Antioxidant Activity of Metal Nanoparticles Coated with Tocopherol-Like Residues—The Importance of Studies in Homo- and Heterogeneous Systems

Abstract

Functionalized nanoparticles (NPs) attract great attention in pharmacy, diagnostics, and biomedical areas due to benefits like localization and unique interactions of NPs with biocomponents of living cells. In the present paper, we prepared and characterized two kinds of gold nanoparticles (AuNPs) coated with α-tocopherol-like residues: 1A were soluble in non-polar solvents and their antioxidant activity was tested during the peroxidation of a model hydrocarbon in a homogeneous system, whereas nanoparticles 1B were soluble in polar solvents and were applied as antioxidants in micellar and liposomal systems. The effectiveness of 1A is comparable to 2,2,5,7,8-pentamethylchroman-6-ol (PMHC, an analogue of α-tocopherol). Taking the results of the kinetic measurements, we calculated an average number of 2150 chromanol residues per one NP, suggesting a thick organic coating around the metal core. In heterogeneous systems, the peroxidation of methyl linoleate dispersed in Triton X-100 micelles or DMPC liposomes resulted in the observation that 1B (545 chromanol residues per one NP) was active enough to effectively inhibit peroxidation in a micellar system, but in a liposomal system, 1B behaved as a retardant (no clear induction period). The importance of microenvironment in heterogeneous systems on the overall antioxidant activity of nanoparticles is discussed.

Antioxidants: Classification, Natural Sources, Activity/Capacity Measurements, and Usefulness for the Synthesis of Nanoparticles

“…Most papers present the synthesis of gold and silver nanoparticles that are easily functionalized with different small molecules of antioxidants, for instance, gold nanoparticles functionalized with tocopherol [ 440 , 441 ], gold nanoparticles coated with chitosan [ 442 ], silver NPs with glutathione [ 443 ], or more complex ones like graphite layered 30 nm cobalt nanomagnets with attached tocopherol derivatives [ 444 ]. Konopko et al [ 440 ] and Nie et al [ 441 ] prepared and characterized gold nanoparticles (AuNPs) coated with α-tocopherol-like residues. Both research groups proved that the assembly of chromanol groups on gold nanoparticles could efficiently enhance the activity of the vitamin E-derived antioxidant.…”

Green Fabrication of Zinc Oxide Nanoparticles Using Phlomis Leaf Extract: Characterization and In Vitro Evaluation of Cytotoxicity and Antibacterial Properties

“…Metal oxide nanoparticles have generated considerable attention in biomedical technology due to their enormous surface area and are widely used in industrial and therapeutic applications [9][10][11]. Both metal and metal oxide nanoparticles exhibit substantial antioxidant and antibacterial properties and are frequently used in the detection of pathogenic microorganisms and in the diagnosis of cancer progression [12][13][14]. At low concentrations, metal oxide nanoparticles such as zinc (Zn), titanium (Ti), and magnesium (Mg) oxide nanoparticles limit microbial development [15][16][17].…”

Relationship between Antioxidant Activity and Ligand Basicity in the Dipicolinate Series of Oxovanadium(IV) and Dioxovanadium(V) Complexes

“…The first are antioxidants that interrupt radical reactions by donating hydrogen atoms or electrons to radicals, which leads to the formation of compounds with greater stability. Such compounds include: tocopherols [6,7], phenols [8], hydroquinones [9]. The second group includes substances whose action is synergistic.…”