Effect of particle concentration on the microstructural and macromechanical properties of biocompatible magnetic hydrogels
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Soft Matter 13 (16), 2928-2941, 2017
SponsorshipThis study was supported by project FIS2013-41821-R (Plan Nacional de Investigación Científica, Desarrollo e Innovación Tecnológica, Ministerio de Economía y Competitividad, Spain, co-funded by ERDF, European Union) and by grant FIS PI14-1343 (Spanish Plan Nacional de Investigación Científica, Desarrollo e Innovación Tecnológica, from the National Ministry of Economy and Competitiveness -Instituto de Salud Carlos III; co-financed by Fondo Europeo de Desarrollo Regional –FEDER-, European Union). J.M.A. acknowledges financial support by CNPq through its postdoctoral fellowship program (Ref. No. 203100/2014-0). A.Z is also grateful to the Russian Fund for Basic Research, 16-58-12003, the Program of Russian Federation Ministry of Science and Education, project 3.1438.2017/PCh. Dr. Laura Rodríguez-Arco is acknowledged for helpful discussion. This work is part of the PhD thesis of A.B.B.-E.
We analyze the effect of nanoparticle concentration on the physical properties of magnetic hydrogels consisting of polymer networks of human fibrin biopolymer with embedded magnetic particles, swollen by a water-based solution. We prepared these magnetic hydrogels by polymerization of mixtures consisting mainly of human plasma and magnetic nanoparticles with OH- functionalization. Microscopic observations revealed that magnetic hydrogels presented some cluster-like knots that were connected by several fibrin threads. By contrast, nonmagnetic hydrogels presented a homogeneous net-like structure with only individual connections between pairs of fibers. The rheological analysis demonstrated that the rigidity modulus, as well as the viscoelastic moduli, increased quadratically with nanoparticle content following a square-like function. Furthermore, we found that time for gel point was shorter in the presence of magnetic nanoparticles. Thus, we can conclude that nanoparticles favor the cross-linking process, serving as nucleation sites for the attachment of the fibrin polymer. Attraction between the positive groups of the fibrinogen, from which the fibrin is polymerized, and the negative OH- groups of the magnetic particle surface qualitatively justifies the positive role of the nanoparticles on the enhancement of the mechanical properties of the magnetic hydrogels. Indeed, we developed a theoretical model that semiquantitatively explains the experimental results by assuming the indirect attraction of the fibrinogen through the attached nanoparticles. Due to this attraction the monomers condense into nuclei of dense phase and by the end of the polymerization process the nuclei (knots) of the dense phase cross-link the fibrin threads, which enhances the mechanical properties