Yeonsu gu, South Korea
Yeonsu gu, South Korea

Time filter

Source Type

Kim M.,Gwangju Institute of Science and Technology | Hong B.,Gwangju Institute of Science and Technology | Lee J.,Gwangju Institute of Science and Technology | Lee J.,Advanced Therapeutics Research Center | And 4 more authors.
Biomacromolecules | Year: 2012

Delivering isolated chondrocytes with matrix is a promising approach to promote the cartilage repair. The present study attempted to combine the advantages of porous scaffold and hydrogel in delivering chondrocytes to partial-thickness cartilage defects. An electrospun, gelatin-incorporated PLCL scaffold mechanically similar to natural cartilage was fabricated, and chondrocytes were seeded using an injectable heparin-based hydrogel for efficient cell seeding. The scaffold/hydrogel composite showed more enhanced expression of chondrogenic genes and production of GAGs than those prepared without hydrogel. In addition, significant cartilage formation showing good integration with surrounding, similar to natural cartilage, was observed by scaffold/hydrogel composite system in partial-thickness defects of rabbit knees while no regeneration was observed in control defects. Although no exogenous chondrogenic factors were added, it was evident that the scaffold/hydrogel composite system was highly effective and better than the scaffold alone system without hydrogel for cartilage regeneration both in vitro and in vivo. © 2012 American Chemical Society.

Kang H.C.,University of Utah | Kang H.C.,Catholic University of Korea | Samsonova O.,University of Utah | Samsonova O.,University of Marburg | And 3 more authors.
Biomaterials | Year: 2012

Although polymers, polyplexes, and cells are exposed to various extracellular and intracellular pH environments during polyplex preparation and polymeric transfection, the impact of environmental pH on polymeric transfection has not yet been investigated. This study aims to understand the influence of environmental pH on polymeric transfection by modulating the pH of the transfection medium or the culture medium. Changes in the extracellular pH affected polymeric transfection by way of complex factors such as pH-induced changes in polymer characteristics (e.g., proton buffering capacity and ionization), polyplex characteristics (e.g., size, surface charge, and decomplexation), and cellular characteristics (e.g., cellular uptake, cell cycle phases, and intracellular pH environment). Notably, acidic medium delayed endocytosis, endosomal acidification, cytosolic release, and decomplexation of polyplexes, thereby negatively affecting gene expression. However, acidic medium inhibited mitosis and reduced dilution of gene expression, resulting in increased transfection efficiency. Compared to pH 7.4 medium, acidic transfection medium reduced gene expression 1.6-7.7-fold whereas acidic culture medium enhanced transfection efficiency 2.1-2.6-fold. Polymeric transfection was affected more by the culture medium than by the transfection medium. Understanding the effects of extracellular pH during polymeric transfection may stimulate new strategies for determining effective and safe polymeric gene carriers. © 2011 Elsevier Ltd.

Kang H.C.,University of Utah | Samsonova O.,University of Utah | Samsonova O.,University of Marburg | Bae Y.H.,University of Utah | Bae Y.H.,Advanced Therapeutics Research Center
Biomaterials | Year: 2010

While multidrug resistance (MDR) has been a significant issue in cancer chemotherapy, delivery resistance to various anti-cancer biotherapeutics, including genes, has not been widely recognized as a property of MDR. This study aims to provide a better understanding of the transfection characteristics of drug-sensitive and drug-resistant cells by tracing microenvironmental pHs of two representative polymer vectors: poly(l-lysine) and polyethyleneimine. Drug-sensitive breast MCF7 cells had four- to seven-times higher polymeric transfection efficiencies than their counterpart drug-resistant MCF7/ADR-RES cells. Polyplexes in MCF7/ADR-RES cells after endocytosis were exposed to a more acidic microenvironment than those in MCF7 cells; the MDR cells show faster acidification rates in endosomes/lysosomes than the drug-sensitive cells after endocytosis (in the case of PLL/pDNA complexes, ∼ pH 5.1 for MCF7/ADR-RES cells vs. ∼ pH 6.8 for MCF7 cells at 0.5 h post-transfection). More polyplexes were identified trapped in acidic subcellular compartments of MCF7/ADR-RES cells than in MCF7 cells, suggesting that they lack endosomal escaping activity. These findings demonstrate that the design of polymer-based gene delivery therapeutics should take into account the pH of subcellular compartments. © 2010 Elsevier Ltd. All rights reserved.

Yin H.,University of Utah | Kang H.C.,Catholic University of Korea | Huh K.M.,Chungnam National University | Bae Y.H.,University of Utah | Bae Y.H.,Advanced Therapeutics Research Center
Journal of Materials Chemistry | Year: 2012

Motivated by the limitations of liposomal drug delivery systems, we designed a novel histidine-based AB 2-miktoarm polymer (mPEG-b-(polyHis) 2) equipped with a phospholipid-mimic structure, low cytotoxicity, and pH-sensitivity. Using "core-first" click chemistry and ring-opening polymerization, mPEG 2kDa-b-(polyHis 29kDa) 2 was successfully synthesized with a narrow molecular weight distribution (1.14). In borate buffer (pH 9), the miktoarm polymer self-assembled to form a nano-sized polymersome with a hydrodynamic radius of 70.2 nm and a very narrow size polydispersity (0.05). At 4.2 μmol per mg polymer, mPEG 2kDa-b-(polyHis 29kDa) 2 strongly buffered against acidification in the endolysosomal pH range and exhibited low cytotoxicity on 5 days exposure. Below pH 7.4 the polymersome transitioned to cylindrical micelles, spherical micelles, and finally unimers as the pH was decreased. The pH-induced structural transition of mPEG 2kDa-b-(polyHis 29kDa) 2 nanostructures may be caused by the increasing hydrophilic weight fraction of mPEG 2kDa-b- (polyHis 29kDa) 2 and can help to disrupt the endosomal membrane through proton buffering and membrane fusion of mPEG 2kDa-b-(polyHis 29kDa) 2. In addition, a hydrophilic model dye 5(6)-carboxyfluorescein encapsulated into the aqueous lumen of the polymersome showed a slow, sustained release at pH 7.4 but greatly accelerated release below pH 6.8, indicating a desirable pH sensitivity of the system in the range of endosomal pH. Therefore, this polymersome that is based on a biocompatible histidine-based miktoarm polymer and undergoes acid-induced transformations could serve as a drug delivery vehicle for chemical and biological drugs. This journal is © The Royal Society of Chemistry.

Park W.,Catholic University of Korea | Park W.,University of Utah | Kim D.,University of Utah | Kang H.C.,Catholic University of Korea | And 3 more authors.
Biomaterials | Year: 2012

For long-term, sustained protein delivery, a new, star-shaped block copolymer composed of methoxy poly(ethylene glycol) (mPEG), branched oligoethylenimine (bOEI), and poly (l-histidine) (pHis) was synthesized via the multi-initiation and ring-opening polymerization (ROP) of His N-carboxy anhydride (NCA) on bOEI with a PEG conjugation. The resulting mPEG-bOEI-pHis (POH) had strong buffering capacity within the neutral-to-acidic pH range and was complexed with insulin (Ins) via an electrostatic attraction plus hydrophobic interactions, resulting in the formation of a dual-interaction complex (DIC, weight ratio 2) of approximately 30-60 nm in size. This DIC tolerated high salt concentrations without destabilization, supporting the existence of hydrophobic interactions, and protected Ins from the organic solvent/water interface. The DIC in poly(lactide-co-glycolide) microspheres (PLGA MS) as a long-term Ins delivery formulation was evenly distributed via a double-emulsion method. The DIC-loaded PLGA MS offered a higher Ins loading and a lower initial burst than Ins-loaded PLGA MS. This formulation possessed near zero-order release kinetics (for at least one month). In streptozotocin (STZ)-induced diabetic rats, a DIC-loaded PLGA MS formulation was able to maintain blood-glucose levels at 200-350 mg/dL for the first two weeks and even lower levels (100-200 mg/dL) for the next two weeks. Thus, a new POH polymer and its complex with a drug protein could have potential biological application as a long-term, sustained protein delivery system. © 2012 Elsevier Ltd.

Tian L.,University of Utah | Kang H.C.,Catholic University of Korea | Bae Y.H.,University of Utah | Bae Y.H.,Advanced Therapeutics Research Center
Biomacromolecules | Year: 2013

Despite the numerous vital functions of proteins in the cytosolic compartment, less attention has been paid to the delivery of protein drugs to the cytosol than to the plasma membrane. To address this issue and effectively deliver charged proteins into the cytoplasm, we used endosomolytic, thiol-triggered degradable polyelectrolytes as carriers. The cationic, reducible polyelectrolyte RPC-bPEI0.8 kDa2 was synthesized by the oxidative polymerization of thiolated branched polyethyleneimine (bPEI). The polymer was converted to the anionic, reducible polyelectrolyte RPA-bPEI0.8 kDa2 by introducing carboxylic acids. The two reducible polyelectrolytes (RPC-bPEI0.8 kDa2 and RPA-bPEI0.8 kDa2) were complexed with counter-charged model proteins (bovine serum albumin (BSA) and lysozyme (LYZ)), forming polyelectrolyte/protein complexes of less than 200 nm in size at weight ratios (WR) of ≥1. The resultant complexes maintained a proton buffering capacity nearly equivalent to that of the polyelectrolytes in the absence of protein complexation and were cytocompatible with MCF7 human breast carcinoma cells. Under cytosol-mimicking thiol-rich conditions, RPC-bPEI 0.8 kDa2/BSA and RPA-bPEI0.8 kDa2/LYZ complexes increased significantly in size and released the loaded protein, unlike the protein complexes with nonreducible polyelectrolytes (bPEI25 kDa and bPEI25 kDaCOOH). The polyelectrolyte/protein complexes showed cellular uptake similar to that of the corresponding proteins alone, but the former allowed more protein to escape into the cytosol from endolysosomes than the latter as a result of the endosomolytic function of the polyelectrolytes. In addition, the proteins in the polyelectrolyte/protein complexes kept their intrinsic secondary structures. In conclusion, the results show the potential of the designed endosomolytic, reducible polyelectrolytes for the delivery of proteins to the cytosol. © 2013 American Chemical Society.

Lee Y.J.,University of Utah | Lee Y.J.,Korea Basic Science Institute | Kang H.C.,University of Utah | Kang H.C.,Catholic University of Korea | And 5 more authors.
Biomacromolecules | Year: 2012

To overcome the limitations of monomeric pH probes for acidic tumor environments, this study designed a mixed micelle pH probe composed of polyethylene glycol (PEG)-b-poly(l-histidine) (PHis) and PEG-b-poly(l-lactic acid) (PLLA), which is well-known as an effective antitumor drug carrier. Unlike monomeric histidine and PHis derivatives, the mixed micelles can be structurally destabilized by changes in pH, leading to a better pH sensing system in nuclear magnetic resonance (NMR) techniques. The acidic pH-induced transformation of the mixed micelles allowed pH detection and pH mapping of 0.2-0.3 pH unit differences by pH-induced "on/off"-like sensing of NMR and magnetic resonance spectroscopy. The micellar pH probes sensed pH differences in nonbiological phosphate buffer and biological buffers such as cell culture medium and rat whole blood. In addition, the pH-sensing ability of the mixed micelles was not compromised by loaded doxorubicin. In conclusion, PHis-based micelles could have potential as a tool to simultaneously treat and map the pH of solid tumors in vivo. © 2012 American Chemical Society.

Nadithe V.,University of Utah | Mishra D.,University of Utah | Bae Y.H.,University of Utah | Bae Y.H.,Advanced Therapeutics Research Center
Biotechnology and Bioengineering | Year: 2012

The objective of this study was to investigate the efficiency of multifunctional poly(ethylene glycol)-based hemoglobin conjugates crosslinked with antioxidant enzymes for their ability to protect an oxygen carrier (hemoglobin) and insulin secreting islets from the combination of hypoxic and free radical stress under simulated transplantation conditions. In this study, RINm5F cells and isolated pancreatic islets were challenged with oxidants (H2O2 or xanthine and xanthine oxidase) and incubated with conjugates (hemoglobin-hemoglobin or superoxide dismutase-catalase-hemoglobin) in normoxia (21% oxygen) or hypoxia (6% or 1% oxygen). Hemoglobin protection, intracellular free radical activity and cell viability in RINm5F cells measured by methemoglobin, dichlorofluorescein-diacetate, and (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay, respectively, showed that cells were better protected by conjugates containing antioxidant enzymes. Insulin secretion from islets and qualitative confocal evaluation of viability showed beta cells were protected by conjugates containing antioxidant enzymes when exposed to induced stress. Our study suggested that antioxidant enzymes play a significant role in hemoglobin protection and thus extended cell protection. © 2012 Wiley Periodicals, Inc..

Hwang H.S.,University of Utah | Kang H.C.,Catholic University of Korea | Bae Y.H.,University of Utah | Bae Y.H.,Advanced Therapeutics Research Center
Biomacromolecules | Year: 2013

Polyplex formation (complexation) and gene release from the polyplexes (decomplexation) are major events in polymeric gene delivery; however, the effect of the decomplexation rate on transfection has been rarely investigated. This study employed mixed polymers of poly(L-lysine) (PLL: MW ∼7.4 kDa) and reducible PLL (RPLL) (MW ∼6.7 kDa) to design decomplexation rate-controllable PLL100-xRPLLx/pDNA complexes (PRLx polyplexes). The transfection efficiency of a model gene (luciferase) in MCF7 and HEK293 cell lines increased with increasing x (RPLL content) in the PRLx polyplexes until peaking at x = 2.5 and 10, respectively, after which point transfection efficiency declined rapidly. In MCF7 cells, PRL2.5 polyplex produced 3 or 223 times higher gene expression than PLL or RPLL polyplexes, respectively. Similarly, the transfection efficiency of PRL10 polyplex-transfected HEK293 cells was 3.8 or 67 times higher than that of PLL or RPLL polyplexes, respectively. The transfection results were not apparently related to the particle size, surface charge, complexation/compactness, cellular uptake, or cytotoxicity of the tested polyplexes. However, the decomplexation rate varied by RPLL content in the polyplexes, which in turn influenced the gene transfection. The nuclear localization of pDNA delivered by PRLx polyplexes showed a similar trend to their transfection efficiencies. This study suggests that an optimum decomplexation rate may result in high nuclear localization of pDNA and transfection. Understanding in decomplexation and intracellular localization of pDNA may help develop more effective polyplexes. © 2012 American Chemical Society.

Chang Kang H.,University of Utah | Bae Y.H.,University of Utah | Bae Y.H.,Advanced Therapeutics Research Center
Biomaterials | Year: 2011

Cationic polymers are potential intracellular carriers for small interfering RNA (siRNA). The short and rigid nature of an siRNA chain often results in larger and more loosely packed particles compared to plasmid DNA (pDNA) after complexing with carrier polycations, and in turn, poor silencing effects are seen against the target mRNAs. A helper polyanion, pDNA, was incorporated along with siRNA to form compact nanosized polyplexes. At C/A (cation/anion) ratios of 2 and 5, poly(l-lysine) (PLL)/siRNA-pGFP and PLL/siRNA-pGFP-OSDZ (oligomeric sulfadiazine (OSDZ) for endosomolysis) complexes produced particles 90-150 nm in size with a 15-45 mV surface charge, while PLL/siRNA complexes yielded particles 1-2 μm in size at the same C/A ratios. The PLL/siRNA-pGFP (C/A 2) complexes showed significantly higher specific gene silencing (50-90% vs. 10-25%) than the complexes formed at C/A 5. PLL/siRNA-pGFP-OSDZ (C/A 2) complexes improved the specific gene silencing (90%) more dramatically than PLL/siRNA-pGFP (C/A 2) complexes (50%), demonstrating a potential role for OSDZ. PLL/siRNA-pGFP-OSDZ (C/A 2) complexes sustained higher specific gene silencing compared with PLL/siRNA-pGFP (C/A 2) complexes. Other oligomeric sulfonamides (OSA) with varying pKa used in PLL/siRNA-pGFP-OSA complexes also caused effective gene silencing. The pGFP in the PLL/siRNA-pGFP complexes successfully expressed GFP protein without interfering with the siRNA. In conclusion, this study demonstrates that long pDNA helps effectively form nanosized siRNA particles and that OSA enhances specific gene silencing. In a single nucleic acid carrier formulation, co-delivery of siRNA and pDNA is feasible to maximize therapeutic effects or to include therapeutic or diagnostic functionalities. © 2011 Elsevier Ltd.

Loading Advanced Therapeutics Research Center collaborators
Loading Advanced Therapeutics Research Center collaborators