In this paper is reported the obtaining of hydrogels from poly hydroxyethyl methacrylate-co-acryla-mide, by simultaneous crosslinking copolymerization from corresponding monomers by gamma photon irradiation. The composition of network chains in the copolymer was estimated from elemental analysis and infrared spectroscopy. Additionally, the toxicity of these materials was tested finding the free acrylamide and biological assay SOS in bacteria. The extracts of washed matrices of copolymers showed low level of free acrylamide. Moreover, they were non toxic on the E. coli cells tested at any time

En el presente trabajo se reporta la obtención de hidrogeles de copolímeros de polimetacrilato de 2-hidroxietilo-co-acrilamida mediante la copolimerización y reticulación simultánea a partir de sus correspondientes monómeros y mediante irradiación con cuantos gamma. La composición del copolímero se determinó mediante análisis elemental y espectroscopia infrarroja. Adicionalmente se muestran los resultados de toxicidad de sus matrices, para ello se evaluó la acrilamida libre y se realizó el ensayo SOS en bacterias. Se comprobó que los extractos de lavados de las matrices de estos copolímeros contenían muy bajos niveles de acrilamida libre y no mostraron efecto tóxico en las células de E. coli para ninguno de los tiempos evaluados

Acrylamide/2-hydroxyethyl methacrylate hydrogels were prepared by simultaneous radiation-induced cross-linking copolymerization of acrylamide (AAm), 2-hydroxyethyl methacrylate (HEMA) and water mixtures at a radiation dose of 10 kGy. Hydrogels were characterized by infrared spectroscopy. Dynamic and equilibrium swelling of hydrogels in water and in buffer solutions were investigated. They were sensitive to pH and temperature. Swelling was non-Fickean and increased with increasing the acrylamide content. Temperature dependence of the equilibrium water uptake of copolymers exhibited a discontinuity around 35 °C resulting from the weakening of the hydrogen bonds between the hydroxyl groups of HEMA and the amide groups of AAm. The thermodynamic and network parameters derived from swelling and mechanical measurements are compared and discussed. They exhibit a strong dependence on the AAm content in the hydrogel. These hydrogels can be considered for applications in fields requiring environmentally responsive hydrogels such as medicine, pharmacy and bioengeneering.

En el presente trabajo se reporta el proceso de formación de geles durante la irradiación gamma de soluciones acuosas de metacrilato de 2 hidroxietilo y acrilamida. El análisis sol/gel del copolímero irradiado permitió estimar importantes parámetros del proceso de irradiación como son: la dosis de gelificación y virtual, las densidades de degradación y reticulación; y los rendimientos químico radiolíticos de la degradación y reticulación, de acuerdo con la ecuación modificada de Charlesby- Rosiak. La correlación de los parámetros antes mencionados permite preparar geles con una estructura apropiada para su uso como sistemas de liberación controlada de fármacos.

ABSTRACT The formation of gels during gamma irradiation of aqueous solutions of 2- hydroxyethyl methacrilate and acrylamide is reported. Sol/Gel analysis of irradiated polymer was carried out and allowed to estimate important radiation parameters as gelation dose, virtual dose, degradation and crosslinking densities, yield of crosslinking and degradation of copolymer according with a modified Charlesby-Rosiak equation. The degree of copolymer conversion as a function of the absorbed dose of irradiation is presented. These parameters can be correlated with some physical and chemical properties of polymeric network formation and this way is able to design and prepare gels with the desired structure suitable as a drug delivery system.