Polyethylene Glycol-phosphatidylethanolamine Research Articles

Polymeric micelles for enhanced lymphatic drug delivery to treat metastatic tumors

Polymeric micelles have been proven to be a promising nano-sized system for drug delivery. Understanding its in vivo behaviors at the whole body, tissue and cellular levels is critical for translating this drug delivery system into clinical practice. In this study, the 14.5nm micelles made of polyethylene glycol-phosphatidylethanolamine (PEG-PE) for delivery of doxorubicin and vinorelbine were investigated. Using confocal and two-photon microscopy imaging of live mice or tissue sections, we observed that after systemic administration, the fluorescently labeled PEG-PE micelles encapsulating doxorubicin migrated through blood vessels in entirety into the interstitial tissue, collected by lymphatic vessels, and accumulated in lymph nodes. Importantly, encapsulated drugs such as vinorelbine (Nanovin), preferentially accumulate in lymph nodes when compared to the free drugs. Moreover, the in vivo bioluminescent imaging showed that Nanovin significantly reduced lymph node metastasis rate (P<0.05) in 4T1-luc2 murine breast tumor bearing mice. Finally, we observed that Nanovin enhanced antitumor activity against primary tumors and lung metastases while having low toxicity in various 4 T1 tumor models. This study suggests that PEG-PE micelle is a promising drug delivery system for the treatment of lymphatic metastases, and may also have important applications in other lymphatic system-related diseases.

Dual ligands modified double targeted nano-system for liver targeted gene delivery

Context: It is now well established that the surface of nanocarriers with specific ligands defines a new biological identity, which assist in targeting and internalization of the nanocarriers to specific cell populations, such as cancers and disease organs.Objective: The aim of this study is to develop systemically administrable dual ligands modified nano-system which could both target cancer cells and macrophages in the liver.Methods: Transferrin (Tf) and mannan (M) were linked onto polyethylene glycol-phosphatidylethanolamine (PEG-PE) and PE separately to get transferrin-PEG-PE (T-PEG-PE) and mannan-PE (M-PE) ligands for the surface modification of carriers. The in vivo transfection efficiency of the novel dual ligands modified (D-modified) vectors were evaluated in tumor bearing animal models.Results: D-modified solid lipid nanoparticles/enhanced green fluorescence protein plasmid (D-SLN/pEGFP) has a particle size of 198 nm and a gene loading quantity of 89%. D-SLN/pEGFP displayed over 25% higher transfection efficiency than M-PE modified SLN/pEGFP (M-SLN/pEGFP) in HepG2 cells and T-PEG-PE modified SLN/pEGFP (T-SLN/pEGFP) in Kupffer cells (KCs) isolated from mice.Conclusion: It could be concluded that T-PEG-PE and M-PE could function as excellent active targeting ligands to improve the cell targeting ability of the carriers and the dual ligands modified vectors could be applied as a promising active targeting gene delivery system.

Micellar formulations of pro-apoptotic DM-PIT-1 analogs and TRAIL in vitro and in vivo

We have developed and characterized micellar formulations of analogs to the recently developed inhibitor of the phosphatidylinositol-3-kinase (PI3K) pathway (N-[(2-hydroxy-5-nitrophenyl)amino]carbonothioyl-3,5-dimethylbenzamide (DM-PIT-1)) for their physicochemical, loading and cytotoxic properties. The first generation inhibitor DM-PIT-1 is a non-lipid, small molecule inhibitor of phosphatidylinositol-3,4,5-triphosphate/Pleckstrin homology (PIP3/PH) binding capable of inhibiting the growth of tumor cells both in vitro and in vivo. A second generation of improved and druggable analogs has been developed. All compounds were successfully loaded (>70%) in PEG2000-PE micelles of 16–20 nm in size with several analogs demonstrating favorable cytotoxic activity against A2780 ovarian carcinoma. These compounds were also successfully incorporated into polyethylene glycol-phosphatidylethanolamine (PEG-PE) micelles combined with surface-bound tumor necrosis factor related apoptosis inducing ligand (TRAIL). The resulting multifunctional combination micelles were able to significantly enhance cytotoxic activity in the TRAIL-resistant A2780 cell line. Additionally, analogs NCL-176 and NCL-240 were effective in inhibiting tumor growth in an in vivo subcutaneous tumor model of A2780. These results indicate the utility of delivering TRAIL and PI3K pathway inhibitors in a combined micellar preparation.

Treatment of Lung Cancer Using Nanoparticle Drug Delivery Systems

One of the leading causes of cancer-associated deaths in most men and women in the Western world is lung cancer. There are various types of treatments depending on the type and the stage of the cancer. A recent type of therapy is targeted gene therapy which aims to target genes that cause lung cancer. However, this therapy has some drawbacks including lack of proper vectors for delivery. These drawbacks can potentially be overcome by using various types of nanoparticles. To review current literature on the treatment of lung cancer with nanoparticles. Researchers have attempted to treat lung cancer with a variety of types of nanoparticle matrices including lipid, polylactide-co-glycolide, albumin, poly (ω-pentadecalactone-co-butylene-co-succinate), cerium oxide, gold, ultra-small superparamagnetic iron oxide nanoparticles, super paramagnetic iron oxide, lipid-polycation-DNA, N-[1-(2,3- dioleoyloxyl)propyl]-NNN-trimethylammoniummethylsulfate, silica-overcoated magnetic cores, and polyethyleneglycol phosphatidylethanolamine. There are various ways in which nanoparticles enhance drug delivery, and these include encapsulation against immune response, tissue penetration, target selectivity and specificity, delivery monitoring, promoting apoptosis, and blocking pathways for cancer initiation and progression. In the past decade, a lot has been said about targeting of NPs for lung and other cancers, but little has been actually successfully delivered to date. Nevertheless, nanoparticles can act as good vectors for delivering drug to the target neoplastic lesions within the lung, increase cellular uptake, increase tissue penetration and help in tracking the drug. In the future, combination therapies may play a key role in the treatment of lung cancer using the existing therapies.

Folic acid-tethered Pep-1 peptide-conjugated liposomal nanocarrier for enhanced intracellular drug delivery to cancer cells: conformational characterization and in vitro cellular uptake evaluation

BackgroundA novel dual ligand–modified liposome, folic acid-tethered Pep-1 peptide-conjugated liposomal nanocarrier (FP-Lipo), was designed to overcome the nonselectivity of conventional penetrating peptide-tagged nanoparticulates and to provide the advantage of selective targeting of the folic acid receptor, which is frequently overexpressed on epithelial cancer cells.MethodsFP-Lipo was prepared by a sequential process of formation of a maleimide-derivatized small unilamellar vesicle, postinsertion of distearoyl phosphatidyl ethanolamine-polyethylene glycol 2000–folate to the vesicle, and Pep-1 peptide conjugation via thiol-maleimide linkage. Conformational and physical characteristics of the FP-Lipo nanocarriers were investigated for the extent of Pep-1 peptide and folic acid on the surface, vesicle size, and zeta potential. In vitro cellular uptake behaviors of the novel carrier containing a fluorescein dextran isothiocyanate probe were examined by spectrophotometry or by confocal laser scanning microscopy.ResultsA novel nanocarrier bearing approximately 750 folate ligands and 100 penetrating peptides per vesicle was successfully prepared. The physical properties were as follows: 140 nm in size; 5 mV in zeta potential; less than 0.3 in polydispersity index. An in vitro cellular uptake study revealed that the FP-Lipo nanocarrier system exhibited more than twofold enhanced translocation into the folic acid receptor–positive HeLa cells compared with the single Pep-1 peptide–modified liposome. Meanwhile, its cellular association and internalization into the folic acid receptor–negative normal HaCaT cells was comparable with that of Pep-1 peptide–modified liposome.ConclusionAn advanced dual ligand-modified liposome is potentially useful for the treatment of folic acid receptor–positive tumors with high translocation capability of the penetrating peptide–modified liposome.

Next step in drug delivery: getting to individual organelles

Next step in drug delivery: getting to individual organelles

Accumulation and toxicity of antibody-targeted doxorubicin-loaded PEG–PE micelles in ovarian cancer cell spheroid model

We describe the evaluation of doxorubicin-loaded PEG–PE micelles targeting using an ovarian cancer cell spheroid model. Most ovarian cancer patients present at an advanced clinical stage and develop resistance to standard of care platinum/taxane therapy. Doxorubicin is also approved for ovarian cancer but had limited benefits in refractory patients. In this study, we used drug-resistant spheroid cultures of ovarian carcinoma to evaluate the uptake and cytotoxicity of an antibody-targeted doxorubicin formulation. Doxorubicin was encapsulated in polyethylene glycol–phosphatidyl ethanolamine (PEG–PE) conjugated micelles. The doxorubicin-loaded PEG–PE micelles (MDOX) were further decorated with a cancer cell-specific monoclonal 2C5 antibody to obtain doxorubicin-loaded immunomicelles (2C5-MDOX). Targeting and resulting toxicity of doxorubicin-loaded PEG–PE micelles were evaluated in three dimensional cancer cell spheroids. Superior accumulation of 2C5-MDOX compared to free doxorubicin or untargeted MDOX in spheroids was evidenced both by flow cytometry, fluorescence and confocal microscopy. Interestingly, even higher toxicity was measured by lactate dehydrogenase release and terminal deoxynucleotidyl transferase dUTP nick end labeling of targeted doxorubicin micelles in Bcl-2 overexpressing adriamycin-resistant spheroids. Overall, these results support use of spheroids to evaluate tumor targeted drug delivery.

Delivery of drugs to cell membranes by encapsulation in PEG–PE micelles

Developing polymer micelles as drug delivery systems requires an in-depth understanding of how they interact with cells and deliver drugs across the cell membrane; however, this investigation faces many problems. In this study, we attempt to show how polyethylene glycol–phosphatidylethanolamine (PEG–PE) micelles deliver drugs across cell membranes by using a series of fluorescence techniques, including de-quenching, FRET and multi-labeling. We demonstrate that PEG–PE copolymers transfer to the cell membrane from micelles due to their amphiphilic properties, and are then internalized through nonspecific endocytosis and distributed in the endoplasmic reticulum and Golgi apparatus without affecting cellular ATP and viability. Hydrophilic drugs and/or hydrophobic dyes can be encapsulated in PEG–PE micelles, which are maintained in an intact form in culture medium before and after incubation with cells. These micelles disassemble and release their payloads at the cell membrane; released agents are accelerated to enter cells due to the increased membrane fluidity caused by PEG–PE insertion. Encapsulation of drugs in micelles does not change their intracellular distribution but increases their cellular accumulation. This investigation provides new insights into the mechanism of polymer micelle delivering drugs into cells, which are helpful for designing a true site-specific delivery carrier.

Incorporation of Beclomethasone Dipropionate into Polyethylene Glycol‐Diacyl Lipid Micelles as a Pulmonary Delivery System

Abstract Strategy, Management and Health Policy Enabling Technology, Genomics, Proteomics Preclinical Research Preclinical Development Toxicology, Formulation Drug Delivery, Pharmacokinetics Clinical Development Phases I‐III Regulatory, Quality, Manufacturing Postmarketing Phase IV Nebulized corticosteroid drugs have several shortcomings due to their poor water solubility and nonoptimal deposition pattern. The aims of this study were to investigate the in vitro and in vivo characteristics of beclomethasone dipropionate (BDP)‐loaded sterically stabilized phospholipid nanomicelles (SSMs) of a polyethylene glycol–phosphatidylethanolamine conjugate as a pulmonary delivery system. The particle size distribution and zeta potential measurements were 14.60 ± 1.11 nm and −46.94 ± 3.27 mV, respectively. The solubility of BDP was highly improved by at least 1,300 times its actual solubility. No chemical interaction was found between the PEGylated polymer and BDP as demonstrated by the Fourier transform infrared results. The in vitro aerodynamic of the aerosolized BDP‐SSMs using an Omron nebulizer showed an improvement in the aerodynamic values, with a significant deposition in the seven‐stage Next Generation Impactor. The BDP‐SSMs showed a prolonged dissolution profile of about 3 days. Intratracheal administration of the BDP‐SSMs (1 mg/kg) 12 or 23 h before a challenge in the asthmatic rat model led to a significant reduction in the inflammatory cell counts in bronchoalveolar lavage fluid samples compared with the administration of solubilized BDP. The SSM system appears to be an effective way of improving the therapeutic index of nebulized, poorly soluble corticosteroids.

Liposomes loaded with paclitaxel and modified with novel triphenylphosphonium-PEG-PE conjugate possess low toxicity, target mitochondria and demonstrate enhanced antitumor effects in vitro and in vivo

Previously, stearyl triphenylphosphonium (STPP)-modified liposomes (STPP-L) were reported to target mitochondria. To overcome a non-specific cytotoxicity of STPP-L, we synthesized a novel polyethylene glycol-phosphatidylethanolamine (PEG-PE) conjugate with the TPP group attached to the distal end of the PEG block (TPP-PEG-PE). This conjugate was incorporated into the liposomal lipid bilayer, and the modified liposomes were studied for their toxicity, mitochondrial targeting, and efficacy in delivering paclitaxel (PTX) to cancer cells in vitro and in vivo. These TPP-PEG-PE-modified liposomes (TPP-PEG-L), surface grafted with as high as 8mol% of the conjugate, were less cytotoxic compared to STPP-L or PEGylated STPP-L. At the same time, TPP-PEG-L demonstrated efficient mitochondrial targeting in cancer cells as shown by confocal microscopy in co-localization experiments with stained mitochondria. PTX-loaded TPP-PEG-L demonstrated enhanced PTX-induced cytotoxicity and anti-tumor efficacy in cell culture and mouse experiments compared to PTX-loaded unmodified plain liposomes (PL). Thus, TPP-PEG-PE can serve as a targeting ligand to prepare non-toxic liposomes as mitochondria-targeted drug delivery systems (DDS).

Transferrin-PEG-PE modified dexamethasone conjugated cationic lipid carrier mediated gene delivery system for tumor-targeted transfection

BackgroundThe main barriers to non-viral gene delivery include cellular and nuclear membranes. As such, the aim of this study was to develop a type of vector that can target cells through receptor-mediated pathways and by using nuclear localization signal (NLS) to increase the nuclear uptake of genetic materials.MethodsA dexamethasone (Dexa)-conjugated lipid was synthesized as the material of the solid lipid nanoparticles (SLNs), and transferrin (Tf) was linked onto polyethylene glycol-phosphatidylethanolamine (PEG-PE) to obtain Tf-PEG-PE ligands for the surface modification of the carriers. The in vitro transfection efficiency of the novel modified vectors was evaluated in human hepatoma carcinoma cell lines, and in vivo effects were observed in an animal model.ResultsTf-PEG-PE modified SLNs/enhanced green fluorescence protein plasmid (pEGFP) had a particle size of 222 nm and a gene loading quantity of 90%. Tf-PEG-PE-modified SLNs/pEGFP (Tf-SLNs/pEGFP) displayed remarkably higher transfection efficiency than non-modified SLNs/pEGFP and the vectors not containing Dexa, both in vitro and in vivo.ConclusionIt can be concluded that Tf and Dexa could function as an excellent active targeting ligand to improve the cell targeting and nuclear targeting ability of the carriers, and the resulting nanomedicine could be a promising active targeting drug/gene delivery system.

Mannosylated liposomes for targeted gene delivery

BackgroundLiposomes can be modified with different ligands to control their biological properties, such as longevity, targeting ability, and intracellular penetration, in a desired fashion. The aim of this study was to modify liposomes with a novel mannosylated polyethylene glycol-phosphatidylethanolamine (M-PEG-PE) ligand to achieve active targeted gene delivery.MethodsRat Kupffer cells were isolated and used as model cells for in vitro evaluation of cytotoxicity and transfection efficiency. The modified liposomes were intravenously injected into the rats, and Kupffer cells were isolated and analyzed by flow cytometry for in vivo gene delivery and expression.ResultsThe M-PEG-PE-modified liposome-enhanced green fluorescence protein plasmid (M-PEG-PE-Lipo-pEGFP) complexes had a particle size of 237 nm and a loading efficiency of 90%. The M-PEG-PE-Lipo-pEGFP complexes displayed remarkably higher transfection efficiency than unmodified Lipo-pEGFP, both in vitro (51%–30%) and in vivo (43%–27%).ConclusionM-PEG-PE could function as an excellent active targeting ligand, and M-PEG-PE-modified liposomes could be promising active targeted drug delivery vectors.

Development of the Novel PEG-PE-Based Polymer for the Reversible Attachment of Specific Ligands to Liposomes: Synthesis and in Vitro Characterization

Surface grafting of liposomes with the wide variety of ligands including antibodies and other proteins is a promising approach for targeted delivery of therapeutics. In this paper, we describe a simple method of synthesizing a hydrazine-functionalized poly(ethylene glycol)-phosphatidylethanolamine (PEG-PE)-based amphiphilic polymer which can conjugate a variety of ligands via a reversible, pH-cleavable bond. In this method, the targeting ligand is attached to the distal end of the PEG chain, which facilitates its easy access to the targeted site of interaction. The reversible attachment of targeting ligands is useful especially in multifunctional liposomal systems, whereafter successfully performing the function of targeting to the specific site, the bulky ligands, such as proteins or antibodies, are cleaved off in response to an environmental stimulus to expose some other functionalities such as ligands for intracellular penetration or organelle-specific targeting. To investigate the applicability of the protocol, the model ligands monoclonal antinucleosome antibody 2C5 and antimyosin antibody 2G4, and glycoproteins concanavalin A (Con-A) and avidin were conjugated to the synthesized polymer and incorporated into liposomes. In vitro assays including biochemical, enzyme-linked immunosorbent, fluorescence microscopy, and flow cytometry were used to confirm three key characteristics of the modified and/or liposome-attached proteins: successful conjugation of the targeting ligands to the polymer, preservation of specific activity of the ligands after the conjugation and liposome attachment, and the facile pH-sensitive ligand detachment. Monoclonal antibody 2C5 and 2G4, immobilized on the liposome surface, retained their binding affinity to corresponding antigens as confirmed by ELISA. The Con A-bearing liposomes showed significantly higher agglutination in the presence of its substrate mannan compared to plain liposomes (PL) and avidin-functionalized liposomes bound specifically with biotin-agarose. The study on the pH-dependence showed that almost 80% of the hydrazone bond was cleaved after rather brief preincubation of the immunoliposomes at pH 5 for 0.5 to 1 h. Fluorescence microscopy and flow cytometry analysis of cancer cells (HeLa and MCF-7) treated with cancer cell-specific targeting ligand mAb 2C5-bearing liposomes showed enhanced cellular binding. Studies at low pH clearly confirmed the easy cleavability of the targeting ligand from the liposomes resulting in significantly less or virtually no cellular association.

Assessment of the Roles of Ordered Lipid Microdomains in Post‐Endocytic Trafficking of Glycosyl‐Phosphatidylinositol‐Anchored Proteins in Mammalian Fibroblasts

We have used artificial phosphatidylethanolamine-polyethylene glycol (PE-PEG)-anchored proteins, incorporated into living mammalian cells, to evaluate previously proposed roles for ordered lipid 'raft' domains in the post-endocytic trafficking of glycosylphosphatidylinositol (GPI)-anchored proteins in CHO and BHK cells. In CHO cells, endocytosed PE-PEG protein conjugates colocalized strongly with the internalized GPI-anchored folate receptor, concentrating in the endosomal recycling compartment, regardless of the structure of the hydrocarbon chains of the PE-PEG 'anchor'. However, internalized PE-PEG protein conjugates with long-chain saturated anchors recycled to the plasma membrane at a slow rate comparable to that measured for the GPI-anchored folate receptor, whereas conjugates with short-chain or unsaturated anchors recycled at a faster rate similar to that observed for the transferrin receptor. These findings support the proposal (Mayor et al. Cholesterol-dependent retention of GPI-anchored proteins in endosomes. EMBO J 1998;17:4628-4638) that the slow recycling of GPI proteins in CHO cells rests on their affinity for ordered lipid domains. In BHK cells, internalized PE-PEG protein conjugates with either saturated or unsaturated 'anchors' colocalized strongly with simultaneously endocytosed folate receptor and, like the folate receptor, gradually accumulated in late endosomes/lysosomes. These latter findings do not support previous suggestions that the sorting of GPI proteins to late endosomes in BHK cells depends on their association with lipid rafts.

Surface modification of liposomes with rhodamine-123-conjugated polymer results in enhanced mitochondrial targeting

A novel mitochondrial-targeted liposomal drug-delivery system was prepared by modification of the liposomal surface with a newly synthesized polymer, rhodamine-123 (Rh123)-PEG-DOPE inserted into the liposomal lipid bilayer. This novel polymer was synthesized by conjugating the mitochondriotropic dye Rh123, with the amphiphilic polyethylene glycol–phosphatidylethanolamine (PEG-PE) conjugate. The modified liposomes showed better uptake by cells (HeLa, B16F10) estimated by fluorescence microscopy and FACS analysis. The co-localization study with stained mitochondria as well as with the isolation of mitochondria of the cultured cells after their treatment with Rh123 liposomes showed a high degree of accumulation of the modified liposomes in the mitochondria. We also prepared mitochondrial-targeted and nontargeted paclitaxel (PCL)-loaded liposomes. Mitochondrial-targeted PCL-loaded liposomes demonstrated enhanced cytotoxicity toward cancer cells compared with nontargeted drug-loaded liposomes or free PCL. Thus, Rh123-modified liposomes target mitochondria efficiently and can facilitate the delivery of a therapeutic payload to mitochondria.

Quantum dot loaded immunomicelles for tumor imaging

BackgroundOptical imaging is a promising method for the detection of tumors in animals, with speed and minimal invasiveness. We have previously developed a lipid coated quantum dot system that doubles the fluorescence of PEG-grafted quantum dots at half the dose. Here, we describe a tumor-targeted near infrared imaging agent composed of cancer-specific monoclonal anti-nucleosome antibody 2C5, coupled to quantum dot (QD)-containing polymeric micelles, prepared from a polyethylene glycol/phosphatidylethanolamine (PEG-PE) conjugate. Its production is simple and involves no special equipment. Its imaging potential is great since the fluorescence intensity in the tumor is twofold that of non-targeted QD-loaded PEG-PE micelles at one hour after injection.MethodsPara-nitrophenol-containing (5%) PEG-PE quantum dot micelles were produced by the thin layer method. Following hydration, 2C5 antibody was attached to the PEG-PE micelles and the QD-micelles were purified using dialysis. 4T1 breast tumors were inoculated subcutaneously in the flank of the animals. A lung pseudometastatic B16F10 melanoma model was developed using tail vein injection. The contrast agents were injected via the tail vein and mice were depilated, anesthetized and imaged on a Kodak Image Station. Images were taken at one, two, and four hours and analyzed using a methodology that produces normalized signal-to-noise data. This allowed for the comparison between different subjects and time points. For the pseudometastatic model, lungs were removed and imaged ex vivo at one and twenty four hours.ResultsThe contrast agent signal intensity at the tumor was double that of the passively targeted QD-micelles with equally fast and sharply contrasted images. With the side views of the animals only tumor is visible, while in the dorsal view internal organs including liver and kidney are visible. Ex vivo results demonstrated that the agent detects melanoma nodes in a lung pseudometastatic model after a 24 hours wash-out period, while at one hour, only a uniform signal is detected.ConclusionsThe targeted agent produces ultrabright tumor images and double the fluorescence intensity, as rapidly and at the same low dose as the passively targeted agents. It represents a development that may potentially serve to enhance early detection for metastases.

Nanoparticles: Crossing barriers and membrane interactions

In recent years, the field of nanotechnology has progressed at an exponential pace and is now at the forefront of medical research. Future nanomedicine (primarily the field of cancer nanotechnology) is projected to have an enormous impact on both diagnostics and treatment modalities to improve human health. Therefore, research and development of engineered multifunctional nanoparticles as imaging tools and pharmaceutical drug carriers is an area of current interest. The field of nanomedicine embraces a number of outstanding questions, critical for successful applications of nanoparticles in disease identification and cure. These include: (a) Technological developments to produce monodisperse drug-loaded nanocarriers, (b) biological factors affecting accumulation of nanocarriers to the diseased tissues including skin; (c) intracellular localization of nanoparticles via receptor-mediated targeting; (d) exploitation of the microenvironment of the tumour tissue for selective targeting of nanoparticles; (e) an understanding of molecular interactions between nanoparticles, biological membranes, intracellular organelles, preferred drug transport mechanisms; and finally (e) strategies for localized drug release intracellularly or in the vicinity of the tumours. It is our intention to address some of these issues in this special issue. Articles from experts in their respective research disciplines in nanomedicine are included to provide a broad overview of the current status of nanoparticle research. The papers present the latest information on the fabrication of nanoparticles, issues related to targeting, effect of route of administration, nano-imaging tools, and on-demand drug release. Each of these research fields provide excellent opportunities for cancer treatment, yet face limitations. The primary modes of nanoparticle delivery include intravenous, topical and oral administration. In either case, the ability of nanoparticles to cross barriers, such as the skin (topical delivery route) or GI tract (oral administration) or blood brain barrier (BBB) is a prerequisite for their success. It is important to understand the molecular mechanisms of nanoparticle-membrane interactions during multiple steps. Therefore the studies aimed at examining the barriers that are posed by various membranes (such as skin, cellular membranes or GI tract) deserve a closer look. In addition, coating of nanoparticles to target specific ligands has been demonstrated to improve intracellular accumulation. Therefore issues related with passive vs. active targeting of nanoparticles will bear their own merits and reservations. Saha and colleagues describe the strategies of fabrication for nanoparticulate drug delivery systems, and critical issues related to production of clinically relevant nanoparticles. The authors further discuss the factors that govern in vivo distribution of the nanoparticles. Along similar lines, Torchilin and Sawant describe another interesting platform, ‘phospholipid micelles’ as versatile pharmaceutical nanocarriers. Here, the authors also address an important issue of in vivo stability by using polyethyleneglycol phosphatidylethanolamine (PEG-PE)-based micellar drug delivery systems. It is worth mentioning that the nanoassemblies bearing pegylated molecules (such as liposomes) have proven to be extremely successful for in vivo drug delivery. Two papers are focused on drug delivery aspects resulting from passive accumulation. Sachdeva, Desai and colleagues discuss the nanoparticle interactions with the skin (first barrier). This article also presents the role of cell penetrating peptides (CPP) in modulating trans-dermal drug delivery. Amiji and colleagues present another clinically viable nanoparticulate assembly for drug delivery based on natural oils

Multifunctionality of lipid-core micelles for drug delivery and tumour targeting

Phospholipid micelles have proven to be the versatile pharmaceutical nanocarrier of choice for the delivery of poorly soluble chemotherapeutics for cancer therapy using various treatment modalities. Phospholipid micelles are typically expected to increase the accumulation of the loaded drugs in tumour tissues by taking advantage of the enhanced permeability and retention effect and by ligand-mediated active targeting. Furthermore, by tailoring the composition of the micelles, it is possible to enhance the intracellular delivery of the cargo. This review highlights the important advancements in our laboratory with polyethyleneglycol phosphatidylethanolamine (PEG-PE)-based micellar drug delivery systems for improvement of the therapeutic efficacy of poorly soluble anticancer drugs.

Palmitoyl Ascorbate-Loaded Polymeric Micelles: Cancer Cell Targeting and Cytotoxicity

To evaluate the potential of palmitoyl ascorbate (PA)-loaded micelles for ascorbate-mediated cancer cell targeting and cytotoxicity. PA was incorporated in polyethylene glycol-phosphatidyl ethanolamine micelles at varying concentrations. The formulations were evaluated for PA content by RP-HPLC. A stable formulation was selected based on size and zeta potential measurements. A co-culture of cancer cells and GFP-expressing non-cancer cells was used to determine the specificity of PA micelle binding. In vitro cytotoxicity of the micellar formulations towards various cancer cell lines was investigated using a cell viability assay. To elucidate the mechanism of action of cell death in vitro, the effect of various H(2)O(2) scavengers and metal chelators on PA-mediated cytotoxicity was studied. The in vivo anti-cancer activity of PA micelles was studied in female Balb/c mice bearing a murine mammary carcinoma (4T1 cells). PA micelles associated preferentially with various cancer cells compared to non-cancer cells in co-culture. PA micelles exhibited anti-cancer activity in cancer cell lines both in vitro and in vivo. The mechanism of cell death was due primarily to generation of reactive oxygen species (ROS). The anti-cancer activity of PA micelles associated with its enhanced cancer cell binding and subsequent generation of ROS.

Paclitaxel-Loaded Polymeric Micelles Modified with MCF-7 Cell-Specific Phage Protein: Enhanced Binding to Target Cancer Cells and Increased Cytotoxicity

Polymeric micelles are used as pharmaceutical carriers to increase solubility and bioavailability of poorly water-soluble drugs. Different ligands are used to prepare targeted polymeric micelles. Earlier, we developed the method for use of specific landscape phage fusion coat proteins as targeted delivery ligands and demonstrated the efficiency of this approach with doxorubicin-loaded PEGylated liposomes. Here, we describe a MCF-7 cell-specific micellar formulation self-assembled from the mixture of the micelle-forming amphiphilic polyethylene glycol-phosphatidylethanolamine (PEG-PE) conjugate, MCF-7-specific landscape phage fusion coat protein, and the hydrophobic drug paclitaxel. These micelles demonstrated a very low cmc value and specific binding to target cells. Using an in vitro coculture model, FACS analysis, and fluorescence microscopy we showed that MCF-7 targeted phage-micelles preferentially bound to target cells compared to nontarget cells. As a result, targeted paclitaxel-loaded phage-micelles demonstrated a significantly higher cytotoxicity toward target MCF-7 cells than free drug or nontargeted micelle formulations, but failed to show such a differential toxicity toward nontarget C166 cells. Overall, cancer cell-specific phage proteins identified from phage display peptide libraries can serve as targeting ligands ("substitute antibody") for polymeric micelle-based pharmaceutical preparations.