Enhanced tumor targeting of doxorubicin by ganglioside GM1-bearing long-circulating liposomes

Penetration of the blood-brain barrier and the anti-tumour effect of a novel PLGA-lysoGM1/DOX micelle drug delivery system

Effective treatment of glioma and other central nervous system (CNS) diseases is hindered by the presence of the blood-brain barrier (BBB). A novel nano-delivery vehicle system composed of PLGA-lysoGM1/DOX micelles was developed to cross the BBB for CNS treatment. We have shown that doxorubicin (DOX) as a model drug encapsulated in PLGA-lysoGM1 micelles can achieve up to 3.8% loading efficiency and 61.6% encapsulation efficiency by the orthogonal test design. Our in vitro experiments demonstrated that PLGA-lysoGM1/DOX micelles had a slow and sustainable drug release under physiological conditions and exhibited a high cellular uptake through the macropinocytosis and the autophagy/lysosomal pathways. In vivo experimental studies in zebrafish and mice confirmed that PLGA-lysoGM1/DOX micelles could cross the BBB and be specifically accumulated in the brain. Moreover, an excellent anti-glioma effect was observed in intracranial glioma-bearing rats. Therefore, PLGA-lysoGM1/DOX micelles not only effectively can cross the BBB, but our results also suggest that they have great potential for anti-glioma therapy and other central nervous system diseases.

Postinfarct active cardiac-targeted delivery of erythropoietin by liposomes with sialyl Lewis X repairs infarcted myocardium in rabbits

We investigated the effect of cardiac-targeting erythropoietin (EPO)-encapsulated liposomes with sialyl LewisX (SLX) on myocardial infarct (MI) size, left ventricular (LV) remodeling and function, and its molecular mechanism for repairing infarcted myocardium. In rabbits, MI was induced by 30 min of coronary occlusion followed by reperfusion. EPO-encapsulated liposomes with SLX (L-EPO group), EPO-encapsulated liposomes without SLX (L-EPO without SLX group), liposomes with SLX without EPO (L group), or saline (saline group) were intravenously administered immediately after MI. MI sizes and numbers of microvessels were assessed 14 days after MI. Prosurvival proteins and signals were assessed by Western blot analysis 2 and 14 days after MI. Confocal microscopy and electron microscopy showed the specific accumulation of liposomes with SLX in the infarcted myocardium. MI and cardiac fibrosis areas were significantly smaller in the L-EPO group than in the other groups. LV function and remodeling were improved in the L-EPO group. The number of CD31-positive microvessels was significantly greater in the L-EPO group than in the other groups. Higher expressions of EPO receptors, phosphorylated (p)Akt, pERK, pStat3, VEGF, Bcl-2, and promatrix metalloproteinase-1 were observed in the infarct area in the L-EPO group than in the other groups. EPO-encapsulated liposomes with SLX selectively accumulated in the infarct area, reduced MI size, and improved LV remodeling and function through activation of prosurvival signals and by exerting antifibrotic and angiogenic effects. EPO-encapsulated liposomes with SLX may be a promising strategy for active targeting treatment of acute MI.

Delivery of nanomedicines to extracellular and intracellular compartments of a solid tumor

Advances in molecular medicines have led to identification of promising targets on cellular and molecular levels. These targets are located in extracellular and intracellular compartments. The latter include cytosol, nucleus, mitochondrion, Golgi apparatus and endoplasmic reticulum. This report gives an overview on the barriers to delivering nanomedicines to various target sites within a solid tumor, the experimental approaches to overcome such barriers, and the potential utility of nanotechnology.

Accumulation of liposome with Sialyl Lewis X to inflammation and tumor region: application to in vivo bio-imaging

We prepared the liposome binding Sialyl Lewis X (SLX) on the surface in order to specifically and efficiently deliver substances (fluorescent materials, chemical substances, proteins, genes, etc.) to inflammation or tumor regions. The liposome with SLX (SLX-Lipo-Cy5.5), in which fluorescent substance Cy5.5 was included, was administered intravenously to arthritis or Ehrlich Ascites Tumor (EAT) bearing mouse, and the accumulation of liposome was observed using two types of in vivo fluorescent imaging equipment. The result was that the accumulation of SLX-Lipo-Cy5.5 to inflammation or tumor regions was significantly higher than the control liposome without sugar chain (Lipo-Cy5.5) at 24 and 48 h after administration. In addition, it was confirmed that this accumulation showed a shift of liposome from blood vessels to the surrounding tissues. Thus, it was proven that this liposome is useful not only as an in vivo bio-imaging reagent but also as a drug delivery system (DDS).

Novel temperature-sensitive liposomes with prolonged circulation time

Hyperthermia increases the efficiency of various chemotherapeutic drugs and is administered as an adjunct to chemotherapy for the treatment of cancer patients. The temperature-dependent effect can be strongly increased by the use of temperature-sensitive liposomes in combination with regional hyperthermia, which specifically releases the entrapped drug in the heated tumor tissue. The novel lipid 1.2-dipalmitoyl-sn-glycero-3-phosphoglyceroglycerol (DPPGOG), which is closely related to the naturally occurring 1.2-dipalmitoyl-sn-glycero-3-phosphoglycerol, in combination with 1.2-dipalmitoyl-sn-glycero-3-phosphocholine and 1.2-distearoyl-sn-glycero-3-phosphocholine provides long-circulating temperature-sensitive liposomes with favorable properties under mildly hyperthermic conditions (41-42 degrees C). DPPGOG facilitates temperature-triggered drug release from these liposomes (diameter, 175 nm) and leads to a substantially prolonged plasma half-life for the encapsulated drug with t(1/2) = 9.6 h in hamsters and t(1/2) = 5.0 h in rats. Quantitative fluorescence microscopy of amelanotic melanoma grown in the transparent dorsal skin fold chamber of hamsters demonstrated a favorable drug accumulation in heated tissue after i.v. application of these liposomes (42 degrees C for 1 h). The mean area under the curve for tissue drug concentration was increased by more than sixfold by application of the new liposomes compared with nonliposomal drug delivery. In summary, we present a new DPPGOG-based liposomal formulation enabling long circulation time combined with fast and efficient drug release under mild hyperthermia. This adds positively to the results with lipid-grafted polyethylenglycol used thus far in temperature sensitive liposomes and widens the possibilities for clinical applications.

The effect of surface coverage and conformation of poly(ethylene oxide) (PEO) chains of poloxamer 407 on the biological fate of model colloidal drug carriers

Poloxamer 407 was adsorbed onto the surface of model colloidal drug carriers, polystyrene nanoparticles of 40, 70 and 137 nm in diameter, and the effect of the degree of surface coverage and the conformation of the poly(ethylene oxide) (PEO) chains on biological fate was studied. The relationship between the physicochemical and the biological properties of the nanoparticle systems was also investigated. The adsorbed layer of poloxamer 407 was characterised in terms of percentage surface coverage, thickness of the adsorbed layer and average surface area per PEO chain. Computer modelling of the adsorbed layer was performed (applying the self-consistent field technique), to obtain the structural information of the PEO chains in the layer. The in vitro interaction of the nanoparticles with different degrees of poloxamer 407 surface coverage with serum components and the in vivo biodistribution in the rat model were assessed. The results demonstrated that an increase in the surface coverage with poloxamer 407 resulted in an increased volume fraction of the PEO in the adsorbed layer, further extension of the PEO chains from the surface and closer packing of the chains at the surface. With regard to the interaction with the serum components, an increased surface coverage resulted in a reduction of the amount of serum proteins adsorbed, and, importantly, affected the type of proteins adsorbed. High molecular weight proteins were not adsorbed onto the nanoparticles with a surface coverage above approx. 25%. Following the intravenous administration to rats, even the nanoparticles with the lowest degree of surface coverage (approx. 5%) showed improved circulation profiles relative to the uncoated nanoparticles. The effect was more pronounced for the 40 nm nanoparticles. A further increase in the surface coverage to approx. 25% resulted in a significant increase in circulation time, as compared to uncoated and 5% coated systems, for all sizes of nanoparticles. Importantly, it was found that a long in vivo blood circulation time could be achieved for nanoparticles with a relatively low degree of surface coverage with PEO chains.

Targeting chemotherapy to solid tumors with long-circulating thermosensitive liposomes and local hyperthermia

The effectiveness of the combination of long-circulating, thermosensitive liposomes and hyperthermia is described. Small-sized, thermosensitive liposomes that encapsulate doxorubicin (DXR-PEG-TSL (SUV)) have a prolonged circulation time and are extravasated to targeted solid tumors in vivo, where they preferentially release the agent in an anatomical site subjected to local hyperthermia. Liposomes were prepared by the incorporation of amphipathic polyethyleneglycol (PEG) to prolong their circulation time. DXR-PEG-TSL (SUV) was retained longest and was accumulated most efficiently in solid tumors in Balb/c mice. The combination of DXR-PEG-TSL (SUV) and hyperthermia at the tumor sites 3 h after injection, gave high concentrations of doxorubicin in tumor tissue and resulted in more effective tumor retardation and increased survival time. A large amount of DXR-PEG-TSL (SUV) was extravasated into the tumors during circulation for 3 h after injection, suggesting that the encapsulated drug was released into the interstitial spaces of the lesions by local hyperthermia. This system is expected to be clinically valuable for the delivery of a wide range of chemotherapeutic agents in the treatment of solid tumors.

Liposome drug delivery system for murine neuroblastoma

PURPOSE

The effects of liposome-infused doxorubicin on C-1300 murine neuroblastoma were studied. The liposome surface was covered with polyethylene glycol to avoid migration toward the reticuloendothelial system and to prolong its presence in the bloodstream. Liposome-infused doxorubicin hydrochloride (DXR), an anthracycline was used as an anticancer antibiotic substance.

METHODS

Each A/J mouse was transplanted with 1 x 10(5) C-1300 murine neuroblastoma cells subcutaneously in the thigh. The experiment was conducted when the maximum tumor dimension was 1 cm. The control group was given only physiological saline solutions, the second group was given DXR alone, and the third group received liposome-infused DXR (Lip-DXR). The survival and doubling times were measured. One, 12, and 24 hours after the injection, the DXR concentration in the cardiac tissues was measured for statistical comparison.

RESULTS

The survival time of the mice was found to be 27+/-5.10 days in the control group, 31.40+/-3.15 days in the DXR group, and 43.86+/-2.13 days in the Lip-DXR group. The Lip-DXR group showed the longest survival time. The tumor-doubling time was found to be 9.07+/-2.30, 10.75+/-3.49, and 19.80+/-3.26 days, for each group, respectively. When comparing the DXR concentration in the heart tissues, the Lip-DXR-administered mice showed significantly lower DXR accumulation in the cardiac tissues after 1 and 12 hours than the DXR-administered mice.

CONCLUSION

This study proved that liposome-infused DXR could be used effectively on murine neuroblastoma (C-1300 tumor cell model) and may reduce the incidence of cardiac toxicity as compared with DXR alone.

In vivo antitumor activity of cis-bis-neodecanoato-trans-R,R-1, 2-diaminocyclohexane platinum(II) formulated in long-circulating liposomes

A lipophilic cisplatin derivative, cis-bis-neodecanoato-trans- R,R-1,2-diaminocyclohexane platinum (II) (NDDP), was formulated in liposomes composed of phosphatidylcholine (PC) and cholesterol (Chol) additionally containing monosialoganglioside (Gm1) or polyethyleneglycol conjugated to phosphatidylethanolamine (PEG-PE). These NDDP-containing long-circulating liposomes were examined for in vivo antitumor activity using the mouse RIF-1 solid tumor as a target residing outside the reticuloendothelial system (RES). Biodistribution studies, using C3H/HeJ mice and 111In-labelled DTPA-SA as a lipid marker, showed that the activity of GM1 and PEG-PE in prolonging the circulation times of liposomes was preserved in the presence of 3.0 mol% of NDDP in the liposome membranes. The high levels of liposomes remaining in the blood for PC/Chol/GM1 and PC/Chol/PEG3000-PE liposomes were associated with high levels of platinum in the blood as determined by atomic absorption spectrophotometry. These NDDP-containing long-circulating liposomes showed approximately a three-fold increase in tumor accumulation as compared to the conventional PC/Chol liposomes. In vitro cytotoxicity studies using RIF-1 tumor cells showed that the presence of PEG-PE, but not Gm1, significantly enhanced the cytotoxicity of liposomal NDDP. RIF-1 tumor-bearing C3H/HeJ mice were treated twice with 25 mg/kp NDDP in various liposomal formulations on days 12 and 16 after tumor cell inoculation. A significant reduction in the tumor growth rate was observed when NDDP was formulated in PC/Chol/PEG3000-PE liposomes which support both efficient tumor accumulation and enhanced cytotoxicity of liposomal NDDP. On the other hand, NDDP formulated in PC/Chol/GM1 liposomes, which display only a high tumor accumulation, had no effect on the tumor growth rate. Furthermore, NDDP formulated in dimyristoylphosphatidylglycerol (DMPG)-containing liposomes, exhibiting in vitro cytotoxicity comparable to NDDP formulated in PC/Chol/PEG3000-PE liposomes, but showing poor tumor accumulation, was also not effective. These results indicate a potential effectiveness of NDDP formulated in PEG-PE-containing liposomes for therapy of tumors in non-RES organs.

The activity of doxorubicin niosomes against an ovarian cancer cell line and three in vivo mouse tumour models

Demonstration of the improved doxorubicin pharmacokinetics and tumoricidal activity, after a single intravenous dose of 10mg kg-1 doxorubicin sorbitan monostearate (Span 60) based niosomes in the mouse adenocarcinoma (MAC) tumour model (Uchegbu et al., 1995) preceded the present study in which the activity of doxorubicin C16G2 (a hexadecyl diglycerol ether) based niosomes was evaluated against naive and established MAC tumour models. C16G2 niosomes were equiactive with doxorubicin solution. It is concluded that while in some tumour models, niosomal formulations demonstrate some advantages over the free drug, caution is advocated in the extrapolation of these results. The activity of doxorubicin C16G2 and Span 60 niosomes was also studied against a human ovarian cancer cell line and its doxorubicin resistant subline. There was a slight reduction in the IC50 against the resistant cell line when the drug was encapsulated in Span 60 niosomes in comparison to the drug in solution. Taking into account the in-vitro release characteristics of the various niosomal formulations, it is concluded that the use of niosomal formulations against multidrug resistance shows sufficiently encouraging results to warrant further study.

Targetability of novel immunoliposomes modified with amphipathic poly(ethylene glycol)s conjugated at their distal terminals to monoclonal antibodies

Distearoyl-N-(3-carboxypropionoyl poly(ethylene glycol) succinyl)phosphatidylethanolamine (DSPE-PEG-COOH) was newly synthesized and used to prepare novel immunoliposomes carrying monoclonal antibodies at the distal ends of the PEG chains (Type C). Liposomes were prepared from egg phosphatidylcholine (ePC) and cholesterol (CH) (2;1, m/m) containing 6 mol% of DSPE-PEG-COOH, and a monoclonal IgG antibody, 34A, which is highly specific to pulmonary endothelial cells, was conjugated to the carboxyl groups of DSPE-PEG-COOH to give various amounts of antibody molecules per liposome. Other immunoliposomes with PEG coating (Type B) or without PEG coating (an earlier type of immunoliposome, Type A) were prepared for comparison. The average molecular weight of PEG in Type B or C immunoliposomes was 2000. Type B and Type C liposomes without antibodies showed prolonged circulation time and reduced reticulo-endothelial system (RES) uptake owing to the presence of PEG. These three different types of 34A-immunoliposomes with 30-35 antibody molecules per vesicle were injected into mice to test the immunotargetability to the lung. The efficiency of lung binding of 34A-Type B was one-half of that of 34A-Type A, though a large amount of 34A-Type B remained in the blood circulation for a long time, suggesting that the steric hindrance of PEG chains reduced not only the immunospecific antibody-antigen binding, but also the RES uptake. The degree of lung binding of 34A-Type C was about 1.3-fold higher than that of 34A-Type A, indicating that recognition by the antibodies attached to the PEG terminal was not sterically hindered and that the free PEG (i.e., that not carrying antibody) was effective in increasing the blood concentration of immunoliposomes by enabling them to evade RES uptake. The latter phenomenon was confirmed by using nonspecific antibody-Type C immunoliposomes (14-Type C), which showed a high blood level for a long time. Our approach provides a simple means of conjugating antibodies directly to the distal end of PEG which is already bound to the liposome membrane, and should contribute to the development of superior targetable drug delivery vehicles for use in diagnostics and therapy.

Enhanced delivery and antitumor activity of doxorubicin using long-circulating thermosensitive liposomes containing amphipathic polyethylene glycol in combination with local hyperthermia

Enhanced delivery of doxorubicin (DXR) to a solid tumor subjected to local hyperthermia was achieved by using long-circulating, thermosensitive liposomes (TSL) composed of dipalmitoyl phosphatidylcholine (DPPC)/distearoyl phosphatidylcholine (DSPC) (9:1, m/m) and 3 mol% amphipathic polyethylene glycol (PEG) in colon 26-bearing mice. Inclusion of 3 mol% of distearoyl phosphatidylethanolamine derivatives of PEG (DSPE-PEG, amphipathic PEG) with a mean molecular weight of 1000 or 5000 in DPPC/DSPC liposomes resulted in decreased reticuloendothelial system (RES) uptake and a concomitant prolongation of circulation time, affording sustained increased blood levels of the liposomes. Concomitantly, DXR levels in blood were also kept high over a long period. The presence of amphipathic PEG did not interfere with the encapsulation of DXR by the pH gradient method (> 90% trapping efficiency) or with the temperature-dependent drug release from the liposomes. The optimal size of these liposomes was 180-200 nm in mean diameter for thermosensitive drug release and prolonged circulation time. The DXR levels in the tumor after injection of long-circulating TSL (DXR-PEG1000TSL or DXR-PEG5000TSL, at a dose of 5 mg DXR/kg) with local hyperthermia were much higher than after treatment with DXR-TSL lacking PEG or with free DXR, reaching 7.0-8.5 DXR micrograms/g tumor (approximately 2 times or 6 times higher than that of DXR-TSL or free DXR, respectively). Furthermore, the combination of DXR-PEGTSL and hyperthermia effectively retarded tumor growth and increased survival time.(ABSTRACT TRUNCATED AT 250 WORDS)