Recent Advances in Zwitterionic Hydrogels: Preparation, Property, and Biomedical Application

Abstract

Nonspecific protein adsorption impedes the sustainability of materials in biologically related applications. Such adsorption activates the immune system by quick identification of allogeneic materials and triggers a rejection, resulting in the rapid failure of implant materials and drugs. Antifouling materials have been rapidly developed in the past 20 years, from natural polysaccharides (such as dextran) to synthetic polymers (such as polyethylene glycol, PEG). However, recent studies have shown that traditional antifouling materials, including PEG, still fail to overcome the challenges of a complex human environment. Zwitterionic materials are a class of materials that contain both cationic and anionic groups, with their overall charge being neutral. Compared with PEG materials, zwitterionic materials have much stronger hydration, which is considered the most important factor for antifouling. Among zwitterionic materials, zwitterionic hydrogels have excellent structural stability and controllable regulation capabilities for various biomedical scenarios. Here, we first describe the mechanism and structure of zwitterionic materials. Following the preparation and property of zwitterionic hydrogels, recent advances in zwitterionic hydrogels in various biomedical applications are reviewed.

Isolation, Maintenance and Expansion of Adult Hematopoietic Stem/Progenitor Cells and Leukemic Stem Cells

“…The LT-/ST-HSCs cells can also be encapsulated into a natural or synthetic polymer solution that is cross-linked to form a hydrogel. Hydrogels are biocompatible, retain large amounts of water and provide excellent permeability [ 318 , 319 ]. Hydrogels are mixed with ECM proteins such as fibronectin, collagen, laminin or glycosaminoglycans to allow attachment of LT-/ST-HSCs [ 309 , 318 ].…”

“…Compared to a PEG scaffold, zwitterionic hydrogels are super-hydrophilic and are more resistant to non-specific protein binding [ 319 , 321 ]. Bai et al set up a zwitterionic hydrogel system to ex vivo culture BM and CB LT-/ST-HSCs, using a metalloproteinase-cleavable zwitterionic peptide to reversibly crosslink the gels.…”

“…The LT-/ST-HSCs-secreted metalloproteinases gradually cleave peptide crosslinker, allowing cells to actively shape their environment [ 320 ]. This improved cell migration, cell-cell contacts and stemness of the HSCs; and proved to be an efficient method to expand functional CD34 + LT-HSCs based on reduced differentiation, diminished reactive oxygen species (ROS) production and a low metabolic rate [ 319 , 320 , 321 ].…”

A Soft Zwitterionic Hydrogel as Potential Coating on a Polyimide Surface to Reduce Foreign Body Reaction to Intraneural Electrodes

“…Notably, surface chemistry and material characteristics as well as hydrophobicity, strongly influence the composition of the adsorbed molecules and the consequent cellular cascade of FBR [ 7 ], thus underlining the importance of the surrounding biomaterial coating around typical Polyimide (PI)-based implants that could impact the biocompatibility and safety of the implanted interface [ 3 , 4 , 8 , 9 , 10 ]. In this regard, poly(ethylene glycol) (PEG) [ 11 , 12 , 13 ] and poly(2-hydroxyethyl methacrylate) (pHEMA) [ 14 , 15 ], which have long been the most common coatings used to overcome the undesired FBR to PI-based implantable interfaces, were recently replaced by the more stable poly(carboxybetaines), poly(phosphobetaines) and poly(sulfobetaines) zwitterionic hydrogels [ 16 , 17 , 18 , 19 ]. These hydrogels present advantageous features in terms of hydrophilicity, biocompatibility and anti-inflammatory and ultra-low fouling characteristics, both in vitro and in vivo [ 20 , 21 , 22 ].…”

Molecular Dynamics Study on Properties of Hydration Layers above Polymer Antifouling Membranes

“…The adsorption of protein on surface is affected by many factors [ 18 , 19 , 20 , 21 ], among which the factors favorable for adsorption mainly include the enthalpy loss from the van der Waals and electrostatic attraction between protein and surface, and the entropic gain from the removal of hydration layer at the surface of material and protein. The disadvantages include the enthalpy gain required for the dehydration of surface and protein, protein’s conformation adjustment, as well as the entropic loss from protein adsorption and exposure of hydrophobic regions.…”