Size-dependent release of carboxyfluorescein from cetylmannoside-modified liposomes in human plasma

Retracted Article: Radio frequency triggered curcumin delivery from thermo and pH responsive nanoparticles containing gold nanoparticles and its in vivo localization studies in an orthotopic breast tumor model

RF responsive gold nanoparticles containing curcumin encapsulated chitosan-graft-poly(N-vinyl caprolactam) induced apoptosis on 4T1 breast cancer cells on RF exposure.

Liposome Opsonization

Adsorption of serum proteins to the liposomal surface plays a critical role in the clearance of liposomes from the blood circulation. In this review, we will discuss the role of the liposomal opsonins proposed so far in liposome clearance. Additional, related topics that will be addressed are the cell-surface receptors that might be involved in liposome elimination from the blood compartment and the effect of poly(ethylene glycol) (PEG) modification on prevention of liposome opsonization.

Influence of particle size on drug delivery to rat alveolar macrophages following pulmonary administration of ciprofloxacin incorporated into liposomes

In order to confirm the efficacy of ciprofloxacin (CPFX) incorporated into liposomes (CPFX-liposomes) for treatment of respiratory intracellular parasite infections, the influence of particle size on drug delivery to rat alveolar macrophages (AMs) following pulmonary administration of CPFX-liposomes was investigated. CPFX-liposomes were prepared with hydrogenated soybean phosphatidylcholine (HSPC), cholesterol (CH) and dicetylphosphate (DCP) in a lipid molar ratio of 7/2/1 by the hydration method and then adjusted to five different particle sizes (100, 200, 400, 1000 and 2000 nm). In the pharmacokinetic experiment, the delivery efficiency of CPFX to rat AMs following pulmonary administration of CPFX-liposomes increased with the increase in the particle size over the range 100-1000 nm and became constant at over 1000 nm. The concentrations of CPFX in rat AMs until 24 h after pulmonary administration of CPFX-liposomes with a particle size of 1000 nm were higher than the minimum inhibitory concentration of CPFX against various intracellular parasites. In a cytotoxic test, no release of lactate dehydrogenase (LDH) from rat lung tissues by pulmonary administration of CPFX-liposomes with a particle size of 1000 nm was observed. These findings indicate that efficient delivery of CPFX to AMs by CPFX-liposomes with a particle size of 1000 nm induces an excellent antibacterial effect without any cytotoxic effects on lung tissues. Therefore, CPFX-liposomes may be useful in the development of drug delivery systems for the treatment of respiratory infections caused by intracellular parasites, such as Mycobacterium tuberculosis, Chlamydia pneumoniae and Listeria monocytogenes.

Biochemical and biophysical characteristics of lipoplexes pertinent to solid tumour gene therapy

Cationic liposomes have become the reagent of choice for transfer of nucleic acids such as plasmids and oligodeoxynucleotides to cells in culture and in vivo. Whilst these reagents have several advantages over other forms of nucleic acid transfer methods, toxicity remains a significant problem, especially in vivo. Recent studies have also highlighted the immunostimulatory nature of these cationic vesicles when complexed to plasmid DNA, a phenomenon that may be harnessed for efficacious usage against tumours. Current research in this dynamic technological field is aimed at the development of cationic lipids that have negligible toxic effects and enhanced transfection capabilities.

Vehicles for oligonucleotide delivery to tumours

The vasculature of a tumour provides the most effective route by which neoplastic cells may be reached and eradicated by drugs. The fact that a tumour's vasculature is relatively more permeable than healthy host tissue should enable selective delivery of drugs to tumour tissue. Such delivery is relevant to carrier-mediated delivery of genetic medicine to tumours. This review discusses the potential of delivering therapeutic oligonucleotides (ONs) to tumours using cationic liposomes and cyclodextrins (CyDs), and the major hindrances posed by the tumour itself on such delivery. Cationic liposomes are generally 100-200 nm in diameter, whereas CyDs typically span 1.5 nm across. Cationic liposomes have been used for the introduction of nucleic acids into mammalian cells for more than a decade. CyD molecules are routinely used as agents that engender cholesterol efflux from lipid-laden cells, thus having an efficacious potential in the management of atherosclerosis. A recent trend is to employ these oligosaccharide molecules for delivering nucleic acids in cells both in-vitro and in-vivo. Comparisons are made with other ON delivery agents, such as porphyrin derivatives (< 1 nm), branched chain dendrimers (approximately 10 nm), polyethylenimine polymers (approximately 10 nm), nanoparticles (20-1,000 nm) and microspheres (> 1 microm), in the context of delivery to solid tumours. A discourse on how the chemical and physical properties of these carriers may affect the uptake of ONs into cells, particularly in-vivo, forms a major basis of this review.

Stealth monensin liposomes as a potentiator of adriamycin in cancer treatment

Small unilamellar stealth monensin liposomes (SMLs) were prepared from multilamellar liposomes (MLVs). The MLVs were prepared by using dipalmitoyl phosphatidylcholine (DPPC), cholesterol, distearoyl glycerophosphoethanolamine coupled to poly(ethylene glycol) (DSPE-PEG) and stearylamine in the molar ratio of 10:5:1.4:1.4 (32.8 mM total lipid). The encapsulation efficiencies of monensin in MLVs and small unilamellar vesicles (SUVs) was 6x10++(-6) and 10(-7) M, respectively. The stability of SMLs was studied at 4 degrees C. The amount of leakage of monensin from SMLs was less than 20% after four weeks of storage. The in vitro release of monensin from SMLs in human serum was determined, and t1/2 was found to be 10 h. Pharmacokinetic studies on SMLs were carried out in BALB/c mice. More than 20% of SMLs remained in blood circulation after 24 h. SMLs increased the uptake of adriamycin (AM) in HL-60-resistant cells by more than two fold, compared to monensin in solution. SMLs potentiated the effect of AM against both sensitive and resistant HL-60 cells (six- and tenfold potentiation, respectively) and human LOVO tumor cells (four- and 200-fold potentiation, respectively). However, the highest potentiation was observed against resistant human breast tumor MCF7 cells, and was found to be 2400 times in comparison to AM alone. Transmission electron microscopic (TEM) studies carried out with HL-60-resistant tumor cells incubated with SMLs showed that SMLs caused dilation of the golgi of tumor cells within 10 min. The dilation of golgi was reversible after reincubation of the cells in fresh medium. SMLs showed considerable potential as a potentiator in combination with AM in overcoming drug resistance.

Synergistic effect between size and cholesterol content in the enhanced hepatic uptake clearance of liposomes through complement activation in rats

PURPOSE

The effect of liposome size and cholesterol (CH) content on the pharmacokinetics of liposomes was investigated in rats.

METHODS

The pharmacokinetics of liposomes was examined using 5(6)-carboxyfluorescein (CF) as an aqueous phase marker. The extent of complement activation (ECA) was also measured by the release of CF from liposomes in serum.

RESULTS

Both the size and the CH content influenced the mean residence time, total body clearance, and the hepatic uptake clearance (CLh) of liposomes. The increase of the size of liposomes increased the CLh at each CH content. There was no CH dependency of CLh in small liposomes (200 nm in diameter), although the CLh increased with the increase in the CH content in large (800 nm) and medium (400 nm) liposomes. A significant interaction effect was observed between liposome size and the CH content on CLh according to the analysis of variance. The good correlation between CLh and ECA indicated the role of complements as opsonins in enhancing the hepatic uptake of liposomes. The interaction effect between the size and CH content on CLh was explained principally by the product of the size and CH content.

CONCLUSIONS

A synergistic effect was observed between the size and the CH content on CLh. An underlying hypothesis of the synergistic effect was postulated based on the size dependent recognition of liposomes by complement system.