DNA–Chitosan Aerogels and Regenerated Hydrogels with Extraordinary Mechanical Properties

It has recently been shown that native ds-DNA and chitosan can coassemble without common phase separation and precipitation, forming a translucent homogeneous hydrogel. This simple approach consists of progressive charging of the polysaccharide through gradual acidification of a solution in the presence of DNA, which slowly strengthens the electrostatic interactions between them, ruling out fast and uncontrolled cooperative association, which is a well-known problem associated with coacervation. Homogeneous hydrogels thus fabricated demonstrated mechanical properties characteristic of quite strong physical hydrogels. Extraordinary mechanical strength and elasticity have been observed in aerogels prepared from an original hydrogel and also in hydrogels, which were restored by the rehydration of aerogels. Aerogels match highly cross-linked synthetic polyurethane foams despite DNA with chitosan being bound only via electrostatic interactions without using a toxic cross-linking agent. Owing to their biocompatibility, biodegradability, and available renewable resources, hydrogels and aerogels might replace typical synthetic polymers. The fabrication of bionanocomposites with luminescent, sensing, and photocatalytic functionalities by entrapping quantum dots, titania nanoparticles, and dyes demonstrates some possible applications.