Novel Poly(Ethylene Glycol) Hydrogels from Silylated PEGs

Abstract

Poly(ethylene glycol) (PEG) and Pluronic® F-127 (PF127) were silylated with 3-isocyanatopropyltriethoxysilane to synthesize PEG-based hydrogels by sol-gel transition of silane. Silanes on different PEG molecules formed covalent bonds by acid-catalyzed hydrolysis and condensation. Addition of monosilylated PEG resulted in the incorporation of dangling PEG chains, which increased the swelling ratio of the hydrogels slightly. PEG hydrogels in microspheres were prepared by emulsifying aqueous silylated PEG solution in oil followed by curing. Crosslinked PF127 hydrogels displayed inverse thermosensitivity. The previously swollen PF127 hydrogels shrank immediately at high temperatures (e.g., 6000), but the welling of shrunken hydrogels at low temperature (e.g., 5°C) took much longer. The release of fluorescein from the PF127 hydrogels was dependent on the temperature of the environment. The release of fluorescein from the PF127 hydrogels was faster at 45°C than at 5°C. This was most likely due to shrinking of the hydrogels leading to squeezing of the incorporated fluorescein. The ability of hydrogel formation by simple sol-gel transition of silylated PEG can be used to prepare new drug delivery systems and biomaterials.

Get full access to this article

View all access options for this article.

References

1. Kofinas, P. , Athanassiou, V. , and Merrill, E.W. : Hydrogels prepared by electron irradiation of poly(ethylene oxide) in water solution: unexpected dependence of cross-link density and protein diffusion coefficients on initial PEO molecular weight, Biomaterials, 17:1547-1550, 1996.

2. Lopina, S.T. , Wu, G. , Merrill, E.W. , and Griffith-Cima, L. : Hepatocyte culture on carbohydrate-modified star polyethylene oxide hydrogels, Biomaterials, 17:559-569, 1996.

3. Gerard, R.L. and Sefton, M.V: Immobilization of poly(ethylene glycol) onto a poly(vinyl alcohol) hydrogen. 1. Synthesis and characterization, Macromolecules, 24:6065-6072, 1991.

4. andreopoulos, F.M. , Deible, C.R. , Stauffer, M.T. , Webber, S.G. , Wagner, W.R. , Beckman, E.J. , and Russell, A.J. : Photoscissable hydrogel synthesis via rapid photopolymerization of novel PEG-based polymers in the absence of photoinitiators, J. Am. Chem. Soc., 118:6235-6240, 1996.

5. Sawhney, A.S. , Pathak, C.P. , and Hubbell, J.A. : Bioerodible hydrogels based on photopolymerized polyethylene glycol)-co-poly(α-hydroxy acid) diacrylate macromers, Macromolecules, 26:581-587, 1993.

6. Cheradame, H. , Desbat, F. , Mercier-Niddam, P. , and Boileau, S. : Characterization of new sonically conducting PEO-based networks by diffusion, elasticity modulus and ionic conductivity measurements, Mat. Res. Soc. Symp. Proc., 293:123-134, 1993.

7. Lestel, L. , Cheradame, H. , and Boileau, S. : Crosslinking of polymer networks by hydrosilylation and related side reactions, Polymer, 31:1154-1158, 1990.

8. Lestel, L. , Guegan, P. , Boileau, S. , Cheradame, H. , and Laupretre, E: Influence of the chemical nature of cross-links on the local dynamics of bulk polyethylene glycol) networks as studied by carbon-13 NMR at temperature well above the glass-transition temperature, Macromolecules, 25:6024-6028,1992.

9. Cihlar, J. : Hydrolysis and polycondensation of ethyl silicates. 1. Effects of pH and catalyst on the hydrolysis and polycondensation of tetraethoxysilane (TEOS), Colloids Surf, A, 70:239-251, 1993.

10.

10. Chen-Chow, P-C. and Frank, S.G. : In vitro release of lidocaine from Pluronic F-127 gels, Int. J. Pharm., 8:89-99, 1981.

11.

11. Attwood, D. , Collett, J.H. , and Tait, C.J. : The micellar properties of the poly(oxyethylene)-poly(oxypropylene) copolymer Pluronic F127 in water and electrolyte solution, Int. J. Pharm., 26:25-33, 1985.

12.

12. Katakam, M. , Ravis, W.R. , and Banga, A.K. : Controlled release of human growth hormone in rats following parenteral administration of poloxamer gels, J. Controlled Rel., 49:21-26, 1997.

13.

13. Linse, P. and Malmsten, M. : Temperature-dependent micellization in aqueous block copolymer solution, Macromolecules, 25:5434-5439, 1992.

14.

14. Miller, S.C. and Drabik, B.R. : Rheological properties of poloxamer vehicles, Int. J. Pharm., 18:269-276, 1984.

15.

15. Rassing, J. and Attwood, D. : Ultrasonic velocity and light-scattering studies on the polyoxyethylene-polyoxypropylene copolymer Pluronic F127 in aqueous solution, Int. J. Pharm., 13:47-55, 1983.

16.

16. Yamamoto, T. , Inada, H. , Isozaki, S. , and M. Okawara: Functionalization and hydridization of polyvinyl chloride) III. transformation of polyvinyl chloride) into water-crosslinkable polymer, Reactive Polym., 22:139-143, 1994.

17.

17. Kazmierski, K. , Chojnowski, J. , and McVie, J. : The acid-catalyzed condensation of methyl substituted model oligosiloxanes bearing silanol and ethoxysilane functions, Eur. Polym. J., 30:515-527, 1994.

18.

18. Nishiyama, N. and Horie, K. : Hydrolysis and condensation mechanisms of a silane coupling agent studied by 13C and 29Si NMR, J. Appl. Polym. Sci., 34:1619-1630, 1987.