Gradient Hydrogels-Overview of Techniques Demonstrating the Existence of a Gradient.

Natalia Zinkovska,Miloslav Pekar,Jiri Smilek

doi:10.3390/polym14050866

Abstract

Gradient hydrogels are promising future materials which could be usable in tissue engineering (scaffolds), pharmaceutical (drug delivery systems with controlled release) and many others related disciplines. These hydrogels exhibit a more complex inner (gradient) structure (e.g., concentration gradient) than simple isotropic hydrogel. Gradient-structured hydrogels could be beneficial in, for example, understanding intercellular interactions. The fabrication of gradient hydrogels has been relatively deeply explored, but a comprehensive description of the physico-chemical techniques demonstrating the existence of a gradient structure is still missing. Here, we summarize the state-of-the-art available experimental techniques applicable in proving and/or describing in physico-chemical terms the inner gradient structure of hydrogels. The aim of this paper is to give the reader an overview of the existing database of suitable techniques for characterizing gradient hydrogels.

Highlights

Gradient hydrogels are a type of special hydrogel with a more sophisticated and controlled architecture [1,2]
Often the gradient structure is inspired by materials found in nature and intended for medical applications [6–8]
We conducted a review of recent advances in the preparation of gradient hydrogels where such aims were reported [9]

Summary

Introduction

Gradient hydrogels are a type of special hydrogel with a more sophisticated and controlled architecture [1,2]. In a response to that paper, an anonymous reviewer suggested that we perform an overview of instrumental techniques used to prove the existence of gradients and to characterize them. This was the motivation for the current paper, which complements the previous review. Authors use multiple techniques to characterize their hydrogels from different points of view, and sometimes gradient observation or verification was performed with more than one method. In those cases, we report on the basic principle of gradient formation at the first appearance of the work referred to. A detailed overview of related techniques is provided in the Supplementary Materials (Table S1)

Visual Inspection

Structural Analyses

Miscellaneous