Biomedical subjects

M A Plasencia

Publications and source records attributed to M A Plasencia.

3 recordsLinked to original sources

PubMed2000

Hydrophilic polymers derived from vitamin E.

Vitamin E containing copolymers for biomedical applications was obtained by copolymerization reaction of vitamin E methacrylate (VEMA) with 2-hydroxyethyl methacrylate (HEMA), N,N-dimethyl acrylamide (DMA) or vinyl pyrrolidone (VP), in different experiments. High molecular weight copolymers prepared by free radical reactions initiated by azobisisobutironitrilo, AIBN, present a random distribution of vitamin E derivatives along the macromolecular chains, and the average composition depends on the initial composition of the reaction medium. The relative flexibility of the polymeric systems was analyzed measuring the glass transition temperature of copolymeric sequences and that of the pure alternating diad (Tg12) obtained by the application of the treatments proposed by Johnston and Barton to all the systems. Tg12 was higher than the average T of both homopolymers (Tg) for the VEMA-HEMA system, Tg12 was lower than Tg for the VEMA-DMA system and Tg12 was similar to Tg for the VEMA-VP system. VEMA-HEMA copolymers gave rise to hydrogels in water, acidic and alkaline media. VEMA-DMA copolymers gave rise to hydrogels in acidic medium and dissolved in water and alkaline medium. VEMA-VP copolymers were soluble in all media. The swelling of all the hydrogels fit a second order kinetics. A VEMA-HEMA hydrogel was selected for in vivo experiments in order to study the influence of vitamin E on the regeneration process of Achilles tendon. The polymeric derivatives of vitamin E stimulated the regenerative process as a consequence of the antiaging effect in the local area of application.

Acrylamides↗

PubMed2000

Hydrophilic polymers derived from vitamin E.

Vitamin E containing copolymers for biomedical applications were obtained by copolymerization reaction of vitamin E methacrylate (VEMA) with 2-hydroxyethyl methacrylate (HEMA), N,N-dimethyl acrylamide (DMA) or vinyl pyrrolidone (VP), in different experiments. High molecular weight copolymers prepared by free radical reactions initiated by azobisisobutironitrilo, AIBN, present a random distribution of vitamin E derivatives along the macromolecular chains, and the average composition depends on the initial composition of the reaction medium. The relative flexibility of the polymeric systems was analyzed measuring the glass transition temperature of copolymeric sequences and that of the pure alternating diad (Tg12) obtained by the application of the treatments proposed by Johnston and Barton to all the systems. Tg12 was higher than the average Tg of both homopolymers (Tg) for the VEMA-HEMA system, Tg12 was lower than Tg for the VEMA-DMA system and Tg12 was similar to Tg for the VEMA-VP system. VEMA-HEMA copolymers gave rise to hydrogels in water, acidic and alkaline media. VEMA-DMA copolymers gave rise to hydrogels in acidic medium and dissolved in water and alkaline medium. VEMA-VP copolymers were soluble in all media. The swelling of all the hydrogels fit a second-order kinetics. A VEMA-HEMA hydrogel was selected for in vivo experiments in order to study the influence of vitamin E on the regeneration process of Achilles tendon. The polymeric derivatives of vitamin E stimulated the regenerative process as a consequence of the antiaging effect in the local area of application.

Animals↗

PubMedDate not supplied

Resorbable polyacrylic hydrogels derived from vitamin E and their application in the healing of tendons.

A hydrogel containing vitamin E (alpha-tocopherol) was prepared by free radical polymerization of 2-hydroxyethyl methacrylate (HEMA) and alpha-tocopheryl methacrylate (VEMA), the latter being synthesized previously to its use. The hydrogel containing 20 wt % of VEMA showed equilibrium water content in the range of those of hydrogel networks, at any pH. The swelling of the hydrogel followed Fick's law, indicating that sorption of water molecules is controlled by diffusion, although the values of diffusion coefficients for the VEMA-containing hydrogel were lower than those of poly-HEMA in any medium. Surface characterization of the VEMA-containing hydrogel revealed a decrease in the surface energy of solid owing to a decrease of the polar component mainly. The application of finely powdered xerogel of HEMA-VEMA copolymer bearing 20 wt % of the vitamin E derivative gave a very fast and positive response showing an activated regeneration capacity, probably due to the stimulation of the cellular proliferation or the more plausible effect, the cellular protection associated to the antioxidant properties of the vitamin E residue.

Journal Article↗