Manifestations of Radiation Hormesis in Biological Fluids Exposed to Low-Flux Neutron Irradiation: Insights from IR Spectroscopy and Biochemical Analysis

This study presents a comprehensive comparative assessment of the structural and functional responses of human serum and hen egg serum to natural aging (3, 5, and 7 days) and low thermal neutron fluxes (1.3×108, 2.16×108, and 3×108 N/cm2). Structural changes were investigated using Fourier transform infrared spectroscopy (FTIR), and biochemical parameters were used to assess functional changes. Natural aging induced progressive negative frequency shifts in the region of 1080-1340 cm-1 consistent with dehydration, increased hydrogen bonding, and decreased mobility of lipid and protein components. In contrast, neutron irradiation produced predominantly positive frequency shifts (+3 to +8 cm-1), with the most pronounced effects observed at an intermediate flux density of 2.16×108 N/cm2. These changes indicate a weakening of hydrogen bonds, a redistribution of electron density within amide and phosphate groups, and a partial reorganization of the protein-lipid matrix. Biochemical analysis correlates with spectroscopic observations: natural aging was associated with a decrease in total protein content and a moderate increase in ALT and AST activities, whereas neutron irradiation stimulated enzymatic activity and metabolic parameters in a nonlinear, flux-dependent manner. It is assumed that the observed non-monotonic reaction with a maximum effect at an intermediate neutron flux is caused by low-flux hormesis of thermal neutrons. Overall, the results show that low-flux neutron irradiation induces adaptive structural and functional responses in biological fluids that are fundamentally different from passive aging processes, highlighting the potential of IR spectroscopy as a sensitive tool for detecting molecular-level changes induced by low-flux neutron exposure. The observed non-monotonic responses are consistent with a hormetic-like interpretation, though further studies are needed to confirm this mechanism.