Objective To explore the biological effects of alginate oligosaccharides with different degrees of lysis of wound
cells and tissues. Methods Alginate oligosaccharides were divided into five groups with molecular weight ranges of <500,
500-1 000, 1 000-5 000, 5 000-10 000, and 10 000-20 000 using dialysis bags with pores of different sizes. The cleavage
degree was distinguished according to molecular weight, and the categories named experimental groups 1-5 respectively. Brown
algal oligosaccharide (0.02% concentration) was used to co-culture with human keratinocytes and macrophages for 24 h, taking
normal cultured cells as the control group. The cell proliferation ability of each group was evaluated, Caspase3 was detected
via immunofluorescence to evaluate cell apoptosis, and an ROS kit was used to evaluate oxidative stress. After co-culture
with macrophages for 24 h, IL-1β, IL-10, and TNF- α were detected using ELISA and the endocytosis ability of the cells was
observed using transmission electron microscopy. The minimum inhibitory concentration (MIC) and minimum bactericidal
concentration (MBC) of fucoidan against Staphylococcus aureus, Escherichia coli, and Candida albicans were detected using
the micro-broth method. SD rats with a full-thickness skin defect wound model on their backs were treated with sodium
alginate solution as positive control group, normal saline dressing was used as negative control group, and 0.02% brown algal
oligosaccharide as the experimental group. Wound healing was observed on days 6 and 12, the wound tissue was stained with HE
to observe histological changes, and inflammatory factors, apoptosis, and oxidative stress were detected. Results At a fucoidan
molecular weight of <500 or 500-1000, both the cell and animal experiments (on day 6) showed effective promotion of cell
proliferation and IL-10 secretion, reduced IL-1 β, TNF- α, and apoptosis levels. Compared with the negative control group, the
effect of promoting wound healing was more obvious when the molecular weight was less than 1 000, especially less than 500, but
the effect of promoting wound healing was weaker than that of the positive control group (P <0.05). However, when the molecular
weight of fucoidan was >1 000, the cell experiments showed no significant differences from the control group (P >0.05). In the
animal experiment, when the molecular weight was 5 000-10 000 or 10 000-20 000, the wound healing rate increased (P <0.05).
Compared with the positive control group, there was no significant difference in wound healing rate (P >0.05). In the experiment,
it formed a thin membrane structure in the wound, but the other indicators did not change significantly (P >0.05). Enhanced
phagocytosis was not observed by transmission electron microscopy. MIC and MBC detection of alginate oligosaccharides with
various molecular weights did not reveal antibacterial or bactericidal effects at 5% concentration. Conclusion The biological
effects of fucoidan are strictly related to its molecular weight (cleavage degree). Low molecular weight fucoidan can improve the
secretion of inflammatory factors, promote cell proliferation, inhibit cell apoptosis, and improve the degree of oxidative stress,
which does not depend on whether fucoidan enters cells. High molecular weight fucoidan has no obvious biological effect, but
forms a membrane and indirectly
