Tethering functional ligands onto shell of ultrasound active polymeric microbubbles.

Hollow (air-filled) microparticles, i.e., microbubbles, provide a promising novel vehicle for both local delivery of therapeutic agents and simultaneous diagnostic ultrasound echo investigations. In this paper, we describe the synthetic routes for decorating the polymeric shell of a poly(vinyl alcohol)-based microbubble with low and high molecular weight ligands with pharmacological relevance. Investigations on physical properties of microbubbles and surface chemical coupling with different cargo molecules such as L-cysteine, L-lysine, poly(L-lysine), chitosan, and beta-cyclodextrin were carried out by CD and NMR spectroscopies, confocal laser scanning microscopy, and microcalorimetry. The in vitro cytotoxicity and biocompatibility of the polymer microbubbles have been also determined toward different cell lines. The results are discussed in terms of the features shown by this device, i.e., injectability, long shelf life, ease of preparation, biocompatibility, loading and cargo capacities, and functional properties.