Hydrogels as Drug Delivery Systems: A Review of Current Characterization and Evaluation Techniques

Abstract

Owing to their tunable properties, controllable degradation, and ability to protect labile drugs, hydrogels are increasingly investigated as local drug delivery systems. However, a lack of standardized methodologies used to characterize and evaluate drug release poses significant difficulties when comparing findings from different investigations, preventing an accurate assessment of systems. Here, we review the commonly used analytical techniques for drug detection and quantification from hydrogel delivery systems. The experimental conditions of drug release in saline solutions and their impact are discussed, along with the main mathematical and statistical approaches to characterize drug release profiles. We also review methods to determine drug diffusion coefficients and in vitro and in vivo models used to assess drug release and efficacy with the goal to provide guidelines and harmonized practices when investigating novel hydrogel drug delivery systems.

Deciphering the Molecular Mechanism of Water Interaction with Gelatin Methacryloyl Hydrogels: Role of Ionic Strength, pH, Drug Loading and Hydrogel Network Characteristics

“…The pH is acidic in the stomach (pH 2) and becomes basic in the intestine (pH 5 to 8) [45]. Blood, on the other hand, has a pH value of 7.4 [46]. The microenvironmental pH can also vary and change during pathogenesis and disease progression, and, for example, become acidic in an immediate tumor environment [47,48], during the wound healing process [49], or in the case of infection [46].…”

“…In the intestinal tract, it varies from close to 0 M in the stomach to 0.4 M in the intestine, in relation to a fed or fasted state [50][51][52][53][54]. The general physiological ionic strength is 150 mM [46].…”

Recent Advances of Taxol-Loaded Biocompatible Nanocarriers Embedded in Natural Polymer-Based Hydrogels

“…In order to be defined a drug delivery system, a formulation should retain the entrapped compound(s), promoting a gradual/controlled/sustained release as a function of time [76]. In this regard, among different factors, it has been reported that the network size of a hydrogel plays a critical role in the choice of the administration route as well as in the modulation of the release kinetic of the entrapped compound [74,77].…”

Smart Hydrogels Meet Carbon Nanomaterials for New Frontiers in Medicine

“…Hydrogels are soft materials that retain high levels of water that are widely used for their adsorption and delivery properties in areas such as drug [ 1 ] or protein [ 2 ] release, tissue engineering [ 3 , 4 ], and wound healing [ 3 , 5 ]. They are typically composed of a three-dimensional network that traditionally arises from chains of polymers [ 6 ], polysaccharides [ 7 ], proteins [ 8 ], or other macromolecules.…”