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Periodate oxidation has been the widely accepted route for obtaining aldehyde group-functionalized polysaccharides but significantly influenced the various physicochemical properties due to the ring opening of the backbone of polysaccharides. The present study, for the first time, presents a novel method for the preparation of aldehyde group-functionalized polysaccharides that could retain the ring structure and the consequent rigidity of the backbone. Pectin was collected as the representative of polysaccharides and modified with cyclopropyl formaldehyde to obtain pectin aldehyde (AP), which was further crosslinked by DL-lysine (LYS) via the Schiff base reaction to prepare injectable hydrogel. The feasibility of the functionalization was proved by FT-IR and 1 H NMR techniques. The obtained hydrogel showed acceptable mechanical properties, self-healing ability, syringeability, and sustained-release performance. Also, as-prepared injectable hydrogel presented great biocompatibility with a cell proliferation rate of 96 %, and the drug-loaded hydrogel exhibited clear inhibition of cancer cell proliferation. Overall, the present study showed a new method for the preparation of aldehyde group-functionalized polysaccharides, and the drug-loaded hydrogel has potential in drug release applications., Competing Interests: Declaration of competing interest The authors declare no competing financial interests., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Injectable hydrogel-based drug delivery systems have attracted more and more attention due to their sustained-release performance, biocompatibility, and 3D network. The present study showed whole pectin-based hydrogel as an injectable drug delivery system, which was developed from oxidized pectin (OP) and diacylhydrazine adipate-functionalized pectin (Pec-ADH) via acylhydrazone linkage. The as-prepared hydrogels were characterized by 1 H NMR, FT-IR, and SEM techniques. The equilibrium swelling ratio of obtained hydrogel (i.e., sample gel 5) was up to 4306.65 % in the distilled water, which was higher than that in PBS with different pH values. Increasing the pH of the swelling media, the swelling ratio of all hydrogels decreased significantly. The results that involved the swelling properties indicated the salt- and pH-responsiveness of the as-prepared hydrogels. The drug release study presented that 5-FU can be persistently released for more than 12 h without sudden release. Moreover, the whole pectin-based hydrogel presented high cytocompatibility toward L929 cell lines, and the drug delivery system showed a high inhibitory effect on MCF-7 cell lines. All these results manifested that the acylhydrazone-derived whole pectin-based hydrogel was an excellent candidate for injectable drug delivery systems., Competing Interests: Declaration of competing interest The authors declare no competing financial interests., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Self-healing hydrogels with pH-responsiveness could protect loaded drugs from being destroyed till it arrives to the target. The pectin-based hydrogel is a candidate due to the health benefit, anti-inflammation, antineoplastic activity, nontoxicity, and biospecific degradation, et al. However, the abundant existence of water-soluble branched heteropolysaccharide chains influenced its performance resulting in limitation of the potential. In the present study, we prepared a series of self-healing pectin/chitosan hydrogels via the Diels-Alder reaction. Moreover, pectin/chitosan composite hydrogel was prepared as a contrast. By comparison, it can be seen that the Diels-Alder reaction greatly improved the cross-linking density of hydrogels. The self-healing experiments showed excellent self-healing performance. In different swelling mediums, significant transformation in the swelling ratio was shown, indicating well-swelling property, pH- and thermo-responsiveness. The drug loading and release studies presented high loading efficiency and sustained release performance. The cytotoxicity assay that showed a high cell proliferation ratio manifested great cytocompatibility., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Injectable hydrogels with self-healing ability present great potential for drug delivery. They could be facilely implanted in vivo and maintained structural and functional integrity till the hydrogel arriving at target sites. Herein, a series of injectable and self-healing composite hydrogel were developed as delivery vehicles for anti-cancer drug. The hydrogels were obtained with varying ratios of oxidized pectin/chitosan to nano γ-Fe 2 O 3 , which present excellent injectable, self-healing, magnetic, high biocompatible, and anti-cancer properties. The nano γ-Fe 2 O 3 with particle size of about 0.25 μm loaded on the surface of hydrogel. Magnetic hysteresis loops of the hydrogel presented S-shape over the applied magnetics and the MS value was 4.86 emu/g. When pH dropped from 7.4 to 6.5 or temperature increased form 36 °C to 37 °C, the percentage increase in the swelling rate of OP4-400 reached to 35.89% and 25.13%, respectively. The composite hydrogels could continuously release water-soluble 5-FU for more than 12 h. In addition, the drug delivery systems indicated acceptable anti-cancer property though trace amounts of 5-FU were added in the hydrogel systems. The addition of γ-Fe 2 O 3 could not only be beneficial to the targeting but also collectively enhance the anti-cancer property., (Copyright © 2020 Elsevier B.V. All rights reserved.)