[show abstract][hide abstract] ABSTRACT: Ultrasound-sensitive (sonosensitive) liposomes for tumor targeting have been studied in order to increase the antitumor efficacy of drugs and decrease the associated severe side effects. Liposomal contrast agents having Gd(III) are known as a nano-contrast agent system for the efficient and selective delivery of contrast agents into pathological sites. The objective of this study was to prepare Gd(III)-DOTA-modified sonosensitive liposomes (GdSL), which could deliver a model drug, doxorubicin (DOX), to a specific site and, at the same time, be capable of magnetic resonance (MR) imaging. The GdSL was prepared using synthesized Gd(III)-DOTA-1,2-distearoyl-sn-glycero-3-phosphoethanolamine lipid. Sonosensitivity of GdSL to 20-kHz ultrasound induced 33% to 40% of DOX release. The relaxivities (r1) of GdSL were 6.6 to 7.8 mM[MINUS SIGN]1 s[MINUS SIGN]1, which were higher than that of MR-bester[REGISTERED SIGN]. Intracellular uptake properties of GdSL were evaluated according to the intensity of ultrasound. Intracellular uptake of DOX for ultrasound-triggered GdSL was higher than that for non-ultrasound-triggered GdSL. The results of our study suggest that the paramagnetic and sonosensitive liposomes, GdSL, may provide a versatile platform for molecular imaging and targeted drug delivery.
Nanoscale Research Letters 08/2012; 7(1):462. · 2.52 Impact Factor
[show abstract][hide abstract] ABSTRACT: Liposomes are nano-scale vesicles that can be used as one of drug carriers. The liposomes are, however, plagued by rapid opsonization of them and hence making their circulation time in bloodstream to be shortened. In this study, cationically charged liposomes of which surface was modified with bovine serum albumin (BSA) were prepared by using electrostatic interaction between cationic liposomes and anionically charged BSA molecules at higher pH than isoelectric point (pI) of BSA. The BSA-coated liposomes (BLs) were denatured by thermal treatment of BL at 100 degrees C. The thermally denatured BSA-coated liposomes (DBLs) have mean particle diameter of 109+/-1 nm. Encapsulation of model drug, doxorubicin (DOX), in the liposomes was carried out by using, so called, remote loading method and loading efficiency of DOX in liposomes was about 90%. DBL800 showed higher stability in plasma compared to Doxil. Results of intracellular uptake evaluated by flow cytometry and confocal microscopy studies showed higher intracellular uptake of DBL800 than that of Doxil. Consequently, the DBL, of which surface was complexed with denatured protein may be applicable as drug delivery carriers for increasing stability in plasma and enhanced cellular uptake efficacy of anticancer drugs.
[show abstract][hide abstract] ABSTRACT: Biocompatible poly-[N-(2-hydroxyethyl)-d,l-aspartamide]-methoxypoly(ethyleneglycol)-hexadecylamine (PHEA-mPEG-C(16)) conjugated with 1,4,7,10-tetraazacyclododecan-1,4,7,10-tetraacetic acid-gadolinium (DOTA-Gd) via ethylenediamine (ED) was synthesized as a magnetic resonance imaging (MRI) contrast agent. Amphiphilic PHEA-mPEG-C(16)-ED-DOTA-Gd forms micelle in aqueous solution. All the synthesized materials were characterized by proton nuclear magnetic resonance ((1)H NMR). Micelle size and shape were examined by dynamic light scattering (DLS) and atomic force microscopy (AFM). Micelles with PHEA-mPEG-C(16)-ED-DOTA-Gd showed higher relaxivities than the commercially available gadolinium contrast agent. Moreover, the signal intensity of a rabbit liver was effectively increased after intravenous injection of PHEA-mPEG-C(16)-ED-DOTA-Gd.
Nanoscale Research Letters 01/2010; 5(12):1970-1976. · 2.52 Impact Factor
[show abstract][hide abstract] ABSTRACT: Liposomes as one of the efficient drug carriers have some shortcomings such as their relatively short blood circulation time, fast clearance from human body by reticuloendothelial system (RES) and limited intracellular uptake to target cells. In this study, polyethylene glycol (PEG)-complexed cationic liposomes (PCL) were prepared by ionic complex of cationically charged liposomes with carboxylated polyethylene glycol (mPEG-COOH). The cationic liposomes had approximately 98.6+/-1.0 nm of mean particle diameter and 45.5+/-1.1 mV of zeta potential value. While, the PCL had 110.1+/-1.2 nm of mean particle diameter and 18.4+/-0.8 mV of zeta potential value as a result of the ionic complex of mPEG-COOH with cationic liposomes. Loading efficiency of model drug, doxorubicin, into cationic liposomes or PCL was about 96.0+/-0.7%. Results of intracellular uptake evaluated by flow cytometry and fluorescence microscopy studies showed higher intracellular uptake of PCL than that of Doxil. In addition, in vitro cytotoxicity of PCL was comparable to cationic liposomes. In pharmacokinetic study in rats, PCL showed slightly lower plasma level of DOX than that of Doxil. In vivo antitumor activity of DOX-loaded PCL was comparable to that of Doxil against human SKOV-3 ovarian adenocarcinoma xenograft rat model. Consequently, the PCL, of which surface was complexed with PEG by ionic complex may be applicable as drug delivery carriers for increasing therapeutic efficacy of anticancer drugs.
International journal of pharmaceutics 09/2009; 382(1-2):254-61. · 2.96 Impact Factor
[show abstract][hide abstract] ABSTRACT: Sterically stabilized liposomes (SSL) were known to be accumulated passively in cancer due to the effect of enhanced permeability and retention (EPR). However, drug delivery via SSL to cancer seemed to show an insufficient improvement of chemotherapeutic efficacy. Herein, carbohydrate-binding proteins (lectins) of cell surface, which express on the plasmic membrane of many malignant cells, can be a good model of surface-modified liposomes. In this study, we investigated the in vitro characteristics of liposomes of which the surface was modified with a disaccharide molecule, sucrose or maltose. The disaccharide-modified lipids such as sucrose-modified lipid and maltose-modified lipid, in which the disaccharide was conjugated to the one end of 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-(polyethylene glycol)-2000 (DSPE-PEG2000), was synthesized. The disaccharide-modified liposomes were prepared by thin film-hydration method and then doxorubicin (DOX), an anticancer drug, was loaded to the prepared liposomes by the remote loading method with ammonium ion gradient. Flow cytometry and confocal microscopy analyses showed that the disaccharide-modified liposomes enhanced the intracellular uptake of liposomes into various cancer cell lines via lectin-mediated endocytosis. The disaccharide-modified liposomes in which DOX was loaded inside of liposomes exhibited higher cytotoxicity against various cancer cells than DOX-loaded SSL did. These results suggest that disaccharide-modified liposomes may be promising cancer targeting carriers which can enhance intracellular uptake and cytotoxicity of the drug-loaded liposomes via lectin-mediated endocytosis.
International journal of pharmaceutics 08/2009; 380(1-2):161-9. · 2.96 Impact Factor
[show abstract][hide abstract] ABSTRACT: Lipid nanoparticles (LNPs) as nano-scale drug carriers that can entrap poorly water-soluble drugs such as amphotericin B (AmB) in aqueous solution with high drug entrapment efficiency were developed and their in vitro and in vivo characteristics were investigated. The AmB-entrapping plain, anionic and PEG (polyethylene glycol)-LNPs were prepared by using spontaneous emulsification and solvent evaporation (SESE) method. Mean particle size of the AmB-entrapping LNPs ranged from 72.9 to 159.1nm according to a variation of their lipid composition. The surface of AmB-entrapping PEG (0.2)-LNPs having 84.4+/-6nm of particle size was negatively charged showing -50.4+/-5mV of zeta-potential value. Entrapment efficiency of AmB in the PEG-LNPs reached up to 76.5+/-5%. Cytotoxicity of the AmB-entrapping LNPs against human kidney cells, 293 cells, was lower than those of the commercialized AmB-formulations such as Fungizone and AmBisome. Hematotoxicity of the AmB-entrapping LNPs against red blood cells was much lower than that of Fungizone but comparable to AmBisome. Antifungal activity in vitro of AmB-entrapping LNPs against Candida albicans and Aspergillus fumigatus was better than the commercialized AmB formulations showing their low minimum inhibitory concentration (MIC) for 90% of growth inhibition of fungi. The AmB-entrapping LNPs increased circulation half life of AmB in blood stream and it was comparable to AmBisome. Antifungal activity in vivo of the AmB-entrapping PEG-LNPs against Aspergillus fumigatus (ATCC 16424)-infected mice was superior to that of AmBisome. The drug-entrapping LNPs, especially PEG-LNPs, can be applicable to entrapment of poorly water-soluble drugs and enhancement of therapeutic efficacy by modulating pharmacokinetic behaviors and/or drug-related toxicities.
European journal of pharmaceutical sciences: official journal of the European Federation for Pharmaceutical Sciences 07/2009; 37(3-4):313-20. · 2.61 Impact Factor
[show abstract][hide abstract] ABSTRACT: Polymer incorporation on liposomal membranes has been extensively studied as a method of enhancing the circulation time of liposomes in the bloodstream. In this study, we investigated the in vitro and in vivo characteristics of liposomes whose surface was modified using a comblike polymer comprised of a poly(methyl methacrylate) (PMMA) backbone and short poly(ethylene oxide) (PEO) side chains. Doxorubicin (DOX)-loaded liposomes incorporating with the comblike polymer were prepared and their circulation time, biodistribution and antitumor activity were evaluated in B16F10 melanoma tumor-bearing mice. The circulation half-life time in the bloodstream of the comblike polymer-incorporated liposomes (CPILs) was approximately 14- or 2-fold higher than those of the conventional or polyethyleneglycol-fixed liposomes (PEG-liposomes), respectively. Additionally, in the biodistribution assay, the accumulation of the CPILs in the tumor was higher than those of the other liposomes. Based on this result, the antitumor activities of the CPILs were higher than those of conventional liposome formulation of DOX or free DOX due to the higher passive targeting efficiency of the long-circulating CPILs to tumor. This study suggests that the incorporation of the comblike polymer on the liposomal membrane is a promising tool to further improve circulation time of liposomes in tumor-bearing mice.
Journal of Controlled Release 08/2007; 120(3):161-8. · 7.63 Impact Factor
[show abstract][hide abstract] ABSTRACT: Tumor specific delivery of anti-cancer drugs is one of the major challenges faced by drug development processes. In this study, we prepared a doxorubicin (DOX)-conjugated liposome (DCL) by incorporating the newly synthesized DSPE-PEG2000-DOX (DPD) into liposomes as a lipid component and tested its anti-tumor activity in vivo. DPD was synthesized by coupling DOX to DSPE-PEG2000-COOH via amide linkage and the chemical structure of resulting DPD was confirmed by (1)H-NMR analysis. DCL having liposome size of 130 nm was prepared through thin film cast-hydration method. DCL was found to have significantly higher cellular uptake than conventional liposomes as confirmed by flow cytometry analysis. Anti-tumor activity of DCL against murine B16F10 melanoma tumor-bearing mice revealed that DCL inhibits tumor growth more efficiently than the conventional liposomes, presumably attributed to DOX mediated endocytosis process.
[show abstract][hide abstract] ABSTRACT: Temperature-sensitive liposomes (TS-liposomes) have been studied for chemotherapeutic purposes to enhance the release of anticancer drugs at tumor sites. In this study, we prepared poly(N-isopropylacrylamide-co-acrylamide) (PNIPAM-AAM) and polyethylene glycol (PEG)-modified TS-liposomes (PETS-liposomes). PETS-liposomes significantly increased in vitro drug release in serum compared with PEG-fixed or PNIPAM-AAM-modified liposomes. Furthermore, incorporation of both PNIPAM-AAM and PEG into PETS-liposomes enhanced the stabilities of liposomes in serum by inhibiting protein adsorption. In addition, to investigate the therapeutic efficacy of doxorubicin (DOX)-loaded PETS-liposomes, the in vivo antitumor activity of liposomes in combination with hyperthermia was evaluated in a B16F10 melanoma tumor-bearing mouse model. PETS-liposomes showed much higher levels of tumor growth inhibition than PEG-fixed or PNIPAM-AAM-modified TS-liposomes. Moreover, the antitumor activity of PETS-liposomes was enhanced significantly when they were administered in combination with hyperthermia. PETS-liposomes were found to be highly efficacious carriers for the in vivo delivery of anticancer drugs, and to have potential anticancer applications in combination with hyperthermia.
Journal of Pharmaceutical Sciences 10/2006; 95(9):1909-17. · 3.13 Impact Factor
[show abstract][hide abstract] ABSTRACT: The purpose of this study was to investigate the effect of heparin conjugation to the surface of doxorubicin (DOX)-loaded liposomes on the circulation time, biodistribution and antitumor activity after intravenous injection in murine B16F10 melanoma tumor-bearing mice. The heparin-conjugated liposomes (heparin-liposomes) were prepared by fixation of the negatively charged heparin to the positively charged liposomes. The existence of heparin on the liposomal surface was confirmed by measuring the changes in the particle size, zeta potential and heparin amount of the liposomes. The stability of the heparin-liposomes in serum was higher than that of the control liposomes, due to the heparin-liposomes being better protected from the adsorption of serum proteins. The DOX-loaded heparin-liposomes showed high drug levels for up to 64 h after the intravenous injection and the half-life of DOX was approximately 8.4- or 1.5-fold higher than that of the control liposomes or polyethyleneglycol-fixed liposomes (PEG-liposomes), respectively. The heparin-liposomes accumulated to a greater extent in the tumor than the control or PEG-liposomes as a result of their lower uptake by the reticuloendothelial system cells in the liver and spleen. In addition, the DOX-loaded heparin-liposomes retarded the growth of the tumor effectively compared with the control or PEG-liposomes. These results indicate the promising potential of heparin-liposomes as a new sterically stabilized liposomal delivery system for the enhancement of the therapeutic efficacy of chemotherapeutic agents.
International Journal of Pharmaceutics 05/2006; 313(1-2):181-8. · 3.46 Impact Factor
[show abstract][hide abstract] ABSTRACT: Di-branched amino acid derivatives, such as dihexadecyl-glutamate-glutamine (DHD-glu-gln), dihexadecyl-glutamate-asparagine (DHD-glu-asn) and dihexadecyl-glutamate-glutamic acid (DHD-glu-glu), were synthesized, and then incorporated into lipid vesicles (liposomes) using dipalmitoylphosphatidylcholine (DPPC). To form binding sites toward glucose, the liposomes containing amino acid derivatives were mixed with glucose above the phase transition temperature (PTT) of DPPC and subsequently the temperature was lowered below the PTT. The glucose-binding affinity of liposomes containing amino acid derivative with or without glucose imprinting was evaluated by surface plasmon resonance (SPR) and equilibrium dialysis technique. SPR of liposomes containing each amino acid derivative or three amino acid derivatives revealed that only the liposomes containing all three amino acid derivatives had glucose-binding affinity and that the glucose-imprinting process was essential to fix the amino acid derivatives into a glucose binding site on the liposomes. Equilibrium dialysis studies of glucose-imprinted liposomes produced curvilinear Scatchard plots, indicating that the amino acid derivatives play a role in glucose binding. Di-branched amino acid derivatives synthesized in this study are promising agent for the development of biocompatible synthetic glucose binding materials.
[show abstract][hide abstract] ABSTRACT: Implantable polymeric device that can release chemotherapeutic agent directly into central nervous system (CNS) has had an impact on malignant glioma therapy. The purpose of our study was to develop an implantable polymeric device, which can release intact 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) for long-term period over 1 month, and to evaluate its cytotoxicity against XF 498 human CNS tumor cells in vitro. BCNU was incorporated into biodegradable poly(D,L-lactide-co-glycolide) (PLGA), by using spray-drying method. BCNU-loaded PLGA microparticles were characterized by scanning electron microscopy (SEM), powder X-ray diffraction, and differential scanning calorimetry. SEM observation of the microparticles showed that the microparticles were spherical, i.e. microspheres. Homogeneous distribution of BCNU in PLGA microsphere was confirmed by significant reduction of crystallinity of BCNU. Microspheres were fabricated into wafers with flat and smooth surface by direct compression method. In vitro release of BCNU in pH 7.4 phosphate buffered saline was prolonged up to 8 weeks after short initial burst period. Antitumor activity of BCNU-loaded PLGA wafer against XF 498 human CNS tumor cells continued over 1 month and, PLGA only did not affect the growth of the cells. Meanwhile, the cytotoxic activity of BCNU powder disappeared within 12 h. These results strongly suggest that the BCNU/PLGA formulations increase release period of carmustine in vivo and also be useful in the development of implantable polymeric device for malignant glioma.
International Journal of Pharmaceutics 02/2003; 251(1-2):1-12. · 3.46 Impact Factor
[show abstract][hide abstract] ABSTRACT: The main goal of this study was to prepare molecularly imprinted polymers (MIPs) with glucose recognition sites and to evaluate their glucose-binding properties for potential applications in glucose sensing and self-regulating insulin delivery devices. To mimic glucose-binding sites of natural proteins, monomers possessing functional groups similar to amino acids were used. Vinyl acetic acid (VAA), acrylamide (AAm), 4-pentenoic acid (PA), and allyl benzene (AB) were copolymerized with a cross-linking agent (N,N'-methylenebisacrylamide, BIS) in the presence of glucose as a template. The binding affinity of glucose to MIPs was examined by using an equilibrium dialysis technique. The dissociation constants of the MIPs were determined by Scatchard analysis. MIPs showed glucose-binding affinity, while polymers synthesized in the absence of glucose template did not show a glucose-binding property. MIPs composed of VAA, AAm, PA, and AB at optimized mole ratios of monomers and cross-linker showed the highest glucose-binding affinity, KD = 1.66 mM, which is comparable to that of a well-known glucose binding protein, concanavalin A (KD = 1.84 mM). The affinity between monomer and glucose was in the order VAA > AAm > AB > PA.