Korean Chemical Engineering Research

The Korean Institute of Chemical Engineers (한국화학공학회)
권호 표지

Synthesis of pH-Sensitive Hydrogel Nanoparticles in Supercritical Carbon Dioxide

초임계 이산화탄소를 이용한 pH 감응성 하이드로젤 입자의 합성

  • Received : 2009.04.03
  • Accepted : 2009.07.06
  • Published : 2009.08.31
Download PDF
⟨ Previous Next ⟩

Abstract

Recently, new methods to synthesize and process polymers without toxic organic solvents are needed in order to solve environmental problems. The use of supercritical carbon dioxide as a solvent for the polymer synthesis is attractive since it is non-toxic, non-flammable, naturally abundant, and the product may be easily separated from the solvent. In this study, we developed the method using super critical $CO_2$ to prepare P(MAA-co-EGMA) hydrogel nanoparticles as an intelligent drug delivery carrier. The effects of concentrations of PtBuMA-PEO as a dispersion stabilizer and AIBN as an initiator on the particle synthesis were investigated. When PtBuMA-PEO concentration increased, the particle size decreased. However, there was no significant difference in the particle size according to the AIBN concentration. There was a drastic change of the equilibrium weight swelling ratio of P(MAA-co-EGMA) hydrogel nanoparticles at a pH of around 5, which is the $pK_a$ of PMAA. At a pH below 5, the hydrogels were in a relatively collapsed state but at a pH higher than 5, the hydrogels swelled to a high degree. In release experiments using Rh-B as a model solute, the P(MAA-co-EGMA) hydrogel nanoparticles showed a pH-sensitive release behavior. At low pH(pH 4.0) a small amount of Rh-B was released while at high pH(pH 6.0) a relatively large amount of Rh-B was released from the hydrogels.

최근 환경문제가 크게 대두됨에 따라 고분자 합성과 가공 공정에서도 유기용매를 사용하지 않는 새로운 친환경적 공정의 개발이 요구되고 있다. 초임계 이산화탄소는 고분자 합성에서 용매로 사용될 경우, 기존의 유기용매와 비교하여 불연성이고 독성이 없으며 생성물과의 분리가 용이하다는 장점을 가지고 있다. 본 연구에서는 초임계 이산화탄소를 이용하여 의약학 및 화장품 분야에서 지능형 약물전달체로 사용할 수 있는 pH 감응형 하이드로젤인 P(MAA-co-EGMA) 하이드로젤을 수 백 nm 수준의 입자 형태로 합성하는 방법을 개발하였다. 그리고 중합과정에서 사용하는 분산안정제인 PtBuMA-PEO와 중합개시제인 AIBN이 하이드로젤 입자의 합성에 미치는 영향을 살펴보았다. 입자의 합성에서 PtBuMA-PEO의 함량이 증가할수록 입자 크기는 감소하였으나 AIBN의 함량에 따른 입자 크기의 변화는 관찰할 수 없었다. 합성된 P(MAA-co-EGMA) 하이드로젤 입자의 pH에 따른 팽윤 실험결과, PMAA의 $pK_a$인 pH 5를 전후하여 급격한 하이드로젤의 평형 질량팽윤비의 변화를 관찰할 수 있었다. 즉, pH 5보다 낮은 pH에서는 낮은 팽윤비를, 반면에 pH 5보다 높은 pH에서는 매우 높은 팽윤비를 나타내었다. 그리고 Rh-B를 이용한 방출실험에서는 높은 pH에서는 다량의 Rh-B가 하이드로젤 입자로부터 방출되었으나 낮은 pH에서는 Rh-B가 거의 방출되지 않는 pH에 따른 선택적 방출 특성을 나타내었다.

Keywords

Acknowledgement

Supported by : 홍익대학교, 지식경제부

References

  1. Clifford, T., Fundamentals of Supercritical Fluids, Oxford University Press, Oxford(1999)
  2. Lee, Y. W., 'Design of Particles using Supercritical Fluids,' HWAHAK KONGHAK, 41(6), 679-688(2003)
  3. Shiho, H. and DeSimone, J. M., "Preparation of Micron-size Polystyrene Particles in Supercritical Carbon Dioxide," J. Polym. Sci. A: Poly. Chem., 37, 2429-2437(1999) https://doi.org/10.1002/(SICI)1099-0518(19990715)37:14<2429::AID-POLA17>3.0.CO;2-B
  4. Kendall, J. L., Canelas, D. A., Young, J. L. and DeSimene, J. M., "Polymerizations in Supercritical Carbon Dioxide," Chem. Rev., 99, 543-563(1999) https://doi.org/10.1021/cr9700336
  5. Watkins, J. J. and McCarthy, T. J., "Polymerization in Supercritical Fluid-swollen Polymers: A New Route to Polymer Blends," Macromolecules, 27, 4845-4847(1994) https://doi.org/10.1021/ma00095a031
  6. Watkins, J. J. and McCarthy, T. J., "Polymerization of Styrene in Supercritical $CO_2$-swollen Poly(chlorotrifluoroehylene)," Macromolecules, 28, 4067-4074(1995) https://doi.org/10.1021/ma00116a004
  7. Kang, S. R. and Ju, C. S., 'Preparation of Porous Polymer Monoliths in Supercritical Carbon Dioxide,' Korean Chem. Eng. Res., 43(1), 21-26(2005)
  8. Kanjickal, D., Lopina, S., Evancho-Chapman, M. M., Schmidt, S., Donovan. D. and Springhetti, S. 'Polymeric Sustained Local Drug Delivery System for The Prevention of Vascular Intimal Hyperplasia,' J. Biomed. Mater. Res., 68A(3), 489-495(2003) https://doi.org/10.1002/jbm.a.20084
  9. Korsmeyer, R. W., Lustig, S. R. and Peppas, N. A., "Solute and Penetrant Diffusion in Swellable Polymers. I. Mathematical Modeling," J. Polym. Sci. B: Polym. Phys., 24, 395-408(1986) https://doi.org/10.1002/polb.1986.090240214
  10. Brazel, C. S. and Peppas, N. A., "Mechanisms of Solute and Drug Transport in Relaxing, Swellable, Hydrophilic Glassy Polymers," Polymer, 40(12), 3383-3398(1999) https://doi.org/10.1016/S0032-3861(98)00546-1
  11. Byun, Y. R., Chang, H. N. and Kim, Y. H., 'Controlled Drug Release by Polymeric Matrix Formulation by Coating and Swelling,' HWAHAK KONGHAK, 27(4), 561-567(1989)
  12. Qiu, Y. and Park, K., "Environment-sensitive Hydrogels for Drug Delivery," Adv. Drug Deliv. Rev., 53, 321-339(2001) https://doi.org/10.1016/S0169-409X(01)00203-4
  13. Lowman, A. M., Peppas, N. A. and Mathiowitz, E., Encyclopedia of Controlled Drug Delivery, Vol.1, Wiley, New York, 397-418(1999)
  14. Brazel, C. S. and Peppas, N. A., "Dimensionless Analysis of Swelling of Hydrophilic Glassy Polymers with Subsequent Drug Release from Relaxing Structures," Biomaterials, 20(8), 721-732 (1999) https://doi.org/10.1016/S0142-9612(98)00215-4
  15. You, J. O., Park, S. B., Park, H. Y., Haam, S. J., Kim, J. H. and Kim, W. S., 'Drug Release Characterization and Proparation of Ca-alginate Microparticle Drug Carrier using Membrane Emulsification Method,' HWAHAK KONGHAK, 37(5), 789-794(1999)
  16. Foss, A. C., Goto, T., Morishita, M. and Peppas, N. A., "Development of Acrylic-Based Copolymers for Oral Insulin Delivery," Eur. J. Pharm. Biopharm., 57(2), 163-169(2004) https://doi.org/10.1016/S0939-6411(03)00145-0
  17. Kim, B., 'pH-Sensitive Dynamic Swelling Behavior of Glucosecontaining Anionic Hydrogels,' Korean Chem. Eng. Res., 43(2), 299-304(2005)
  18. Peppas, N. A., Keys, K. B., Torres-Lugo, M. and Lowman, A. M., "Poly(ethylene glycol)-containing Hydrogels in Drug Delivery," J. Control. Release, 62(1-2), 81-87(1999) https://doi.org/10.1016/S0168-3659(99)00027-9
  19. Torres-Lugo, M. and Peppas, N. A., "Molecular Design and in vitro Studies of Novel pH-Sensitive Hydrogels for the Oral Delivery of Calcitonin," Macromolecules, 32(20), 6646-6651(1999) https://doi.org/10.1021/ma990541c
  20. Kim, B. and Peppas, N. A., "In vitro Release Behavior and Stability of Insulin in Complexation Hydrogels as Oral Drug Delivery Carriers," Int. J. Pharm., 266, 29-27(2003) https://doi.org/10.1016/S0378-5173(03)00378-8
  21. Shin, Y., Kim, K. S. and Kim, B., 'Loading Behavior of pH-Responsive P(MAA-co-EGMA) Hydrogel Microparticles for Intelligent Drug Delivery Applications,' Polym.(Korea), 32(5), 421-426(2008)