HiTrap™-assisted single cell ICP-MS for elucidating intestinal permeability of TiO₂ and SiO₂ (nano)particles from...

Reliable assessment of the intestinal fate inorganic particles requires analytical strategies capable of quantifying both epithelial transport and cellular uptake under realistic exposure conditions. However, the accurate quantification of intracellular particle uptake remains challenging because interference from extracellularly bound material can bias measurements, highlighting the need for effective purification approaches. In this work, simulated gastrointestinal digestion, Caco-2 Transwell® assays, a HiTrap™ Con A 4B purification step, and single cell inductively coupled plasma mass spectrometry (scICP-MS) were combined to investigate the bioavailability TiO₂ and SiO₂ (nano)particles from food matrices.

Bioaccessible fractions obtained from pure cocoa, soluble cocoa, and custard powder were used to evaluate matrix-dependent effects on particle translocation. TiO₂ transport ranged from 54 to 74% for standard dispersions and from 17 to 84% in food digests, whereas SiO₂ transport decreased from 43-78% to 1.3-33% in the presence of food matrices. Accurate determination of intracellular titanium by scICP-MS required incorporation of a HiTrap™ Con A 4B purification step to remove extracellular particle residues prior to analysis. Following purification, single cell measurements revealed marked heterogeneity in titanium accumulation, with median levels of 233-306 fg Ti cell^-1. Silicon accumulated at lower levels, with particulate SiO₂ reaching 84-86 fg Si cell^-1 and ionic silicon 51-54 fg Si cell^-1.

The results demonstrate that food matrix composition and particle speciation influence intestinal transport and cellular accumulation. Importantly, the HiTrap™ Con A 4B purification strategy was essential to ensure reliable intracellular quantification by eliminating extracellular particle contributions, thereby enabling robust single cell assessment of TiO₂ (nano)particle uptake.