Papers by Author: Mi Kyong Yoo

Abstract: To improve the specific accumulation in tumor sites and aqueous solubility of atRA, the core-shell type of folate-PEG-g-PEI/atRA nanoparticles were prepared by complexation between cationic PEI segments in the copolymers and anionic charged atRA, and then characterized by 1HNMR, ELS, XRD, and TEM. In vitro atRA release from the nanoparticles was investigated as a function of drug content in sink condition. Cytotocicity of atRA against HepG2, KB cell lines were also evaluated by MTT assay. The lower the drug content, the faster atRA release. atRA incorporated in folate-PEG-g-PEI/atRA nanoparticles showed much higher cytotoxic effect compared with atRA itself.

Abstract: The aim of this study is to prepare mucoadhesive chitosan microspheres for protein drug to deliver to intestine through oral administration. The thiolated Eudragit was synthesized by reaction between L-cysteine hydrochloride and Eudragit® L-100. About 8 mol-% of cysteine was introduced to the Eudragit-cysteine conjugate. The conjugate was used to coat bovine serum albumin (BSA)-loaded chitosan microspheres. The average particle sizes of BSA-loaded thiolated Eudragit-coated chitsoan microspheres (TECMs) were 4.06±0.74 .m and the uniform sizedistribution was shown. The in vitro release of BSA from BSA-loaded TECMs was pH-dependent. Our results indicated that thiolated Eudragit might be a good candidate as a coating material for oral delivery of protein drug owing to mucoadhesive and pH-sensitive properties.

Abstract: Thiolated polymers have been studied by many researchers because of the mucoadhesive properties of thiol group. Alginate is a natural and biocompatible polymer that has been widely used in drug delivery. In this study, thiolated chitosan microspheres (TCMs) were prepared by ionic gelation process with tripolyphosphate and then, the bovine growth hormone (BGH) was loaded as a model drug. Finally, the BGH-loaded TCMs (BTCMs) were coated with alginate to improve the stability in gastrointestinal (GI) track. The alginate-coated BTCMs (ABTCMs) were observed as spherical shapes. The average particle sizes of ABTCMs were 6.97±0.55 -m and the sizedistribution was shown uniformly. Release of BGH from ABTCMs was decreased by coating with alginate and increased rapidly with the change in medium pH from 1.2 to 7.4. Results indicate that the ABTCMs have a potential as a drug carrier for oral drug delivery.

Abstract: The objective of this study is to develop a new type of cationic nanoparticles for the intracellular drug delivery to breast cancer. Poly(ester amine) (PEA) based on polyethylenimine and polycaprolactone was synthesized to make cationic PEA nanoparticles for all-trans retinoic acid (RA). In the 1H-NMR study, the proton signals of RA appeared in the spectrum of RA-loaded PEA nanoparticles in CDCL3, whereas they disappeared in D2O, suggesting that hydrophobic inner-core with hydrophilic outer-shell formed in water. RA release was faster at lower drug content and RA was released over a period of 20 days. RA-loaded PEA nanoparticles showed enhanced cytotoxicity compared with RA itself, whereas nanoparticles of PEA themselves did not show it. These results indicated that the cationic PEA provided an efficient intracellular delivery of RA.

Abstract: The ideal dermal matrix should be able to provide the right physical and biological environment to ensure homogenous cell and extracellular matrix (ECM) distribution, as well as the biocompatible interactions with tissue. Chitosan (CS)/poloxamer semi-interpenetrating polymer networks (SIPNs) was prepared by crosslinking of poloxamer macromer in the presence of CS in order to improve its mechanical property required in skin tissue engineering application. Furthermore, we also prepared CS/poloxamer SIPNs with ShebaTM, human acellular dermis, to overcome a low biocompatibility of the CS/poloxamer SIPNs. The CS/poloxamer SIPNs/ShebaTM showed remarkably highly cell attachment and viability in the two-dimensional (2D) culture and similar cell morphology on the CS/poloxamer SIPNs/ShebaTM compared with on tissue culturing polystylene (TCPS) as a positive control. These results suggest that CS/poloxamer SIPNs containing ShebaTM have good possibility for artificial skin system application.

Abstract: In this study, novel polycaprolactone/hydroxyapatite (PCL/HA) scaffolds were prepared to increase mechanical properties and degradation of PCL/HA ones for bone tissue engineering. PCL macromers were synthesized through the reaction of PCL diol (Mn: 530, 1250, and 2000) and PCL triol (Mn: 900) with acryloyl chloride and confirmed using nuclear magnetic resonance spectrometer (NMR) and fourier transform infrared (FTIR). The PCL/HA scaffolds were prepared by cross-linking of PCL macromer in the presence of HA by UV treatment and freeze drying methods. Mechanical property and porosity as well as degradability of the PCL/HA scaffolds were also investigated. PCL/HA scaffolds showed faster degradation and higher compressive modulus than those of PCL itself due to their low crystallinity and modification of terminal groups. The pore morphology and pore sizes of the PCL/HA scaffold were checked by scanning electron microscope (SEM). Cell cytotoxicity and proliferation of MG-63 osteoblast cultured onto the PCL/HA scaffold was assessed by lactate dehydrogenase (LDH) assay and Alamar blue assay, respectively. The novel PCL/HA scaffold appears to be suitable for bone substitutes.