Among the various physical forms of chitosan, viz. films, fibres, nanoparticles, gels, sponges, solution, etc., gels hold the most commercial importance. They are widely used in many areas, ranging from biomedicine to agriculture. This review discusses the recent advances in the chitosan-based hydrogels while highlighting its evolution from covalently crosslinked systems to ionotropically crosslinked super-absorbents. Distinctions into first, second and third generations of chitosan-based hydrogels are drawn based on the nature of crosslinks, environmental stability, mechanical strength and toxicity. While the first generation comprises chemically and metal-coordination crosslinked hydrogels, which were among the earliest to be identified, the second generation comprises of those physically crosslinked. Although the latter lack strength and stability, they are biocompatible in nature. The third generation, on the other hand, comprises of dense physical crosslinks that contribute to the strength and stability, without compromising on the biocompatibility.

在壳聚糖的各种物理形式中，即。薄膜，纤维，纳米粒子，凝胶，海绵，溶液等，凝胶具有最重要的商业意义。它们被广泛应用于从生物医学到农业的许多领域。这篇综述讨论了基于壳聚糖的水凝胶的最新进展，同时强调了其从共价交联体系到离子交联超吸收剂的演变。基于交联的性质，环境稳定性，机械强度和毒性，区分了第一，第二和第三代壳聚糖水凝胶。虽然第一代包括化学和金属配位交联的水凝胶，它们是最早被鉴定的，但第二代包括那些物理交联的凝胶。尽管后者缺乏强度和稳定性，但它们本质上是生物相容的。另一方面，第三代包含致密的物理交联键，这些交联键有助于强度和稳定性，而不会影响生物相容性。