Editorial on the Special Issue "Modification of Hydrogels and Their Applications in Biomedical Engineering"

Advances in chitosan and chitosan derivatives for biomedical applications in tissue engineering: An updated review

In recent years, chitosan (CS) has received much attention as a functional biopolymer for various applications, especially in the biomedical field. It is a natural polysaccharide created by the chemical deacetylation of chitin (CT) that is nontoxic, biocompatible, and biodegradable. This natural polymer is difficult to process; however, chemical modification of the CS backbone allows improved use of functional derivatives. CS and its derivatives are used to prepare hydrogels, membranes, scaffolds, fibers, foams, and sponges, primarily for regenerative medicine. Tissue engineering (TE), currently one of the fastest-growing fields in the life sciences, primarily aims to restore or replace lost or damaged organs and tissues using supports that, combined with cells and biomolecules, generate new tissue. In this sense, the growing interest in the application of biomaterials based on CS and some of its derivatives is justifiable. This review aims to summarize the most important recent advances in developing biomaterials based on CS and its derivatives and to study their synthesis, characterization, and applications in the biomedical field, especially in the TE area.

Engineering of PVA/PVP Hydrogels for Agricultural Applications

Hydrogels have gained significant popularity in agricultural applications in terms of minimizing waste and mitigating the negative environmental impact of agrochemicals. This review specifically examines the utilization of environmentally friendly, shapable hydrogels composed of polyvinyl alcohol (PVA) and polyvinylpyrrolidone (PVP) in various casings for crop protection against different pests, fertilizing, and watering. To activate their effectiveness, PVA/PVP hydrogels were loaded with both hydrophilic and hydrophobic environmentally friendly pesticides, namely hydrogen peroxide (HP), the essential oil thymol, and urea as a fertilizer, either separately or in combination. This review covers various physical and chemical approaches used for loading, shaping, and controlling the release profiles of pesticides and fertilizers. Additionally, it explores the evaluation of the chemical composition, structure, classification, rheology, and morphology of the hydrogels as well as their impact on the thermal stability of the encapsulated pesticides and fertilizer, followed by biological tests. These hydrogels significantly contribute to the stabilization and controlled release of essential nutrients and biocides for plants, while maintaining excellent biocidal and fertilizing properties as well as sustainability characteristics. By shedding light on the latest insights into the concepts, applications, and results of these hydrogels, this review demonstrates their immense potential for widespread future use in agriculture.