Bio-Nanocomposite Hydrogel Based on Zinc Alginate/Graphene Oxide: Morphology, Structural Conformation, Thermal Behavior/Degradation, and Dielectric Properties.

Roser Sabater i Serra,Constantino Torregrosa-Cabanilles,José María Meseguer Dueñas,Ángel Serrano-Aroca,José Molina-Mateo,Andreu Andrio-Balado

doi:10.3390/polym12030702

Abstract

Bio-nanocomposite hydrogels based on sodium alginate (SA) as polymer matrix and graphene oxide (GO) nanosheets with zinc as crosslinking agent were synthesized with the aim of incorporating the intrinsic properties of their constituents (bioactivity and antimicrobial activity). Thus, stable and highly interconnected networks were obtained from GO nanosheets dispersed in SA matrices through interactions with low amounts of zinc. The GO nanosheets were successfully incorporated into the alginate matrix in the form of a complex nano-network involving different interactions: Bonds between alginate chains induced by Zn ions (egg box structure), interactions between GO nanosheets through Zn ions and hydrogen bonds between alginate chains, and GO nanosheets. The molecular interactions and morphology were confirmed by Fourier-transform infrared spectroscopy and transmission electron microscopy. The composite’s structural organization showed enhanced thermal stability. The glass transition temperature shifted to a higher temperature due to the reduced mobility induced by additional crosslinking bonds after incorporating the GO nanosheets and Zn into the polymer matrix. Finally, the dielectric behavior revealed that charge carrier mobility was hampered by the compact structure of the nanonetwork, which reduced conductivity. The combined properties of these nanocomposite hydrogels make them attractive biomaterials in the field of regenerative medicine and wound care since both surface bioactivity and antibacterial behavior are two critical factors involved in the success of a biomaterial.

Highlights

Polymer-based nanocomposites are produced by including nanomaterials distributed in the pristine polymer matrix with at least one phase in the nanoscale dimension
graphene oxide (GO) nanosheets have recently been incorporated in calcium alginate hydrogels to improve their mechanical behavior, water diffusion, and many other physical properties [14,15,16,17], while its antibacterial capacity and negligible cytotoxicity in mammalian cells have been probed at very low GO concentrations [18]
The GO powder used in this study presented a morphology of approximately 200–400-nm-long nanosheets stacked together by van der Waals forces and π-π interactions, as shown in HR-transmission electron microscopy (TEM)

Summary

Introduction

Polymer-based nanocomposites are produced by including nanomaterials distributed in the pristine polymer matrix with at least one phase in the nanoscale dimension. The presence of the nanomaterial within the polymer matrix improves the properties, such as higher thermal stability or better mechanical performance, but can generate a new set of properties that depend on the type of nanomaterial incorporated [1]. In this regard, carbon nanomaterials (CNMs) such as graphene and Polymers 2020, 12, 702; doi:10.3390/polym12030702 www.mdpi.com/journal/polymers. Polymers 2020, 12, 702 graphene oxide (GO) are rapidly emerging as a new class of fillers to produce nanocomposites with enhanced properties [2]. GO nanosheets have recently been incorporated in calcium alginate hydrogels to improve their mechanical behavior, water diffusion, and many other physical properties [14,15,16,17], while its antibacterial capacity and negligible cytotoxicity in mammalian cells have been probed at very low GO concentrations [18]

Methods

Results

Conclusion