Bioresorbable and nonresorbable macroporous thermosensitive hydrogels prepared by cryopolymerization. Role of the cross-linking agent.
Macroporous poly( N-isopropylacrylamide) (pNIPA) gels (so-called cryogels), cross-linked with different bis-acrylic compounds, N,N'-methylenebisacrylamide (MBAAm) and dimethacrylate-tyrosine-lysine-tyrosine (DMTLT), were prepared through free-radical polymerization at subzero temperature in dioxane/water media. DMTLT is a hydrolytically degradable cross-linker with relatively hydrophobic character. The effects of different synthesis conditions, namely the concentration of monomers, the cross-linker, and the initiator in the reaction mixture, on the structure of the pNIPA-cryogels have been studied. The equilibrium swelling ratio of the DMTLT cross-linked pNIPA cryogels at temperatures below lower critical solution temperature (LCST) of pNIPA, was over ten times higher than that of the gels synthesized at room temperature from the same feed composition. The MBAAm cross-linked pNIPA cryogels synthesized in water exhibited the highest equilibrium swelling and the fastest response. The critical transition temperature, T c, was lower ( T c approximately 31 degrees C) for pNIPA-cryogels synthesized in dioxane/water media or cross-linked with DMTLT as compared to MBAAm cross-linked pNIPA cryogels synthesized in water (T c approximately 33 degrees C). Scanning electron microscopy (SEM) revealed different porous structure and pore surface morphology depending on the cross-linker (MBAAm or DMTLT) and the solvent (water or dioxane/water) used. Gels and cryogels were also characterized by SAXS, showing that the nanostructure of the samples is related to swelling.
Perez
Paloma
P
Instituto de Ciencia y Tecnología de Polímeros, CSIC, C/Juan de la Cierva 3, 28006 Madrid, Spain.
Plieva
Fatima
F
Gallardo
Alberto
A
San Roman
Julio
J
Aguilar
Maria Rosa
MR
Morfin
Isabelle
I
Ehrburger-Dolle
Françoise
F
Bley
Francoise
F
Mikhalovsky
Sergey
S
Galaev
Igor Yu
IY
Mattiasson
Bo
B
D001672:Biocompatible Materials; D003432:Cross-Linking Reagents / Q000737:chemistry*; D005615:Freezing; D020100:Hydrogels / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008855:Microscopy, Electron, Scanning
D001672:Biocompatible Materials; D003432:Cross-Linking Reagents; D020100:Hydrogels