| 학회 | 한국고분자학회 |
| 학술대회 | 2005년 봄 (04/14 ~ 04/15, 전경련회관) |
| 권호 | 30권 1호, p.672 |
| 발표분야 | 의료용 고분자 부문위원회 |
| 제목 | Characterizations of Thermosensitive Nanoparticles using Poly(N-isopropylacrylamide-b-ε-caprolactone) and Poly(ethylene glycol-b-ε-caprolactone) |
| 초록 | INTRODUCTION Polymeric amphiphiles, containing hydrophilic and hydrophobic components, have been extensively studied in biotechnology and pharmaceutical fields due to their unique properties of micelle or micelle-like self-aggregate formation in aqueous milieu [1]. Among various hydrophilic and hydrophobic segments, hydrophilic polymers of PNIPAAm and PEG, and hydrophobic PCL have unique characteristics such as thermosensitivity, biocompatibility, and biodegradation. PNIPAAm is a well-known water-soluble thermosensitive polymer showing reversible hydrated extended coil to globule transition by increasing temperature over the lower critical solution temperature (LCST)[2]. PEG, another hydrophilic block, has been frequently employed for preparation of polymeric amphiphiles due to its unique biocompatibility and solubility. PCL, as the hydrophobic segment, is well known biodegradable hydrophobic polymer [3]. In this study, the well-defined PNIPAAm-PCL and PEG-PCL block copolymers were synthesized by ring-opening polymerization of e-caprolactone using mPEG-OH and PNIPAAm-OH, prepared by telomerization of NIPAAm, as initiators. Thermosensitive nanaparticles according to various ratios of PNIPAAm-PCL and PEG-PCL were prepared by a dialysis method. And then, we investigated physicochemical properties of the formed thermosensitive nanoparticles by 1H NMR, DSC, DLS and fluorescence spectroscopy. EXPERIMENTAL METHOD Synthesis and characterization of PNIPAAm-OH, PNIPAAm-PCL and PEG-PCL diblock copolymer The PNIPAAm-OH was synthesized in methanol by temomerization of NIPAAm using ME as a chain transfer agent. PNIPAAm-PCL and PEG-PCL diblock copolymer were synthesized by ring opening polymerization of e-caprolactone mPEG-OH and PNIPAAm-OH as initiators with trace amount of stannous octate (SnOct) as a catalyst. The polymerization was performed at 140℃ for 24h in xylene. After reaction, the copolymers were dissolved in dichloromethane and precipitated in an excess amount of diethyl ether and dried in vacuo for 48h. The synthesis of PNIPAAm-PCL and PEG-PCL diblock copolymers were confirmed by 1H-NMR and GPC. Preparation and characterization of thermosensitive nanoparticles Thermosensitive nanaparticles according to various ratios of PNIPAAm-PCL and PEG-PCL were prepared by a solvent evaporation method. The particle sizes and size distribution, morphology of nanoparticles, aggregation behavior in aqueous environment, and microscopic physicochemical properties of the aggregates were investigated by DLS, AFM, 1H NMR, and fluorescence spectroscopy, respectively. RESULT AND DISCUSSION The 1H NMR spectra and shifted chromatogram to higher MW range obtained by GPC of the copolymers clearly reveled that the block copolymers were successfully synthesized. The formed self-aggregates, with different compositions, showed different physicochemical properties such as particle size, LCST . The thermosensitive properties were critically affected by compositions of PNIPAAm block. The introduction of PNIPAAm-PCL into the self-aggregates endowed the unique characters, originated from thermosensitive PNIPAAm block, such as LCST, decrease of particle size by increasing temperature, and micropolarity changes. The particle size and CAC decreased with increment of PEG-PCL component due to increased PCL content and reduced bulky PNIPAAm block. The obtained aggregation numbers of PCL blocks in a hydrophobic microdomain, measured by fluorescence quenching method, were in the range of 7 ~ 14 with increasing the values by increasing PEG-PCL content. The results revealed that M1, containing bulky hydrophilic block, required relatively smaller number of PCL block to form a hydrophobic microdomain than M5. REFERENCES 1. Kataoka K. et al. ADDR 2001, 47, 113 2. Feil H. et al. Macromolecules 1993, 26, 2496 3. Savic R. et al. Science 2003, 300, 615 |
| 저자 | 최창용1, 채수영1, 공병기1, 장미경1, 권중근2, 조종수3, 나재운1 |
| 소속 | 1순천대, 2조선이공대, 3서울대 |
| 키워드 | Thermosensitive; Nanopartkcle; Drug delivery |
