Cell culture and animal studies for intracerebral delivery of borocaptate in liposomal formulation

The efficacy of a liposomal formulation for intracerebral delivery of borocaptate (BSH) to brain tumor cells has been investigated using cell culture to study BSH uptake and persistence and using tumor-bearing rats to determine BSH distribution in the brain. During a 16-hr incubation, cellular uptake of BSH solution or BSH liposomal formulation was similar. However, the cellular persistence of BSH greatly increased when BSH was present in liposome. The differences in cellular persistence for BSH solution and BSH-loaded liposomes were significant both in 12-hr and 24-hr incubation experiments (p < 0.05 and p < 0.01, respectively). For the studies involving tumor-bearing rats, BSH level in tumor tissue was significantly higher than that in normal brain tissue at 2 hr and 6 hr after intracerebral injection of BSH-loaded liposomes (p < 0.01). Our study indicated that the liposomal formulation enhanced cellular persistence of BSH in tumor cells and therefore favored the boron accumulation in the cells. With the prolonged physical retention of liposomes at the local injection site and the cellular retention of BSH enhanced by the liposomes, the intracerebral delivery of BSH using liposomal formulation may provide an effective boron delivery approach for boron neutron capture therapy of brain tumors.     

Brain tissue reaction following intracerebral injection of free or liposomally encapsulated BSH

Abstract

Boron neutron capture therapy (BNCT) is a potentially valuable treatment of malignant brain gliomas. A primary requirement for successful BNCT is achieving high local concentration of boron drugs in tumors. Intratumoral injection of liposomes containing boron drug has potential to meet this requirement and could prove to be of significance for BNCT. The brain tissue reaction following the intracerebral injection of a boron drug, BSH, either in solution form or in liposomally encapsulated form, was studied in rats. On histological examination, no evidence of tissue reaction was found after injecting BSH solution, suggesting that high local concentration of BSH was well tolerated. Injection of liposomal BSH was characterized by phagocytic activity at the site of injection, which was regressing by 24 h. Neither group of animals exhibited any signs of abnormal behavior or neurologic deficit. Direct intracerebral injection of BSH liposomes as per-formed in this report could be regarded as tolerable.     

Brain tissue reaction following intracerebral injection of free or liposomally encapsulated BSH

Boron neutron capture therapy (BNCT) is a potentially valuable treatment of malignant brain gliomas. A primary requirement for successful BNCT is achieving high local concentration of boron drugs in tumors. Intratumoral injection of liposomes containing boron drug has potential to meet this requirement and could prove to be of significance for BNCT. The brain tissue reaction following the intracerebral injection of a boron drug, BSH, either in solution form or in liposomally encapsulated form, was studied in rats. On histological examination, no evidence of tissue reaction was found after injecting BSH solution, suggesting that high local concentration of BSH was well tolerated. Injection of liposomal BSH was characterized by phagocytic activity at the site of injection, which was regressing by 24 h. Neither group of animals exhibited any signs of abnormal behavior or neurologic deficit. Direct intracerebral injection of BSH liposomes as per-formed in this report could be regarded as tolerable.     

A Microsphere-Liposome (Microplex) Vector for Targeted Gene Therapy of Cancer. II. In Vivo Biodistribution Study in a Solid Tumor Model

Cationic liposomes are commonly used for transfection of plasmids into mammalian cells, while microspheres have been traditionally used for selective delivery of anticancer agents into tumor vasculature. We have developed a novel vector, comprised of cationic liposomes electrostatically bound to ion-exchange microspheres (termed 'microplex') for targeted gene therapy of solid tumors. The delivery modes tested in a rat solid tumor model were free plasmids, plasmids bound to microspheres, to liposomes, or to the combination vector. The greatest amount of chloramphenicol acetyltransferase (CAT) reporter gene expression in tumors was achieved using the microplex vector; 3.4-fold compared with free, and 1.8-fold compared with both microspherical and liposomal deliveries (p &lt; 0.01). Tumor-to-normal kidney tissue CAT expression ratios were as follows: free 1.9:1; microspherical 3.7:1; liposomal 1.4:1 and microplexical 2.7:1. Expression between the two types of tissues was significantly different (p &lt; 0.01) for all delivery modes. Microspheres targeted the plasmids to the tumors, while the action of cationic liposomes on cellular membranes allowed more plasmids to breach the cell membrane. This study has proven that the novel microplex vector is capable of selective delivery of genes to tumors and has the potential to target genes in clinical trials.     

In Vitro Characterization of a Liposomal Formulation of Celecoxib Containing 1,2-Distearoyl-sn-Glycero-3-Phosphocholine,Cholesterol, and Polyethylene Glycol and its Functional Effects Against Colorectal Cancer Cell Lines

Nanosized liposomal drug delivery systems are well suited for selective drug delivery at tumor sites. Celecoxib (CLX) is a highly hydrophobic cyclooxygenase-2 inhibitor that can reduce the incidence of colorectal polyps; however, the adverse cardiovascular effects limit its applicability. Here, we report a liposomal formulation of CLX using 1,2-Distearoyl-sn-glycero-3-phosphocholine, cholesterol, and polyethylene glycol. Encapsulation efficiency of the drug was greater than 70%; the release was slow and sustained with only 12%–20% of CLX released in the first 12 h. Flow cytometry and confocal microscopy studies using the colon cancer cell lines HCT-116 and SW620 showed significantly higher cellular association and internalization of the liposomes after incubation for 6 h when compared with 30 min. The liposomes did not colocalize with transferrin, but had a punctuate appearance, indicating vesicular localization. Cell proliferation was inhibited by 95% and 78%, respectively, in SW620 and HT29 cells after incubation with 600 μM liposomal CLX for 72 h. Moreover, cellular motility, as shown by a scratch wound healing assay, was also significantly (p = 0.006) inhibited when SW620 cells were incubated with 400 μM liposomal CLX. This is the first report of the successful encapsulation of CLX in a long-circulating liposomal formulation that could be effective against colorectal cancer.     

Cellular uptake and transport of gold nanoparticles incorporated in a liposomal carrier

Recent interest in using gold nanoparticles (Au NPs) for therapy in radiation medicine has motivated development of a liposome-based system to enhance their delivery to cells. In this study, liposomes were demonstrated to perform like a “Trojan Horse” to deliver small (1.4 nm) Au NPs into tumor cells by overcoming the energetically unfavorable endocytosis process for small NPs. The results reveal that the liposomal approach provides a thousand-fold enhancement in the cellular uptake of the small Au NPs. Real-time intracellular tracking of the Au NP–liposomes revealed an average speed of 12.48 ± 3.12 μm/hr for their intracellular transport. Analysis of the time-dependent intracellular spatial distribution of the Au NP–liposomes demonstrated that they reside in lysosomes (final degrading organelles) within 40 minutes of incubation. Knowledge gained in these studies opens the door to pursuing liposomes as a viable strategy for delivery of Au NPs in radiation therapy applications.From the Clinical EditorGold nanoparticles (Au NPs) as part of an optimized liposome-based delivery system have been proposed for therapy in radiation medicine. The approach resulted in a thousand-fold enhancement in the cellular uptake of Au NPs compared to conventional delivery methods, with the nanoparticles residing in lysosomes within 40 minutes of incubation.     

Liposomal boron delivery system for neutron capture therapy

Boron neutron capture therapy (BNCT) is a binary cancer treatment based on the nuclear reaction of two essentially nontoxic species, (10)B and thermal neutrons. High accumulation and selective delivery of boron into tumor tissue are the most important requirements to achieve efficient neutron capture therapy of cancers. This review focuses on the liposomal boron delivery system (BDS) as a recent promising approach that meets these requirements for BNCT. BDS involves two strategies: (1) encapsulation of boron in the aqueous core of liposomes and (2) accumulation of boron in the liposomal bilayer. Various boronated liposomes have been developed and significant boron accumulation into tumor tissue with high tumor/blood boron ratios has been achieved by BDS.     

Enhanced transdermal delivery of acyclovir sodium via elastic liposomes

The elastic liposomes bearing acyclovir sodium were prepared for its enhanced transdermal delivery by conventional rotary evaporation method and characterized for various parameters such as vesicle shape and surface morphology, size and size distribution, entrapment efficiency, elasticity, polydispersity index, turbidity and in vitro release pattern. Permeability studies of acyclovir sodium incorporated in elastic liposomes were performed across artificial membranes and rat skin. Skin permeation potential of the developed formulation was assessed using confocal laser scanning microscopy, that revealed an enhanced permeation of the formulation to the deeper layers of the skin (up to 160 microm) following channel like pathways. Skin permeation profile of elastic liposomal formulation bearing acyclovir sodium was observed and the investigations revealed an enhanced transdermal flux (6.21 +/- 1.8 microg/cm(2)/hr) and decreased lag time (0.6 hr) for acyclovir sodium. The obtained flux was nearly 2.0 and 6.3 times higher than conventional liposomal formulation bearing acyclovir sodium and plain drug solution, respectively (p < 0.01). The elastic liposomal formulation for transdermal delivery of acyclovir sodium provides better transdermal flux, higher entrapment efficiency, ability as a self-penetration enhancer and effectiveness for transdermal delivery as compared with conventional liposomes. In vivo studies showed that on transdermal application of elastic liposomes, the concentration of acyclovir sodium in plasma was found to be 105 +/- 9.4 ng/ml after 24 hr which is about 4.2 times compared with conventional liposomes. Thus it is concluded that the elastic liposomes may be promising vehicles for the transdermal delivery of acyclovir sodium.     

Dual Functionalized 5-Fluorouracil Liposomes as Highly Efficient Nanomedicine for Glioblastoma Treatment as Assessed in an In Vitro Brain Tumor Model

Drug delivery to the brain has been a major challenge due to the presence of the blood-brain barrier, which limits the uptake of most chemotherapeutics into brain. We developed a dual-functionalized liposomal delivery system, conjugating cell penetrating peptide penetratin to transferrin-liposomes (Tf-Pen–conjugated liposomes) to enhance the transport of an anticancer chemotherapeutic drug, 5-fluorouracil (5-FU), across the blood-brain barrier into the tumor cells. The in vitro cellular uptake study showed that the dual-functionalized liposomes are capable of higher cellular uptake in glioblastoma (U87) and brain endothelial (bEnd.3) cells monolayer. In addition, dual-functionalized liposomes demonstrated significantly higher apoptosis in U87 cells. The liposomal nanoparticles showed excellent blood compatibility and in vitro cell viability, as studied by hemolysis and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, respectively. The 5-FU–loaded dual-functionalized liposomes demonstrated higher transport across the brain endothelial barrier and delivered 5-FU to tumor cells inside poly(lactic-co-glycolic acid)-chitosan scaffold (an in vitro brain tumor model), resulting in significant tumor regression.     

Preparation and optimisation of anionic liposomes for delivery of small peptides and cDNA to human corneal epithelial cells

Drug delivery to corneal epithelial cells is challenging due to the intrinsic mechanisms that protect the eye. Here, we report a novel liposomal formulation to encapsulate and deliver a short sequence peptide into human corneal epithelial cells (hTCEpi). Using a mixture of Phosphatidylcholine/Caproylamine/Dioleoylphosphatidylethanolamine (PC/CAP/DOPE), we encapsulated a fluorescent peptide, resulting in anionic liposomes with an average size of 138.8?±?34?nm and a charge of ?18.2?±?1.3?mV. After 2?h incubation with the peptide-encapsulated liposomes, 66% of corneal epithelial (hTCEpi) cells internalised the FITC-labelled peptide, demonstrating the ability of this formulation to effectively deliver peptide to hTCEpi cells. Additionally, lipoplexes (liposomes complexed with plasmid DNA) were also able to transfect hTCEpi cells, albeit at a modest level (8% of the cells). Here, we describe this novel anionic liposomal formulation intended to enhance the delivery of small cargo molecules in situ.     

Development and characterization of polymer-coated liposomes for vaginal delivery of sildenafil citrate

Vaginal administration of sildenafil citrate has shown recently to develop efficiently the uterine lining with subsequent successful embryo implantation following in vitro fertilization. The aim of the present study was to develop sildenafil-loaded liposomes coated with bioadhesive polymers for enhanced vaginal retention and improved drug permeation. Three liposomal formulae were prepared by thin-film method using different phospholipid:cholesterol ratios. The optimal liposomal formulation was coated with bioadhesive polymers (chitosan and HPMC). A marked increase in liposomal size and zeta potential was observed for all coated liposomal formulations. HPMC-coated liposomes showed the greater bioadhesion and higher entrapment efficiency than chitosan-coated formulae. The in vitro release studies showed prolonged release of sildenafil from coated liposomes as compared to uncoated liposomes and sildenafil solution. Ex vivo permeation study revealed the enhanced permeation of coated relative to uncoated liposomes. Chitosan-coated formula demonstrated highest drug permeation and was thus selected for further investigations. Transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR) confirmed the successful coating of the liposomes by chitosan. Histopathological in vivo testing proved the efficacy of chitosan-coated liposomes to improve blood flow to the vaginal endometrium and to increase endometrial thickness. Chitosan-coated liposomes can be considered as potential novel drug delivery system intended for the vaginal administration of sildenafil, which would prolong system's retention at the vaginal site and enhance the permeation of sildenafil to uterine blood circulation.     

Enhancement of Tissue Delivery and Receptor Occupancy of Methylprednisolone in Rats by a Liposomal Formulation

A liposomal formulation of methylprednisolone (L-MPL) was developed to improve localization of this immunosuppressant in lymphatic tissues. Liposomes containing MPL were formulated from a mixture of phosphatydylcholine and phosphatydylglycerol (molar ratio, 9:1) and sized by extrusion through a 0.1-µm membrane. Male Sprague–Dawley rats received a bolus dose of 2 mg/kg of L-MPL or free MPL in solution (control). Samples of blood, spleen, liver, thymus, and bone marrow were collected at intervals over a 66-hr period. Concentrations of MPL in plasma and organs and free cytosolic glucocorticoid receptors (GCR) in spleen and liver were determined. The plasma MPL profiles for free and L-MPL were bi- and triexponential. Although the alpha phase kinetics of both dosage forms were similar, L-MPL showed a substantially slower elimination phase than did free drug. Incorporation of MPL into liposomes caused the following increases: terminal half-life, from 0.48 (MPL) to 30.13 hr (L-MPL); MRT, from 0.42 to 11.95 hr, V _ss, from 2.10 to 21.87 L/kg; and AUC, from 339 to 1093 ng · hr/mL. Uptake of liposomes enhanced significantly the delivery of drug to lymphatic tissues and liver; AUC tissue:plasma ratios for spleen increased 77-fold; for liver, 9-fold; and for thymus, 27-fold. The duration of GCR occupancy was extended 10-fold in spleen and 13-fold in liver by the liposomal formulation. Lymphatic tissue selectivity and extended receptor binding of liposome-delivered MPL offer promise for enhanced immunosuppression.     

Minimally invasive cytoselective radiation therapy using boron neutron capture reaction

The cell-killing effect of boron neutron capture therapy (BNCT) is due to the nuclear reaction of two essentially nontoxic species, boron-10 ((10)B) and thermal neutrons, whose destructive effect is well observed in boron-loaded tissues. High accumulation and selective delivery of boron into tumor tissue are the most important requirements to achieve efficient neutron capture therapy of cancers. This review focuses on liposomal boron delivery system (BDS) as a recent promising approach that meet these requirements for BNCT. BDS involves two strategies: (1) encapsulation of boron in the aqueous core of liposomes and (2) accumulation of boron in the liposomal bilayer. In this review, recent development of liposomal boron delivery system is summarized.     

PEGylated elastic liposomal formulation for lymphatic targeting of zidovudine

The present study was aimed at in vitro and in vivo evaluation of PEGylated elastic liposomal formulation for lymphatic targeting of zidovudine (AZT). PEGylated elastic liposomal formulation was prepared and characterized for characteristic in vitro, ex-vivo and in vivo parameters. The plain and PEGylated elastic liposomal formulation showed transdermal flux of 99.8+/-5.8 and 119.5+/-5.2 microg/cm(2)/hr, respectively across the rat skin. Results of biodistribution study indicated 27-fold higher accumulation of AZT in lymphoid tissues after application of PEGylated elastic liposomes as compared to free drug. The efficient localization of elastic liposomal formulation in lymphatic system is of particular interest for HIV therapy, taking in account that replication of HIV mainly takes place in the lymphoid system. The Cellular uptake studies showed significantly higher cellular uptake in lymphoid cells (MT-2 cell line) from PEGylated elastic liposomal formulation (88.9+/-8.7%) in comparison to phosphate buffer saline (PBS, pH 7.4) solution of drug (27.1+/-2.8%). The entrapment of AZT into PEGylated elastic liposomes represents a potential approach for overcoming the toxicity by its selective uptake in lymphoid organs. This represents attractive approach for sustained and targeted delivery of AZT.     

Targeted thermosensitive liposomes: an attractive novel approach for increased drug delivery to solid tumors

Introduction: Currently available chemotherapy is hampered by a lack in tumor specificity and resulting toxicity. Small and long-circulating liposomes can preferentially deliver chemotherapeutic drugs to tumors upon extravasation from tumor vasculature. Although clinically used liposomal formulations demonstrated significant reduction in toxicity, enhancement of therapeutic activity has not fully met expectations.

Areas covered: Low drug bioavailability from liposomal formulations and limited tumor accumulation remain major challenges to further improve therapeutic activity of liposomal chemotherapy. The aim of this review is to highlight strategies addressing these challenges. A first strategy uses hyperthermia and thermosensitive liposomes to improve tumor accumulation and trigger liposomal drug bioavailability. Image-guidance can aid online monitoring of heat and drug delivery and further personalize the treatment. A second strategy involves tumor-specific targeting to enhance drug delivery specificity and drug internalization. In addition, we review the potential of combinations of the two in one targeted thermosensitive-triggered drug delivery system.

Expert opinion: Heat-triggered drug delivery using thermosensitive liposomes as well as the use of tumor vasculature or tumor cell-targeted liposomes are both promising strategies to improve liposomal chemotherapy. Preclinical evidence has been encouraging and both strategies are currently undergoing clinical evaluation. A combination of both strategies rendering targeted thermosensitive liposomes (TTSL) may appear as a new and attractive approach promoting tumor drug delivery.     

Translocation of liposomes into cancer cells by cell-penetrating peptides penetratin and tat: a kinetic and efficacy study

Unlike conventional liposomes, sterically stabilized liposomes, with their smaller volume of distribution and reduced clearance, preferentially convey encapsulated drugs into tumor sites. Despite these improvements, intracellular delivery is hampered by the stable drug retention of the liposomes, which diminishes the efficacy of the liposomal drug. To facilitate uptake of liposomal drugs into cells, two cell-penetrating peptides, penetratin (PEN) and TAT, derived from the HIV-1 TAT protein, were studied. In contrast to control peptides, both TAT and PEN enhanced the translocation efficiency of liposomes in proportion to the number of peptides attached to the liposomal surface. A peptide number of as few as five could enhance the intracellular delivery of liposomes. The kinetics of uptake was peptide- and cell-type dependent. Intracellular accumulation of TAT-liposomes increased with incubation time, but PEN-liposomes peaked at 1 h and then declined gradually. After treatment with 1 microg/ml doxorubicin equivalents of liposome for 2 h, TAT increased the doxorubicin uptake of A431 cells by 12-fold. However, the improvement of uptake of liposomal doxorubicin was not reflected by cytotoxicity in vitro or tumor control in vivo. Our results demonstrated that merely adding CPP to a liposome encapsulating anticancer drug was inadequate in improving its antitumor activity. An additional approach to enhance the intracellular release of the encapsulated drug is obviously necessary.     

Liposomes for brain delivery

Introduction: Development of drug delivery systems for brain delivery is one of the most challenging research topics in pharmaceutical areas, mainly due to the presence of the blood–brain barrier (BBB), which separates the blood from the cerebral parenchyma thus limiting the brain uptake of the majority of therapeutic agents. Among the several carriers, which have been studied to overcome this problem, liposomes have gained increasing attention as promising strategies for brain-targeted drug delivery. The most advantageous features of liposomes are their ability to incorporate and deliver large amounts of drug and the possibility to decorate their surface with different ligands.

Areas covered: The purpose of this review is to explore the different approaches studied to transport and deliver therapeutics and imaging agents to the brain by using liposomes. In the first part of the review, particular attention is paid to describe the anatomy of the BBB and different physiological transport mechanisms available for drug permeation. In the second part, the different strategies for the delivery of a drug to the brain using liposomes are reviewed for each transport mechanism.

Expert opinion: Over the last decade, there have been significant developments concerning liposomal brain delivery systems conjugated with selected ligands with high specificity and low immunogenicity. An universally useful liposomal formulation for brain targeting does not exist but liposome design must be modulated by the appropriate choice of the specific homing device and transport mechanism.     

Selective boron drug delivery to brain tumors for boron neutron capture therapy

Malignant glioma is one of the most deadly forms of cancer in humans and remains refractory to presently available treatments. Boron neutron capture therapy (BNCT) is a promising therapeutic modality for the treatment of malignant brain tumors. For successful BNCT, a sufficient quantity of boron atoms must be selectively delivered to individual brain tumor cells while at the same time the boron concentration in the normal brain tissue should be kept low to minimize the damage to normal brain tissue. However, the brain entry of drugs is restricted by the blood-brain barrier (BBB), even though the permeability of the pathological area of this barrier may be partially increased due to the present of brain tumors. Therefore, selective delivery of boron to tumor cells across the BBB is a major challenge to the BNCT of brain tumors. This review briefly discusses four main mechanisms responsible for drug transport across the BBB. Brain tumor-localizing boron compounds are described, such as borocaptate sodium, p-boronophenylalanine, boronated porphyrins and boronated nucleosides. Strategies employed to selectively deliver boron drug into brain tumors are reviewed including hyperosmotic BBB modification, biochemical opening of BBB, electropermeabilization and direct intracerebral delivery of boron drugs. Conjugation of boron drugs to macromolecules like monoclonal antibodies and epidermal growth factor are discussed for active tumor targeting. Boron delivery via microparticles such as liposomes, high density lipoproteins and nanoparticles is also covered for their potential utilization in BNCT of brain tumors.     

Liposome-Mediated Therapy of Intracranial Brain Tumors in a Rat Model

Purpose. Malignant brain tumors represent a serious therapeutic challenge, and survival often is low. We investigated the delivery of doxorubicin (DXR) to rat brain tumors in situ vialiposomes, to test the hypothesis that intact liposomes undergo deposition in intracranial tumor through a compromised blood-tumor vasculature. Both therapeutic effect and intra-tumor drug carrier distribution were evaluated to identify variables in carrier-mediated delivery having impact on therapy. Methods. The rat 9L gliosarcoma tumor was implanted orthotopically in Fischer 344 rats in the caudate-putamen region. The tumor-bearing rats were treated with DXR, either free or encapsulated in long-circulating, sterically-stabilized liposomes. Anti-tumor efficacy was assessed by survival time. In parallel, liposomes labeled with a fluorescent phospholipid analog were injected into tumor-bearing rats. At predetermined intervals, the brains were perfused with fixative, sectioned, and imaged with laser scanning confocal microscope (LSCM) to investigate the integrity of the tumor vascular bed and the intratumor deposition of liposomes. Results. Free DXR given in 3 weekly iv injections was ineffective in increasing the life span of tumor-bearing rats at cumulative doses 17 mg/kg, and at the highest dose (17 mg/kg) decreased survival slightly, compared to saline-treated controls. In contrast, DXR encapsulated in long-circulating liposomes mediated significant increases in life span at 17 mg/kg. Rats showed a 29% percent increase in median survival, respectively, compared to saline-control animals. The delay of treatment after tumor implantation was a major determinant of therapeutic effect. Fluorescent liposomes were deposited preferentially in tumor rather than normal brain, and were distributed non-uniformly, in close proximity to tumor blood vessels. Conclusions. Liposomes can be used to enhance delivery of drugs to brain tumors and increase therapeutic effect. The therapeutic effect may arise from release of drug from liposomes extravasated in discrete regions of the tumor vasculature and the extravascular space.     

Vascular targeting of doxorubicin using cationic liposomes

Tumor vessel has been recognized as an important target for anticancer therapy. Cationic liposomes have been shown to selectively target tumor endothelial cells, thus can potentially be used as a carrier for chemotherapy agents. In this study, cationic liposomes containing 20 mol% cationic lipid dimethyl dioctadecyl ammonium bromide (DDAB) and loaded with doxorubicin (DOX) were prepared and characterized. The cationic liposomal DOX showed 10.8 and 9.1 times greater cytotoxicity than control PEGylated liposomal DOX in KB oral carcinoma and L1210 murine lymphocytic leukemia cells, and 7.7- and 6.8-fold greater cytotoxicity compared to control neutral non-PEGylated liposomal DOX, repectively, in these two cell lines. Although cationic liposomal DOX had higher tumor accumulation at 30 min after intravenous administration compared to control liposomes (p<0.05), DOX uptake of these liposomes at 24h post-injection was similar to that of PEGylated liposomal DOX (p>0.05) and approximately twice the levels of the free drug and non-PEGylated liposomes. In a murine tumor model generated using L1210 cells, increased survival rate was obtained with cationic liposomal DOX treatment compared to free DOX (p<0.01), neutral liposome control (p<0.01), as well as PEGylated liposomes (p<0.05). In conclusion, the cationic liposomal DOX formulation produced superior in vitro cytotoxicity and in vivo antitumor activity, and warrants further investigation.