# Silicon Dioxide Nanoparticles Affect the In Vitro Digestion of Sodium Caseinate but Not the Formation and Functionality of Bioactive Peptides

## TL;DR

This study shows that silicon dioxide nanoparticles change how sodium caseinate digests in the lab but do not affect the bioactive peptides formed.

## Contribution

The study reveals that SiO2 nanoparticles alter the structure and digestion of sodium caseinate without impacting bioactive peptide functionality.

## Key findings

- SiO2 nanoparticles alter the tertiary structure of sodium caseinate.
- SiO2 reduces the proteolysis rate of sodium caseinate during in vitro digestion.
- Bioactive peptide properties remain unaffected by SiO2 interactions.

## Abstract

Silicon dioxide (SiO2) nanoparticles (NPs) are among the most commonly utilized inorganic NPs in the food industry because of their ability to enhance the quality of a variety of foods. In the present study, the impact of SiO2 on the NaCN structure and digestibility was examined. The study also aimed to ascertain the bioactive peptide formation as affected by the interactions between SiO2 and NaCN. The CD spectrum signals in the 250–290‐nm region were altered in the presence of SiO2 at 14 mg/mL, indicating an alteration in the tertiary structure of NaCN. Additionally, the hydrodynamic size of NaCN micelles increased nearly 2‐fold upon interaction with SiO2. Gathering of casein micelles was observed in the presence of SiO2, especially at high NP concentrations. At the end of the in vitro digestion simulation, SiO2 led to a reduced proteolysis rate of NaCN from 8.3 mM Leu to 6.9 mM Leu in the stomach and from 17.4 mM Leu to 15.3 mM Leu in the intestine, as revealed by the OPA assay. The observed phenomenon is likely attributed to the aggregation of sodium caseinate following its interaction with SiO2 NPs, as evidenced by electron microscope imaging. However, there were no significant alterations in the overall peptide profile. Antioxidant, antimicrobial, and ACE‐inhibitory properties of the < 3‐kDa peptide fraction remained unaffected by SiO2, which is consistent with a similar peptide profile.

This study aimed to investigate the effect of SiO2 nanoparticles on sodium caseinate structure and digestibility. SiO2 nanoparticles change the secondary and tertiary structures of NaCN. Also, SiO2 nanoparticles influence in vitro digestibility of NaCN. However, it does not affect the bioactivity of the < 3‐kDa peptide fraction.