delivery of Peptide Nucleic Acids as Anti-MicroRNA Therapies

Self-assembled polymer/porous silicon nanocomposites overcome intracellular and systemic barriers for in vivo application of peptide nucleic acid (PNA) anti-microRNA therapeutics. Porous silicon (PSi) is leveraged as a biodegradable scaffold with high drug-cargo-loading capacity. Functionalization with a diblock polymer improves PSi nanoparticle colloidal stability, in vivo pharmacokinetics, and intracellular bioavailability through endosomal escape, enabling PNA to inhibit miR-122 in vivo.

In-vivo disposition characteristics of PEG niosome and its interaction with serum proteins

Three different nonionic surfactants (Brij 72, Span 20 and Tween 60) were used to prepare various naked and PEG niosomes. In-vivo study demonstrated that PEGylation dramatically increased the AUC and decreased the affinity to the liver of Brij 72 and Span 20 niosomes in rats. Liver perfusion experiments suggested that the hepatic uptake of naked Brij 72 and Span 20 niosomes could mainly be ascribed to the receptor-mediated uptake, while PEGylation of these niosomes could diminish the receptor-mediated hepatic disposition. Evaluation of serum proteins associated with niosomes revealed that PEGylation of these niosomes significantly reduced the association of serum proteins with them, including typical opsonins such as IgG and C3. On the other hand, in the case of Tween 60 niosomes, naked Tween 60 niosome showed large AUC and its PEGylation did not show any additional effect on the in-vivo pharmacokinetics. Furthermore, PEGylation of Tween 60 niosome did not significantly affect the hepatic disposition or the association of serum proteins with Tween 60 niosome. These results demonstrated that niosomes would exhibit distinct in-vivo disposition characteristics depending on the physicochemical properties of surfactants used and that PEGylation of niosomes with adequate compositions would be a powerful tool to improve their in-vivo behavior.

Temporal assessment of nanoparticle accumulation after experimental brain injury: Effect of particle size

Nanoparticle (NP) based therapeutic and theranostic agents have been developed for various diseases, yet application to neural disease/injury is restricted by the blood-brain-barrier (BBB). Traumatic brain injury (TBI) results in a host of pathological alterations, including transient breakdown of the BBB, thus opening a window for NP delivery to the injured brain tissue. This study focused on investigating the spatiotemporal accumulation of different sized NPs after TBI. Specifically, animal cohorts sustaining a controlled cortical impact injury received an intravenous injection of PEGylated NP cocktail (20, 40, 100, and 500 nm, each with a unique fluorophore) immediately (0 h), 2 h, 5 h, 12 h, or 23 h after injury. NPs were allowed to circulate for 1 h before perfusion and brain harvest. Confocal microscopy demonstrated peak NP accumulation within the injury penumbra 1 h post-injury. An inverse relationship was found between NP size and their continued accumulation within the penumbra. NP accumulation preferentially occurred in the primary motor and somatosensory areas of the injury penumbra as compared to the parietal association and visual area. Thus, we characterized the accumulation of particles up to 500 nm at different times acutely after injury, indicating the potential of NP-based TBI theranostics in the acute period after injury.

A brief perspective on the diverging theories of lymphatic targeting with colloids

For targeted delivery of colloids to the lymphatic system, the colloids should efficiently reach and remain in the lymphatics for a considerable period of time. As per the current knowledge, diffusion and phagocytosis are the two mechanisms through which colloids reach the lymphatic system. Several parameters including particle size and charge have been shown to affect the direct uptake of colloids by the lymphatic system. Although many researchers attached ligands on the surface of colloids to promote phagocytosis-mediated lymphatic delivery, another school of thought suggests avoidance of phagocytosis by use of carriers like polyethylene glycol (PEG)ylated colloids to impart stealth attributes and evade phagocytosis. In this perspective, we weigh up the paradoxical theories and approaches available in the literature to draw conclusions on the conditions favorable for achieving efficient lymphatic targeting of colloids.

Lipid-Based Drug Delivery Systems in Cancer Therapy: What Is Available and What Is Yet to Come

Cancer is a leading cause of death in many countries around the world. However, the efficacy of current standard treatments for a variety of cancers is suboptimal. First, most cancer treatments lack specificity, meaning that these treatments affect both cancer cells and their normal counterparts. Second, many anticancer agents are highly toxic, and thus, limit their use in treatment. Third, a number of cytotoxic chemotherapeutics are highly hydrophobic, which limits their utility in cancer therapy. Finally, many chemotherapeutic agents exhibit short half-lives that curtail their efficacy. As a result of these deficiencies, many current treatments lead to side effects, noncompliance, and patient inconvenience due to difficulties in administration. However, the application of nanotechnology has led to the development of effective nanosized drug delivery systems known commonly as nanoparticles. Among these delivery systems, lipid-based nanoparticles, particularly liposomes, have shown to be quite effective at exhibiting the ability to: 1) improve the selectivity of cancer chemotherapeutic agents; 2) lower the cytotoxicity of anticancer drugs to normal tissues, and thus, reduce their toxic side effects; 3) increase the solubility of hydrophobic drugs; and 4) offer a prolonged and controlled release of agents. This review will discuss the current state of lipid-based nanoparticle research, including the development of liposomes for cancer therapy, different strategies for tumor targeting, liposomal formulation of various anticancer drugs that are commercially available, recent progress in liposome technology for the treatment of cancer, and the next generation of lipid-based nanoparticles.

Illuminating the physiology of extracellular vesicles

Extracellular vesicles play a crucial role in intercellular communication by transmitting biological materials from donor cells to recipient cells. They have pathophysiologic roles in cancer metastasis, neurodegenerative diseases, and inflammation. Extracellular vesicles also show promise as emerging therapeutics, with understanding of their physiology including targeting, distribution, and clearance therefore becoming an important issue. Here, we review recent advances in methods for tracking and imaging extracellular vesicles in vivo and critically discuss their systemic distribution, targeting, and kinetics based on up-to-date evidence in the literature.

Illuminating the physiology of extracellular vesicles

Extracellular vesicles play a crucial role in intercellular communication by transmitting biological materials from donor cells to recipient cells. They have pathophysiologic roles in cancer metastasis, neurodegenerative diseases, and inflammation. Extracellular vesicles also show promise as emerging therapeutics, with understanding of their physiology including targeting, distribution, and clearance therefore becoming an important issue. Here, we review recent advances in methods for tracking and imaging extracellular vesicles in vivo and critically discuss their systemic distribution, targeting, and kinetics based on up-to-date evidence in the literature.

DAFODIL: A novel liposome-encapsulated synergistic combination of doxorubicin and 5FU for low dose chemotherapy

PEGylated liposomes have transformed chemotherapeutic use of doxorubicin by reducing its cardiotoxicity; however, it remains unclear whether liposomal doxorubicin is therapeutically superior to free doxorubicin. Here, we demonstrate a novel PEGylated liposome system, named DAFODIL (Doxorubicin And 5-Flurouracil Optimally Delivered In a Liposome) that inarguably offers superior therapeutic efficacies compared to free drug administrations. Delivery of synergistic ratios of this drug pair led to greater than 90% reduction in tumor growth of murine 4T1 mammary carcinoma in vivo. By exploiting synergistic ratios, the effect was achieved at remarkably low doses, far below the maximum tolerable drug doses. Our approach re-invents the use of liposomes for multi-drug delivery by providing a chemotherapy vehicle which can both reduce toxicity and improve therapeutic efficacy. This methodology is made feasible by the extension of the ammonium-sulfate gradient encapsulation method to nucleobase analogues, a liposomal entrapment method once conceived useful only for anthracyclines. Therefore, our strategy can be utilized to efficiently evaluate various chemotherapy combinations in an effort to translate more effective combinations into the clinic.

(18)F-labeling syntheses and preclinical evaluation of functionalized nanoliposomes for Alzheimer's disease

The aim of the present study was to synthesize functionalized (18)F-labeled NLs ((18)F-NLs) and evaluate their biological behavior in mouse models of Alzheimer's disease (AD) using positron emission tomography (PET) and ex vivo brain autoradiography. (18)F-fluorine was introduced to (18)F-NLs either by using a core forming (18)F-lipid or by encapsulating a (18)F-tracer, (18)F-treg-curcumin inside the NLs. Phosphatidic acid (PA) and curcumin derivative (Curc) functionalized (18)F-NLs with or without additional mApoE functionalization were produced using thin film hydration. The biodistribution and β-amyloid plaque-binding ability of (18)F-NLs were studied in wild type mice and AD mouse models using in vivo PET imaging and ex vivo brain autoradiography at 60min after (18)F-NL injection. Functionalized (18)F-NLs were successfully synthesized. The preclinical evaluation in mice showed that the functional group affected the biodistribution of (18)F-NLs. Further functionalization with mApoE increased the brain-to-blood ratio of (18)F-NLs but the overall brain uptake remained low with all functionalized (18)F-NLs. The liposomal encapsulation of (18)F-treg-curcumin was not successful and preclinical results of encapsulated (18)F-treg-curcumin and plain (18)F-treg-curcumin were identical. Although the studied functionalized (18)F-NLs were not suitable for PET imaging as such, the synthesis techniques introduced in this study can be utilized to modify the biological behavior of (18)F-labeled NLs.

Stearylamine Liposomal Delivery of Monensin in Combination with Free Artemisinin Eliminates Blood Stages of Plasmodium falciparum in Culture and P. berghei Infection in Murine Malaria

The global emergence of drug resistance in malaria is impeding the therapeutic efficacy of existing antimalarial drugs. Therefore, there is a critical need to develop an efficient drug delivery system to circumvent drug resistance. The anticoccidial drug monensin, a carboxylic ionophore, has been shown to have antimalarial properties. Here, we developed a liposome-based drug delivery of monensin and evaluated its antimalarial activity in lipid formulations of soya phosphatidylcholine (SPC) cholesterol (Chol) containing either stearylamine (SA) or phosphatidic acid (PA) and different densities of distearoyl phosphatidylethanolamine-methoxy-polyethylene glycol 2000 (DSPE-mPEG-2000). These formulations were found to be more effective than a comparable dose of free monensin in Plasmodium falciparum (3D7) cultures and established mice models of Plasmodium berghei strains NK65 and ANKA. Parasite killing was determined by a radiolabeled [(3)H]hypoxanthine incorporation assay (in vitro) and microscopic counting of Giemsa-stained infected erythrocytes (in vivo). The enhancement of antimalarial activity was dependent on the liposomal lipid composition and preferential uptake by infected red blood cells (RBCs). The antiplasmodial activity of monensin in SA liposome (50% inhibitory concentration [IC50], 0.74 nM) and SPC:Chol-liposome with 5 mol% DSPE-mPEG 2000 (IC50, 0.39 nM) was superior to that of free monensin (IC50, 3.17 nM), without causing hemolysis of erythrocytes. Liposomes exhibited a spherical shape, with sizes ranging from 90 to 120 nm, as measured by dynamic light scattering and high-resolution electron microscopy. Monensin in long-circulating liposomes of stearylamine with 5 mol% DSPE-mPEG 2000 in combination with free artemisinin resulted in enhanced killing of parasites, prevented parasite recrudescence, and improved survival. This is the first report to demonstrate that monensin in PEGylated stearylamine (SA) liposome has therapeutic potential against malaria infections.

The effects of nanoparticle drug loading on the pharmacokinetics of anticancer agents

Major advances in carrier-mediated agents, which include nanoparticles, nanosomes and conjugates, have revolutionized drug delivery capabilities over the past decade. While providing numerous advantages, such as greater solubility, duration of exposure and delivery to the site of action over their small-molecule counterparts, there is substantial variability in systemic clearance and distribution, tumor delivery and pharmacologic effects (efficacy and toxicity) of these agents. This review provides an overview of factors that affect the pharmacokinetics and pharmacodynamics of carrier-mediated agents in preclinical models and patients.

Effect of pegylated phosphatidylserine-containing liposomes in experimental chronic arthritis

Background

Phosphatidylserine-containing liposomes (PSL) have been shown to reduce inflammation in experimental models of acute arthritis, by mimicking the apoptotic process. The aim of this study was to evaluate the effect of pegylated PSL (PEG-PSL) on chronic inflammation of collagen induced arthritis (CIA) in DBA/1J mice.

Methods

CIA was induced in 24 DBA/1J mice (n = 6/group), which were divided into control (0.9 % saline) or treated with PEG-PSL (5, 10 and 15 mg/kg/day, subcutaneously for 20 days). Clinical score, limb histology and measurement of cytokines in knee joints of animals by ELISA and cytometric bead array (CBA) were evaluated. The in vitro study employed macrophage cultures stimulated with 100 ng/ml of LPS plus 10 ng/ml of PMA and treated with 100 μM PEG-PSL.

Results

Resolution of the disease in vivo and the inflammatory process in vitro were not observed. PEG-PSL, in doses of 10 and 15 mg/kg, were not shown to reduce the score of the disease in animals, whereas with the dose of 5 mg/kg, the animals did not show the advanced stage of the disease when compared to the controls. The PEG- PSL 5, 10 and 15 mg/kg treatment groups did not show significant reduction of TNF-α, IL-1β, IL-6, IL-2 and IFN-γ when compared to the controls. Disease incidence and animal weights were not affected by treatment. Regarding the paw histology, PEG-PSL did not yield any reductions in the infiltrating mononuclear, synovial hyperplasia, extension of pannus formation, synovial fibrosis, erosion of cartilage, bone erosion or cartilage degradation. The concentration of 100 μM of PEG-PSL has not been shown to reduce inflammation induced by LPS/PMA in the in vitro study. Treated groups did not show any reduction in inflammatory cytokines in the knee joints of animals affected by the disease compared to the control, although there were higher concentrations of TGF-β1 in all experimental groups.

Conclusion

The experimental model showed an expression of severe arthritis after the booster. TGF-β1 as well other pro inflammatory cytokines were presented in high concentrations in all groups. PEG-PSL had no impact on the clinical score, the histopathology from tibial-tarsal joints or the production of cytokines in the knee joints. Other alternatives such as dosage, route of administration, and as an adjunct to a drug already on the market, should be evaluated to support the use of PEG-PSL as a new therapeutic tool in inflammatory diseases.

Codelivery of dual drugs from polymeric micelles for simultaneous targeting of both cancer cells and cancer stem cells

AIM

Phenformin-loaded micelles (Phen M) were used in combination with gemcitabine-loaded micelles (Gem M) to study their combined effect against H460 human lung cancer cells and cancer stem cells (CSCs) in vitro and in vivo.

MATERIALS & METHODS

Gem M and Phen M were prepared via self-assembly of a mixture of a diblock copolymer of PEG and urea-functionalized polycarbonate (PEG-PUC) and a diblock copolymer of PEG and acid-functionalized polycarbonate (PEG-PAC) through hydrogen bonding and ionic interactions. Gem M and Phen M were characterized and tested for efficacy both in vitro and in vivo against cancer cells and CSCs.

RESULTS

The combination of Gem M/Phen M exhibited higher cytotoxicity against CSCs and non-CSCs than Gem M and Phen M alone, and showed significant cell cycle growth arrest in vitro. The combination therapy had superior tumor suppression and apoptosis in vivo without inducing toxicity to liver and kidney.

CONCLUSION

The combination of Gem M and Phen M may be potentially used in lung cancer therapy.

Nano-antioxidants: An emerging strategy for intervention against neurodegenerative conditions

Oxidative stress has for long been linked to the neuronal cell death in many neurodegenerative conditions. Conventional antioxidant therapies have been less effective in preventing neuronal damage caused by oxidative stress due to their inability to cross the blood brain barrier. Nanoparticle antioxidants constitute a new wave of antioxidant therapies for prevention and treatment of diseases involving oxidative stress. It is believed that nanoparticle antioxidants have strong and persistent interactions with biomolecules and would be more effective against free radical induced damage. Nanoantioxidants include inorganic nanoparticles possessing intrinsic antioxidant properties, nanoparticles functionalized with antioxidants or antioxidant enzymes to function as an antioxidant delivery system. Nanoparticles containing antioxidants have shown promise as high-performance therapeutic nanomedicine in attenuating oxidative stress with potential applications in treating and preventing neurodegenerative conditions. However, to realize the full potential of nanoantioxidants, negative aspects associated with the use of nanoparticles need to be overcome to validate their long term applications.

Formulation and physiologic factors affecting the pharmacology of carrier-mediated anticancer agents

INTRODUCTION

Major advances in carrier-mediated agents (CMAs), which include nanoparticles and conjugates, have revolutionized drug delivery capabilities over the past decade. While providing numerous advantages such as increased exposure duration, greater solubility and delivery to tumor sites over their small molecule counterparts, there is substantial variability in how individual CMA formulations affect the pharmacology, pharmacokinetics and pharmacodynamics (efficacy and toxicity) of these agents.

AREAS COVERED

CMA formulations are complex in nature compared to their small molecule counterparts and consist of multiple components and variables that can affect the pharmacological profile. This review provides an overview of factors that affect the pharmacologic profiles observed in CMA-formulated chemotherapy, primarily in liposomal formulations, that are currently in preclinical or early clinical development.

EXPERT OPINION

Despite the numerous advantages that CMA formulations provide, their clinical use is still in its infancy. It is critical that we understand the mechanisms and effects of CMAs in navigating biological barriers and how these factors affect their biodistribution and delivery to tumors. Future studies are warranted to better understand the complex pharmacology and interaction between CMA carriers and biological systems, such as the mononuclear phagocyte system and tumor microenvironment.

Time-controlled phagocytosis of asymmetric liposomes: Application to phosphatidylserine immunoliposomes binding HIV-1 virus-like particles

Macrophage immune functions such as antibody-mediated phagocytosis are strongly impaired in individuals affected by HIV-1. Nevertheless, infected macrophages are still able to phagocytose apoptotic cells. For this reason, we recently developed antibody-decorated phosphatidylserine (PS)-containing liposomes that bind HIV-1 virus-like particles and, by mimicking apoptotic cells, are efficiently internalized by macrophages. In the context of an in vivo application, it would be extremely important to initially protect immunoliposomes from macrophages, in order to provide enough time to redistribute through the body and achieve maximum virus binding. To this end, we have designed asymmetric immunoliposomes in which the PS is initially confined to the inner leaflet and thus cannot be recognized by macrophages. Spontaneous PS flip-flop to the outer surface leads to a time-delay in internalization by macrophages in vitro. Such a delay can be fine-tuned by altering the molecular composition of the immunoliposomes.

FROM THE CLINICAL EDITOR

In the fight against HIV-1, macrophage plays an important role. Ironically, the phagocytic functions of these cells are often impaired by HIV-1. In this interesting article, the authors described the development of asymmetric liposomes, which would bind HIV-1 with prolonged systemic circulation, such that the clearance of virus by macrophages is enhanced. This system represents a promising effective approach to utilize the phagocytic capability of macrophages.

Epidermal growth factor receptor-targeted immunoliposomes for delivery of celecoxib to cancer cells

Cyclooxygenase-2 (COX-2) is highly expressed in many different cancers. Therefore, the inhibition of the COX-2 pathway by a selective COX-2 inhibitor, celecoxib (CLX), may be an alternative strategy for cancer prevention and therapy. Liposomal drug delivery systems can be used to increase the therapeutic efficacy of CLX while minimizing its side effects. Previous studies have reported the encapsulation of CLX within the non-targeted long circulating liposomes and functional effect of these formulations against colorectal cancer cell lines. However, the selectivity and internalization of CLX-loaded liposomes can further be improved by grafting targeting ligands on their surface. Cetuximab (anti-epidermal growth factor receptor - EGFR - monoclonal antibody) is a promising targeting ligand since EGFR is highly expressed in a wide range of solid tumors. The aim of this study was to develop EGFR-targeted immunoliposomes for enhancing the delivery of CLX to cancer cells and to evaluate the functional effects of these liposomes in cancer cell lines. EGFR-targeted ILs, having an average size of 120nm, could encapsulate 40% of the CLX, while providing a sustained drug release profile. Cell association studies have also shown that the immunoliposome uptake was higher in EGFR-overexpressing cells compared to the non-targeted liposomes. In addition, the CLX-loaded-anti-EGFR immunoliposomes were significantly more toxic compared to the non-targeted ones in cancer cells with EGFR-overexpression but not in the cells with low EGFR expression, regardless of their COX-2 expression status. Thus, selective targeting of CLX with anti-EGFR immunoliposomes appears to be a promising strategy for therapy of tumors that overexpress EGFR.

Enzymatic synthesis of poly(ω-pentadecalactone-co-butylene-co-3,3′-dithiodipropionate) copolyesters and self-assembly of the PEGylated copolymer micelles as redox-responsive nanocarriers for doxorubicin delivery

The PEG-polyester copolymers bearing disulfide groups were synthesized to serve as redox-responsive anticancer drug carriers with an enhanced efficacy.

Biophysical, biopharmaceutical and toxicological significance of biomedical nanoparticles

Understanding of interplay between nanoparticles physicochemical and biophysical properties, and their impact on pharmacokinetic biodistribution and toxicological properties help designing of appropriate nanoparticle products for biomedical applications.

Development and Challenges of Nanovectors in Gene Therapy

In recent years, hundreds of genes have been linked to a variety of human diseases, and the field of gene therapy has emerged as a way to treat this wide range of diseases. The main goal of gene therapy is to find a gene delivery vehicle that can successfully target diseased cells and deliver therapeutic genes directly to their cellular compartment. The two main types of gene delivery vectors currently being investigated in clinical trials are recombinant viral vectors and synthetic nonviral vectors. Recombinant viral vectors take advantage of the evolutionarily optimized viral mechanisms to deliver genes, but they can be hard to specifically target in vivo and are also associated with serious side effects. Synthetic nonviral vectors are made out of highly biocompatible lipids or polymers, but they are much less efficient at delivering their genetic payload due to the lack of any active delivery mechanism. This mini review will introduce the current state of gene delivery in clinical trials, and discuss the specific challenges associated with each of these vectors. It will also highlight some specific gaps in knowledge that are limiting the advancement of this field and touch on the current areas of research being explored to overcome them.

Delivery of antisense oligonucleotides using poly(alkylene oxide)-poly(propylacrylic acid) graft copolymers in conjunction with cationic liposomes

The clinical application of gene silencing is hindered by poor stability and low delivery efficiency of naked oligonucleotides. Here, we present the in vitro and in vivo behaviors of a rationally designed, ternary, self-assembled nanoparticle complex, consisting of an anionic copolymer, cationic DOTAP liposome, and antisense oligonucleotide (AON). The multifunctional copolymers are based on backbone poly(propylacrylic acid) (PPAA), a pH-sensitive hydrophobic polymer, with grafted poly(alkylene oxides) (PAOs) varying in extent of grafting and PAO chemistry. The nanoparticle complexes with PPAA-g-PAO copolymers enhance antisense gene silencing effects in A2780 human ovarian cancer cells. A greater amount of AON is delivered to ovarian tumor xenografts using the ternary copolymer-stabilized delivery system, compared to a binary DOTAP/AON complex, following intraperitoneal injection in mice. Further, intratumoral injection of the nanoparticle complexes containing 1 mol% grafted PAO reduced tumoral bcl-2 expression by up to 60%. The data for complexes across the set of PAO polymers support a strong role for the hydrophilic-lipophilic balance of the graft copolymer in achieving serum stability and cellular uptake. Based upon these results, we anticipate that this novel nanoparticle delivery system can be extended to the delivery of plasmid DNA, siRNA, or aptamers for preclinical and clinical development.

pH-sensitive stearoyl-PEG-poly(methacryloyl sulfadimethoxine) decorated liposomes for the delivery of gemcitabine to cancer cells

Novel, acid-sensitive liposomes that respond to physiopathological pH for tumour targeting applications were obtained by surface decoration with 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)] (mPEG-DSPE) and stearoyl-poly(ethylene glycol)-poly(methacryloyl sulfadimethoxine) copolymer (stearoyl-PEG-polySDM). The pH-sensitive stearoyl-PEG-polySDM copolymer contained an average of seven methacryloyl sulfadimethoxines per molecule and was found to possess an apparent pKa of 7.2. Preliminary cloud point studies showed that the hydrophilic/hydrophobic copolymer conversion occurred at pH 7.0. The copolymer was soluble above pH 7.0 and underwent aggregation at lower pH. Liposome formulations were prepared with 0.2:0.6:100, 0.5:1.5:100 and 1:3:100 mPEG-DSPE/stearoyl-PEG-polySDM/lipids molar ratios. All of the liposome formulations were stable at pH 7.4, even in the presence of foetal bovine serum, but they underwent rapid size increase at pH 6.5. TEM analysis showed that, at pH 6.5, the formulations coated with a stearoyl-PEG-polySDM/lipids molar ratio greater than 1:100 underwent aggregation. At pH 7.4, the liposomes showed negative zeta potential that significantly decreased after incubation at pH 6.5. Cell-culture studies indicated that the liposomes were not toxic up to 10mg/mL. Fluorescence spectroscopy, cytofluorimetry and confocal microscopy showed that at pH 6.5, the incubation of MCF-7 tumour cells with fluorescein-labelled 1:3:100 mPEG-DSPE/stearoyl-PEG-polySDM/lipids molar ratio liposomes resulted in time-dependent cell association, while at pH 7.4 the cell interaction was significantly lower. The same pH-responsive liposome formulation loaded with gemcitabine (98.2±4.7nmol gemcitabine/lipid μmol loading capacity) was stable at pH 7.4 for several hours, while at pH 6.5 it rapidly aggregated. At pH 6.5, these liposomes displayed higher cytotoxicity than at pH 7.4 or compared to non-responsive control liposomes at both incubation pH. Notably, treatment with free gemcitabine did not yield cytotoxic effects, indicating that the carrier can efficiently deliver the anticancer drug to the cytosolic compartment.

Determinants for in vivo antitumor effect of angiogenesis inhibitor SU5416 formulated in PEGylated emulsion

Angiogenesis, the sprouting of capillaries from preexisting ones, is essential for the sustained growth of solid tumors. In this study, we used SU5416, a hydrophobic molecule with potent tyrosine kinase inhibitor of type 2 receptor for vascular endothelial growth factor (VEGF), as PEGylated emulsion (SU5416-PE), and evaluated the antitumor potency of this formulation in Lewis lung cancer (LLC), Colon-26 (C26), and B16BL6 melanoma (B16) tumor-bearing mice. Intravenous injection of SU5416-PE into tumor-bearing mice significantly suppressed the growth of C26 and B16 tumors, but had no effect on the growth of LLC tumors. MTT assay revealed that SU5416 inhibited the proliferation of human umbilical vein endothelial cells in a concentration-dependent manner but did not show such an inhibitory effect on all types of tumor cells examined, demonstrating the specificity of SU5416 for endothelial cells. Considering that VEGF levels within C26 and B16 tumors were found to be about 10-fold and 20-fold higher than that in LLC tumors, respectively, it was suggested that SU5416-PE would inhibit angiogenesis in certain types of tumor tissue such as C26 and B16 where VEGF plays a major role for promoting angiogenesis, leading to the suppression of in vivo tumor growth.

Hyaluronan polymer length, grafting density, and surface poly(ethylene glycol) coating influence in vivo circulation and tumor targeting of hyaluronan-grafted liposomes

Hyaluronan-grafted liposomes (HA-liposomes) preferentially target CD44-overexpressing tumor cells in vitro via receptor-mediated endocytosis. We investigated the pharmacokinetics and biodistribution of HA-liposomes with various sizes of HA (MW 5-8, 50-60, and 175-350 kDa) in mice. Incorporation of negatively charged HA on the liposome surface compromised its blood circulation time, which led to decreased tumor accumulation in CD44+ human breast cancer MDA-MB-231 xenografts compared to PEGylated liposomes (PEG-5000). Clearance of HA-liposomes was HA polymer length-dependent; high MW (175-350 kDa, highest ligand binding affinity) HA-liposomes displayed faster clearance compared to low MW (5-8, 50-60 kDa) HA-liposomes or PEGylated liposomes. Surface HA ligand density can also affect clearance of HA-liposomes. Thus, HA is not an effective stealth coating material. When dual coating of PEG and HA was used, the PEG-HA-liposomes displayed similar blood circulation time and tumor accumulation to that of the PEGylated liposomes; however, the PEG-HA-liposomes displayed better cellular internalization capability in vivo. Tumor histology showed that PEG-HA-liposomes had a more direct association with CD44+ cancer cells, while PEGylated liposomes located predominantly in the tumor periphery, with less association with CD44+ cells. Flow cytometry analysis of ex vivo tumor cells showed that PEG-HA-liposomes had significantly higher tumor cell internalization compared to PEGylated liposomes. This study demonstrates that a long blood circulation time is critical for active tumor targeting. Furthermore, the use of the tumor-targeting ligand HA does not increase total tumor accumulation of actively targeted liposomes in solid tumors; however, it can enhance intracellular delivery.

Formulation development of a novel targeted theranostic nanoemulsion of docetaxel to overcome multidrug resistance in ovarian cancer

OBJECTIVE

Ovarian cancer is a highly lethal disease in which the majority of patients eventually demonstrate multidrug resistance. Develop a novel active targeted theranostic nanomedicine designed to overcome drug efflux mechanisms, using a Generally Regarded As Safe (GRAS) grade nanoemulsion (NE) as a clinically relevant platform.

MATERIALS AND METHODS

The NEs surface-functionalized with folate and gadolinium, were made using GRAS grade excipients and a high-shear microfluidization process. Efficacy was evaluated in ovarian cancer cells, SKOV3 and SKOV3TR. The NE accumulation in tumors was evaluated in SKOV3 tumor-bearing mice by magnetic resonance imaging (MRI).

RESULTS AND DISCUSSION

The NE with particle size < 150 nm were stable in plasma and parenteral fluids for 24 h. Ovarian cancer cells in vitro efficiently took up the non-targeted and folate-targeted NEs; improved cytotoxicity was observed for the folate-targeted NEs showing a 270-fold drop in the IC50 in SKOV3TR cells as compared to docetaxel alone. The addition of gadolinium did not affect cell viability in vitro, but showed relaxation times comparable to Magnevist®. Folate-targeted NEs accumulated in tumors for prolonged period of time compared to Magnevist® and showed enhanced contrast compared to non-targeted NEs with MRI in SKOV3 tumor-bearing mice suggesting active targeting of NEs due to folate modification.

CONCLUSIONS

A folate-targeted, theranostic NE delivers docetaxel by receptor mediated endocytosis that shows enhanced cytotoxicity capable of overcoming ABC transporter mediated taxane resistance. The diagnostic capability of the targeted nanomedicine showed enhanced contrast in tumors compared to clinically relevant MRI contrast agent Magnevist®.

Liposomes physically coated with peptides: preparation and characterization

Physically coating liposomes with peptides of desirable functions is an economic, versatile, and less time-consuming approach to prepare drug delivery vehicles. In this work, we designed three peptides-Ac-WWKKKGGNNN-NH2 (W2K3), Ac-WWRRRGGNNN-NH2(W2R3), Ac-WWGGGGGNNN-NH2(W2G3)-and studied their coating ability on negatively charged liposomes. It was found that the coating was mainly driven by the electrostatic interaction between the peptides' cationic side groups and the acidic lipids, which also mediated the "anchoring " of Trp residuals in the interfacial region of lipid bilayers. At the same conditions, the amount of the coated W2R3 was more than that of W2K3, but the stability of the liposome coated with W2R3 was deteriorated. This was caused by the delocalized charge of the guanidinium group of arginine. The coating of the peptide rendered the liposome pH-responsive behavior but did not prominently change the phase transition temperature. The liposome coated with peptides displayed appropriate pH/temperature dual responsive characteristics and was able to release the content in a controlled manner.

Development of EGFR-targeted nanoemulsion for imaging and novel platinum therapy of ovarian cancer

PURPOSE

Platinum-based chemotherapy is the treatment of choice for malignant epithelial ovarian cancers, but generalized toxicity and platinum resistance limits its use. Theranostic nanoemulsion with a novel platinum prodrug, myrisplatin, and the pro-apoptotic agent, C6-ceramide, were designed to overcome these limitations.

METHODS

The nanoemulsions, including ones with an EGFR binding peptide and gadolinium, were made using generally regarded as safe grade excipients and a high shear microfluidization process. Efficacy was evaluated in ovarian cancer cells, SKOV3, A2780 and A2780CP.

RESULTS

The nanoemulsion with particle size <150 nm were stable in plasma and parenteral fluids for 24 h. Ovarian cancer cells in vitro efficiently took up the non-targeted and EGFR-targeted nanoemulsions; improved cytotoxicity was observed for the these nanoemulsions with the latter showing a 50-fold drop in the IC50 in SKOV3 cells as compared to cisplatin alone. The addition of gadolinium did not affect cell viability in vitro, but showed relaxation times comparable to Magnevist(®).

CONCLUSION

The myrisplatin/C6-ceramide nanoemulsion synergistically enhanced in vitro cytotoxicity. An EGFR binding peptide addition further increased in vitro cytotoxicity in EGFR positive cancer cells. The diagnostic version showed MR imaging similar to the clinically relevant Magnevist® and may be suitable as a theranostic for ovarian cancer.

RGD and interleukin-13 peptide functionalized nanoparticles for enhanced glioblastoma cells and neovasculature dual targeting delivery and elevated tumor penetration

As the most common malignant brain tumors, glioblastoma multiforme (GBM) was characterized by angiogenesis and tumor cells proliferation. Dual targeting to neovasculature and GBM cells could deliver cargoes to these two kinds of cells, leading to a combination treatment. In this study, polymeric nanoparticles were functionalized with RGD and interleukin-13 peptide (IRNPs) to construct a neovasculature and tumor cell dual targeting delivery system in which RGD could target αvβ3 on neovasculature and interleukin-13 peptide could target IL13Rα2 on GBM cells. In vitro, interleukin-13 peptide and RGD could enhance the uptake by corresponding cells (C6 and human umbilical vein endothelial cells). Due to the expression of both receptors on C6 cells, RGD also could enhance the uptake by C6 cells. Through receptor labeling, it clearly showed that αvβ3 could mediate the internalization of RGD modified nanoparticles and IL13Rα2 could mediate the internalization of interleukin-13 peptide modified nanoparticles. The ligand functionalization also resulted in a modification on endocytosis pathways, which changed the main endocytosis pathways from macropinocytosis for unmodified nanoparticles to clathrin-mediated endocytosis for IRNPs. IRNPs also displayed the strongest penetration ability according to tumor spheroid analysis. In vivo, IRNPs could effectively deliver cargoes to GBM with higher intensity than monomodified nanoparticles. After CD31-staining, it demonstrated IRNPs could target both neovasculature and GBM cells. In conclusion, IRNPs showed promising ability in dual targeting both neovasculature and GBM cells.

Cancer nanotechnology: the impact of passive and active targeting in the era of modern cancer biology

Cancer nanotherapeutics are progressing at a steady rate; research and development in the field has experienced an exponential growth since early 2000's. The path to the commercialization of oncology drugs is long and carries significant risk; however, there is considerable excitement that nanoparticle technologies may contribute to the success of cancer drug development. The pace at which pharmaceutical companies have formed partnerships to use proprietary nanoparticle technologies has considerably accelerated. It is now recognized that by enhancing the efficacy and/or tolerability of new drug candidates, nanotechnology can meaningfully contribute to create differentiated products and improve clinical outcome. This review describes the lessons learned since the commercialization of the first-generation nanomedicines including DOXIL® and Abraxane®. It explores our current understanding of targeted and non-targeted nanoparticles that are under various stages of development, including BIND-014 and MM-398. It highlights the opportunities and challenges faced by nanomedicines in contemporary oncology, where personalized medicine is increasingly the mainstay of cancer therapy. We revisit the fundamental concepts of enhanced permeability and retention effect (EPR) and explore the mechanisms proposed to enhance preferential "retention" in the tumor, whether using active targeting of nanoparticles, binding of drugs to their tumoral targets or the presence of tumor associated macrophages. The overall objective of this review is to enhance our understanding in the design and development of therapeutic nanoparticles for treatment of cancers.

Synthesis, characterization, and evaluation of a novel amphiphilic polymer RGD-PEG-Chol for target drug delivery system

An amphiphilic polymer RGD-PEG-Chol which can be produced in large scale at a very low cost has been synthesized successfully. The synthesized intermediates and final products were characterized and confirmed by ¹H nuclear magnetic resonance spectrum (¹H NMR) and Fourier transform infrared spectrum (FT-IR). The paclitaxel- (PTX-) loaded liposomes based on RGD-PEG-Chol were then prepared by film formation method. The liposomes had a size within 100 nm and significantly enhanced the cytotoxicity of paclitaxel to B16F10 cell as demonstrated by MTT test (IC₅₀ = 0.079  μg/mL of RGD-modified PTX-loaded liposomes compared to 9.57  μg/mL of free PTX). Flow cytometry analysis revealed that the cellular uptake of coumarin encapsulated in the RGD-PEG-Chol modified liposome was increased for HUVEC cells. This work provides a reasonable, facile, and economic approach to prepare peptide-modified liposome materials with controllable performances and the obtained linear RGD-modified PTX-loaded liposomes might be attractive as a drug delivery system.

Synthesis of poly(ethylene glycol)-b-poly(N-(2-hydroxypropyl) methacrylamide) block copolymers with well-defined structures and their influence on in vivo circulation and biodistribution

PEG-b-PHPMA block copolymers with a precisely controlled composition were synthesized and showed a good biodistribution pattern and long circulation time.

Factors controlling the pharmacokinetics, biodistribution and intratumoral penetration of nanoparticles

Nanoparticle drug delivery to the tumor is impacted by multiple factors: nanoparticles must evade clearance by renal filtration and the reticuloendothelial system, extravasate through the enlarged endothelial gaps in tumors, penetrate through dense stroma in the tumor microenvironment to reach the tumor cells, remain in the tumor tissue for a prolonged period of time, and finally release the active agent to induce pharmacological effect. The physicochemical properties of nanoparticles such as size, shape, surface charge, surface chemistry (PEGylation, ligand conjugation) and composition affect the pharmacokinetics, biodistribution, intratumoral penetration and tumor bioavailability. On the other hand, tumor biology (blood flow, perfusion, permeability, interstitial fluid pressure and stroma content) and patient characteristics (age, gender, tumor type, tumor location, body composition and prior treatments) also have impact on drug delivery by nanoparticles. It is now believed that both nanoparticles and the tumor microenvironment have to be optimized or adjusted for optimal delivery. This review provides a comprehensive summary of how these nanoparticle and biological factors impact nanoparticle delivery to tumors, with discussion on how the tumor microenvironment can be adjusted and how patients can be stratified by imaging methods to receive the maximal benefit of nanomedicine. Perspectives and future directions are also provided.

Nanocarriers for intravenous injection--the long hard road to the market

Nanodispersed drug delivery systems for the intravenous injection have successfully overcome the hurdle of drug approval in the European Union and the United States. Although there is a need for highly advanced nanocarrier devices they have not been the result of a rational formulation design but were developed as stand-alone products in a long chain of case-by-case studies. This review focuses on aspects in development, composition, and manufacture of these innovative dosage forms that are relevant for the translation into new drug products.