Dissolution, translocation, and disposition have been shown to play a key role in the fate and effects of inhaled particles and fibers. Concepts that have been applied in the micron size range may be usefully applied to the nanoscale range, but new challenges are presented based on the small size and possible change in the dissolution:translocation relationship. The size of the component molecule itself may be on the nanoscale. Solute concentration, surface area, surface morphology, surface energy, dissolution layer properties, adsorbing species, and aggregation are relevant parameters in considering dissolution at the nanoscale. With regard to the etiopathology caused by these types of particulates, the metrics of dose (particle number, surface area, mass or shape) is not yet well defined. Analytical procedures for assessing dissolution and translocation include chemical assay and particle characterization. Leaching of substituents from particle surfaces may also be important. Compartmentalization within the respiratory tract may add another dimension of complexity. Dissolution may be a critical step for some nanoscale materials in determining fate in the environment and within the body. This review, combining aspects of particle toxicology, material science, and analytical chemistry, is intended to provide a useful basis for developing relevant dissolution assay(s) for nanoscale particles.

Fractal geometry developed by Mandelbrot is finding many applications in the description of rugged fineparticles and fineparticle systems such as packed powder beds. In the earlier publications dealing with the fractal structure of fineparticle boundaries a great deal of the experimental work was carried out manually. This was time consuming and limited the amount of investigative work which could be undertaken in a given context. In this communication several algorithms for automating the evaluation of the fractal dimensions of rugged fineparticle boundaries by automated image analysis are explored. Comparative data generated by the various procedures are presented.

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