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Products of lipid peroxidation induce detrimental structural changes in cell membranes, such as the formation of water pores, which occur in the presence of lipids with partially oxidized chains. However, the influence of another class of products, dicarboxylic acids, is still unclear. These products have greater mobility in the lipid bilayer, which enables their aggregation and the formation of favorable sites for the appearance of pores. Therefore, dodecanedioic acid (DDA) was selected as a model product. Additionally, the influence of several structurally different flavonoids on DDA aggregation via formation of hydrogen bonds with carboxyl groups was investigated. The molecular dynamics of DDA in DOPC lipid bilayer revealed the formation of aggregates extending over the hydrophobic region of the bilayer and increasing its polarity. Consequently, water penetration and the appearance of water wires was observed, representing a new step in the mechanism of pore formation. Furthermore, DDA molecules were found to interact with lipid polar groups, causing them to be buried in the bilayer. The addition of flavonoids to the system disrupted aggregate formation, resulting in the displacement of DDA molecules from the center of the bilayer. The placement of DDA and flavonoids in the lipid bilayer was confirmed by small-angle X-ray scattering. Atomic force microscopy and electron paramagnetic resonance were used to characterize the structural properties. The presence of DDA increased bilayer roughness and decreased the ordering of lipid chains, confirming its detrimental effects on the membrane surface, while flavonoids were found to reduce or reverse these changes.

Iron nanoparticles are used as a targeted drug delivery system. The nanocarrier itself can be genotoxic, trigger oxidative stress or cell death. Therefore, we developed an AC/DC magnetic syringe for injecting, stimulating drug release and safe removing of the nanocarrier. Alongside we optimized the method for nanoparticles’ drug release kinetics and testing cytotoxicity in vitro. • This paper presents detailed instructions for construction of AC/DC magnetic syringe device for stimulated drug release, injection and ejection of magnetic nanoparticles; nanoparticles preparation; adsorbing methylene blue on nanoparticles; determination of drug release kinetics from nanocarriers on the example of methylene blue • Gomori´s Prussian blue reaction for differentiated SH-SY5Y human neuroblastoma cell line; MTT viability assay optimized for differentiated SH-SY5Y human neuroblastoma cell line and antioxidant enzymes activities assay and lipid peroxidation methods are optimized for cell analyses cell cultivation for nanoparticles cytotoxicity testing in vitro. • Those protocols are the first step toward further testing the effect of nanoparticles in vivo, on brain tissue.