Molecular Antioxidants Maintain Synergistic Radical Scavenging Activity upon Co-Immobilization on Clay Nanoplatelets

Unbalanced levels of reactive oxygen species (ROS) result in oxidative stress, affecting both biomedical and industrial processes. Antioxidants can prevent ROS overproduction and thus delay or inhibit their harmful effects. Herein, activities of two molecular antioxidants (gallic acid (GA), a well-known phenolic compound, and nicotinamide adenine dinucleotide (NADH), a vital biological cofactor) were tested individually and in combination to assess possible synergistic, additive, or antagonistic effects in free radical scavenging and in redox capacity assays. GA was a remarkable radical scavenger, and NADH exhibited moderate antioxidant activity, while their combination at different molar ratios led to a synergistic effect since the resulting activity was superior to the sum of the individual GA and NADH activities. Their coimmobilization was performed on the surface of delaminated layered double hydroxide clay nanoplatelets by electrostatic interactions, and the synergistic effect was maintained upon such a heterogenization of these molecular antioxidants. The coimmobilization of GA and NADH expands the range of their potential applications, in which separation of antioxidant additives is important during treatments or manufacturing processes

Selektivno jetkani nizovi p–n spojeva u GaAs

Simultaneous S and Zn doping was applied to obtain multi-layered vapour phase epitaxial structures of GaAs. SIMS studies have shown that the simultaneous presence of S and Zn in the gas phase does not influence the incorporation of S or of Zn during the growth process. Epitaxial structures with n-p-n-p-n-p-n series of layers have been obtained by variation of S doping at constant Zn partial pressure. The layer thicknesses were 0.3 and 3 mm. SIMS profiles show good abruptness of the junctions, so n-type GaAs lamellae have been obtained by selective electrochemical etching from such layered structures. Results show a possible way for fabrication of micro-machined devices from GaAs.Primijenjeno je istovremeno dodavanje S i Zn tijekom rasta višeslojnih epitaksijskih struktura GaAs iz plinovite faze. SIMS mjerenja ukazuju da prisutnost S i Zn tijekom rasta sloja ne utječe na njihovo ugrađivanje. Epitaksijske strukture sa n– p–n–p–n–p–n nizom slojeva postignute su mijenjanjem dodavanja S pri stalnom parcijalnom tlaku Zn para. Debljine slojeva bile su 0.3 i 3 µm. SIMS profili pokazuju oštre granice spojeva. Selektivnim elektrokemijskim jetkanjem postignute su lamele GaAs n–tipa

Optimization of Interfacial Properties Improved the Stability and Activity of the Catalase Enzyme Immobilized on Plastic Nanobeads

The immobilization of catalase (CAT), a crucial oxidoreductase enzyme involved in quenching reactive oxygen species, on colloids and nanoparticles presents a promising strategy to improve dispersion and storage stability while maintaining its activity. Here, the immobilization of CAT onto polymeric nanoparticles (positively (AL) or negatively (SL) charged) was implemented directly (AL) or via surface functionalization (SL) with water-soluble chitosan derivatives (glycol chitosan (GC) and methyl glycol chitosan (MGC)). The interfacial properties were optimized to obtain highly stable AL-CAT, SL-GC-CAT, and SL-MGC-CAT dispersions, and confocal microscopy confirmed the presence of CAT in the composites. Assessment of hydrogen peroxide decomposition ability revealed that applying chitosan derivatives in the immobilization process not only enhanced colloidal stability but also augmented the activity and reusability of CAT. In particular, the use of MGC has led to significant advances, indicating its potential for industrial and biomedical applications. Overall, the findings highlight the advantages of using chitosan derivatives in CAT immobilization processes to maintain the stability and activity of the enzyme as well as provide important data for the development of processable enzyme-based nanoparticle systems to combat reactive oxygen species