Magnetic response of gelatin ferrogels across the sol–gel transition: the influence of high energy crosslinking on thermal stability

Abstract

As emerging responsive materials, ferrogels have demonstrated significant potential for applications in areas of engineering to regenerative medicine. Promising techniques to study the behavior of magnetic nanoparticles (MNPs) in such matrices include magnetic particle spectroscopy (MPS) and magnetorelaxometry (MRX). This work investigated the magnetic response of gelatin-based ferrogels with increasing temperatures, before and after high energy crosslinking. The particle response was characterized by the nonlinear magnetization using MPS and quasistatic magnetization measurements as well as MRX to discriminate between Néel and Brownian relaxation mechanisms. The effective magnetic response of MNPs in gelatin was suppressed, indicating that the magnetization of the ferrogels was strongly influenced by competing dipole-dipole interactions. Significant changes in the magnetic behavior were observed across the gelatin sol-gel transition, as influenced by the matrix viscosity. These relaxation processes were modeled by Fourier transformation of the Langevin function, combined with a Debye term for the nonlinear magnetic response, for single core MNPs embedded in matrices of changing viscosities. Using high energy electron irradiation as a crosslinking method, modified ferrogels exhibited thermal stability on a range of timescales. However, MRX relaxation times revealed a slight softening around the gelatin sol-gel transition felt by the smallest particles, demonstrating a high sensitivity to observe local changes in the viscoelasticity. Overall, MPS and MRX functioned as non-contact methods to observe changes in the nanorheology around the native sol-gel transition and in crosslinked ferrogels, as well as provided an understanding of how MNPs were integrated into and influenced by the surrounding matrix.

Viscosity and degradation controlled injectable hydrogel for esophageal endoscopic submucosal dissection

“…2 A). For all groups of hydrogels, G′ was always higher than G″ and G′ showed lightly increased in the range of 0.1–100 rad/s, which can prove that the hydrogels were crosslinked and exhibited mechanical robust [ [66] , [67] , [68] ] ( Fig. 2 D).…”

Magnetically responsive composites: electron beam assisted magnetic nanoparticle arrest in gelatin hydrogels for bioactuation

“…As coercivity is too small to account for this behavior (Table 1), due to the virtual absence of magnetic coupling ( Fig. 1 and our previous MRX/MPI studies on similar ferrogels 9 ), we surmise that a stick-slip type of friction at the wall, combined with the viscoelastic response of the hydrogel matrix, might be the cause for this.…”

“…This approach constitutes a biocompatible procedure that also facilitates thermal stabilization and allows for tuning of mechanical properties to mimic, e.g., the desired extracellular matrix (ECM) properties. [9][10][11][12] Gelatin itself is an advantageous material as it is biopolymerderived and of very little complexity such that it exhibits less irregularities and is simple to handle. Compared to collagen of which it is a derivative, it also shows less antigenicity.…”

“…We have previously evaluated the central properties of similar ferrogels, including homogeneous synthesis, strength of mechanical nanoparticle-matrix coupling and long-term stability, within an extensive previous study centered around magnetic particle spectroscopy (MPS) and magnetorelaxometry (MRX) assessment. 9 The paper is organized as follows. Section 2 presents methods to synthesize, crosslink and deform ferrogels within external magnetic fields.…”

Design Principles for Aqueous Interactive Materials: Lessons from Small Molecules and Stimuli‐Responsive Systems

“…One of the first reports in 1996 by Zrinyi et al investigated the deformation of polyvinylalcohol‐based ferrogels using a nonuniform magnetic field 69. Subsequently, substrates including synthetic polymers (e.g., polyacrylamide),70 LC elastomers,71 natural polymers (alginate,72 chitosan,73 gelatin74,75) alone or as part of composite materials (e.g., with cellulose nanocrystals) have been used to obtain ferromagnetic materials with remarkable magnetic response times and properties 76–78. To mediate gelation in ferrogels, several strategies can be employed.…”