• Journal of Pharmaceutical Investigation
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• v.22 no.3
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• pp.211-217
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• 1992

Stabilization of liposomes against degradation by bile salts has been investigated in order to develop a liposomal model system for oral drug delivery. Two polysaccharides, amylopectin (AP) and chitin (CT), were employed to coat both empty liposomes and bromthymol blue (BTB)-encapsulated liposomes by adsorption-coating techniques. Turbidity changes and BTB-release characteristics in pH 5.6 buffer solutions with or without bile salts, sodium cholate and sodium glycocholate, were observed to compare the differences between uncoated liposomes and polysaccharide-coated liposomes. Initial turbidities of both uncoated and polysaccharide-coated liposomes in buffer solution were kept constant within 3% range during 4 hours of experiments. But they were decreased in a different manner in bile salts-containing buffer solutions, showing 10% or less decrease for polysaccharide-coated liposomes and 25% or more decrease for uncoated liposomes. BTB release from uncoated liposomes has been greatly increased upto 90% after 4 hours in bile salts-containing buffer solution, which is a clue for breakdown of liposomal vesicles. However, polysaccharide-coated liposomes showed the controlled-release pattern which is proportional to square-root of time, followed by around 50% release for the same time period. Consequently, it is possible to conclude that these polysaccharide-coated liposomes might be an available system for oral delivery of a drug which is unstable in gut environment.

• Archives of Pharmacal Research
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• v.13 no.1
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• pp.64-68
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• 1990

The stabilization effect of .alpha.-tocopherol incorporated into liposomal phospholipid membrane was investigated by fluorospectrophotometry and UV-visible spectretarded by the presence of .alpha.-tocopherol in the bilayer of liposomal phospholipid membrane relative to cholesterol-containing liposomes and pure phospholipid liposomes. .alpha.-tocopherol-containing liposomes prolonged the oxidation of liposomes-embedded heme as those of cholesterol-containing liposomes and pure phospholipid liposomes. Thus .alpha.-tocopherol-containing liposomes may be useful for the carrier systems of nutrients and drugs to phospholipid bilayer and stabilized liposomes.

• Applied Microscopy
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• v.19 no.2
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• pp.1-16
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• 1989

To investigate the research of the tumor seeker using liposomes with negatively stained. The fine structure and size in liposomes composed of PC, DSPC, DAPC and SM phospholipid were observed. And the yield of vesicle affected with sonication by mechanical force were determined. The results were as follows. 1. The stain of 2% UA are obtained a good resolution from electron microscopic observation to compare the negatively liposomes with PTA, AM and UA solution. 2. The fine structure of liposomes except DAPC, PC and CH alone samples could be observed from EM experiment of liposomes composed of PC, DSPC, DAPC and SM phospholipid. 3. The results of experiment from 10, 20, 40 and 60 times sonication with 30sec, prepared 0.1mM NTA-SM-liposomes were obtained unilamella vesicles from groups of multilamella vesicles of phospholipid. 4. About 50nm diameter liposomes obtained through membration filtration step to prepare homogenized liposomes.

• Archives of Pharmacal Research
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• v.14 no.4
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• pp.336-341
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• 1991

The effect of bovine serum albumin (BSA) on the encapsulation efficiency and stability of liposomes containing methotrexate (MTX) having different surface charges and cholesterol contents were investigated. The encapsulation efficiency of MTX was lower and the release of MTX was faster by the addition of BSA. The leaking of MTX from lipid bilayer depends upon the BSA concentrations. These results may be derived from the interaction of BSA with lipid bilayers. The dynamic structural changes of BSA were monitored indirectly using circular dichroism spectra. Observed dynamic structural changes of BSA with liposomes are presumed to reflect the interaction of BSA with liposomes. Negatively charged liposomes have more strong interaction with BSA than neutral and positively charged liposomes. BSA attacks lipid bilayers whether it is at the inner or at the outer phase of lipid bilayer and induces leakage of entrapped MTX. Especially, negatively charged liposomes are more sensitive than others. The inclusion of cholesterol in the lipid layers inhibits the interaction of BSA with liposomes and shows protective effect against BSA-induced leakage of MTX. To endure the attacking of BSA liposomes as drug carriers should be made using cholesterol.

• Journal of Pharmaceutical Investigation
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• v.38 no.1
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• pp.15-21
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• 2008

Liposomes as one of the efficient drug carriers have some shortcomings such as their short circulation time, fast clearance from human body by reticuloendothelial system (RES) and limited intracellular uptake to target cell. In this study, polyethylenglycol (PEG)-incorporated cationic liposomes were prepared by ionic complexation of positively charged liposomes with carboxylated polyethyleneglycol (mPEG-COOH). The cationic liposomes had approximately $98.6{\pm}1.0nm$ of mean particle diameter and $42.8{\pm}0.8mV$ of zeta potential value. The PEG-incorporated cationic liposomes had $110.1{\pm}1.2nm$ of mean particle diameter with an increase of about 10 nm compared to the cationic liposomes. Zeta potential value of them was $12.9{\pm}0.6mV$ indicating 30mV decrease of cationic charge compared to the cationic liposomes. The amount of PEG which was incorporated onto the cationic liposomes was assayed by using picrate assay method and the incorporation efficiency was $58.4{\pm}1.1%$. Loading efficiency of model drug, doxorubicin, into cationic liposomes or PEG-incorporated cationic liposomes was about $96.0{\pm}0.7%$. Results of intracellular uptake which were evaluated by flow cytometry analysis of doxorubicin loaded liposomes showed that intracellular uptake of PEG-incorporated cationic liposomes was higher than the cationic liposomes or DSPE-mPEG liposomes. In addition, cytotoxicity of PEG-incorporated cationic liposomes was comparable to cationic liposomes. Consequently, the PEG-incorporated cationic liposomes of which surface was incorporated with PEG by ionic complex may be applicable as anticancer drug carriers that can increase therapeutic efficacy.

• Journal of the Korean Applied Science and Technology
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• v.27 no.4
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• pp.391-398
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• 2010

Soybean lecithin liposomes composed phosphatidyl choline, phosphatidyl ethanolamine, phosphatidyl inositol and phosphatidic acid were prepared by using the previously developed supercritical reverse phase evaporation method. The effect of phospholipid composition on the formation of liposomes and physicochemical properties were examined by means of trapping efficiency measurements, transmission electron microscopy, dynamic light scattering and zeta potential measurements. The trapping efficiency of liposomes for D-(+)-glucose made of CNA-Ⅰ which contains approximately 95% phosphatidyl choline is higher than that of CNA-II and CNA-O which contain approximately 32% phosphatidyl choline. However there is no any difference between the trapping efficiency of liposomes for D-(+)-glucose made of CNA-II which has saturated hydrocarbons tails and that of liposomes made of CNA-O which has unsaturated hydrocarbon chains. The electron micrographs of liposomes made of CNA-II and CNA-O show small spherical liposomes with diameter of $0.1\sim0.25{\mu}m$, while that of CNA-I shows large unilamellar liposomes with diameter of $0.2\sim1.2{\mu}m$. These results clearly show that phospholipid structure of phosphatidylcholine allows an efficient preparation of large unilamellar liposomes and a high trapping efficiency for water soluble substances. Liposomes made of CNA-II and CNA-O remained well-dispersed for at least 14 days, while liposome suspension made of CNA-I separated in two phase at 14 days due to aggregation and fusion of liposomes. The dispersibility of liposomes made of CNA-I is lower than that of CNA-II and CNA-O due to the smallar zeta potential of CNA-I.

• Archives of Pharmacal Research
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• v.28 no.8
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• pp.988-994
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• 2005

The purpose of the present study was to prepare multivesicular liposomes with a high drug loading capacity and to investigate its potential applicability in the oral delivery of a peptide, human epidermal growth factor (rhEGF). The multivesicular liposomes containing rhEGF was prepared by a two-step water-in-oil-in-water double emulsification process. The loading efficiency was increased as rhEGF concentration increased from 1 to 5mg/mL, reaching approximately $60\%$ at 5 mg/mL. Approximately $47\%$ and $35\%$ of rhEGF was released from the multivesicular liposomes within 6 h in simulated intra-gastric fluid (pH 1.2) and intra-intestinal fluid (pH 7.4), respectively. rhEGF-loaded multivesicular liposomes markedly suppressed the enzymatic degradation of the peptide in an incubation with the Caco-2 cell homogenate. However, the transport of rhEGF from the multivesicular liposomes to the basolateral side of Caco­2 cells was two times lower than that of the rhEGF in aqueous solution. The gastric ulcer healing effect of rhEGF-loaded multivesicular liposomes was significantly enhanced compared with that of rhEGF in aqueous solution; the healing effect of the liposomes was comparable to that of the cimetidine in rats. Collectively, these results indicate that rhEGF-loaded multivesicular liposomes may be used as a new strategy for the development of an oral delivery system in the treatment of peptic ulcer diseases.

• Journal of Pharmaceutical Investigation
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• v.26 no.4
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• pp.291-297
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• 1996

Liposomes of $pSV-{\beta}-Galactosidase$ vector plasmid DNA with various lipid composition were prepared by the thin-film method. Size distribution, shape and the efficiency of plasmid DNA encapsulation were investigated. Effect of sonication time on the plasmid DNA entrapment in liposomes and stability at $4^{\circ}C$ were also examined. Sizes of neutral liposomes were about 100-200 nm and above $1\;{mu}m$, and those of cationic liposomes were about 400-600 nm and above $1\;{mu}m$. Shapes of liposomes entrapped plasmid DNA were spherical. Proper sonication time for better entrapment was below 15 minutes and stability at $4^{\circ}C$ was decreased rapidly after 1 day. Plasmid DNA entrapments of complex liposomes of various lipids were higher than those of liposomes made from one sort of lipid. Plasmid DNA entrapments of cationic liposomes were higher than those of neutral liposomes.

• Bulletin of the Korean Chemical Society
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• v.18 no.7
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• pp.761-766
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• 1997

Phospholipase C from Clostridium perfringens is known to catalyze the hydrolysis of phospholipids in biological membranes. In this study, a simple and sensitive method for assaying phospholipase C was developed by using liposomes entrapping calcein as a fluorescent marker. Phospholipase C-induced lysis of liposomes was determined by measuring the fluorescence intensity of calcein released out from liposomes, Various liposomes with different compositions were prepared by reverse-phase evaporation method to investigate the effect of liposomal composition on the lytic activity of phospholipase C. The calcein-entrapping efficiency of liposomes was affected by the chain length of fatty acid in phosphatidylcholine constituting liposomes. The lytic activity of phospholipase C was the highest against liposomes prepared with eggPC. The lytic activity decreased with increasing chain length of fatty acid in phosphatidylcholine. Incorporation of cholesterol more than 20% into the liposomal bilayer inhibited the phospholipase C-induced lysis. The lysis of liposomes was more greatly increased by the addition of 10 mM of calcium. The lytic activity of phospholipase C was also affected by the surface charge of liposomes. Taken together, it was concluded that reverse-phase evaporation vesicles composed of dipalmitoylphosphatidylcholine and cholesterol in the molar ratio of 9 : 1 allowed to detect the lowest concentration of phospholipase C (0.10 μg/assay volume). This study suggested that the use of liposomes can provide a simple, sensitive and inexpensive method for assaying phospholipase C.

• Biomedical Science Letters
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• v.25 no.2
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• pp.159-169
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• 2019

Breast cancer stem cells (BCSCs) in breast cancer cells have self-renewal ability and differentiation potential. They are also resistant to drugs after chemotherapy. To overcome this resistance, we designed negatively charged 1,2-dimyristoyl-sn-glycero-3-phosphoglycerol (DMPG)-based liposomes for drug delivery. These liposomes have enhanced the therapeutic effects of a range of antitumor therapies by increasing the cellular uptake and improving drug delivery to targets sites. In this study, we investigated whether DMPG-POPC liposomes, including the neutral lipid 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholin (POPC), can specifically bind to MCF-7 breast cancer cells and increase cellular uptake compared with that by CHOL-POPC liposomes. We also estimated the cytotoxicity of DMPG-POPC liposomes encapsulated with both metformin (Met) and sodium salicylate (Sod) against breast cancer cells and BCSCs compared with that of the free drugs. Our results demonstrated that these dual drug-encapsulated liposomes significantly enhanced the cytotoxic and anti-colony formation abilities compared with individual drug-encapsulated liposomes or free drugs in BCSCs. Overall, our results suggest that DMPG-POPC liposomes containing two drugs (Met + Sod) show promise for synergistic anti-cancer therapy of breast cancer by increasing drug delivery efficiency into breast cancer cells and BCSCs.