Methods of preparation of multifunctional microbubbles and their in vitro / in vivo assessment of stability, functional and structural properties.

Microbubbles (MBs) are ultrasound responsive colloidal particles with a strong potential to become theranostic agents, combining the contrast agent activity with therapeutic functionality. In the last decades, MBs have played a significant role as ultrasound contrast agents in diagnostic imaging. MBs have also shown great potential in applications such as molecular imaging, drug delivery, gene therapy and sonothrombolysis. A full understanding of all physical processes underlying the MBs' stability and acoustic behavior is available in the literature. Efforts have been now addressed to the study of chemical and biological features of multifunctional lipid, protein, or polymer shelled MBs. A number of methods of preparation of "smart" MBs for ultrasound image-guided therapy have been recently developed. In this review, different approaches utilized in preparing multifunctional MBs are discussed with specific attention to the current strategies adopted to design MBs with specialized functions. In vitro / in vivo assessment of MBs' stability and activity will be discussed with a particular emphasis on the emerging applications of MBs for the multiple imaging modalities, the effective opening of blood brain barrier, BBB, and for the therapeutic treatment of antimicrobial films.

Receptor-mediated endocytosis of biofilm-forming Enterococcus faecalis by rat peritoneal macrophages.

BACKGROUND & OBJECTIVES: Enterococci are important nosocomial pathogens that are increasingly difficult to treat due to intrinsic and acquired resistance to antibiotics. Studies were taken up to identify virulence factors and to characterise pathogenic mechanisms of such infections to evaluate potential targets for treatments alternative to antibiotic therapy. This study was carried out to evaluate the contribution of extracellular polysaccharide expressed by Enterococcus faecalis to resistance to phagocytosis and survival within rat peritoneal macrophages. METHODS: Six E. faecalis clinical isolates were tested for their ability to survive within rat peritoneal macrophages. Cytochalasin D, colchicine and monodansylcadaverine were used to investigate the route of enterococcal entry inside macrophages. RESULTS: Four of the isolates were able to produce extracellular polysaccharide and form biofilm after growth in glucose-supplemented medium, while no production could be detected in glucose deficient medium. Two isolates were polysaccharide-negative in both conditions. Isolates expressing extracellular polysaccharide were able to survive for more than 24 h compared to polysaccharide-negative bacterial cells of the same strain grown in glucose-deficient medium, which were readily cleared. Cytochalasin D virtually abolished the number of viable intracellular bacteria, after growth in either trypticase soy broth (TSB) or TSB supplemented with glucose; colchicine and monodansylcadaverine strongly affected survival of polysaccharide-positive bacteria, significantly more than that of polysaccharide-negative ones. INTERPRETATION & CONCLUSION: Biofilm-forming E. faecalis survived within rat peritoneal macrophages significantly better than polysaccharide-negative isolates. Perturbators of cytoskeleton and of surface receptors turnover, indicated receptors-mediated endocytosis as the most likely route for enterococcal entry into macrophages.