Simulated Gastrointestinal Fluids Impact the Stability of Polymer-Functionalized Selenium Nanoparticles: Physicochemical Aspects.

Background: Selenium (Se) is a vital micronutrient for maintaining homeostasis in the human body. Selenium nanoparticles (SeNPs) have demonstrated improved bioavailability compared to both inorganic and organic forms of Se. Therefore, supplementing with elemental Se in its nano-form is highly promising for biomedical applications related to Se deficiency.

Purpose: The primary objective of this study was to evaluate the impact of the main gastrointestinal proteins on the physicochemical properties and stability of polymer-coated SeNPs.

Methods: SeNPs functionalized with thiolated chitosan or hyaluronic acid were characterized based on their composition, morphology, size, and zeta potential. The stability of these particles was evaluated in simulated gastric and intestinal fluids. Additionally, the interaction propensity between major gastric proteins, such as pepsin and pancreatin, and functionalized SeNPs was investigated with FTIR, fluorescence quenching titrations, and in situ adsorption measurements.

Results: The composition of the media, including pH and ionic strength, the chemistry of polymers, and the presence of the proteins, influence the size and zeta potential of the SeNPs. The increase in NP size due to the formation of large agglomerates, along with the decrease in zeta potential magnitude, confirmed the formation of a protein corona. Both pepsin and pancreatin showed a strong affinity to the particle surface. Based on the values of the apparent equilibrium dissociation constant this affinity was more pronounced for positively charged thiolated chitosan coated SeNPs compared to those coated with negatively charged hyaluronic acid. The polymer coated SeNPs displayed antioxidative potential, which could be very beneficial for health conditions associated with Se-deficiency.

Conclusion: This study highlights the importance of exploring the characteristics of polymer-functionalized SeNPs under gastrointestinal conditions. Such investigations are important for developing nutritional supplements that can gradually release Se from SeNPs, thereby improving selenium absorption, bioavailability, and safety.