• KSBB Journal
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• v.10 no.2
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• pp.204-211
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• 1995

A target-sensitive liposome was prepared by using a dioleoyl-phosphatidylethanolamine(DOPE) and a palmitic acid coupled antibody(p-IgG). For the preparation of stable PE-liposomes, the key factors such as antibody modification method with palmitic acrid, molar ratio of p-IgG to lipid and the amount of various additives, were examined. The optimum molar ratio of p-IgG to lipid was found to be $2.5{\times}10^{-4}$ and the final concentration of deoxycholate for the stable liposome formation was about 0.09%. Two kinds of target-sensitive liposomes, containing polyclonal anti-SRBC(Sheep Red Blood Cell)-antibody and monoclonal anti-${\beta}$-HCG(Human Chorionic Gonadotropin)-antibody, were successfully prepared. The destabilization of liposomes was examined by measuring the release of calcein entrapped in the liposome vesicles. Calcein was released only when the liposomes were contacted with the specific target cells. The calcein release with non-specific target cells was negligible. From this result, it is clear that p-IgG is indispensible for the maintenance of stable PE-liposome and the calcein release is mainly due to the specific interactions between the liposomes containing antibody and the target cells containing antigen.

• Macromolecular Research
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• v.13 no.1
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• pp.54-61
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• 2005

We prepared temperature-sensitive liposomes (TS-liposomes) modified with a thermo sensitive polymer, such as poly(N-isopropylacrylamide) (PNIPAAm), to increase the degree of drug release from liposomes at the hyperthermic temperature. A PNIPAAm hydrogel containing TS-Iiposomes was also prepared to obtain a hydrogel complex at body temperature. In addition, a depot system for local drug delivery using the polymer hydrogel was developed to enhance therapeutic efficacy and prevent severe side effects in the whole body. The PNIPAAm-mod­ified TS-liposome was fixed into the PNIPAAm hydrogel having a high temperature-sensitivity. The release behavior of calcein, a model drug, from TS-liposomes in the PNIPAAm hydrogel was then initiated by external hyperthermia; the results indicated that sustained release as a function of temperature and time was caused by the thermosensitivity of the liposome surface and diffusion of the drug into the PNIPAAm hydrogel. Our results indicated that TS-liposomes in a PNIPAAm hydrogel represented a plausible system for local drug delivery.

• Journal of Pharmaceutical Investigation
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• v.20 no.3
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• pp.135-144
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• 1990

The effects of bile salts (BS) on the stability of dioleoylphosphatidylethanolamine (DOPE) liposomes were investigated, observing apparent absorbance of vacant liposomes and calcein release from entrapped liposomes. Unilamellar liposomes were prepared by using a small quantity of palmitoly-immunoglobulin G(IgG) ($2.5{\times}10^{-4}$ mo1/lipid mol) to stabilize the bilayer phase of the unsaturated DOPE which by itself does not form stable liposomes. The destabilization of PE immunoliposomes by papain, clearly demonstrates that the IgG is essential for stabilization of PE bilayer. Approximately 4% of the entrapped calcein was released from the PE liposomes after 1 hr from liposome formation. Calcein release and absorbance of liposomes depended on the BS/lipid ratio because of the solubilization of lipid molecule in bilayer and the formation of mixed micelles. At very low BS concentrations, the incorporation of BS induced BS/lipid aggregates in the outer vesicles monolayer, while high BS concentrations, mixed micelles were formed. Chelate and its conjugates as $3{\alpha},\;7{\alpha},\;12{\alpha}-trihydroxy$ BS induce the concentration of the $3{\alpha}$, $12{\alpha}-dihydroxy$ BS at half-maximal solubilization of immunoliposomes to approximately 2.5-, or 5-fold. Conjugation of BS with glycine or taurine slightly enhanced their capacities to perturb membranes.

• KSBB Journal
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• v.10 no.4
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• pp.428-434
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• 1995

Target-sensitive(TG-S) liposomes, which have the antibodies coupled on the surface of liposome and can release their entrapped contents by the binding of antibodies with the specigic target cells, were prepared and employed to study the release of calcein and the selective delivery of an anticancer agent, doxorubicin(DOX). The monoclonal antibody, Y3, used for the preparation of the TG-S liposome was one against major histocompatibility complex class 1 of mouse(MHCI, H-2Kｂtype) and the target cells were EL-4 and RMA, which have the MHC1, H-2Kbtype on their membrane surfacem. The release of calcein from TG-S liposome occurred when the target cells were contacted with liposomes and it was proportionally increased with the rise of binding capacity of antibody coupled on the surface of liposome to the target cells. The experimental results of drug delivery were similar to the cases of calcein release. The viability of specific target cell, EL-4 with liposomal DOX was not so different from that with the free DOX, while for the non-specific target cell, Yacl(H-2Kf), the cell viability with Iiposomal DOX was much higher than that with free DOX. This shows the fact that the liposomal DOX can be efficiently delivered to the specific target cells, while it was not the case for the non-specific target cells. And the drug delivery was lnhibited when the free antibody of Y3 was added in the contact process between EL-4 and TG-S liposomes, which means the drug delivery occurred mainly by the destabilization of TG-S liposomes. From these results, we could conclude that the selective drug delivery to specific target cell using the TG-S liposome would be feasible.

• Applied Chemistry for Engineering
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• v.8 no.1
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• pp.59-66
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• 1997

Di(10-hemisuccinyloxy)decyl muconate(DDM) and di(6-hemisuccinyloxy)hexyl muconate(DHM) were synthesized, and showed a phase transition in an aqueous solution at 97 and $79^{\circ}C$, respectively. They did not form liposomes by themselves or even in the presence of cholesterol or dioleoylphosphatidylethanolamine(DOPE), but did form liposomes when they were mixed with phosphatidylcholine(PC). DHM molecules in liposome membranes were readily polymerized via 1,2-polymerization process on exposure to 254nm. Liposomes composed of DOPE/dioleoylphosphatidylcholine(DOPC)/DHM(3/3/1) were stable at neutral pH, but leaky at weakly acidic pH. The leakage of entrapped calcein from liposomes in phosphate-buffered saline (PBS, $37^{\circ}C$) of pH 4.8 and 5.8 was complete within 30 and 50 min, respectively. The release of toke entrapped calcein was increased with decreasing pH such that 50% and 100% of the calcein were released at pH near 5.5 and 5.0, respectively.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.10a
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• pp.958-960
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• 2015

Sickle cells possess a unique combination of traits that may enable their use as models for novel synthetic tumor targeting controlled release drug carriers with the ability to treat disseminated tumors in advanced metastatic disease. In this study, we assess the ability of light-activated release sickle cells to enhance tumor delivery of the fluorescent dye calcein by delayed photolysis controlled release compared to free systemic administration of calcein. Sickle cells from mouse models of the disease were shown to preferentially accumulate in tumors compared to adjacent tissue, in 4T1 tumors in mice on a time scale about 12 hours. Sickle cells photosensitized with protoporphyrin IX achieved delayed release of 50% of contents 8-16 hours after photoactivation, which was deemed useful for in vivo delivery of cargo to tumors given the tumor accumulation time of the sickle cells. Sickle cells may be useful as a model for new synthetic drug carrier particles with delayed photolysis controlled release properties.

• Journal of Pharmaceutical Investigation
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• v.22 no.2
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• pp.115-124
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• 1992

The characteristics and stabilities of phosphatidylcholine liposomes covalently coupled with immunoglobulin fragments prepared by the REV method were investigated by the dynamic light scattering, absorbance and calcein release. Using a sulfhydryl-reactive phospholipid derivative of N-[4$({\rho}-maleimido-phenyl)$ butyl] phosphatidylethanolamine (MPB-PE), Fab' antibody fragments were covalently combined with preformed large unilamellar vesicles (LUV), Coupling ratio was $250\;{\mu}g$ of $Fab'/{\mu}mol$ of phospholipid in vesicles, From dynamic light scattering, it was found that the size of the vesicles increases as the ratio of cholesterol to lipid increases, but that apparently, the size of liposomes was not sensitive to the existence of Fab' fragments. Regardless of inserting Fab' fragments, the absorbance of liposomes decreased as the amounts of bile salt (BS) added. At very low BS concentrations, BS/lipid aggregates would be formed in the outer vesicles monolayer, while, at the high BS concentrations, mixed micelles would be preferred. The vesicles incorporated with Fab' fragments, however, are more resistant to the bile salts than the MPB-PE vesicle are. The absorbance of vacant liposomes and calcein release resulted in that the Fab' vesicles and MPB-PE vesicles by the REV method are very stable, but that those by the sonication method sufferred the significant change of turbidities.

• Bulletin of the Korean Chemical Society
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• v.19 no.6
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• pp.645-649
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• 1998

In order to develop pH-sensitive liposomes that are stable in plasma, liposomes containing membrane-spanning bipolar amphiphiles as protonatable components were studied. Sonicated small unilamellar liposomes composed of dioleoylphosphatidylethanol amine (DOPE), dioleoylphosphatidylcholine (DOPC) and bis(6-hemisuccinyloxyhexyl) fumarate (BHF) in a 3 : 1 : 1 molar ratio are stable at neutral pH, but destabilized at weakly acidic pH with 50% leakage of entrapped materials at about pH 5.5. The liposomes are relatively stable in plasma such that only a few percent entrapped calcein was released in 50% plasma within 1.5 h incubation at 37 ℃, while about 10% entrapped calcein was released from sonicated liposomes composed of DOPE, DOPC, and oleic acid (OA) in a 3 : 1 : 1 molar ratio under the identical conditions. The aqueous contents mixing and lipid components mixing experiments suggest that the protonation of BHF may induce fusion between the liposomes, followed by the release of the entrapped materials.

• Applied Chemistry for Engineering
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• v.17 no.2
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• pp.138-143
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• 2006

Ethosome is a liquid crystalline vesicle prepared by hydration of ethanol-dissolved lecithin with a solution containing hydrophilic components. Investigation of factors affecting the entrapment efficiency and particle size of ethosomes was carried out, because the high entrapment efficiency and small particle size are prerequisite in developing ethosomes as a drug delivery system. The variations of properties of ethosomes with constituent composition and preparation method were examined using a calcein as a hydrophilic marker. It was observed that the amount of ethanol and calcein solution, phosphatidyl choline content in lecithin, preparation temperature, stirring rate, and PBS addition method had a considerable effect on the properties of ethosome. Sonication treatment resulted in the reduction of entrapment efficiency of ethosome, which was due to the release of entrapped components in the vesicles by strong sonication vibration.

• BMB Reports
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• v.39 no.3
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• pp.270-277
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• 2006

Helices 4 and 5 of the Bacillus thuringiensis Cry4Ba $\delta$-endotoxin have been shown to be important determinants for mosquito-larvicidal activity, likely being involved in membrane-pore formation. In this study, the Cry4Ba mutant protein containing an additional engineered tryptic cleavage site was used to produce the $\alpha4$-$\alpha5$ hairpin peptide by an efficient alternative strategy. Upon solubilization of toxin inclusions expressed in Escherichia coli and subsequent digestion with trypsin, the 130-kDa mutant protoxin was processed to protease-resistant fragments of ca. 47, 10 and 7 kDa. The 7-kDa fragment was identified as the $\alpha4$-loop-$\alpha5$ hairpin via N-terminal sequencing and mass spectrometry, and was successfully purified by size-exclusion FPLC and reversed-phase HPLC. Using circular dichroism spectroscopy, the 7-kDa peptide was found to exist predominantly as an $\alpha$-helical structure. Membrane perturbation studies by using fluorimetric calcein-release assays revealed that the 7-kDa helical hairpin is highly active against unilamellar liposomes compared with the 65-kDa activated full-length toxin. These results directly support the role of the $\alpha4$-loop-$\alpha5$ hairpin in membrane perturbation and pore formation of the full-length Cry4Ba toxin.