Impact of mucin protein corona on the gastrointestinal behavior and antioxidant activity of food carbon dots extracted from bread crust

Abstract

Bread products are widely consumed around the globe as they are a staple food in many countries. Recent studies have shown that the elevated temperatures and prolonged times used during bread baking can lead to the formation of appreciable amounts of carbon dots, which may have adverse effects on human health. Consequently, it is important to elucidate the potential fate of these carbon dots within the gastrointestinal tract. In this study, we characterized the properties of bread-derived carbon dots (BDCDs) and then investigated their interactions with mucin. The average diameter of the individual BDCDs was 5.81 nm but they tended to exist as clusters (around 91 nm) in aqueous environments. The BDCDs mainly consisted of carbon (70.9%), oxygen (27.6%), and nitrogen (1.5%). Like other types of carbon dots, the BDCDs were found to exhibit natural fluorescence. In simulated saliva, the carbon dots interacted with mucin to form BDCD–mucin complexes. These interactions caused the zeta potential of the BDCDs to change from −5.97 to −11.07 mV and their hydrodynamic diameters to increase from 91.3 to 122.4 nm. Moreover, these interactions caused changes in the conformation of the mucin. Furthermore, in vitro simulated digestion studies showed that the BDCDs induced conformational changes in pepsin, reducing its enzymatic activity by around 20.8%. However, this effect was mitigated when BDCD–mucin complexes were used instead of BDCDs, highlighting the important role that mucin plays in mediating carbon dot–enzyme interactions. Moreover, the BDCD–mucin complexes were better at attenuating reactive oxygen species generation in Caco-2 cells than BDCDs, which led to higher cell viability. This study provides new insights into the role of mucin coronas in modulating the gastrointestinal behavior of carbon dots, highlighting their potential impact on human health.