# Fabrication of Protein–Polysaccharide-Based Hydrogel Composites Incorporated with Magnetite Nanoparticles as Acellular Matrices

## TL;DR

This paper describes a new hydrogel composite made of protein, polysaccharide, and magnetite nanoparticles that mimics natural tissues and has improved mechanical stability.

## Contribution

The novel contribution is the fabrication of a Gel-SA hydrogel with magnetite nanoparticles, enhancing mechanical and thermal stability for tissue engineering.

## Key findings

- Gel-SA-Fe3O4 hydrogels showed mechanical properties comparable to soft tissues at low nanoparticle concentrations.
- Magnetite incorporation improved thermal resilience during heating cycles compared to Gel-SA gels.
- FTIR confirmed physical interactions and metal coordination bonds in the composite hydrogel.

## Abstract

Hydrogels with protein–polysaccharide combinations are widely used in the field of tissue engineering, as they can mimic the in vivo environments of native tissues, specifically the extracellular matrix (ECM). However, achieving stability and mechanical properties comparable to those of tissues by employing natural polymers remains a challenge due to their weak structural characteristics. In this work, we optimized the fabrication strategy of a hydrogel composite, comprising gelatin and sodium alginate (Gel-SA), by varying reaction parameters. Magnetite (Fe3O4) nanoparticles were incorporated to enhance the mechanical stability and structural integrity of the scaffold. The changes in hydrogel stiffness and viscoelastic properties due to variations in polymer mixing ratio, crosslinking time, and heating cycle, both before and after nanoparticle incorporation, were compared. FTIR spectra of crosslinked hydrogels confirmed physical interactions of Gel-SA, metal coordination bonds of alginate with Ca2+, and magnetite nanoparticles. Tensile and rheology tests confirmed that even at low magnetite concentration, the Gel-SA-Fe3O4 hydrogel exhibits mechanical properties comparable to soft tissues. This work has demonstrated enhanced resilience of magnetite-incorporated Gel-SA hydrogels during the heating cycle, compared to Gel-SA gel, as thermal stability is a significant concern for hydrogels containing gelatin. The interactions of thermoreversible gelatin, anionic alginate, and nanoparticles result in dynamic hydrogels, facilitating their use as viscoelastic acellular matrices.