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 (SR) 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 SR ratio between 2 and 4, where the smaller size particles exhibit a higher SR ratio. The resultant SR 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.