Interactions between DPPC as a component of lung surfactant and amorphous silica nanoparticles investigated by HILIC-ESI–MS

• In this study we quantitatively demonstrated the effects induced by amorphous SiO2-NPs in biologically relevant samples.
• Utilizing a rapid HILIC-ESI-MS technique we found an approx. 50% DPPC decrease in cell culture medium during exposure to amorphous SiO2-NPs.
• A substantial affinity of small SiO2-NPs to DPPC standard solution compared to bigger SiO2-NPs was not confirmed for biological specimens.
• HILIC-ESI-MS revealed that A549 cells internalized DPPC during growth in medium complemented with DPPC containing serum.

This paper reports a rapid HILIC-ESI–MS assay to quantify dipalmitoylphosphatidylcholine (DPPC) as component of lung surfactant for nanosafety studies. The technique was used to investigate the concentration-dependent sorption of DPPC to two-sizes of amorphous SiO2 nanoparticles (SiO2-NPs) in a MeOH:H2O (50/50 v/v) mixture and in cell culture medium. In MeOH:H2O (50/50 v/v), the sorption of DPPC was positively correlated with the nanoparticles concentration. A substantial affinity of small amorphous SiO2-NPs (25 nm) to DPPC standard solution compared to bigger SiO2-NPs (75 nm) was not confirmed for biological specimens. After dispersion of SiO2-NPs in DPPC containing cell culture medium, the capacity of the SiO2-NPs to bind DPPC was reduced in comparison to a mixture of MeOH:H2O (50/50 v/v) regardless from the nanoparticles size.Furthermore, HILIC-ESI–MS revealed that A549 cells internalized DPPC during growth in serum containing medium complemented with DPPC. This finding was in a good agreement with the potential of alveolar type II cells to recycle surfactant components.Binding of lipids present in the cell culture medium to amorphous SiO2-NPs was supported by means of HILIC-ESI–MS, TEM and ICP-MS independently.

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