Effect of polyethyleneglycol (PEG) chain on cell uptake of PEG-modified liposomes

Study on tumour cell-derived hybrid exosomes as dasatinib nanocarriers for pancreatic cancer therapy

Pancreatic ductal adenocarcinoma (PDAC) is one of the leading causes of cancer-related death. Therefore, we intend to explore novel strategies against PDAC. The exosomes-based biomimetic nanoparticle is an appealing candidate served as a drug carrier in cancer treatment, due to its inherit abilities. In the present study, we designed dasatinib-loaded hybrid exosomes by fusing human pancreatic cancer cells derived exosomes with dasatinib-loaded liposomes, followed by characterization for particle size (119.9 ± 6.10 nm) and zeta potential (-11.45 ± 2.24 mV). Major protein analysis from western blot techniques reveal the presence of exosome marker proteins CD9 and CD81. PEGylated hybrid exosomes showed pH-sensitive drug release in acidic condition, benefiting drug delivery to acidic cancer environment. Dasatinib-loaded hybrid exosomes exhibited significantly higher uptake rates and cytotoxicity to parent PDAC cells by two-sample t-test or by one-way ANOVA analysis of variance, as compared to free drug or liposomal formulations. The results from our computational analysis demonstrated that the drug-likeness, ADMET, and protein-ligand binding affinity of dasatinib are verified successfully. Cancer derived hybrid exosomes may serve as a potential therapeutic candidate for pancreatic cancer treatment.

Co-delivery of simvastatin and microRNA-21 through liposome could accelerates the wound healing process

The gene delivery approach, mainly microRNAs (miRNA) as key wound healing mediators, has recently received extensive attention. MicroRNA-21 (miR-21) has strongly impacted wound healing by affecting the inflammation and proliferation phases. Previous studies have also demonstrated the beneficial effect of simvastatin on wound healing. Therefore, we designed a dual-drug/gene delivery system using PEGylated liposomes that could simultaneously attain the co-encapsulation and co-delivery of miRNA and simvastatin (SIM) to explore the combined effect of this dual-drug delivery system on wound healing. The PEG-liposomes for simvastatin and miR-21 plasmid (miR-21-P/SIM/Liposomes) were prepared using the thin-film hydration method. The liposomes showed 85 % entrapment efficiency for SIM in the lipid bilayer and high physical entrapment of miR-21-P in the inner cavity. In vitro studies demonstrated no cytotoxicity for the carrier on normal human dermal fibroblast cells (NHDF) and 97 % cellular uptake over 2 h incubation. The scratch test revealed excellent cell proliferation and migration after treatment with miR-21-P/SIM/Liposomes. For the in vivo experiments, a full-thickness cutaneous wound model was used. The wound closure on day 8 was higher for Liposomal formulation containing miR-21-P promoting faster re-epithelialization. On day 12, all treated groups showed complete wound closure. However, following histological analysis, the miR-21-P/SIM/Liposomes revealed the best tissue regeneration, similar to normal functional skin, by reduced inflammation and increased re-epithelialization, collagen deposition and angiogenesis. In conclusion, the designed miR-21-P/SIM/Liposomes could significantly accelerate the process of wound healing, which provides a new strategy for the management of chronic wounds.

Effect of phospholipid head group on ultrasound-triggered drug release and cellular uptake of immunoliposomes

Liposomes are the most successful nanoparticles used to date to load and deliver chemotherapeutic agents to cancer cells. They are nano-sized vesicles made up of phospholipids, and targeting moieties can be added to their surfaces for the active targeting of specific tumors. Furthermore, Ultrasound can be used to trigger the release of the loaded drugs by disturbing their phospholipid bilayer structure. In this study, we have prepared pegylated liposomes using four types of phospholipids with similar saturated hydrocarbon tails including a phospholipid with no head group attached to the phosphate head (DPPA) and three other phospholipids with different head groups attached to their phosphate heads (DPPC, DPPE and DPPG). The prepared liposomes were conjugated to the monoclonal antibody trastuzumab (TRA) to target the human epidermal growth factor receptor 2 (HER2) overexpressed on HER2-positive cancer cells (HER2+). We have compared the response of the different formulations of liposomes when triggered with low-frequency ultrasound (LFUS) and their cellular uptake by the cancer cells. The results showed that the different formulations had similar size, polydispersity, and stability. TRA-conjugated DPPC liposomes showed the highest sensitivity to LFUS. On the other hand, incubating the cancer cells with TRA-conjugated DPPA liposomes triggered with LFUS showed the highest uptake of the loaded calcein by the HER2+ cells.

Liposomes in Cancer Therapy: How Did We Start and Where Are We Now

Since their first discovery in the 1960s by Alec Bangham, liposomes have been shown to be effective drug delivery systems for treating various cancers. Several liposome-based formulations received approval by the U.S. Food and Drug Administration (FDA) and European Medicines Agency (EMA), with many others in clinical trials. Liposomes have several advantages, including improved pharmacokinetic properties of the encapsulated drug, reduced systemic toxicity, extended circulation time, and targeted disposition in tumor sites due to the enhanced permeability and retention (EPR) mechanism. However, it is worth noting that despite their efficacy in treating various cancers, liposomes still have some potential toxicity and lack specific targeting and disposition. This explains, in part, why their translation into the clinic has progressed only incrementally, which poses the need for more research to focus on addressing such translational limitations. This review summarizes the main properties of liposomes, their current status in cancer therapy, and their limitations and challenges to achieving maximal therapeutic efficacy.

Polysarcosine-based lipid formulations for intracranial delivery of mRNA

Messenger RNA (mRNA) is revolutionizing the future of therapeutics in a variety of diseases, including neurological disorders. Lipid formulations have shown to be an effective platform technology for mRNA delivery and are the basis for the approved mRNA vaccines. In many of these lipid formulations, polyethylene glycol (PEG)-functionalized lipid provides steric stabilization and thus plays a key role in improving the stability both ex vivo and in vivo. However, immune responses towards PEGylated lipids may compromise the use of those lipids in some applications (e.g., induction of antigen specific tolerance), or within sensitive tissues (e.g., central nervous system (CNS)). With respect to this issue, polysarcosine (pSar)-based lipopolymers were investigated as an alternative to PEG-lipid in mRNA lipoplexes for controlled intracerebral protein expression in this study. Four polysarcosine-lipids with defined sarcosine average molecular weight (M_n = 2 k, 5 k) and anchor diacyl chain length (m = 14, 18) were synthesized, and incorporated into cationic liposomes. We found that the content, pSar chain length and carbon tail lengths of pSar-lipids govern the transfection efficiency and biodistribution. Increasing carbon diacyl chain length of pSar-lipid led up to 4- and 6-fold lower protein expression in vitro. When the length of either pSar chain or lipid carbon tail increased, the transfection efficiency decreased while the circulation time was prolonged. mRNA lipoplexes containing 2.5% C14-pSar2k resulted in the highest mRNA translation in the brain of zebrafish embryos through intraventricular injection, while C18-pSar2k-liposomes showed a comparable circulation with DSPE-PEG2k-liposomes after systemic administration. To conclude, pSar-lipid enable efficient mRNA delivery, and can substitute PEG-lipids in lipid formulations for controlled protein expression within the CNS.

Dendritic lipopeptide liposomes decorated with dual-targeted proteins

Due to their homing effects, cell and cell membrane-derived nanocarriers have been widely used to enhance drug target delivery. Inspired by the protein-anchored cell membrane architecture, we here report a tumor-targeted liposome, dtDLP, which was constructed through the electrostatic interaction between dendritic lipopeptide liposomes and a dual-targeted recombinant protein, achieving superior tumor homing, cellular endocytotic and penetration abilities. The dual-targeted recombinant protein consists of an anti-epidermal growth factor receptor single domain antibody and a peptide ligand for the integrin α_vβ₃. dtDLPs substantially reduced macrophage phagocytosis and increased drug internalization in both 4T1 cells and HeLa cells by providing more endocytic pathways. In addition, the dtDLPs showed great penetration ability in both multicellular spheroids and tumor tissues. Due to the improved cancer cellular uptake and tumor penetration, the dtDLPs exhibited a superior anticancer effect in both HeLa and 4T1 tumor-bearing mice. This work will be helpful for the design of cell-specific liposomes with admirable tumor targeting, endocytotic and penetration abilities.

Metallated phthalocyanines and their hydrophilic derivatives for multi-targeted oncological photodynamic therapy

BACKGROUND AND AIM

A photosensitizer (PS) delivery and comprehensive tumor targeting platform was developed that is centered on the photosensitization of key pharmacological targets in solid tumors (cancer cells, tumor vascular endothelium, and cellular and non-cellular components of the tumor microenvironment) before photodynamic therapy (PDT). Interstitially targeted liposomes (ITLs) encapsulating zinc phthalocyanine (ZnPC) and aluminum phthalocyanine (AlPC) were formulated for passive targeting of the tumor microenvironment. In previous work it was established that the PEGylated ITLs were taken up by cultured cholangiocarcinoma cells. The aim of this study was to verify previous results in cancer cells and to determine whether the ITLs can also be used to photosensitize cells in the tumor microenvironment and vasculature. Following positive results, rudimentary in vitro and in vivo experiments were performed with ZnPC-ITLs and AlPC-ITLs as well as their water-soluble tetrasulfonated derivatives (ZnPCS4 and AlPCS4) to assemble a research dossier and bring this platform closer to clinical transition.

METHODS

Flow cytometry and confocal microscopy were employed to determine ITL uptake and PS distribution in cholangiocarcinoma (SK-ChA-1) cells, endothelial cells (HUVECs), fibroblasts (NIH-3T3), and macrophages (RAW 264.7). Uptake of ITLs by endothelial cells was verified under flow conditions in a flow chamber. Dark toxicity and PDT efficacy were determined by cell viability assays, while the mode of cell death and cell cycle arrest were assayed by flow cytometry. In vivo systemic toxicity was assessed in zebrafish and chicken embryos, whereas skin phototoxicity was determined in BALB/c nude mice. A PDT efficacy pilot was conducted in BALB/c nude mice bearing human triple-negative breast cancer (MDA-MB-231) xenografts.

RESULTS

The key findings were that (1) photodynamically active PSs (i.e., all except ZnPCS4) were able to effectively photosensitize cancer cells and non-cancerous cells; (2) following PDT, photodynamically active PSs were highly toxic-to-potent as per anti-cancer compound classification; (3) the photodynamically active PSs did not elicit notable systemic toxicity in zebrafish and chicken embryos; (4) ITL-delivered ZnPC and ZnPCS4 were associated with skin phototoxicity, while the aluminum-containing PSs did not exert detectable skin phototoxicity; and (5) ITL-delivered ZnPC and AlPC were equally effective in their tumor-killing capacity in human tumor breast cancer xenografts and superior to other non-phthalocyanine PSs when appraised on a per mole administered dose basis.

CONCLUSIONS

AlPC(S4) are the safest and most effective PSs to integrate into the comprehensive tumor targeting and PS delivery platform. Pending further in vivo validation, these third-generation PSs may be used for multi-compartmental tumor photosensitization.

Surface modification with cholesteryl acetyl carnitine, a novel cationic agent, elevates cancer cell uptake of the PEGylated liposomes

The present study aimed to synthesize cholesteryl acetyl carnitine (CAC), and surface modify the PEGylated liposomes with the intention of enhanced cancer cell uptake. For this, CAC synthesis was performed in amine-free esterification conditions and then four liposomal formulations of unmodified, CAC/PEG, and CAC + PEG-modified were prepared by ethanol injection method. Cytotoxicity of the liposomes was investigated in A549 cells, followed by cellular uptake assessments of coumarin 6 (C6)-loaded liposomes. The results of ATR-FTIR, ¹HNMR, and ¹³CNMR demonstrated successful formation of CAC. A molecular docking study showed efficient binding affinities rather than carnitine to the active site of four carnitine transporters. Liposomal formulations possessed spherical morphology with a mean particle size range of 112-138 nm, narrow size distribution, and negative surface charge. All formulations had low cytotoxicity at 0.5 mg/ml, but high cytotoxicity at around 2.5 mg/ml. The lowest IC50 was obtained for CAC modified liposomes. CAC + PEG-modified liposomes had the highest cellular uptake. In conclusion, CAC + PEG modification of liposomes is an effective approach for increasing A549 cellular uptake, with low cytotoxicity at commonly applied liposome concentrations. The elevated uptake may be due to the involvement of the organic cation transporter, cationic structure, and the metabolic preference of CAC in cancer cells.

Preparation, Characterization, and In Vitro Pharmacodynamics and Pharmacokinetics Evaluation of PEGylated Urolithin A Liposomes

Urolithin A (Uro-A), a metabolite of ellagitannins in mammals' intestinal tract, displays broad biological properties in preclinical models, including anti-oxidant, anti-inflammatory, and anti-tumor effects. However, the clinical application of Uro-A is restricted because of its low aqueous solubility and short elimination half-life. Our purpose was to develop a delivery system to improve the bioavailability and anti-tumor efficacy of Uro-A. To achieve this goal, urolithin A-loaded PEGylated liposomes (Uro-A-PEG-LPs) were prepared for the first time and its physicochemical properties and anti-tumor efficacy in vitro were evaluated. The morphology of Uro-A-PEG-LPs displayed a uniform sphere under transmission electron microscope. The particle size, polydispersity index, zeta potential, and encapsulation efficiency of Uro-A-PEG-LPs were 122.8 ± 7.4 nm, 0.25 ± 0.16, - 25.5 ± 2.3 mV, and 94.6 ± 1.6%, respectively. Moreover, Uro-A-PEG-LPs possessed higher stability and could be stably stored at 4°C for a long time. In vitro release characteristics indicated that Uro-A-PEG-LPs possessed superior sustained release properties. The results of confocal laser scanning microscopy experiment showed that the coumarin 6-loaded PEGylated liposomes (C6-PEG-LPs) have superior cellular uptake than that of conventional liposomes. In addition, in vitro tests demonstrated that Uro-A-PEG-LPs elevated cytotoxicity and pro-apoptotic effect in human hepatoma cells comparing with free Uro-A. Furthermore, the results of pharmacokinetic experiments showed that the t_1/2, AUC_0-t, and MRT_0-t of Uro-A-PEG-LPs increased to 4.58-fold, 2.33-fold, and 2.43-fold than those of free Uro-A solution, respectively. Collectively, these manifested that PEGylated liposomes might be a potential delivery system for Uro-A to prolonging in vivo circulation time, promoting cellular uptake, and enhancing its anti-tumor efficacy.

Role of stealth lipids in nanomedicine-based drug carriers

The domain of nanomedicine owns a wide-ranging variety of lipid-based drug carriers, and novel nanostructured drug carriersthat are further added to this range every year. The primary goal behind the exploration of any new lipid-based nanoformulation is the improvement of the therapeutic index of the concerned drug molecule along with minimization in the associated side-effects. However, for maintaining a sustained delivery of these intravenously injected lipoidal nanomedicines to the targeted tissues and organ systems in the body, longer circulation in the bloodstream, as well as their stability, are important. After administration, upon recognition as foreign entities in the body, these systems are rapidly cleared by the cells associated with the mononuclear phagocyte system. In order to provide these lipid-based systems with long circulation characteristics, techniques such as coating of the lipoidal surface with an inert polymeric material like polyethylene glycol (PEG) assists in imparting 'stealth properties' to these nanoformulations for avoiding recognition by the macrophages of the immune system. In this review, detailed importance is given to the hydrophilic PEG polymer and the role played by PEG-linked lipid polymers in the field of nanomedicine-based drug carriers. The typical structure and classification of stealth lipids, clinical utility, assemblage techniques, physicochemical characterization, and factors governing the in-vivo performance of the PEG-linked lipids containing formulations will be discussed. Eventually, the novel concept of accelerated blood clearance (ABC) phenomenon associated with the use of PEGylated therapeutics will be deliberated.

Dual pH-sensitive liposomes with low pH-triggered sheddable PEG for enhanced tumor-targeted drug delivery

Aim: pH-sensitive liposomes (pSL) have emerged as promising nanocarriers due to their endo/lysosome-escape abilities, however, their pH sensitivity is compromised by poly(ethylene glycol) (PEG) coating. This study investigates whether an intracellular PEG-detachment strategy can overcome this PEG dilemma. Materials & methods: First, PEG2000 was conjugated with a phospholipid via an acid-labile hydrazide-hydrazone bond (-CO-NH-N = CH-), which was postinserted into pSL, forming PEG-cleavable pSL (CL-PEG-pSL). Their endo/lysosomal-escape abilities in MIA PaCa-2 cells, pharmacokinetics and tumor accumulation abilities were studied using PEG-pSL as reference. Results: CL-PEG-pSL showed rapid endo/lysosome-escape abilities in the cancer cells and higher tumor accumulation in MIA PaCa-2 xenograft model in contrast to PEG-pSL. Conclusion: Cleavable PEGylation is an efficient strategy to ameliorate the PEG dilemma of pSL for cancer drug delivery.

Bispecific antibodies (anti-mPEG/anti-HER2) for active tumor targeting of docetaxel (DTX)-loaded mPEGylated nanocarriers to enhance the chemotherapeutic efficacy of HER2-overexpressing tumors

Anti-mPEG/anti-human epidermal growth factor receptor 2 (HER2) bispecific antibodies (BsAbs) non-covalently bound to a docetaxel (DTX)-loaded mPEGylated lecithin-stabilized micellar drug delivery system (LsbMDDs) were endowed with active targetability to improve the chemotherapeutic efficacy of DTX. DTX-loaded mPEGylated LsbMDDs formulations were prepared using lecithin/DSPE-PEG(2K or 5K) nanosuspensions to hydrate the thin film, and then they were subjected to ultrasonication. Two BsAbs (anti-mPEG/anti-DNS or anti-HER2) were simply mixed with the LsbMDDs to form BsAbs-LsbMDDs formulations, respectively, referred as the DNS-LsbMDDs and HER2-LsbMDDs. Results demonstrated that the physical characteristics of the BsAbs-LsbMDDs were similar to those of the plain LsbMDDs but more slowly released DTX than that from the LsbMDDs. Results also showed that the HER2-LsbMDDs suppressed the growth of HER2-expressing MCF-7/HER2 tumors, increasing the amount taken up via an endocytosis pathway leading to high drug accumulation and longer retention in the tumor. In conclusion, the BsAbs-LsbMDDs preserved the physical properties of the LsbMDDs and actively targeted tumors with a drug cargo to enhance drug accumulation in tumors leading to greater antitumor activity against antigen-positive tumors.

Effective and safe in vivo gene delivery based on polyglutamic acid complexes with heterocyclic amine modified-polyethylenimine

Polyethylenimine (PEI) has been extensively used for non-viral gene delivery. Increasing the molecular weight of PEI often improves transfection efficiency, but enhances cytotoxicity and non-specific interaction with plasma proteins, limiting its use in clinical applications. In this study, poly-l-glutamic acid (L-PGA) as an anionic polymer, was introduced to piperazine-modified PEI to improve its in vivo properties. The physicochemical properties, cytotoxicity, in vitro and in vivo tranfection efficiency of these carriers were evaluated. Conjugation of 50% of primary amines of PEI 25 kDa with piperazine in the presence of PGA_1% (PEI₂₅Pip_50%/PGA_1%) could significantly increase transfection efficiency even in the presence of serum compared to PEI 25 kDa. Increasing the PGA content led to lower cytotoxicity of DNA/PEI₂₅Pip_50%/PGA_1% triplexes. Systemic administration of triplexes in Balb/c mice resulted in significant enhancement of luciferase gene expression in brain, spleen, and liver compared to PEI 25 kDa. In a 30-day survival study, no significant changes were observed in mice body weights in DNA/PEI₂₅Pip_50%/PGA_1% group. Moreover, this group exhibited a survival rate of 100% compared to 0% in mice receiving PEI 25 kDa. This novel PEI₂₅Pip_50%/PGA_1% carrier could be used to overcome the serum inhibitory effects on gene expression in vivo, providing a promising gene delivery system for tissue-specific targeting.

Improved efficacy of doxycycline in liposomes against Plasmodium falciparum in culture and Plasmodium berghei infection in mice

The rate at which Plasmodium falciparum is developing resistance to clinically used antimalarial drugs is alarming. Therefore, there is a compelling need to develop an efficient drug delivery system to improve the efficacy of existing antimalarial agents and circumvent drug resistance. Here, we report the antibacterial drug doxycycline (DOXY) in liposomal formulations exhibits enhanced antiplasmodial activity against blood stage forms of P. falciparum (3D7) in culture and established Plasmodium berghei NK-65 infection in murine model. Parasite killing on blood stage forms in culture was determined by a radiolabeled [³H] hypoxanthine incorporation assay and infected erythrocytes stained with Giemsa were counted using microscopy in vivo. The 50% inhibitory concentration (IC₅₀) of DOXY-stearylamine liposome (IC₅₀ 0.36 μM) and DOXY-SPC:Chol-liposome (IC₅₀ 0.85 μM) exhibited marked growth inhibition of parasites compared with free DOXY (IC₅₀ 14 μM), with minimal toxicity to normal erythrocytes. Administration of polyethylene glycol distearoyl phosphatidylethanolamine-methoxy-polyethylene glycol2000 (DSPE-mPEG-2000) coated liposomes loaded with DOXY at 2.5 mg/kg per day resulted in efficacious killing of blood parasites with improved survival in mice relative to the free drug in both chloroquine sensitive and resistant strains of P. berghei infection. This is the first report to demonstrate that DOXY in liposomal system has immense chemotherapeutic potential against plasmodial infections at lower dosages.

Hyper-cell-permeable micelles as a drug delivery carrier for effective cancer therapy

Although PEGylated liposomes (PEG-LS) have been intensively studied as drug-delivery vehicles, the rigidity and the hydrophilic PEG corona of liposomal membranes often limits cellular uptake, resulting in insufficient drug delivery to target cells. Thus, it is necessary to develop a new type of lipid-based self-assembled nanoparticles capable of enhanced cellular uptake, tissue penetration, and drug release than conventional PEGylated liposomes. Herein, we describe a simple modification of bicellar formulation in which the addition of a PEGylated phospholipid produced a dramatic physicochemical change in morphology, i.e., the disc-shaped bicelle became a uniformly distributed ultra-small (∼12 nm) spherical micelle. The transformed lipid-based nanoparticles, which we termed hyper-cell-permeable micelles (HCPMi), demonstrated not only prolonged stability in serum but also superior cellular and tumoral uptake compared to a conventional PEGylated liposomal system (PEG-LS). In addition, HCPMi showed rapid cellular uptake and subsequent cargo release into the cytoplasm of cancer cells. Cells treated with HCPMi loaded with docetaxel (DTX) had an IC₅₀ value of 0.16 μM, compared with 0.78 μM with PEG-LS loaded with DTX, a nearly five-fold decrease in cell viability, indicating excellent efficiency in HCPMi uptake and release. In vivo tumor imaging analysis indicated that HCPMi penetrated deep into the tumor core and achieved greater uptake than PEG-LS. Results of HCPMi (DTX) treatment of allograft and xenograft mice in vivo showed high tumoral uptake and appreciable tumor retardation, with ∼70% tumor weight reduction in the SCC-7 allograft model. Taken together, these findings indicate that HCPMi could be developed further as a highly competent lipid-based drug-delivery system.

Nanoformulations of anticancer thiosemicarbazones to reduce methemoglobin formation and improve anticancer activity

Triapine and two derivatives were encapsulated into polymeric nanoparticles as well as liposomes. The most stable formulation showed strongly reduced methemoglobin formation and improved anticancer activity.

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

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

Fluorescence microscopy colocalization of lipid-nucleic acid nanoparticles with wildtype and mutant Rab5-GFP: A platform for investigating early endosomal events

Endosomal entrapment is known to be a major bottleneck to successful cytoplasmic delivery of nucleic acids (NAs) using cationic liposome-NA nanoparticles (NPs). Quantitative measurements of distributions of NPs within early endosomes (EEs) have proven difficult due to the sub-resolution size and short lifetime of wildtype EEs. In this study we used Rab5-GFP, a member of the large family of GTPases which cycles between the plasma membrane and early endosomes, to fluorescently label early endosomes. Using fluorescence microscopy and quantitative image analysis of cells expressing Rab5-GFP, we found that at early time points (t<1h), only a fraction (≈35%) of RGD-tagged NPs (which target cell surface integrins) colocalize with wildtype EEs, independent of the NP's membrane charge density. In comparison, a GTP-hydrolysis deficient mutant, Rab5-Q79L, which extends the size and lifetime of EEs yielding giant early endosomes (GEEs), enabled us to resolve and localize individual NPs found within the GEE lumen. Remarkably, nearly all intracellular NPs are found to be trapped within GEEs implying little or no escape at early time points. The observed small degree of colocalization of NPs and wildtype Rab5 is consistent with recycling of Rab5-GDP to the plasma membrane and not indicative of NP escape from EEs. Taken together, our results show that endosomal escape of PEGylated nanoparticles occurs downstream of EEs i.e., from late endosomes/lysosomes. Our studies also suggest that Rab5-Q79L could be used in a robust imaging assay which allows for direct visualization of NP interactions with the luminal membrane of early endosomes.

Nanodevices for studying nano-pathophysiology

Nano-scaled devices are a promising platform for specific detection of pathological targets, facilitating the analysis of biological tissues in real-time, while improving the diagnostic approaches and the efficacy of therapies. Herein, we review nanodevice approaches, including liposomes, nanoparticles and polymeric nanoassemblies, such as polymeric micelles and vesicles, which can precisely control their structure and functions for specifically interacting with cells and tissues. These systems have been successfully used for the selective delivery of reporter and therapeutic agents to specific tissues with controlled cellular and subcellular targeting of biomolecules and programmed operation inside the body, suggesting a high potential for developing the analysis for nano-pathophysiology.

cRGD-conjugated magnetic-fluorescent liposomes for targeted dual-modality imaging of bone metastasis from prostate cancer

We reported the development of multifunctional liposomes as a dual-modality probe to facilitate targeted magnetic resonance and fluorescent imaging of bone metastasis from advanced cancer. Multifunctional liposomes consisted of liposomes as a carrier, hydrophobic CdSe QDs in phospholipid bilayer, hydrophilic iron oxide nanoparticles in interior vesicle, lipid-PEG derivative on the surface and cRGDyk peptide conjugated to distal ends of lipid-PEG derivative. Excellent stability, effective detection signal, low toxicity, high resistance to phagocytosis by macrophages and good specificity to tumor of multifunctional liposomes were confirmed by in vitro characterization. The in vivo results demonstrated that multifunctional liposomes accumulated mainly in tumor and liver, indicating that targeted dual-modality imaging was achieved, and the results from two kinds of modalities were consistent and complementary. These findings provide a helpful strategy for detection of bone metastases in a more effective manner for initiation of appropriate therapy.

Uptake and transfection efficiency of PEGylated cationic liposome-DNA complexes with and without RGD-tagging

Steric stabilization of cationic liposome-DNA (CL-DNA) complexes is required for in vivo applications such as gene therapy. PEGylation (PEG: poly(ethylene glycol)) of CL-DNA complexes by addition of PEG2000-lipids yields sterically stabilized nanoparticles but strongly reduces their gene delivery efficacy. PEGylation-induced weakening of the electrostatic binding of CL-DNA nanoparticles to cells (leading to reduced uptake) has been considered as a possible cause, but experimental results have been ambiguous. Using quantitative live-cell imaging in vitro, we have investigated cell attachment and uptake of PEGylated CL-DNA nanoparticles with and without a custom synthesized RGD-peptide grafted to the distal ends of PEG2000-lipids. The RGD-tagged nanoparticles exhibit strongly increased cellular attachment as well as uptake compared to nanoparticles without grafted peptide. Transfection efficiency of RGD-tagged PEGylated CL-DNA NPs increases by about an order of magnitude between NPs with low and high membrane charge density (σM; the average charge per unit area of the membrane; controlled by the molar ratio of cationic to neutral lipid), even though imaging data show that uptake of RGD-tagged particles is only slightly enhanced by high σM. This suggests that endosomal escape and, as a result, transfection efficiency of RGD-tagged NPs is facilitated by high σM. We present a model describing the interactions between PEGylated CL-DNA nanoparticles and the anionic cell membrane which shows how the PEG grafting density and membrane charge density affect adhesion of nanoparticles to the cell surface.

Efficacy of Liposomal Monensin on the Enhancement of the Antitumour Activity of Liposomal Ricin in Human Epidermoid Carcinoma (KB) Cells

The monensin, known to enhance the cytotoxicity of ricin and ricin-based immunotoxins is a very hydrophobic molecule and this limits its administration in optimum doses under in vivo conditions. In order to realise its full potential, monensin was intercalated into various liposomal formulations and its ability to potentiate the cytotoxicity of ricin liposomes in human epidermoid carcinoma (KB) cells was studied. It was observed that ricin cytotoxicity enhancing ability of monensin liposome depends on the surface charge as well as density and chain length of distearoyl phosphatidylethanolamine-methoxy polyethylene glycol present on the surface of liposomal monensin. Maximum potentiation on the cytotoxicity of liposomal ricin was observed by monensin entrapped in neutral liposome (106.5 fold) followed by negatively charged (94.2 fold) and positively charged liposome (90 fold). Studies on the effect of variation of density and chain length of distearoyl phosphatidylethanolamine-methoxy polyethylene glycol showed that neutral monensin liposomes having 2.5 mol% distearoyl phosphatidylethanolamine-methoxy polyethylene glycol with chain length of 2000 exhibits maximum potentiation (117.6 fold) on the cytotoxicity of ricin liposomes when the cellular uptake of monensin liposome was maximum (42.0%) and the zeta potential value on the surface of liposomes was -0.645. The present study has clearly shown that liposomal monensin is very effective in enhancing the cytotoxicity of liposomal ricin in human cancer cells and liposome can be used as in vivo deliver vehicle for monensin to potentiate the cytotoxicity of liposomal ricin to eliminate cancer cells.

Oleanolic acid liposomes with polyethylene glycol modification: promising antitumor drug delivery

BACKGROUND

Oleanolic acid is a pentacyclic triterpene present in many fruits and vegetables, and has received much attention on account of its biological properties. However, its poor solubility and low bioavailability limit its use. The objective of this study was to encapsulate oleanolic acid into nanoliposomes using the modified ethanol injection method.

METHODS

The liposomes contain a hydrophobic oleanolic acid core, an amphiphilic soybean lecithin monolayer, and a protective hydrophilic polyethylene glycol (PEG) coating. During the preparation process, the formulations described were investigated by designing 3⁴ orthogonal experiments as well as considering the effects of different physical characteristics. The four factors were the ratios of drug to soybean phosphatidylcholine (w/w), cholesterol (w/w), PEG-2000 (w/w), and temperature of phosphate-buffered saline at three different levels. We identified the optimized formulation which showed the most satisfactory lipid stability and particle formation. The morphology of the liposomes obtained was determined by transmission electron microscopy and atomic force microscopy. The existence of PEG in the liposome component was validated by Fourier transform infrared spectrum analysis.

RESULTS

The PEGylated liposomes dispersed individually and had diameters of around 110-200 nm. Encapsulation efficiency was more than 85%, as calculated by high-performance liquid chromatography and Sephadex® gel filtration. Furthermore, when compared with native oleanolic acid, the liposomal formulations showed better stability in vitro. Finally, the cytotoxicity of the oleanolic acid liposomes was evaluated using a microtiter tetrazolium assay.

CONCLUSION

These results suggest that PEGylated liposomes would serve as a potent delivery vehicle for oleanolic acid in future cancer therapy.

Cellular delivery of PEGylated PLGA nanoparticles

OBJECTIVES

The objective of this study was to investigate the efficiency of uptake of PEGylated polylactide-co-gycolide (PLGA) nanoparticles by breast cancer cells.

METHODS

Nanoparticles of PLGA containing various amounts of polyethylene glycol (PEG, 5%-15%) were prepared using a double emulsion solvent evaporation method. The nanoparticles were loaded with coumarin-6 (C6) as a fluorescence marker. The particles were characterized for surface morphology, particle size, zeta potential, and for cellular uptake by 4T1 murine breast cancer cells.

KEY FINDINGS

Irrespective of the amount of PEG, all formulations yielded smooth spherical particles. However, a comparison of the particle size of various formulations showed bimodal distribution of particles. Each formulation was later passed through a 1.2 µm filter to obtain target size particles (114-335 nm) with zeta potentials ranging from -2.8 mV to -26.2 mV. While PLGA-PEG di-block (15% PEG) formulation showed significantly higher 4T1 cellular uptake than all other formulations, there was no statistical difference in cellular uptake among PLGA, PLGA-PEG-PLGA tri-block (10% PEG), PLGA-PEG di-block (5% PEG) and PLGA-PEG di-block (10% PEG) nanoparticles.

CONCLUSION

These preliminary findings indicated that the nanoparticle formulation prepared with 15% PEGylated PLGA showed maximum cellular uptake due to it having the smallest particle size and lowest zeta potential.

Enhanced killing of human epidermoid carcinoma (KB) cells by treatment with ricin encapsulated into sterically stabilized liposomes in combination with monensin

Ricin was encapsulated in various charged liposomes having 5 mol% PEG of different chain length on the surface. The cytotoxicity of ricin entrapped in these liposomal formulations was examined in human epidermoid carcinoma (KB) cells with a view to develop an optimum delivery system for ricin in vivo. It was observed that the cytotoxicity of ricin entrapped in various charged liposomes was significantly dependent on the surface charge as well as chain length of PEG. The maximum cytotoxicity of ricin was observed when it was delivered through negatively charged liposomes having 5 mol% PEG-2000 on the surface. Monensin enhances the cytotoxicity of ricin entrapped in various charged liposomes depending on the surface charge. Maximum potentiation of cytotoxicity of ricin was observed when it was delivered through negatively charged liposomes having 5 mol% PEG-2000 on the surface. Studies on the kinetics of inhibition of protein synthesis by ricin revealed that the lag period of inhibition of protein synthesis is significantly lengthened following its delivery through various charged liposomes. Monensin significantly reduced the lag period of action of ricin. It was also observed that the efficacies of monensin on the enhancement of cytotoxicity of ricin entrapped in various charged PEG-liposomes were highly related to their amount of cell association. The current study has demonstrated that by suitable adjustment of charge, density, and chain length of PEG on the surface of liposomes it would be possible to direct liposomal ricin to human tumor cells for their selective elimination in combination with monensin.

In-vitro cytotoxicity, in-vivo biodistribution and anti-tumour effect of PEGylated liposomal topotecan

In attempt to increase the accumulation of topotecan in tumours and improve its anti-cancer activity, PEGylated liposome (H-PEG) containing topotecan was prepared. The in-vitro cytotoxicity, in-vivo biodistribution pattern and anti-tumour effect of H-PEG were studied systemically. Compared with free topotecan or conventional liposome (H-Lip), H-PEG improved the cytotoxic effect of topotecan against human ovarian carcinoma A2780 and human colon carcinoma HCT-8 cells. The IC50 value (concentration leading to 50% cell-killing) of H-PEG decreased 5 fold (P&lt;0.01) and 9 fold (P&lt;0.01) against A2780 and HCT-8 cells compared with H-Lip, respectively. The results of biodistribution studies in sarcoma S180 tumour-bearing mice showed that liposomal encapsulation increased the concentration of total topotecan and the ratio of lactone form in plasma. H-PEG resulted in a 70-fold and 3.7-fold increase in AUC0→24h compared with free topotecan and H-Lip, respectively. Moreover, H-PEG increased the accumulation of topotecan in tumours and the relative tumour uptake ratio compared with free topotecan was 5.2, and higher than that of H-Lip. The anti-cancer effect studies in murine heptocarcinoma H22 tumour-bearing mice showed that H-PEG improved the therapeutic efficiency of topotecan and decreased the toxicity of topotecan to a certain extent compared with H-Lip. These results indicated that PEG-modified liposome might be an efficient carrier of topotecan.

[Characterization and cytotoxicity of mixed PEG-DSG modified liposomes]

It is known that polyethyleneglycol (PEG) modification of the liposome surface leads to the formation of a fixed aqueous layer around the liposomes due to interaction between the PEG polymer and water molecules, which prevents the attraction of opsonins. When a combination of PEG-distearolyglycerol (PEG-DSG) whose characteristics are remarkably different is used, interaction between molecules occurs, leading to increased fixed aqueous layer thickness (FALT). From this speculation, we studied the effect of both modification of PEG900-DSG and PEG2000-DSG modified liposome on FALT, cell uptake and biodistribution. The FALT of mixed PEG modified liposome increased, compared to that of each single PEG modified liposome. In this mixed modification, maximum FALT was shown at liposome modified by added PEG-2000:PEG-900=2:1. This most suitable additional ratio was equal to actual incorporated ratio. On the other hand, cell uptake of mixed modified liposome containing doxorubicin (DOX) was similar with that of PEG2000 modified liposome. Furthermore, mixed PEG modification of liposome was tendency to increase cytotoxicity, compared to that of other modifications. After DOX contained liposome treatment, DOX distribution in the tumor and antitumor activity of DOX increase by mixed PEG modification. In conclusion, it was suggested that mixed PEG liposome (PEG-2000:PEG-900=2:1) was useful for cancer chemotherapy.