Experimental determination of ultrafine TiO 2 deagglomeration in a surrogate pulmonary surfactant: Preliminary results

Although a number of studies have demonstrated an association between the surface area of low-solubility particles and biological response within the respiratory system, the use of agglomerated particles has led to ambiguities over the interpretation of results in many cases. A clear understanding of the role of particle size and total available surface area requires some knowledge of the degree of deagglomeration that takes place following deposition in the lungs. Samples of ultrafine TiO 2 (primary particle diameter - 1/420 nm) have been suspended in a surrogate pulmonary surfactant, and the size distribution of the suspended particles was measured using transmission electron microscopy. Comparison with airborne particle size distributions indicates a shift in modal diameter from - 1/4300 nm to - 1/4100 nm following suspension in the surfactant. There was no indication of particle deagglomeration to primary particles. It is hypothesized that the manufacturing process of materials such as ultrafine TiO 2 leads to the formation of primary agglomerates - clusters of primary particles held together by partial sintering - and that these represent the limit of deagglomeration following lung deposition.