Impact of Magneto-Deformation Effect in Ferrogels on the Echogenicity of Magnetic Composites

Basically, this study was carried out in the context of the development of ferrogel-based biocompatible soft tissue implants, in particular, for the needs of regenerative medicine and replacement therapy. The magneto-deformation effect (MDE) of ferrogels (FGs) and the possibility of its visualization with the use of medical ultrasound were in the focus of this work. The aim of this investigation was addressed to search a possible relationship between the extent of MDE and the intensity of the reflected echo signal at the gel/water interface and in the gel interior. Cylindrical FGs similar to 12mm in diameter and similar to 7mm in height based on polyacrylamide (PAAm) with interpenetrating physical network of natural polysaccharide (Guar) filled with 200-300nm Fe3O4 magnetic microparticles (MPs) with weight fraction of 12% or 23% were investigated. MDE was studied using an ultrasonic medical device Sonoline Adara (Siemens, Germany), and estimated by the relative compression of FGs after application the constant gradient magnetic field (MF) up to 500 Oe by an electromagnet. Viscoelastic and acoustic properties of FGs in the absence of the application of an MF were determined as well. It was found that an increase of the weight fraction of MPs in FGs resulted in the significant increase of the ferrogel's density, the elastic storage modulus, the loss modulus, the acoustic impedance, the reflection coefficient and some decrease of the ultrasonic velocity in FGs. At a given MPs concentration, the MDE in FGs was increased according to a quadratic law with the gradual increase of MF strength. The growth of MDE in FGs accompanies by an increase in the intensity of the reflected echo signal both from the gel/water interface and from the interior of the FGs. The obtained results are discussed from the viewpoint of the effects of MPs on the interaction of an ultrasonic wave with the structure of FGs in the course of MF application.

Automated summary

This study investigated the magneto-deformation effect of ferrogels and its visualization using medical ultrasound. It was found that an increase in the weight fraction of magnetic particles in ferrogels resulted in an increase in density, elastic modulus, loss modulus, acoustic impedance, reflection coefficient, and a slight decrease in ultrasonic velocity. The deformation effect in ferrogels increased with the strength of the magnetic field, accompanied by an increase in the intensity of the reflected echo signal.