Chitosan derivatives, and more specifically, glycosylated derivatives, are nowadays attracting much attention within the scientific community due to the fact that this set of engineered polysaccharides finds application in different sectors, spanning from food to the biomedical field. Overcoming chitosan (physical) limitations or grafting biological relevant molecules, to mention a few, represent two cardinal strategies to modify parent biopolymer; thereby, synthetizing high added value polysaccharides. The present review is focused on the introduction of oligosaccharide side chains on the backbone of chitosan. The synthetic aspects and the effect on physical-chemical properties of such modifications are discussed. Finally, examples of potential applications in biomaterials design and drug delivery of these novel modified chitosans are disclosed.

Mounting evidences have recognized that dual cross‐link and double‐network gels can promisingly recapitulate the complex living tissue architecture and overcome mechanical limitations of conventional scaffolds used hitherto in regenerative medicine. Here, dual cross‐link gels formed of a bioactive lactose‐modified chitosan reticulated via both temporary (boric acid‐based) and permanent (genipin‐based) cross‐linkers are reported. While boric acid rapidly binds to lactitol flanking diols increasing the overall viscosity, a slow temperature‐driven genipin binding process takes place allowing for network strengthening. Combination of frequency and stress sweep experiments in the linear stress–strain region shows that ultimate gel strength, toughness, and viscoelasticity depend on polymer‐to‐genipin molar ratio. Notably, herewith it is demonstrated that linear stretching correlates with strain energy dissipation through boric acid binding/unbinding dynamics. Strain‐hardening effect in the nonlinear regime, along with good biocompatibility in vitro, points at an interesting role of present system as biological extracellular matrix substitute.

Strain hardening has recently emerged as a near-universal response of biological tissues to mechanical stimulation as well as a powerful regulator of cell fate. Understanding the mechanistic basis for this nonlinear elasticity is crucial for developing bioinspired materials that mimic extracellular matrix mechanics. Here, we show that covalent networks built from highly acetylated chitosans exhibit strain hardening at physiological pH and osmolarity. While varying the chitosan physical–chemical composition and network connectivity, we provide evidence that temporary nodes arising from the entangling of chains between stable cross-links are at the root of nonlinear elasticity. The contour length (L c) of the said chains revealed that the larger the chain length between the cross-links, the greater is the entanglement over disentanglement upon network stretching. To this end, we calculated that the minimum number of Khun’s segments in L c that contributes to the onset of strain hardening is 15. Furthermore, we identified a relationship between critical strain marking nonlinear elasticity and the network connectivity, being similar to that found for the cytoskeletal collagen matrix, indicating the potential use of semiflexible (neutral pH-soluble) chitosans in assembling extracellular matrix mimics.