In this study, we investigated the pathways (including the formation of hydroxyl radicals and chloramines) leading to luminol chemiluminescence induced by hypochlorite generated in a suspension of stimulated rabbit polymorphonuclear leukocytes. Chemiluminescence of leukocytes stimulated by phorbol myristate acetate, which was enhanced by luminol (0.02 mM), did not change in the presence of dimethyl sulfoxide at moderate concentrations (0.02–2.6 mM), under which the latter should manifest the specific ability to scavenge hydroxyl radicals. This indicates that stimulation of polymorphonuclear leukocytes is not accompanied by the generation of hydroxyl radicals with the involvement of superoxide anion and hypochlorite synthesized by myeloperoxidase. At high concentrations of dimethyl sulfoxide (260 mM), chemiluminescence markedly declined because dimethyl sulfoxide directly reacts with hypochlorite. The luminol emission intensity considerably increased after its addition to a suspension of leukocytes that were preliminarily stimulated for 10 min. This effect was caused by the accumulation of hydrogen peroxide rather than chloramines. Exogenous amino acids and taurine at high concentrations (3–15 mM) quench chemiluminescence. All these data indicate that chemiluminescence in the system studied is largely determined by the direct initial reaction of hypochlorite with luminol, the emission intensity increasing as a result of oxidation of luminol transformation products by hydrogen peroxide.

Fucoidan is of considerable interest for the development of drug carriers. The inclusion of fucoidan allows calcium carbonate microparticles in the form of vaterite to acquire new properties, enabling their use in the immobilization of protein preparations. In this work, we investigated the properties of hybrid vaterite microparticles with fucoidan from Fucus vesiculosus obtained by co-precipitation and loaded with recombinant human lactoferrin from goats. The hybrid microparticles had a smaller diameter (3–4 µm), larger surface area (35–36 m²g⁻¹), smaller pore size (5–10 nm average), and more negative ζ-potential (−(11–13) mV) than the control vaterite microparticles. The incorporation of lactoferrin into the microparticles by co-precipitation in complex with fucoidan was greater than when the protein was adsorbed onto the hybrid microparticles. Microparticles with fucoidan and lactoferrin were stable in acidic environments, released both components over a prolonged period at pH 7.4, and possessed mucoadhesive properties and anticoagulant activity. The antibacterial properties of hybrid microparticles with fucoidan and lactoferrin against Bacillus subtilis were characterized. Microparticles of vaterite with fucoidan can serve as a platform for the microfabrication of effective means of delivering therapeutic proteins.

The application of vaterite microparticles for mucosal delivery depends on their interaction with mucin and immune cells. As we have shown previously, the binding of mucin onto particles enhances the generation of reactive oxygen species by neutrophils. The attenuation of the pro-oxidant effect of the bound mucin through the modification of vaterite could improve its biocompatibility. Hybrid microparticles composed of vaterite and pectin (CCP) were prepared using co-precipitation. In comparison with vaterite (CC), they had a smaller diameter and pores, a greater surface area, and a negative zeta-potential. We aimed to study the cytotoxicity and mucin-dependent neutrophil-activating effect of CCP microparticles. The incorporated pectin did not influence the neutrophil damage according to a lactate dehydrogenase test. The difference in the CC- and CCP-elicited luminol or lucigenin chemiluminescence of neutrophils was insignificant, with no direct pro- or antioxidant effects from the incorporated pectin. Unlike soluble pectin, the CCP particles were ineffective at scavenging radicals in an ABAP–luminol test. The fluorescence of SYTOX Green demonstrated a CCP-stimulated formation of neutrophil extracellular traps (NETs). The pre-treatment of CC and CCP with mucin resulted in a 2.5-times-higher CL response of neutrophils to the CC-mucin than to the CCP-mucin. Thus, the incorporation of pectin into vaterite microspheres enabled an antioxidant effect to be reached when the neutrophils were activated by mucin-treated microparticles, presumably via exposed ligands.