Synthesis of low-molecular weight fucoidan derivatives and their binding abilities to SARS-CoV-2 spike proteins

Fucoidan from Ascophyllum nodosum and Undaria pinnatifida attenuate SARS-CoV-2 infection in vitro and in vivo by suppressing ACE2 and alleviating inflammation

The global healthcare challenge posed by COVID-19 necessitates the continuous exploration for novel antiviral agents. Fucoidans have demonstrated antiviral activity. However, the underlying structure-activity mechanism responsible for the inhibitory activity of fucoidans from Ascophyllum nodosum (FUCA) and Undaria pinnatifida (FUCU) against SARS-CoV-2 remains unclear. FUCA was characterized as a homopolymer with a backbone structure of repeating (1 → 3) and (1 → 4) linked α-l-fucopyranose residues, whereas FUCU was a heteropolysaccharide composed of Fuc1-3Gal1-6 repeats. Furthermore, FUCA demonstrated significantly higher anti-SARS-CoV-2 activity than FUCU (EC50: 48.66 vs 69.52 μg/mL), suggesting the degree of branching rather than sulfate content affected the antiviral activity. Additionally, FUCA exhibited a dose-dependent inhibitory effect on ACE2, surpassing the inhibitory activity of FUCU. In vitro, both FUCA and FUCU treatments downregulated the expression of pro-inflammatory cytokines (IL-6, IFN-α, IFN-γ, and TNF-α) and anti-inflammatory cytokines (IL-10 and IFN-β) induced by viral infection. In hamsters, FUCA demonstrated greater effectiveness in attenuating lung and gastrointestinal injury and reducing ACE2 expression, compared to FUCU. Analysis of the 16S rRNA gene sequencing revealed that only FUCU partially alleviated the gut microbiota dysbiosis caused by SARS-CoV-2. Consequently, our study provides a scientific basis for considering fucoidans as poteintial prophylactic food components against SARS-CoV-2.

Fucoidan-based antibody-free magnetic nanoparticle for on-site detection of waterborne SARS-CoV-2

The portable and sensitive point-of-care-test (POCT) method is in urgent need to detect severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) for ensuring public health and safety. However, detection of trace number of pathogens in real water sample from the environment still faces challenges, because complex environment disruptors can rapidly degrade targets. Herein, magnetic beads coated with fucoidan and polydopamine (Fuc-PDA-MBs) were introduced as the capture carrier for pretreatment of samples. Fucoidan, a sulfated polysaccharide, can recognize the SARS-CoV-2 spike (S1) protein receptor-binding domain (S1 RBD) and was chosen for replacement of antibody in enrichment. Environmental water seeded with SARS-CoV-2 spike pseudovirus was applied to test performance of Fuc-PDA-MBs method. Under optimal conditions, the use of Fuc-PDA-MBs showed average 76 % capture efficiency at SARS-CoV-2 spike pseudovirus concentration ranging from 107.62 to 104.34 gene copies (gc)/L. Compared with Electronegative filtration (ENF), Fuc-PDA-MBs showed better virion sorption effectiveness. Fuc-PDA-MBs also validated by raw contaminated urban wastewater and showed high recovery results for SARS-CoV-2 variants. To rapidly detect virus in POCT, nucleic acid extraction-free Loop-Mediated Isothermal Amplification (LAMP) was used for simplifying experimental process. The Fuc-PDA-MBs-LAMP assay showed the quantitation limit of sample (LOQ) was 105.49 gc/L. The whole procedure could be completed within 90 min, including 30 min for virus pre-enrichment, 10 min nucleic acid release and 45 min LAMP analysis. Compared with regular antibody-based immunodetection, this integrated system provides broad-spectrum, economic way to detect SARS-CoV-2 mutants in complex environments and also adaptable for high throughput test, which might be used for on-site early warning of SARS-CoV-2 outbreaks in developing area.

Post-COVID-19 syndrome management: Utilizing the potential of dietary polysaccharides

The COVID-19 pandemic has caused significant global impact, resulting in long-term health effects for many individuals. As more patients recover, there is a growing need to identify effective management strategies for ongoing health concerns, such as post-COVID-19 syndrome, characterized by persistent symptoms or complications beyond several weeks or months from the onset of symptoms. In this review, we explore the potential of dietary polysaccharides as a promising approach to managing post-COVID-19 syndrome. We summarize the immunomodulatory, antioxidant, antiviral, and prebiotic activities of dietary polysaccharides for the management of post-COVID-19 syndrome. Furthermore, the review investigates the role of polysaccharides in enhancing immune response, regulating immune function, improving oxidative stress, inhibiting virus binding to ACE2, balancing gut microbiota, and increasing functional metabolites. These properties of dietary polysaccharides may help alleviate COVID-19 symptoms, providing a promising avenue for effective treatment strategies.

Fucoidan-Containing, Low-Adhesive Siloxane Coatings for Medical Applications: Inhibition of Bacterial Growth and Biofilm Development

The deposition of low-adhesive siloxane coatings is a current trend for the non-toxic control of bacterial growth and biofilm formation. Total elimination of biofilm formation has not been reported so far. The aim of this investigation was to study the ability of a non-toxic, natural, biologically active substance, such as fucoidan, to inhibit bacterial growth on similar medical coatings. The fucoidan amount was varied, and its impact on the bioadhesion-influencing surface characteristics, as well as on bacterial cell growth, was investigated. The inclusion of up to 3-4 wt.% brown algae-derived fucoidan in the coatings increases their inhibitory effect, more significantly on the Gram-positive bacterium S. aureus than on the Gram-negative bacterium Escherichia coli. The biological activity of the studied siloxane coatings was ascribed to the formation of a low-adhesive, biologically active surface top layer consisting of siloxane oil and dispersed water-soluble fucoidan particles. This is the first report on the antibacterial activity of fucoidan-containing medical siloxane coatings. The experimental results give reason to expect that relevantly selected, natural biologically active substances can be efficient in the non-toxic control of bacterial growth on medical devices and, as a result, medical device-associated infections.

Pharmacology of Heparin and Related Drugs: An Update

Heparin has been used extensively as an antithrombotic and anticoagulant for close to 100 years. This anticoagulant activity is attributed mainly to the pentasaccharide sequence, which potentiates the inhibitory action of antithrombin, a major inhibitor of the coagulation cascade. More recently it has been elucidated that heparin exhibits anti-inflammatory effect via interference of the formation of neutrophil extracellular traps and this may also contribute to heparin's antithrombotic activity. This illustrates that heparin interacts with a broad range of biomolecules, exerting both anticoagulant and nonanticoagulant actions. Since our previous review, there has been an increased interest in these nonanticoagulant effects of heparin, with the beneficial role in patients infected with SARS2-coronavirus a highly topical example. This article provides an update on our previous review with more recent developments and observations made for these novel uses of heparin and an overview of the development status of heparin-based drugs. SIGNIFICANCE STATEMENT: This state-of-the-art review covers recent developments in the use of heparin and heparin-like materials as anticoagulant, now including immunothrombosis observations, and as nonanticoagulant including a role in the treatment of SARS-coronavirus and inflammatory conditions.

Fucoidan-Derived Functional Oligosaccharides: Recent Developments, Preparation, and Potential Applications

Oligosaccharides derived from natural resources are attracting increasing attention as both food and nutraceutical products because of their beneficial health effects and lack of toxicity. During the past few decades, many studies have focused on the potential health benefits of fucoidan. Recently, new interest has emerged in fucoidan, partially hydrolysed into fuco-oligosaccharides (FOSs) or low-molecular weight fucoidan, owing to their superior solubility and biological activities compared with fucoidan. There is considerable interest in their development for use in the functional food, cosmetic, and pharmaceutical industries. Therefore, this review summarises and discusses the preparation of FOSs from fucoidan using mild acid hydrolysis, enzymatic depolymerisation, and radical degradation methods, and discusses the advantages and disadvantages of hydrolysis methods. Several purification steps performed to obtain FOSs (according to the latest reports) are also reviewed. Moreover, the biological activities of FOS that are beneficial to human health are summarised based on evidence from in vitro and in vivo studies, and the possible mechanisms for the prevention or treatment of various diseases are discussed.