Effect of cholesterol and other selected physiological parameters on in vitro lung bioaccessibility of particle-bound potentially toxic elements

Abstract

In recent years, the number of studies on in vitro lung bioaccessibility of potentially toxic elements (PTEs) has increased; however, physiological parameters for these tests have yet to be optimized. This study aims to (1) evaluate the effect of adding cholesterol to synthetic lung fluid on PTEs bioaccessibility, and to (2) assess the effect of other selected test parameters on bioaccessibility. The bioaccessibility of Cd, Co, Cr, Cu, Mn, Ni, Pb, Sb, V, and Zn have been investigated using seven formulations of Gamble’s solution (GS, with/without cholesterol/DPPC) and one artificial lysosomal fluid (ALF) on two reference materials (SRM 2691, BGS 102). The bioaccessibility of certain PTEs increased in GS modified with 5% DPPC (e.g., V in BGS 102 from 2.87 to 8.35%), 0.25% cholesterol (e.g., Cr in SRM 2691 from 27.3 to 31.5%), and 2% DPPC + 0.25% cholesterol (e.g., Cu in BGS 102 from 43.9 to 46.2%). Using DPPC + cholesterol may be recommended for bioaccessibility testing. The effect of the tested solid-to-liquid ratio (S/L) was sample/element-specific. Overall, lower S/L led to higher bioaccessibility in ALF (e.g., for Pb: 94.8% at 1/500 vs. 36.5% at 1/100). The peak bioaccessibility was reached at a 4-week extraction, suggesting a longer testing duration when feasible. Higher agitation (100 vs. 20 rpm) increased the bioaccessibility of some PTEs (e.g., 91.0% vs. 79.7% for Cd in BGS 102). Method modifications would prove valuable when used together with highly needed in vivo validation studies for in vitro lung bioaccessibility.