Nanocomposites and nanomaterials

Formation of polyacrylamide hydrogels filled with magnetite
Nahorniak М.І., Vasylyshyn Т.М., Yakoviv M.V., Voronovska A.V., Varvarenko S.M.
1 Department of organic chemistry, Lviv Polytechnic National University, 12, Stepan Bandera str., Lviv-79013, Ukraine. 
E-mail: vorven08@meta.ua

Hydrogels are quite new smart nanocomposites with a wide prospect in application in biomedical engineering, due to their hydrated environment and properties (e.g., mechanical, chemical, biocompatible). However, challenges still exist regarding utilizing hydrogels in applications such as engineering 3D tissue constructs and active targeting in drug delivery, due to the lack of controllability, actuation, and quick‐response properties. Magnetic hydrogel nanoparticles form a class of soft materials with remote controllable properties that have attracted great attention due to their applications in biomedical engineering, including tissue engineering, drug delivery and release, enzyme immobilization and cancer therapy.
In this regard, hydrogels modified with magnetite nanoparticles (Fe3O4) were obtained. In order to synthesize particles of magnetized hydrogel or precursors of magnetite (iron salts), the input components were introduced into the aqueous phase of a mixture of prepolymers (polyacrylamide and poly-N-hydroxyacrylamide structurant) at 343 K and pH = 2.
Within the investigation, the influence of insertion of magnetite particles into the system or their precursors on the swelling parameters of hydrogel was studied. Just as in the case with basic hydrogel (without additives), when magnetite particles or their precursors are introduced, the structuring time of 12 h ensures the achievement of stable hydrogel characteristics. However, the addition of additives affects the dynamics of the hydrogel formation. 
The introduction of magnetite particles slows the structuring of hydrogel during the first 5 hours, but on 9 hour of the process, the parameters of hydrogel with magnetite reach values that are typical for a fully structured hydrogel without additives. When the salts of the iron were introduced, there is a decrease in the equilibrium degree of swelling in almost 2 times, meanwhile during the first two hours the hydrogel structuring does not occur at all.
Thus, the introduction of additional components effects on the structuring of hydrogel only in the initial stages. In the end of the process, magnetic hydrogels are practically no different from the basic, in terms of their ability to swell, which makes it possible to receive hydrogels, filled with magnetite, with controlled characteristics.