Targeted delivery of doxorubicin using stealth liposomes modified with transferrin

Transferrin liposomes of docetaxel for brain-targeted cancer applications: formulation and brain theranostics

Diagnosis and therapy of brain cancer was often limited due to low permeability of delivery materials across the blood-brain barrier (BBB) and their poor penetration into the brain tissue. This study explored the possibility of utilizing theranostic d-alpha-tocopheryl polyethylene glycol 1000 succinate mono-ester (TPGS) liposomes as nanocarriers for minimally invasive brain-targeted imaging and therapy (brain theranostics). The aim of this work was to formulate transferrin conjugated TPGS coated theranostic liposomes, which contain both docetaxel and quantum dots (QDs) for imaging and therapy of brain cancer. The theranostic liposomes with and without transferrin decoration were prepared and characterized for their particle size, polydispersity, morphology, drug encapsulation efficiency, in-vitro release study and brain theranostics. The particle sizes of the non-targeted and targeted theranostic liposomes were found below 200 nm. Nearly, 71% of drug encapsulation efficiency was achieved with liposomes. The drug release from transferrin conjugated theranostic liposomes was sustained for more than 72 h with 70% of drug release. The in-vivo results indicated that transferrin receptor-targeted theranostic liposomes could be a promising carrier for brain theranostics due to nano-sized delivery and its permeability which provided an improved and prolonged brain targeting of docetaxel and QDs in comparison to the non-targeted preparations.

Drug delivery system targeting advanced hepatocellular carcinoma: Current and future

Hepatocellular carcinoma (HCC) has a fairly high morbidity and is notoriously difficult to treat due to long latent period before detection, multidrug resistance and severe drug-related adverse effects from chemotherapy. Targeted drug delivery systems (DDS) that can selectively deliver therapeutic drugs into tumor sites have demonstrated a great potential in cancer treatment, which could be utilized to resolve the limitations of conventional chemotherapy. Numerous preclinical studies of DDS have been published, but targeted DDS for HCC has yet to be made for practical clinical use. Since rational targeted DDS design should take cancer-specific properties into consideration, we have reviewed the biological and physicochemical properties of HCC extensively to provide a comprehensive understanding on HCC, and recent DDS studies on HCC, aiming to find some potential targeted DDSs for HCC treatment and a meaningful platform for further development of HCC treatments.

FROM THE CLINICAL EDITOR

Hepatocellular carcinoma has a high incidence worldwide and is known to be multidrug resistant. Thus, intensive research is being carried out to find better chemotherapeutic agents as well as new drug delivery systems. In this article, the authors reviewed in depth the current challenges facing new drug designs and also outlined novel targeted drug delivery systems (DDS) in the fight against HCC.

Aptamer mediated niosomal drug delivery

Development of nanoscale carrier systems for targeted drug delivery is crucial for cancer treatment.

How can nanomedicines overcome cellular-based anticancer drug resistance?

This review discusses the mechanisms of anticancer drug resistance according to its cellular level of action and outlines the nanomedicine-based strategies adopted to overcome it.

An Overview of Nanoparticle Based Delivery for Treatment of Inner Ear Disorders

Nanoparticles offer new possibilities for inner ear treatment as they can carry a variety of drugs, protein, and nucleic acids to inner ear. Nanoparticles are equipped with several functions such as targetability, immuno-transparency, biochemical stability, and ability to be visualized in vivo and in vitro. A group of novel peptides can be attached to the surface of nanoparticles that will enhance the cell entry, endosomal escape, and nuclear targeting. Eight different types of nanoparticles with different payload carrying strategies are available now. The transtympanic delivery of nanoparticles indicates that, depending on the type of nanoparticle, different migration pathways into the inner ear can be employed, and that optimal carriers can be designed according to the intended cargo. The use of nanoparticles as drug/gene carriers is especially attractive in conjunction with cochlear implantation or even as an inclusion in the implant as a drug/gene reservoir.

Interleukin-4 receptor-targeted liposomal doxorubicin as a model for enhancing cellular uptake and antitumor efficacy in murine colorectal cancer

Our previous studies showed that colorectal tumor has high interleukin-4 receptor α (IL-4Rα) expression, whereas adjacent normal tissue has low or no IL-4Rα expression. We also observed that human atherosclerotic plaque-specific peptide-1 (AP1) can specifically target to IL-4Rα. In this study, we investigated the therapeutic efficacy and systemic toxicity of AP1-conjuagted liposomal doxorubicin. AP1 bound more strongly to and was more efficiently internalized into IL-4Rα-overexpressing CT26 cells than CT26 control cells. Selective cytotoxicity experiment revealed that AP1-conjugated liposomal doxorubicin preferentially killed IL-4Rα-overexpressing CT26 cells. AP1-conjugated liposomal doxorubicin administered intravenously into mice produced significant inhibition of tumor growth and showed decreased cardiotoxicity of doxorubicin. These results indicated that AP1-conjugated liposomal doxorubicin has a potent and selective anticancer potential against IL-4Rα-overexpressing colorectal cancer cells, thus providing a model for targeted anticancer therapy.

Nanotherapeutics With Anthracyclines: Methods of Determination and Quantification of Anthracyclines in Biological Samples

Anthracyclines, e.g. doxorubicin, pirarubicin, are widely used as cytostatic agents in the polymer nanotherapeutics designed for the highly effective antitumor therapy with reduced side effects. However, their precise dosage scheme needs to be optimized, which requires an accurate method for their quantification on the cellular level in vitro during nanocarrier development and in body fluids and tissues during testing in vivo. Various methods detecting the anthracycline content in biological samples have already been designed. Most of them are highly demanding and they differ in exactness and reproducibility. The cellular uptake and localization is predominantly observed and determined by microscopy techniques, the anthracycline content is usually quantified by chromatographic analysis using fluorescence detection. We reviewed and compared published methods concerning the detection of anthracycline nanocarriers.

A Novel Isoquinoline Derivative Anticancer Agent and Its Targeted Delivery to Tumor Cells Using Transferrin-Conjugated Liposomes

We have screened 11 isoquinoline derivatives and α-methylene-γ-butyrolactones using the 3-(4,5-dimethylthi-azol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) cytotoxicity assay in HeLa and HEK-293T cells. Compound 2 was identified as potential anticancer agent. To further improve its therapeutic potential, this agent was incorporated into transferrin (Tf)-conjugated liposomes (LPs) for targeted delivery to tumor cells. We have demonstrated Tf-LP-Compound 2 have superior antitumor activity compared to non-targeted controls and the free drug. These data show Tf-LP-Compound 2 to be a promising agent that warrants further evaluation.

Targeted delivery of chemically modified anti-miR-221 to hepatocellular carcinoma with negatively charged liposomes

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related death. Gene therapy was established as a new strategy for treating HCC. To explore the potential delivery system to support the gene therapy of HCC, negatively charged liposomal delivery system was used to deliver miR-221 antisense oligonucleotide (anti-miR-221) to the transferrin (Tf) receptor over expressed HepG2 cells. The liposome exhibited a mean particle size of 122.5 nm, zeta potential of −15.74 mV, anti-miR-221 encapsulation efficiency of 70%, and excellent colloidal stability at 4°C. Anti-miR-221-encapsulated Tf-targeted liposome demonstrated a 15-fold higher delivery efficiency compared to nontargeted liposome in HepG2 cells in vitro. Anti-miR-221 Tf-targeted liposome effectively delivered anti-miR-221 to HepG2 cells, upregulated miR-221 target genes PTEN, P27^kip1, and TIMP3, and exhibited greater silencing efficiency over nontargeted anti-miR-221 liposome. After intravenous injection into HepG2 tumor-bearing xenografted mice with Cy3-labeled anti-miR-221 Tf-targeted liposome, Cy3-anti-miR-221 was successfully delivered to the tumor site and increased the expressions of PTEN, P27^kip1, and TIMP3. Our results demonstrate that the Tf-targeted negatively charged liposome could be a potential therapeutic modality in the gene therapy of human HCC.

[The influence of doxorubicin incorporated in phospholipid drug delivery nanosystem on HEPG2 cells proteome]

A phospholipid drug delivery nanosystem with particle size up to 30 nm elaborated at the Institute of Biomedical Chemistry has been used earlier for incorporation of doxorubicin (Doxolip). This system demonstrated higher antitumor effect in vivo as compared with free doxorubicin. In this study the effect of this nanosystem containing doxorubicin on HepG2 cell proteome has been investigated. Cells were incubated in a medium containing phospholipid nanoparticles (0.5 mg/ml doxorubicin, 10 mg/mL phosphatidylcholine). After incubation for 48 h their survival represented 10% as compared with untreated cells. Cell proteins were analyzed by quantitative two-dimensional gel electrophoresis followed by identification of differentially expressed proteins with MALDI-TOF mass spectrometry. The phospholipid transport nanosystem itself insignificantly influenced the cell proteome thus confirming previous data on its safety. Doxorubicin, as both free substance and Doxolip (i.e. included into phospholipid nanoparticles) induced changes in expression of 28 proteins. Among these proteins only four of them demonstrated different in response to the effect of the free drug substance and Doxolip. Doxolip exhibited a more pronounced effect on expression of certain proteins; the latter indirectly implies increased penetration of the drug substance (included into nanoparticles) into the tumor cells. Increased antitumor activity of doxorubicin included into phospholipid nanoparticles may be associated with more active increase of specific protein expression.

Synthesis and characterization of tumor-targeted copolymer nanocarrier modified by transferrin

To increase the encapsulation of hydrophilic antitumor agent daunorubicin (DNR) and multidrug resistance reversal agent tetrandrine (Tet) in the drug delivery system of nano-particles (NPs), a functional copolymer NP composed of poly(lactic-co-glycolic acid) (PLGA), poly-L-lysine (PLL), and polyethylene glycol (PEG) was synthesized and then loaded with DNR and Tet simultaneously to construct DNR/Tet–PLGA–PLL–PEG-NPs using a modified double-emulsion solvent evaporation/diffusion method. And to increase the targeted antitumor effect, DNR/Tet–PLGA–PLL–PEG-NPs were further modified with transferrin (Tf) due to its specific binding to Tf receptors (TfR), which is highly expressed on the surface of tumor cells. In this study, the influence of the diversity of formulation parameters was investigated systematically, such as drug loading, mean particle size, molecular weight, the concentration of PLGA–PLL–PEG–Tf, volume ratio of acetone to dichloromethane, the concentration of polyvinyl alcohol (PVA) in the external aqueous phase, the volume ratio of the internal aqueous phase to the external aqueous phase, and the type of surfactants in the internal aqueous phase. Meanwhile, its possible effect on cell viability was evaluated. Our results showed that the regular spherical DNR/Tet–PLGA–PLL–PEG–Tf-NPs with a smooth surface, a relatively low polydispersity index, and a diameter of 213.0±12.0 nm could be produced. The encapsulation efficiency was 70.23%±1.91% for DNR and 86.5%±0.70% for Tet, the moderate drug loading was 3.63%±0.15% for DNR and 4.27%±0.13% for Tet. Notably, the accumulated release of DNR and Tet could be sustained over 1 week, and the Tf content was 2.18%±0.04%. In cell viability tests, DNR/Tet–PLGA–PLL–PEG–Tf-NPs could inhibit the proliferation of K562/ADR cells in a dose-dependent manner, and the half maximal inhibitory concentration value (total drug) of DNR/Tet–PLGA–PLL–PEG–Tf-NPs was lower than that of DNR, a mixture of DNR and Tet, and DNR/Tet–PLGA–PLL–PEG-NPs. These results clearly indicate that the PLGA–PLL–PEG formulation is a potential drug delivery system for hydrophilic and hydrophobic drugs, and that Tf modification may increase its targeting properties.

Characterization of 9-nitrocamptothecin-in-cyclodextrin-in-liposomes modified with transferrin for the treating of tumor

Encapsulation of hydrophobic drugs in the form of drug-cyclodextrin (CD) complex in liposomes has been applied as a novel strategy to combine the relative advantages of CDs and liposomes into one system, naming drug-in-CD-in-liposome (DCL). In the present study, soluble 9-NC/hydroxypropyl-β-cyclodextrin (HP-β-CD) inclusion complexes were prepared using the freeze-drying technique. Then 9-NC inclusion complexes were further encapsulated into liposomes by ethanol injection method and transferrin (Tf) was conjugated to the surface of 9-NC DCL to obtain Tf modified 9-NC DCL (Tf-9-NC-CL). Compared to PEGylated 9-NC DCL (P-9-NC-CL), the lactone stability and vesicle stability of Tf-9-NC-CL were significantly increased. Both 9-NC and HP-β-CD were found to release from the DCL and Tf modification resulted in reduced release of them. The enhanced targeting efficiency of the Tf-modified liposomes was demonstrated by flow cytometry and confocal microscopy. In vivo pharmacokinetics in rats showed improved lactone stability of 9-NC following intravenous injection of Tf-9-NC-CL. The cytotoxicity of Tf-9-NC-CL against tumor cells and normal cells was investigated in vitro and the antitumor efficacy was evaluated in S180 tumor-bearing mice in vivo. Compared with free 9-NC, 9-NC inclusion complexes and P-9-NC-CL, Tf-9-NC-CL demonstrated the strongest cytotoxicity to tumor cells. And the inhibitory rate of tumor (IRT) values were determined to be 43.08%, 56.92%, 67.69% and 80.00% for 9-NC solution, inclusion complexes, P-9-NC-CL and Tf-9-NC-CL, respectively. In conclusion, Tf modification can be useful in increasing vesicle stability, targeting drug delivery efficiency and antitumor efficacy of DCL containing hydrophobic antitumor drugs, such as 9-NC.

Cancer active targeting by nanoparticles: a comprehensive review of literature

PURPOSE

Cancer is one of the leading causes of death, and thus, the scientific community has but great efforts to improve cancer management. Among the major challenges in cancer management is development of agents that can be used for early diagnosis and effective therapy. Conventional cancer management frequently lacks accurate tools for detection of early tumors and has an associated risk of serious side effects of chemotherapeutics. The need to optimize therapeutic ratio as the difference with which a treatment affects cancer cells versus healthy tissues lead to idea that it is needful to have a treatment that could act a the "magic bullet"-recognize cancer cells only. Nanoparticle platforms offer a variety of potentially efficient solutions for development of targeted agents that can be exploited for cancer diagnosis and treatment. There are two ways by which targeting of nanoparticles can be achieved, namely passive and active targeting. Passive targeting allows for the efficient localization of nanoparticles within the tumor microenvironment. Active targeting facilitates the active uptake of nanoparticles by the tumor cells themselves.

METHODS

Relevant English electronic databases and scientifically published original articles and reviews were systematically searched for the purpose of this review.

RESULTS

In this report, we present a comprehensive review of literatures focusing on the active targeting of nanoparticles to cancer cells, including antibody and antibody fragment-based targeting, antigen-based targeting, aptamer-based targeting, as well as ligand-based targeting.

CONCLUSION

To date, the optimum targeting strategy has not yet been announced, each has its own advantages and disadvantages even though a number of them have found their way for clinical application. Perhaps, a combination of strategies can be employed to improve the precision of drug delivery, paving the way for a more effective personalized therapy.

Functional liposomes in the cancer-targeted drug delivery

Cancer is considered as one of the most severe health problems and is currently the third most common cause of death in the world after heart and infectious diseases. Novel therapies are constantly being discovered, developed and trialed. Many of the current anticancer agents exhibit non-ideal pharmaceutical and pharmacological properties and are distributed non-specifically throughout the body. This results in death of the both normal healthy and malignant cells and substantially leads to accruing a variety of serious toxic side effects. Therefore, the efficient systemic therapy of cancer is almost impossible due to harmful side effects of anticancer agents to the healthy organs and tissues. Furthermore, several problems such as low bioavailability of the drugs, low drug concentrations at the site of action, lack of drug specificity and drug-resistance also cause many restrictions on clinical applications of these drugs in the tumor therapy. Different types of the liposomal formulations have been used in medicine due to their distinctive advantages associated with their structural flexibility in the encapsulation of various agents with different physicochemical properties. They can also mediate delivery of the cargo to the appropriate cell type and subcellular compartment, reducing the effective dosage and possible side effects which are related to high systemic concentrations. Therefore, these novel systems were found very promising and encouraging dosage forms for the treatment of different types of cancer by increasing efficiency and reducing the systemic toxicity due to the specific drug delivery and targeting.

A novel anti-VEGF165 monoclonal antibody-conjugated liposomal nanocarrier system: physical characterization and cellular uptake evaluation in vitro and in vivo

Vascular endothelial growth factor (VEGF) is an important target for cancer therapy. In the present study, we conjugated the novel fully-human anti-VEGF165 monoclonal antibody, mAb165, with a PEGylated liposome (lip) to produce a monoclonal antibody-conjugated PEGylated liposome (mAb-lip). Physical characterization of mAb-lips showed an average particle size of 108nm. Using a bicinchoninic acid (BCA) assay, the coupling efficiency of mAb165 conjugated to the liposome was 69.8±0.5μg mAb/μmol phospholipid. In addition, we confirmed that conjugation between mAb165 and the liposome did not affect the structure and VEGF binding affinity of the antibody. Cell uptake of mAb-lips was assessed in four cell lines: MCF-7, HepG-2, SGC-7901, and L02 cells. Confocal microscopy and flow cytometry demonstrated that there was no significant difference in cell uptake between mAb-lips and mAb-free liposome either in VEGF-expressing tumor cells or normal cells. Moreover, the cytotoxicity of paclitaxel encapsulated in mAb-lips was not increased in the four cell lines. However, in BALB/c nude mice bearing MCF-7 xenografts, mAb-lips showed superior targeting activity to tumor tissues when compared with the unmodified liposome, which was demonstrated by the fact that rhodamine-labeled mAb-lips exhibited higher fluorescence intensity in tumor tissues than the unmodified liposome. Thus, our study indicated that mAb-lips may have the potential to enhance the therapeutic index of anticancer agents through targeted delivery to tumor cells in vivo.

Multifunctional, stimuli-sensitive nanoparticulate systems for drug delivery

The use of nanoparticulate pharmaceutical drug delivery systems (NDDSs) to enhance the in vivo effectiveness of drugs is now well established. The development of multifunctional and stimulus-sensitive NDDSs is an active area of current research. Such NDDSs can have long circulation times, target the site of the disease and enhance the intracellular delivery of a drug. This type of NDDS can also respond to local stimuli that are characteristic of the pathological site by, for example, releasing an entrapped drug or shedding a protective coating, thus facilitating the interaction between drug-loaded nanocarriers and target cells or tissues. In addition, imaging contrast moieties can be attached to these carriers to track their real-time biodistribution and accumulation in target cells or tissues. Here, I highlight recent developments with multifunctional and stimuli-sensitive NDDSs and their therapeutic potential for diseases including cancer, cardiovascular diseases and infectious diseases.

Multifunctional, stimuli-sensitive nanoparticulate systems for drug delivery

The use of nanoparticulate pharmaceutical drug delivery systems (NDDSs) to enhance the in vivo effectiveness of drugs is now well established. The development of multifunctional and stimulus-sensitive NDDSs is an active area of current research. Such NDDSs can have long circulation times, target the site of the disease and enhance the intracellular delivery of a drug. This type of NDDS can also respond to local stimuli that are characteristic of the pathological site by, for example, releasing an entrapped drug or shedding a protective coating, thus facilitating the interaction between drug-loaded nanocarriers and target cells or tissues. In addition, imaging contrast moieties can be attached to these carriers to track their real-time biodistribution and accumulation in target cells or tissues. Here, I highlight recent developments with multifunctional and stimuli-sensitive NDDSs and their therapeutic potential for diseases including cancer, cardiovascular diseases and infectious diseases.

Improved efficacy and reduced toxicity of doxorubicin encapsulated in sulfatide-containing nanoliposome in a glioma model

As a glycosphingolipid that can bind to several extracellular matrix proteins, sulfatide has the potential to become an effective targeting agent for tumors overexpressing tenasin-C in their microenvironment. To overcome the dose-limiting toxicity of doxorubicin (DOX), a sulfatide-containing nanoliposome (SCN) encapsulation approach was employed to improve treatment efficacy and reduce side effects of free DOX. This study analysed in vitro characteristics of sulfatide-containing nanoliposomal DOX (SCN-DOX) and assessed its cytotoxicity in vitro, as well as biodistribution, therapeutic efficacy, and systemic toxicity in a human glioblastoma U-118MG xenograft model. SCN-DOX was shown to achieve highest drug to lipid ratio (0.5∶1) and a remarkable in vitro stability. Moreover, DOX encapsulated in SCN was shown to be delivered into the nuclei and displayed prolonged retention over free DOX in U-118MG cells. This simple two-lipid SCN-DOX nanodrug has favourable pharmacokinetic attributes in terms of prolonged circulation time, reduced volume of distribution and enhanced bioavailability in healthy rats. As a result of the improved biodistribution, an enhanced treatment efficacy of SCN-DOX was found in glioma-bearing mice compared to the free drug. Finally, a reduction in the accumulation of DOX in the drug's principal toxicity organs achieved by SCN-DOX led to the diminished systemic toxicity as evident from the plasma biochemical analyses. Thus, SCN has the potential to be an effective and safer nano-carrier for targeted delivery of therapeutic agents to tumors with elevated expression of tenascin-C in their microenvironment.

Solid lipid nanoparticles for potential doxorubicin delivery in glioblastoma treatment: preliminary in vitro studies

The major obstacle to glioblastoma pharmacological therapy is the overcoming of the blood-brain barrier (BBB). In literature, several strategies have been proposed to overcome the BBB: in this experimental work, solid lipid nanoparticles (SLN), prepared according to fatty acid coacervation technique, are proposed as the vehicle for doxorubicin (Dox), to enhance its permeation through an artificial model of BBB. The in vitro cytotoxicity of Dox-loaded SLN has been measured on three different commercial and patient-derived glioma cell lines. Dox was entrapped within SLN thanks to hydrophobic ion pairing with negatively charged surfactants, used as counterions. Results indicate that Dox entrapped in SLN maintains its cytotoxic activity toward glioma cell lines; moreover, its permeation through hCMEC/D3 cell monolayer, assumed as a model of the BBB, was increased when the drug was entrapped in SLN. In conclusion, SLN proved to be a promising vehicle for the delivery of Dox to the brain in glioblastoma treatment.

In vitro and in vivo antitumor effects of folate-targeted ursolic acid stealth liposome

The antitumor efficacy of ursolic acid (UA) was limited by poor hydrophilicity and low bioavailability. To overcome this issue, UA was encapsulated in liposomes modified with folate conjugates for better solubility and bioavailability. This novel agent was prepared by a thin-film dispersion method and characterized by mean diameter, zeta potential, and entrapment efficiency (160.1 nm, -21.2 mV, and 88.9%, respectively). In vitro, cellular uptake efficiency, cytotoxicity, apoptosis, and cell cycle analyses were performed to show that folate-receptor (FR) positive cells endocytose more FR-targeted liposome (FTL-UA) than nontargeted PEGylated liposome (PL-UA) and that FTL-UA induced more cytotoxicity and higher apoptosis than PL-UA. Pharmacokinetic assessments showed advantages of systemic bioavailability of FTL-UA (AUC = 218.32 mg/L·h, t1/2 = 7.61 h) over free UA (AUC = 36.88 mg/L·h, t1/2 = 0.78 h). In vivo, FTL-UA showed significantly higher human epidermoid carcinoma (KB) inhibition in Balb/c nu/nu mice compared to PL-UA or free UA. The results indicate the great potential of FTL-UA against KB tumor.

NANOMATERIALS FOR PROTEIN MEDIATED THERAPY AND DELIVERY

There has been a significant amount of research done on liposomes and nanoparticles as drug carriers for protein drugs. Proteins and enzymes have been used both as targeting moieties and for their therapeutic potential. High specificity and rapid reaction rates make proteins and enzymes excellent candidates for therapeutic treatment, but some limitations exist. Many of these limitations can be addressed by a well studied nanotechnology based delivery system. Such a system can provide a medium for delivery, stabilization of the drugs, and enable site specific accumulation of drugs. Nanomedicines such as these have great potential to revolutionize the pharmaceutical industry and improve healthcare worldwide.

Human mesenchymal stem cells promote cancer motility and cytokine secretion in vitro

Interactions of human mesenchymal stem cells (hMSC) with tumors are controversially discussed since there is evidence for both tumor progression as well as tumor inhibition by hMSC. The objective of the present study is to investigate whether hMSC support cell motility and cytokine secretion in a head and neck squamous cell carcinoma cell line (HLaC 78). A spheroid model was generated in which the ultrastructure of spheroids was analyzed using scanning electron microscopy (SEM). The migration capability was monitored in a monolayer as well as in a spheroid model. The variation in migration and secretion of interleukin (IL)-6, IL-8 and vascular endothelial growth factor (VEGF), as well as the expression of the multidrug resistance gene (MDR-1) was investigated. Finally, the alteration in the cell cycle was analyzed by flow cytometry. SEM showed a tight cell-cell contact with extensive secretion of extracellular matrix. The migration and invasion capability of HLaC 78 was enhanced by hMSC. Cancer cell motility was also increased by hMSC as well as secretion of the cytokines IL-6, IL-8 and VEGF. hMSC did not induce the expression of MDR-1 in HLaC 78, and there was no alteration in the cell cycle of HLaC 78 after cocultivation with hMSC. Our results confirm the important role of hMSC in cancer biology since both an enhancement of cell motility as well as cytokine secretion could be shown. However, based on these findings and those in the current literature, caution must be applied when using hMSC as a carrier for tumor therapy in cancer treatment.

Targeted transferrin-modified polymeric micelles: enhanced efficacy in vitro and in vivo in ovarian carcinoma

In this study, transferrin (Tf)-modified poly(ethylene glycol)-phosphatidylethanolamine (mPEG-PE) micelles loaded with the poorly water-soluble drug, R547 (a potent and selective ATP-competitive cyclin-dependent kinase (CDK) inhibitor), were prepared and evaluated for their targeting efficiency and cytotoxicity in vitro and in vivo to A2780 ovarian carcinoma cells, which overexpress transferrin receptors (TfR). At 10 mM lipid concentration, both Tf-modified and plain micelles solubilized 800 μg of R547. Tf-modified micelles showed enhanced interaction with A2780 ovarian carcinoma cells in vitro. The involvement of TfR in endocytosis of Tf-modified micelles was confirmed by colocalization studies of micelle-treated cells with the endosomal marker Tf-Alexa488. We confirmed endocytosis of micelles in an intact form with micelles loaded with a fluorescent dye and additionally labeled with fluorescent lipid. The in vitro cytotoxicity and in vivo tumor growth inhibition studies in A2780-tumor bearing mice confirmed the enhanced efficacy of Tf-modified R547-loaded micelles compared to free drug solution and to nonmodified micelles. The results of this study demonstrate the potential application of Tf-conjugated polymeric micelles in the treatment of tumors overexpressing TfR.

Ligand-targeted liposome design: challenges and fundamental considerations

Nanomedicine, particularly liposomal drug delivery, has expanded considerably over the past few decades, and several liposomal drugs are already providing improved clinical outcomes. Liposomes have now progressed beyond simple, inert drug carriers and can be designed to be highly responsive in vivo, with active targeting, increased stealth, and controlled drug-release properties. Ligand-targeted liposomes (LTLs) have the potential to revolutionize the treatment of cancer. However, these highly engineered liposomes generate new problems, such as accelerated clearance from circulation, compromised targeting owing to non-specific serum protein binding, and hindered tumor penetration. This article highlights recent challenges facing LTL strategies and describes the advanced design elements used to circumvent them.

Transferrin-conjugated pluronic niosomes as a new drug delivery system for anticancer therapy

An efficient tumor-targeted niosomal delivery system for the vehiculation of doxorubicin hydrochloride as an anticancer agent was designed. Niosomes were prepared from a mixture of an opportunely modified Pluronic L64 surfactant and cholesterol as a membrane additive and characterized in terms of size and related distribution function and drug entrapment efficiency. After the preparation, transferrin was conjugated to niosomes to produce transferrin (Tf) niosomes, and the cytotoxicity of the final formulation was studied. The specific uptake of Tf niosomes into cells was evaluated via incubation of MCF-7 and MDA-MB-231 cells with fluorescently rhodamine-loaded Tf niosomes for various times and concentration intervals and further investigated by fluorescence microscopy. Results showed that doxorubicin can be easily encapsulated into niosomes, which are regular and spherical in shape. Moreover, transferrin conjugate niosomes demonstrated far greater extents of cellular uptake by MCF-7 and MDA-MB-231 cells, suggesting that they were mainly taken up by transferrin receptor-mediated endocytosis. Doxorubicin-loaded niosome anticancer activity was also achieved against MCF-7 and MDA-MB-231 tumor cell lines, and a significant reduction in viability in a dose- and time-related manner was observed. Finally, our formulation could be potentially useful as a target doxorubicin delivery system in anticancer therapy.

Delivery of therapeutic nucleic acids via transferrin and transferrin receptors: lipoplexes and other carriers

INTRODUCTION

The overexpression of transferrin (Tf) receptors on cancer cells renders them a useful target for the delivery of small-molecule drugs and nucleic acid therapeutics to these cells. This approach could alleviate the non-target effects of the drugs.

AREAS COVERED

The function of the Tf receptor, the development of Tf-lipid-DNA complexes (Tf lipoplexes), therapeutic use of lipoplexes and polymer-DNA complexes (poylplexes), and the therapeutic use of Tf-lipoplexes and anti-Tf-receptor antibody-lipoplexes are outlined. The literature search for this review was based primarily on the terms 'lipoplexes,' 'lipopolyplexes' 'transferrin,' 'transferrin receptor,' and 'gene therapy.' However, the review was not intended to be comprehensive.

EXPERT OPINION

Complexes of Tf with cationic liposomes and nucleic acids, or liposomes with covalently attached Tf or anti-transferrin receptor antibodies have been used for the delivery of therapeutic genes, antisense oligodeoxynucleotides, and short interfering RNA. Although such targeted nonviral delivery vehicles may benefit from further enhancement of their efficacy, current achievements at the cell culture and animal model level should be translated into clinical applications, restricted initially to localized delivery into accessible tissues to avoid potential systemic side-effects and non-target delivery.

Current trends in the use of liposomes for tumor targeting

The use of liposomes for drug delivery began early in the history of pharmaceutical nanocarriers. These nanosized, lipid bilayered vesicles have become popular as drug delivery systems owing to their efficiency, biocompatibility, nonimmunogenicity, enhanced solubility of chemotherapeutic agents and their ability to encapsulate a wide array of drugs. Passive and ligand-mediated active targeting promote tumor specificity with diminished adverse off-target effects. The current field of liposomes focuses on both clinical and diagnostic applications. Recent efforts have concentrated on the development of multifunctional liposomes that target cells and cellular organelles with a single delivery system. This review discusses the recent advances in liposome research in tumor targeting.

Transferrin and the transferrin receptor for the targeted delivery of therapeutic agents to the brain and cancer cells

The potential use of many promising novel drugs is limited by their inability to specifically reach their site of action after intravenous administration, without secondary effects on healthy tissues. In order to remediate this problem, the protein transferrin (Tf) has been extensively studied as a targeting molecule for the transport of drug and gene delivery systems to the brain and cancer cells. A wide range of delivery approaches have been developed to target the Tf receptor and they have already improved the specific delivery of Tf-bearing therapeutic agents to their site of action. This review provides a summary of the numerous delivery strategies used to target the Tf receptor and focuses on recent therapeutic advances.

Glioma targeting and blood-brain barrier penetration by dual-targeting doxorubincin liposomes

Effective chemotherapy for glioblastoma requires a carrier that can penetrate the blood-brain barrier (BBB) and subsequently target the glioma cells. Dual-targeting doxorubincin (Dox) liposomes were produced by conjugating liposomes with both folate (F) and transferrin (Tf), which were proven effective in penetrating the BBB and targeting tumors, respectively. The liposome was characterized by particle size, Dox entrapment efficiency, and in vitro release profile. Drug accumulation in cells, P-glycoprotein (P-gp) expression, and drug transport across the BBB in the dual-targeting liposome group were examined by using bEnd3 BBB models. In vivo studies demonstrated that the dual-targeting Dox liposomes could transport across the BBB and mainly distribute in the brain glioma. The anti-tumor effect of the dual-targeting liposome was also demonstrated by the increased survival time, decreased tumor volume, and results of both hematoxylin-eosin staining and terminal deoxynucleotidyl transferase dUTP nick end labeling analysis. The dual-targeting Dox liposome could improve the therapeutic efficacy of brain glioma and were less toxic than the Dox solution, showing a dual-targeting effect. These results indicate that this dual-targeting liposome can be used as a potential carrier for glioma chemotherapy.

Second generation liposomal cancer therapeutics: transition from laboratory to clinic

Recent innovations and developments in nanotechnology have revolutionized cancer therapeutics. Engineered nanomaterials are the current workhorses in the emerging field of cancer nano-therapeutics. Lipid vesicles bearing anti-tumor drugs have turned out to be a clinically feasible and promising nano-therapeutic approach to treat cancer. Efficient entrapment of therapeutics, biocompatibility, biodegradability, low systemic toxicity, low immunogenicity and ability to bypass multidrug resistance mechanisms has made liposomes a versatile drug/gene delivery system in cancer chemotherapy. The present review attempts to explore the recent key advances in liposomal research and the vast arsenal of liposomal formulations currently being utilized in treatment and diagnosis of cancer.

Recent trends in multifunctional liposomal nanocarriers for enhanced tumor targeting

Liposomes are delivery systems that have been used to formulate a vast variety of therapeutic and imaging agents for the past several decades. They have significant advantages over their free forms in terms of pharmacokinetics, sensitivity for cancer diagnosis and therapeutic efficacy. The multifactorial nature of cancer and the complex physiology of the tumor microenvironment require the development of multifunctional nanocarriers. Multifunctional liposomal nanocarriers should combine long blood circulation to improve pharmacokinetics of the loaded agent and selective distribution to the tumor lesion relative to healthy tissues, remote-controlled or tumor stimuli-sensitive extravasation from blood at the tumor's vicinity, internalization motifs to move from tumor bounds and/or tumor intercellular space to the cytoplasm of cancer cells for effective tumor cell killing. This review will focus on current strategies used for cancer detection and therapy using liposomes with special attention to combination therapies.

Optimization of an anti-HER2 monoclonal antibody targeted delivery system using PEGylated human serum albumin nanoparticles

Human serum albumin (HSA) nanoparticles represent an attractive strategy for active targeting of therapeutics into tumor cells due to the presence of superficial functional groups. HER2 is highly expressed in a significant proportion of cancers and monoclonal antibodies (mAbs) directed against HER2 hold great promise for effective therapy. Herein, covalent coupling of a novel mAb (1F2) directed against the extracellular domain of HER2 to the surface of HSA nanoparticles was evaluated to obtain nanoparticles with highest cellular uptake. HER2 reactivity of 1F2-conjugated nanoparticles produced under different conditions was screened by an indirect ELISA and flow cytometry techniques. Monoclonal antibody thiolation with 100-fold molar excess of 2-iminothiolane and the ratio of 10:1 for the thiolated 1F2 (μg) to PEGylated nanoparticles (mg), were optimum for the attachment process. Under this condition, 23±4% of 1F2 was conjugated to nanoparticles. The flow cytometry results show that 1F2-modified nanoparticles interact with nearly all HER2 receptors on the surface of BT474 cells. In addition, no cellular uptake was observed on MCF7 cells. In vitro analyses showed no significant cytotoxicity of produced system against BT474 cells. Therefore, 1F2-attached HSA nanoparticles represent a potential delivery system for targeted transport of therapeutic agents into HER2-positive tumor cells.

Characteristics of sequential targeting of brain glioma for transferrin-modified cisplatin liposome

Methods on how to improve the sequential targeting of glioma subsequent to passing of drug through the blood-brain barrier (BBB) have been occasionally reported. However, the characteristics involved are poorly understood. In the present study, cisplatin (Cis) liposome (lipo) was modified with transferrin (Tf) to investigate the characteristics of potential sequential targeting to glioma. In bEnd3/C6 co-culture BBB models, higher transport efficiency across the BBB and cytotoxicity in basal C6 cells induced by Cis-lipo(Tf) than Cis-lipo and Cis-solution, suggest its sequential targeting effect. Interestingly, similar liposomal morphology as that of donor compartment was first demonstrated in the receptor solution of BBB models. Meanwhile, a greater acquisition in the lysosome of bEnd3, distributed sequentially into the nucleus of C6 cells were found for the Cis-lipo(Tf). Pre-incubation of chlorpromazine and Tf inhibited this process, indicating that a clathrin-dependent endocytosis is involved in the transport of Cis-lipo(Tf) across the BBB.

Targeting receptor-mediated endocytotic pathways with nanoparticles: rationale and advances

Targeting of drugs and their carrier systems by using receptor-mediated endocytotic pathways was in its nascent stages 25 years ago. In the intervening years, an explosion of knowledge focused on design and synthesis of nanoparticulate delivery systems as well as elucidation of the cellular complexity of what was previously-termed receptor-mediated endocytosis has now created a situation when it has become possible to design and test the feasibility of delivery of highly specific nanoparticle drug carriers to specific cells and tissue. This review outlines the mechanisms governing the major modes of receptor-mediated endocytosis used in drug delivery and highlights recent approaches using these as targets for in vivo drug delivery of nanoparticles. The review also discusses some of the inherent complexity associated with the simple shift from a ligand-drug conjugate versus a ligand-nanoparticle conjugate, in terms of ligand valency and its relationship to the mode of receptor-mediated internalization.