Bo Keun Lee - Academia.edu (original) (raw)

Papers by Bo Keun Lee

Research on developing functional polymeric scaffolds has been conducted in diverse tissue engine... more Research on developing functional polymeric scaffolds has been conducted in diverse tissue engineering applications for a few decades. The functionalized polymeric scaffolding system that can modulate the host’s microenvironment may guide fully autologous tissue regeneration in situ through host stem cell recruitment. Numerous biomaterial-based approaches have been reported as a potential therapeutic approach for in situ tissue regeneration. In this chapter, a comprehensive overview of the state-of-the-art and rapidly developing functionalized polymeric scaffolds has been outlined.

Polymer, 2018

Temperature-responsive hydrogels have been widely developed for biomedical applications. In this ... more Temperature-responsive hydrogels have been widely developed for biomedical applications. In this study, 4-benzyloxy-ε-caprolactone (CL-OBn) was synthesized and the subsequent ring opening polymerization (ROP) of ε-caprolactone (CL) and CL-OBn monomers was performed by using the hydroxyl group of methoxy polyethylene glycol (MPEG) in the presence of HCl$Et 2 O as a monomer activator. MPEG-b-poly (ε-caprolactone) (MC) with benzyl pendant groups (MC-OBn) was successfully obtained in almost quantitative yield and the segment ratios and molecular weights were close to the theoretical values. Deprotection of the benzyl pendant groups successfully provided MC with hydroxyl pendant groups (MC-OH). Suspensions of MC-OBn and MC-OH exhibited distinct sol-to-gel phase transitions as a function of the temperature. The sol-to-gel phase transition of the MC-OBn and MC-OH diblock copolymers depended on the type (benzyl or hydroxyl) and amount of pendant groups in the diblock copolymer structure. The pendant group on the MC-OBn and MC-OH diblock copolymers either stabilized and/or destabilized hydrophobic aggregation between the MC segments. The hydrophobic aggregation was confirmed by the detection of crystallinity in the MC-OBn and MC-OH diblock copolymer suspensions. In conclusion, MC-OBn and MC-OH diblock copolymers were successfully prepared and served as temperature-responsive hydrogels.

Tissue Engineering and Regenerative Medicine, 2018

BACKGROUND: To develop the biodegradability and thermoresponsive hydrogel, in this work we design... more BACKGROUND: To develop the biodegradability and thermoresponsive hydrogel, in this work we designed a pendantfunctionalized, thermoresponsive, amphiphilic block copolymer. METHODS: Methoxy poly(ethylene glycol) (MPEG)-b-[poly(e-caprolactone)-ran-poly(e-caprolactone-3-one)-ran-polylactic acid] (MCL) and (MPEG-b-[PCL-ran-POD-ran-PLA]) [MCL-(CO)] block copolymers were prepared by ringopening polymerization of e-caprolactone, OD and lactide monomers. The subsequent derivatization of MCL-(CO) provided MPEG-b-[PCL-ran-poly(e-caprolactone-3-COOH)-ran-PLA] [MCL-(COOH)] with COOH pendant groups and MPEG-b-[PCL-ran-poly(e-caprolactone-3-NH 2)-ran-PLA] [MCL-(NH 2)] with NH 2 pendant groups. RESULTS: The measured segment ratios of MCL-(CO), MCL-(COOH), and MCL-(NH 2) agreed well with the target ratios. The abundances of the COOH and NH 2 groups in the MCL-(COOH) and MCL-(NH 2) copolymers were determined by 1 Hand 13 C-nuclear magnetic resonance spectroscopy, and agreed well with the target abundances. MCL-(CO), MCL-(COOH), and MCL-(NH 2) formed homogeneous, white, opaque emulsions at room temperature. Rheological analysis of the block copolymer suspensions indicated a solution-to-hydrogel phase transition as a function of temperature. The solution-to-hydrogel phase transitions and the biodegradation of MCL-(CO), MCL-(COOH), and MCL-(NH 2) were affected by varying the type (ketone, COOH, or NH 2) and abundance of the pendant groups. CONCLUSION: MCL-(CO), MCL-(COOH), and MCL-(NH 2) with ketone, COOH, and NH 2 pendant groups showed solution-to-hydrogel phase transitions and biodegradation behaviors that depended on both the type and number of pendant groups.

Biomaterials, 2018

To the best of our knowledge, no studies have yet examined the electrostatic interaction of polye... more To the best of our knowledge, no studies have yet examined the electrostatic interaction of polyelectrolytes with electrolyte drugs for the treatment of rheumatoid arthritis (RA). Here, an injectable, electrostatically interacting drug depot is described. We prepared methoxy polyethylene glycol-b-poly(ε-caprolactone)-ran-poly(l-lactic acid) (MC) diblock copolymers with a carboxylic acid group (MC-C) at the pendant position. MC-C was polyelectrolytes that exhibited negative zeta potentials. Sulfasalazine [Sul(-)] and minocycline [Min(+)], electrolyte RA drugs, exhibited negative and positive zeta potentials, respectively. The electrolyte RA drugs were loaded into the polyelectrolyte MC-C solution to prepare injectable, electrostatically interacting depot formulations. The formulation with an attractive electrostatic interaction [Min(+)-MC-C] exhibited gradual release of Min(+) from the MC-C depot over an extended period and suppressed the growth of inflammatory RAW 264.7 cells withou...

Polymers, 2017

Recently, several thermogelling materials have been developed for biomedical applications. In thi... more Recently, several thermogelling materials have been developed for biomedical applications. In this study, we prepared methoxy polyethylene glycol (MPEG)-b-(poly(ε-caprolactone)-ran-poly(2chloride-ε-caprolactone) (PCL-ran-PfCL)) (MP-Cl) diblock copolymers at room temperature via the ring-opening polymerization of caprolactone (CL) and 2-chloride-ε-caprolactone (fCL) monomers, using the terminal alcohol of MPEG as the initiator in the presence of HCl. MPEG-b-(poly(εcaprolactone)-ran-poly(2-azide-ε-caprolactone) (PCL-ran-PCL-N 3)) (MP-N 3) was prepared by the reaction of MP-Cl with sodium azide. MPEG-b-(poly(ε-caprolactone)-ran-poly(2-amine-ε-caprolactone) (PCL-ran-PCL-NH 2)) (MP-NH 2) was subsequently prepared by Staudinger reaction. MP-Cl and MP-N 3 showed negative zeta potentials, but MP-NH 2 had a positive zeta potential. MP-Cl, MP-N 3 , and MP-NH 2 solutions formed opaque emulsions at room temperature. The solutions exhibited a solution-to-hydrogel phase transition as a function of the temperature and were affected by variation of the chloride, azide, and the amine pendant group, as well as the amount of pendant groups present in their structure. Additionally, the phase transition of MP-Cl, MP-N 3 , and MP-NH 2 copolymers was altered by pendant groups. The solution-to-hydrogel phase transition was adjusted by tailoring the crystallinity and hydrophobicity of the copolymers in aqueous solutions. Collectively, MP-Cl, MP-N 3 , and MP-NH 2 with various pendant-group contents in the PCL segment showed a solution-to-hydrogel phase transition that depended on both the type of pendant groups and their content.

J. Mater. Chem. B, 2015

To develop an appropriate drug carrier for drug delivery systems, we prepared random poly(lactide... more To develop an appropriate drug carrier for drug delivery systems, we prepared random poly(lactide-co-glycolide-co-ε-caprolactone) (PLGC) copolymers in comparison to commercial poly(lactic acid-co-glycolic acid) (PLGA) grades.

Scientific reports, Jan 26, 2017

This is the first report on the development of a covalently bone morphogenetic protein-2 (BMP2)-i... more This is the first report on the development of a covalently bone morphogenetic protein-2 (BMP2)-immobilized hydrogel that is suitable for osteogenic differentiation of human periodontal ligament stem cells (hPLSCs). O-propargyl-tyrosine (OpgY) was site-specifically incorporated into BMP2 to prepare BMP2-OpgY with an alkyne group. The engineered BMP2-OpgY exhibited osteogenic characteristics after in vitro osteogenic differentiation of hPLSCs, indicating the osteogenic ability of BMP2-OpgY. A methoxy polyethylene glycol-(polycaprolactone-(N3)) block copolymer (MC-N3) was prepared as an injectable in situ-forming hydrogel. BMP2 covalently immobilized on an MC hydrogel (MC-BMP2) was prepared quantitatively by a simple biorthogonal reaction between alkyne groups on BMP2-OpgY and azide groups on MC-N3 via a Cu(I)-catalyzed click reaction. The hPLSCs-loaded MC-BMP2 formed a hydrogel almost immediately upon injection into animals. In vivo osteogenic differentiation of hPLSCs in the MC-BMP2...

International journal of molecular sciences, Jan 21, 2017

To develop a biodegradable polymer possessing elasticity and flexibility, we synthesized MPEG-b-(... more To develop a biodegradable polymer possessing elasticity and flexibility, we synthesized MPEG-b-(PCL-co-PLA) copolymers (PCxLyA), which display specific rates of flexibility and elasticity. We synthesize the PCxLyA copolymers by ring-opening polymerization of ε-caprolactone and l-lactide. PCxLyA copolymers of various compositions were synthesized with 500,000 molecular weight. The PCxLyA copolymers mechanical properties were dependent on the mole ratio of the ε-caprolactone and l-lactide components. Cyclic tensile tests were carried out to investigate the resistance to creep of PCxLyA specimens after up to 20 deformation cycles to 50% elongation. After in vivo implantation, the PCxLyA implants exhibited biocompatibility, and gradually biodegraded over an eight-week experimental period. Immunohistochemical characterization showed that the PCxLyA implants provoked in vivo inflammation, which gradually decreased over time. The copolymer was used as a drug carrier for locally implantabl...

Macromolecular bioscience, Aug 14, 2016

In this study, human dental pulp stem cells (hDPSCs) are examined as a cellular source for bone t... more In this study, human dental pulp stem cells (hDPSCs) are examined as a cellular source for bone tissue engineering using an in vivo-forming hydrogel. The hDPSCs are easily harvested in large quantities from extracted teeth. The stemness of harvested hDPSCs indicates their relative tolerance to ex vivo manipulation in culture. The in vitro osteogenic differentiation of hDPSCs is characterized using Alizarin Red S (ARS), von Kossa (VK), and alkaline phosphatase (ALP) staining. The solution of hDPSCs and a methoxy polyethylene glycol-polycaprolactone block copolymer (PC) is easily prepared by simple mixing at room temperature and in no more than 10 s it forms in vivo hydrogels after subcutaneous injection into rats. In vivo osteogenic differentiation of hDPSCs in the in vivo-forming hydrogel is confirmed by micro-computed tomography (CT), histological staining, and gene expression. Micro-CT analysis shows evidence of significant tissue-engineered bone formation in hDPSCs-loaded hydroge...

Journal of Polymer Research, 2014

To compare methoxy poly (ethylene glycol) (MPEG)-b-poly (ε-caprolactone) (M 7 C 10 L 0) and MPEG-... more To compare methoxy poly (ethylene glycol) (MPEG)-b-poly (ε-caprolactone) (M 7 C 10 L 0) and MPEG-bpoly (L-lactide) (M 7 C 0 L 10), we performed block copolymerization of ε-caprolactone (CL) and L-lactide (LA) to synthesize block copolymers composed of MPEG-b-poly (εcaprolactone-co-L-lactide) (M x C y L z). The obtained M x C y L z , M 7 C 10 L 0 , and M 7 C 0 L 10 had molecular weights close to the theoretical values calculated from the CL and/or LA to MPEG molar ratios and exhibited monomodal gel permeation chromatography (GPC) curves. The micellar characterization of M x C y L z block copolymers in an aqueous phase was carried out by using NMR, dynamic light scattering (DLS), and fluorescence techniques. The diameters of micelles, measured by DLS, were 30-370 nm. The critical micelle concentration (CMC) and partition equilibrium constant (K v) depended on the block lengths and compositions of block copolymers. The degradation of the M x C y L z block copolymers mainly depends on both the length of hydrophilic MPEG segments and the proportion of the CL and LA in the hydrophobic segments present in their structure. We confirmed that M x C y L z block copolymers formed biodegradable micelles suitable for biomedical applications.

Biomaterials research, 2015

Hydrolyzed polyacrylonitrile (HPAN) has attracted much attention as a hydrogel for a broad range ... more Hydrolyzed polyacrylonitrile (HPAN) has attracted much attention as a hydrogel for a broad range of biomedical applications. Therefore, in this study, we prepared HPAN derivatives with controllable compositions by the radical polymerization of acrylonitrile (AN), methacrylic acid (MAA) and N-isopropylacrylamide (NIPAM) monomers. The prepared poly(AN-co-MAA-co-NIPAM) copolymers had different ratios of AN, MAA, and NIPAM and molecular weights ranging from 2000 to 50,000. The copolymers were prepared as films to examine their properties. The prepared copolymer films showed different solubilities, contact angles, and swelling ratios. The properties of the copolymer films were affected by the hydrophobic PAN segments and the hydrophilic PMAA or PNIPAM segments. Thus, we conclude that introducing PMAA and PNIPAM segments with different ratios and lengths into PAN segments could represent a method of controlling the hydrogel properties of copolymers.