Biomedical subjects

Kun Na

Publications and source records attributed to Kun Na.

At least 19 recordsLinked to original sources

PubMed2006

Protein release behavior from porous microparticle with lysozyme/hyaluronate ionic complex.

Porous microparticles (PMs) with a low density (<0.4 g/cm3) for pulmonary protein delivery were prepared by the water-in-oil-in-water (W1/O/W2) multi-emulsion method using a cyclodextrin derivative as a porogen. The complexation of positively charged lysozyme (Lys) and negative-charged hyaluronate (HA) was investigated for long-term protein release from PMs. The interaction of Lys and HA not only increased protein encapsulation efficiency but also stabilized Lys against a denaturing organic solvent (dichloromethane). Furthermore, PMs with Lys/HA complexes increased the Lys release period up to 7 days, as opposed to a 4h Lys release time from PMs without Lys/HA complexes. In particular, PMs containing 10mg of HA and 50mg of Lys showed almost zero-order Lys release kinetic for 7 days and preserved the bioactivity of Lys more than 98% during its entire release period. This result suggests that PMs with Lys/HA complexes may be applied in long-term pulmonary administration of protein or peptide drugs, including those that require particles to arrive at a deep lung epithelium with the help of low density (high porosity) of PMs.

Emulsions↗

PubMed2006

Synergistic effect of TGFbeta-3 on chondrogenic differentiation of rabbit chondrocytes in thermo-reversible hydrogel constructs blended with hyaluronic acid by in vivo test.

In this study, a hydrogel composite, based on the thermo-reversible hydrogel of p(NiPAAm-co-AAc) and hyaluronic acid (HA) was used as an injectable cell and growth factor carrier for cartilage tissue engineering applications. Rabbit chondrocytes were embedded in blended hydrogel composites co-encapsulated with the transforming growth factor beta-3 (TGFbeta-3). The blended hydrogel with the embedded chondrocytes and HA co-encapsulating unloaded growth factors and those with the thermo-reversible hydrogel were used as the controls to examine the effects of TGFbeta-3 on neocartilage formation. The blended hydrogel loaded with TGFbeta-3 embedded with chondrocytes were injected subcutaneously into the nude mice. The mice were monitored for 8 weeks after the injection. Both the differentiation and level of cartilage-specific ECM production were significantly higher in the presence of HA and growth factor than in the control without the growth factor. The level of cartilage associated ECM proteins was examined by immunohistochemical staining (collagen types II and X) as well as by Safranin-O and Alcian blue (GAG) staining. The results showed the potential application of blended hydrogel mixed with the growth factor to neocartilage formation.

Acrylamides↗

PubMed2006

Delivery of dexamethasone, ascorbate, and growth factor (TGF beta-3) in thermo-reversible hydrogel constructs embedded with rabbit chondrocytes.

The aim of this study was to assess the efficacy of poly(N-isopropylacrylamide-co-acrylic acid) (p(NiPAAm-co-AAc)) as an injectable drug delivery vehicle and a cell therapeutic agent in the form of a supporting matrix for the chondrogenic differentiation of rabbit chondrocytes. The p(NiPAAm-co-AAc) hydrogel itself without specific differentiation-inducing drugs was used as a control in order to determine the effects of these materials on chondrogenic differentiation. The level of cartilage associated extracellular matrix (ECM) proteins was examined by immunohistochemical staining for collagen type II as well as Safranin-O and Alcian blue (GAG) staining. These results highlight the potential of a thermo-reversible hydrogel mixed with chondrocytes and differentiation materials as an injectable delivery vehicle for use in neocartilage formation.

Animals↗

PubMed2006

In vitro study of lysozyme in poly(lactide-co-glycolide) microspheres with sucrose acetate isobutyrate.

This study investigated the suitability of microsphere formulations for extended protein delivery and complete protein release. These microspheres were prepared by a multi-emulsion method and prepared using a mixture of poly(lactide-co-glycolide) (PLGA), RG 502H (lactide:glycolide=50:50, M(W) 9300) and sucrose acetate isobutyrate (SAIB). SAIB embedded into the microspheres and mixed with PLGA, improved the efficiency of enzyme encapsulation. The in vitro release rate of lysozyme (Lys) from the microspheres was reduced due to the high viscosity of the added SAIB and less degradation of PLGA by SAIB. These properties enabled prolonged release of Lys for up to 2 months, characterized by a minimal initial burst of Lys and nearly zero-order protein release kinetics result from co-administration of sorbitan monooleate 80. When it is considered that degradation products of SAIB are inactive for labile proteins, SAIB may be regarded as a promising candidate for long-acting protein delivery.

Delayed-Action Preparations↗

PubMed2006

pH-responsive sulfonamide/PEI system for tumor specific gene delivery: an in vitro study.

The feasibility of pH-sensitive polymeric nanoparticles that effectively target the acidic extracellular matrix of tumors is demonstrated. Plasmid DNA was complexed with polyethyleneimine (PEI) and further with a pH-sensitive diblock copolymer, poly(methacryloyl sulfadimethoxine) (PSD)-block-PEG (PSD-b-PEG), to obtain naonparticles. The shielding/deshielding of nanoparticles was tested along with cell viability and transfection efficiency at physiological and tumor pH. The nanoparticles composed of DNA/PEI/PSD-b-PEG were 300 nm in size and showed low cytotoxicity and transfection at pH 7.4 due to shielding of PEI by PSD-b-PEG. The PSD-b-PEG bound to PEI/DNA complex decreased the interaction of PEI positive charges with cells and reduced the cytotoxicity by 60%. At pH 6.6, the nanoparticles demonstrated high cytotoxicity and transfection, indicating PSD-b-PEG detachment from the nanoparticles and permit PEI to interact with cells. PSD-b-PEG is able to discern the small difference in pH between normal and tumor tissues and hence has remarkable potential in drug targeting to tumor areas.

Cations↗

PubMed2006

Stimuli-sensitive polymeric micelles as anticancer drug carriers.

Amphiphilic block copolymers often form core-shell type micelles by self-organization of the blocks in an aqueous medium or under specific experimental conditions. Polymeric micelles constructed from these polymers that contain a segment whose physical or chemical properties respond to small changes in environmental conditions are collectively called 'stimuli-sensitive' micelles. This class of nano-scaled constructs has been investigated as a promising anti-cancer drug carrier because the micelles are able to utilize small environmental changes and modify drug release kinetics, biodistribution and the interactions with tissues and cells. This review summarizes the recent progress in stimuli-sensitive micelles for tumor chemotherapy, particularly for those responding to hyperthermic conditions, tumor pH and endosomal/lysosomal pH.

Animals↗

PubMed2005

Biodegradable thermo-sensitive nanoparticles from poly(L-lactic acid)/poly(ethylene glycol) alternating multi-block copolymer for potential anti-cancer drug carrier.

In order to produce biodegradable thermo-sensitive nanoparticles, alternating multi-block copolymers (MBC) were synthesized by coupling dicarboxylated poly(ethylene glycol) (PEG; M(w) 2000) with poly(L-lactic acid) (PLLA)/PEG/PLLA triblock copolymers. Three different multi-block copolymers were synthesized by varying PLLA molecular weight (800 (MBC1), 1600 (MBC2), and 2800 (MBC3)). The MBC formed self-assembled nanoparticles with a unimodal size distribution during a dialysis process. The nanoparticles (NP) had a spherical shape with a size range of 90-330 nm in diameter and critical aggregation concentrations in a range of 5.6-12.6 microg/mL, depending on PLLA length in MBC. The thermo-sensitivity of MBC NP was monitored by the changes in particle size and interior structure as a function of temperature. The particle size slightly decreased as increasing temperature from 37 to 42 degrees C. The interior structure of the NP responded to temperature by altering microviscosity. The microviscosity, measured by the anisotropy (r value) of a fluorescence probe, of MBC1 NP significantly changed with increasing temperature (r = 0.187 at 25 degrees C and 0.216 at 42 degrees C), while MBC2 and MBC3 showed negligible changes in the microviscosity. This indicates that the temperature-dependent interior structure of the NP relied on the portion of PLLA in MBC. The thermo-sensitivity affected to the drug release behavior and cell cytotoxicity. At 42 degrees C, doxorubicin (DOX) loaded MBC1 NP showed enhanced cytotoxicity (approximately 20 times) against Lewis Lung Carcinoma (LLC) cells when compared to that at 37 degrees C.

Animals↗

PubMed2005

Doxorubicin loaded pH-sensitive polymeric micelles for reversal of resistant MCF-7 tumor.

In order to overcome multidrug resistance in solid tumors, doxorubicin (DOX) loaded pH-sensitive micelles of which surface was decorated with folate (PHSM/f) were evaluated both in vitro and in vivo experiments. PHSM/f were fabricated from a mixture of two block copolymers of poly(L-histidine) (M(n): 5K)-b-PEG (M(n): 2K)-folate (polyHis/PEG-folate) (75 wt.%) and poly(L-lactic acid) (M(n): 3K)-b-PEG (M(n): 2K)-folate (PLLA/PEG-folate) (25 wt.%). The PHSM/f showed more than 90% cytotoxicity of DOX resistant MCF-7 (MCF-7/DOX(R)) when cultured with PHSM/f at a concentration of 10 microg/ml DOX. The result was interpreted by a sequential event of active internalization of PHSM/f via folate-receptor mediated endocytosis and ionization of His residues which result in micelle destabilization and probably disturbance of endosomal membranes. This potential mechanism may endow the drug carriers to bypass Pgp efflux pump and sequestration of DOX in acidic intracellular compartments, yielding high cytotyoxicity. Experimental evaluation of tumor regression was carried out in a small animal model bearing s.c. MCF-7 or MCF-7/DOX(R) xenografts. The tumor (MCF-7/DOX) volumes of mice treated with PHSM/f were significantly less than control groups treated with free DOX or similar micelles but without folate (PHSM). In the MCF-7/DOX(R) xenograft model, the accumulated DOX level of PHSM/f in solid tumors was 20 times higher than free DOX group, and 3 times higher than PHSM group. The results demonstrate that PHSM/f is a viable means for treating drug resistant tumors.

Animals↗

PubMed2005

Enhancement of the adhesion of fibroblasts by peptide containing an Arg-Gly-Asp sequence with poly(ethylene glycol) into a thermo-reversible hydrogel as a synthetic extracellular matrix.

In an effort to regulate the behavior of mammalian cell entrapped in a gel, the gels were functionalized with the putative cell-binding (-Arg-Gly-Asp-) (RGD) domain. The adhesion molecules composed of Gly-Arg-Gly-Asp-Ser (GRGDS) peptides and the cell recognition ligands were inculcated into the thermo-reversible hydrogel composed of N-isopropylacrylamide, with a small amount of succinyl poly(ethylene glycol) (PEG) acrylate (MW 2000) used as the biomimetic extracellular matrix (ECM). The GRGDS-containing p(NiPAAm-co-PEG) copolymer gel was examined in vitro for its ability to promote cell spreading and to increase the viability of the cells by introducing PEG spacers. ECM poorly adhered to hydrogel lacking adhesion molecules permitting only a 20% spread of the seeded cells after 10 days. When the PEG spacer arms, which were immobilized by a peptide linkage, had been integrated into the hydrogel, the conjugation of RGD improved cell spreading by 600% in a 10-day trial.

3T3-L1 Cells↗

PubMed2005

Phenotype of hepatocyte spheroids behavior within thermo-sensitive poly(NiPAAm-co-PEG-g-GRGDS) hydrogel as a cell delivery vehicle.

Aggregates (spheroids) of specific cells are often regarded as a better form in artificial organs and mammalian cell bioreactors for improved cell-specific functions. Freshly harvested primary rat hepatocytes, cultivated as spheroids and entrapped in an adhesion molecules of Arg-Gly-Asp (RGD)-conjugated extracellular matrix, have been examined for differentiated morphology and enhanced liver-specific functions. A copolymer of RGD conjugated p(NiPAAm-co-PEG) hydrogel was used to entrap hepatocytes in the forms of spheroids. Over 28 days, entrapped the spheroids had a higher viability and produced albumin and urea at constant rates, while there was slight increase in cell numbers and reduction of albumin secretion in single cell culture in the hydrogel. Hepatocytes cultured in this way are a potentially useful three-dimensional cell system for application in a bioartificial liver device and bioreactor.

Acrylamides↗

PubMed2005

Preparation and characterization of solid lipid nanoparticles (SLN) made of cacao butter and curdlan.

Solid lipid nanoparticles (SLN) were prepared using cacao butter, as the lipid core, and curdlan, as the shell material. Tween 80 was used as a co-surfactant in order to prevent aggregation and gelling of the curdlan. Mannitol was used as a cryoprotectant in order to prevent aggregation during redispersion. No significant change in the size of the SLN was observed up to a lipid concentration of 1.0%, and the particle size ranged from 140 to 200 nm with a unimodal distribution. When an alternating pH between 7 and 11 was used to test the physical stability of an SLN solution, the change in the particle size remained within a narrow range up to a lipid concentration of 0.5%. Above 0.5%, the particles began to aggregate due to the insufficient amount of the coating material, curdlan and Tween 80. The critical aggregation concentration at pH 7.4 was found to be 6.95 x 10(-4) mg/ml. Pyrene was used as a fluorescence probe. As the temperature increased, pyrene was gradually released from the SLN. The loading efficiency was >75% when the verapamil to lipid ratios were 1:10 and 1:5 and decreased significantly as the ratio became 1:1. The release rate was significantly delayed when verapamil was loaded into the SLN.

Cacao↗

PubMed2005

Super pH-sensitive multifunctional polymeric micelle.

To endow enhanced tumor specificity and endosome disruption property on the carrier, a multifunctional polymeric micelle was investigated. The micelle exposes the cell interacting ligand (biotin) on the surface under slightly acidic environmental conditions of various solid tumors and is internalized by biotin receptor-mediated endocytosis in a short time period. The micelle also showed pH-dependent dissociation, causing the enhanced release of doxorubicin from the carrier in early endosomal pH. The dissociated micellar components subsequently disrupt endosomal membrane.

Adenocarcinoma↗

PubMed2005

Insulinoma cell line (MIN6) adhesion and spreading mediated by Arg-Gly-Asp (RGD) sequence conjugated in thermo-reversible gel.

We have functionalized gels with a putative cell-binding (-Arg-Gly-Asp-) (RGD) domain in an effort to regulate mammalian cell behavior in cells entrapped with gel. Adhesion molecules composed of Gly-Arg-Gly-Asp-Ser (GRGDS) peptides and cell recognition ligands were inculcated into thermo-reversible hydrogel composed of N-isopropylacrylamide, with a small amount of succinyl poly(ethylene glycol) (PEG) acrylate (MW 2000) used as a biomimetic extracellular matrix (ECM). The GRGDS-containing p(NiPAAm-co-PEG) copolymer gel was studied in vitro for its ability to promote cell spreading and to increase the viability of cells by introducing PEG spacers. Hydrogel lacking the adhesion molecules proved to be a poor ECM for adhesion, permitting only a 20% spread of the seeded cells after 10 d. When PEG spacer arms, immobilized by a peptide linkage, had been integrated into the hydrogel, conjugation of RGD promoted cell spread by 300% in a 28-d trial. In addition, in a serum-free medium, only GRGDS peptides conjugated with the spacer arm were able to promote cell spread.

Adsorption↗

PubMed2004

pH-sensitivity and pH-dependent interior structural change of self-assembled hydrogel nanoparticles of pullulan acetate/oligo-sulfonamide conjugate.

pH-sensitive hydrogel nanoparticles that respond to the local acidic pH found in various diseased states such as tumors, ischemia and inflammation were prepared from pullulan acetate/oligo-sulfadimethoxine (PA/OSDM) conjugates. PA/OSDM nanoparticles prepared by dialysis at pH 9.5 had a spherical shape with a size range of 50-140 nm and low critical aggregation concentration (CAC) (<12 x 10(-3) mg/ml), dependent on the degree of substitution of OSDM (DS). With a decrease in dialysis pH (pHdia), the CAC gradually decreased due to the increase in the hydrophobic nature of OSDM. The nanoparticles prepared at pHdia 8.0 from the polymer with DS 1.0 aggregated in a pH range of 6.6-7.2 while the aggregation of nanoparticles prepared below pHdia 7.4 occurred in a broader pH range with a downshifted transition pH. These results indicate that the CAC and sharpness of the pH sensitivity of self-assembled hydrogel nanoparticles can be controlled by the pH of the dialysis buffer. In addition, the photophysical and photochemical characteristics of the nanoparticles were examined by a fluorescence probe technique. The micropolarity was monitored by pyrene and the microviscosity was measured by 1,6-diphenyl-1,3,5,-hexatriene (DPH) in the core of nanoparticles. Both properties dramatically changed as the pH decreased from 7.2 to 6.8, indicating that the interior restructuring of the hydrogel nanoparticles changed rapidly in this pH range. This is probably due to recruitment of hydrophobic group of deionized OSDM into the core. The pH sensitivity of the nanoparticles affected their drug release behavior. Doxorubicin (DOX) release from the PA/OSDM nanoparticles showed pH-dependent profiles around physiological pH and was significantly promoted at pH<6.8.

Acetates↗

PubMed2004

Immobilization of Arg-Gly-Asp (RGD) sequence in sugar containing copolymer for culturing of pheochromocytoma (PC12) cells.

A copolymer that included a Gly-Arg-Gly-Asp-Ser (GRGDS) sequence and sugar moieties was synthesized to culture pheochromocytoma cells (PC12). PC12 cells attached to poly(N-p-vinylbenzyl-D-maltonamide-co-6-(p-vinylbenzamido)-hexanoic acid-g-GRGDS) [p(VMA-co-VBGRGDS)]-coated dishes showed greater proliferation than on other polymer-coated surfaces. Enhancement in cell growth correlated with the ability of soluble Arg-Gly-Asp (RGD) to inhibit cell adhesion to surfaces coated with p(VMA-co-VBGRGDS). This method for promoting cell proliferation may be useful for the culturing of anchorage-dependent cells. Furthermore, about 80% greater dopamine secretion from PC12 cells was produced with the p(VMA-co-VBGRGDS) as compared with PC12 cells on unmodified surfaces.

Journal Article↗

PubMed2003

Polymeric micelle for tumor pH and folate-mediated targeting.

Novel pH-sensitive polymeric mixed micelles composed of poly(L-histidine) (polyHis; M(w) 5000)/PEG (M(n) 2000) and poly(L-lactic acid) (PLLA) (M(n) 3000)/PEG (M(n) 2000) block copolymers with or without folate conjugation were prepared by diafiltration. The micelles were investigated for pH-dependent drug release, folate receptor-mediated internalization and cytotoxicity using MCF-7 cells in vitro. The polyHis/PEG micelles showed accelerated adriamycin release as the pH decreased from 8.0. When the cumulative release for 24 h was plotted as a function of pH, the gradual transition in release rate appeared in a pH range from 8.0 to 6.8. In order to tailor the triggering pH of the polymeric micelles to the more acidic extracellular pH of tumors, while improving the micelle stability at pH 7.4, the PLLA/PEG block copolymer was blended with polyHis/PEG to form mixed micelles. Blending shifted the triggering pH to a lower value. Depending on the amount of PLLA/PEG, the mixed micelles were destabilized in the pH range of 7.2-6.6 (triggering pH for adriamycin release). When the mixed micelles were conjugated with folic acid, the in vitro results demonstrated that the micelles were more effective in tumor cell kill due to accelerated drug release and folate receptor-mediated tumor uptake. In addition, after internalization polyHis was found to be effective for cytosolic ADR delivery by virtue of fusogenic activity. This approach is expected to be useful for treatment of solid tumors in vivo.

Antibiotics, Antineoplastic↗

PubMed2003

Poly(L-histidine)-PEG block copolymer micelles and pH-induced destabilization.

Poly(L-histidine)-poly(ethylene glycol) diblock copolymers (polyHis-b-PEG) were prepared and used for the construction of polymeric micelles responding to local pH changes in the body. PolyHis was synthesized by ring opening polymerization of L-histidine N-carboxyanhydride, the imidazole amine group of which was protected by the dinitrophenyl group. The resulting polymer (M(n): 5,000 g/mole) was coupled to poly(ethylene glycol) (M(n): 2,000 g/mole) via an amide linkage using the dicyclohexyl carbodiimide and N-hydroxysuccinimide-mediated reaction. The block copolymer in dimethyl sulfoxide formed polymeric micelles on diafiltration against a borate buffer at pH 8. Dynamic light scattering and atomic force microscopy showed the micelles were spherical, diameter approximately 114 nm, with a unimodal distribution. The critical micelle concentration (CMC) at pH 8.0 was 2.3 mg/l. The CMC increased markedly on decreasing the pH of the diafiltration medium below 7.2. Micelles prepared at pH 8.0 were gradually destabilized below pH 7.4, as evidenced by a slight increase in light transmittance, an alteration in size distribution, and a decrease in the pyrene fluorescence intensity. It was concluded that the ionization of the polyHis block forming the micelle core determined the pH-dependent CMC and stability. After further optimization of the pH-sensitivity, pH-sensitive micelles are expected to have application for solid tumor treatment, exploiting the fact that most solid tumors have an acidic extracellular pH.

Buffers↗

PubMed2003

Adriamycin loaded pullulan acetate/sulfonamide conjugate nanoparticles responding to tumor pH: pH-dependent cell interaction, internalization and cytotoxicity in vitro.

The cytotoxicity of adriamycin (ADR)-loaded and pH-sensitive nanoparticles made of pullulan acetate (PA) and sulfonamide (sulfadimethoxine; SDM) (PA/SDM) conjugate to a breast tumor cell line (MCF-7) was investigated to test the feasibility of the nanoparticles in targeting acidic tumor extracellular pH (pH(e)). At pH 6.8, ADR loaded PA/SDM nanoparticles showed cytotoxicity in the cell culture experiment, comparable to that of free ADR at the same ADR concentrations, while the relative cytotoxicity at pH 7.4 was low at the tested concentration range. This pronounced cytotoxicity of the nanoparticles at low pH was attributed to the accelerated release of ADR triggered by pH, enhanced interaction with cells, and internalization. At pH 6.8 and 6.4, the PA/SDM nanoparticles aggressively bounded to MCF-7 cells, probably due to interactions of the cells with hydrophobized nanoparticle surfaces caused by SDM deionization. A confocal laser microscopic study revealed intracellular localization of the drug-loaded nanoparticles. Based on these findings, the pH-sensitive nanoparticles deserve further investigation with an in vivo animal model as a targeted carrier of pH(e).

Acetates↗