Effects of Modified Magnetite Nanoparticles on Bacterial Cells and Enzyme Reactions

Current paper presents biological effects of magnetite nanoparticles (MNPs). Relations of MNP’ characteristics (zeta-potential and hydrodynamic diameters) with effects on bacteria and their enzymatic reactions were the main focus. Photobacterium phosphoreum and bacterial enzymatic reactions were chosen as bioassays. Three types of MNPs were under study: bare Fe3O4, Fe3O4 modified with 3-aminopropyltriethoxysilane (Fe3O4/APTES), and humic acids (Fe3O4/HA). Effects of the MNPs were studied at a low concentration range (< 2 mg/L) and attributed to availability and oxidative activity of Fe3+, high negative surface charge, and low hydrodynamic diameter of Fe3O4/HA, as well as higher Fe3+ content in suspensions of Fe3O4/HA. Low-concentration suspensions of bare Fe3O4 provided inhibitory effects in both bacterial and enzymatic bioassays, whereas the MNPs with modified surface (Fe3O4/APTES and Fe3O4/HA) did not affect the enzymatic activity. Under oxidative stress (i.e., in the solutions of model oxidizer, 1,4-benzoquinone), MNPs did not reveal antioxidant activity, moreover, Fe3O4/HA demonstrated additional inhibitory activity. The study contributes to the deeper understanding of a role of humic substances and silica in biogeochemical cycling of iron. Bioluminescence assays, cellular and enzymatic, can serve as convenient tools to evaluate bioavailability of Fe3+ in natural dispersions of iron-containing nanoparticles, e.g., magnetite, ferrihydrite, etc.

Set of enzymatic bioassays for assessment of soil pollution

A concept of the comprehensive assessment of soil contamination is proposed. In this concept, the conclusion regarding the presence of toxic substances in a sample, which is being analyzed, is connected with the inhibition of enzymatic reactions that are responsible for various functions of a live organism, such as luminescence, respiration, etc., these functions are taken as test functions in classical bioassays, which are using live objects (luminous bacteria, daphnia, algae, etc.). The regularities of the impact of different classes of toxicants on the activity of individual enzymes or coupled oligo-enzyme chains have been established. These enzyme reactions are selected as potential test objects - markers of pollution. The set of enzymatic bioassays consists of three enzyme systems with maximum sensitivity to different classes of toxicants: butyrylcholinesterase, NAD(P)H:FMN‑oxidoreductase + luciferase and lactate dehydrogenase + NAD(P)H:FMN‑oxidoreductase + luciferase. The possibility of using enzymes instead of living organisms in the bioassay of natural complex systems is shown.

Highly sensitive colorimetric detection of glucose and uric acid in biological fluids using chitosan-modified paper microfluidic devices

This paper describes the modification of microfluidic paper-based analytical devices (μPADs) with chitosan to improve the analytical performance of colorimetric measurements associated with enzymatic bioassays.