No decomposition of titanium dioxide particles observed in lung surfactant

Modeling was used to calculate whether the main component found in lung surfactant, dipalmitoylphosphatidiylcholin (DPPC) can dissolve the bonds in titanium dioxide aggregates and agglomerates. This would only be possible if the bonds formed between the titanium dioxide (TiO2) and DPPC were more stable than those within the aggregates and agglomerates. The calculations showed that 1 J/m² energy would be needed to dissolve the hydrogen bridges bonding the micrometer-scale titanium dioxide agglomerates. To split the even firmer bonds in titanium aggregates into nanoparticles, 10 J/m² would be required. The interaction energy at the interface between titanium dioxide and DPPC is only 0.05 J/m². This shows that the interaction with DPPC is far weaker than that within the titanium dioxide agglomerates and aggregates so the agglomerates are not likely to decompose.

The theoretical findings were validated by a lab trial simulating the physiological conditions. Titanium dioxide and various concentrations of DPPC were added to a buffered solution of common salt at pH 6.5. Particle size distribution measurements did not indicate any change resulting from the addition of DPPC. No isolated particles with dimensions of less than 100 nm were found.

The scientists therefore concluded that DPPC, which is the main component in lung surfactant, envelops the titanium dioxide agglomerates but does not dissolve the agglomerates or aggregates. The theoretical and experimental did not produce any evidence that the titanium dioxide agglomerates studied form nanoparticles under physiological conditions.