Hollow spherical nanoparticulate aggregates as potential ultrasound contrast agent: shell thickness characterization

Objective: The objective of this work is to manufacture hollow spherical nanoparticulate aggregates for use as an ultrasound contrast agent by means of spray drying of nanoparticulate suspension at a fast drying rate. Methodology: Biocompatible PMMA-MeOPEGMA and silica nanoparticles are used as the model nanoparticles. The impacts of changing the nanoparticle concentration, pH, and spray drying operating condition on the size and shell thickness-to-particle radius (S R) ratio, which governs the shell mechanical stability, are investigated. Results and conclusion: The results indicate that the hollow microspheres size varies between 2 and 10 μm having S R ratio between 2% and 4%, where the smaller size particles exhibit a higher S R ratio. The resultant S R ratio is found to be more influenced by process parameters acting at the nanoparticle scale (e.g., suspension pH) than by the spray drying operating condition.