Lymphocytes favor the attachment of CD11A-targeted microbubbles with endothelial cells in vitro

Ultrasound molecular imaging may provide new insights into the early detection and diagnose of diseases, such as atherosclerosis, thrombosis as well as inflammations by the attachment of various targeted contrast agents with disordered endothelium. However, molecular imaging of disordered endothelium in large and middle-sized arteries by site-specific accumulation of contrast agents is still difficult to achieve due to wall shear stress conditions in these vessels. Here, we provided an alternative strategy to improve the attachment of targeted contrast agents with endothelium with the aid of lymphocytes. Given the fact that lymphocytes are naturally equipped to adhere selectively to endothelium and to resist physiologic shear stresses in large- and middle-sized arteries, in this study, the targeted microbubbles were prepared by conjugating anti-CD11a antibodies to the biotinylated microbubbles through biotin-avidin linkage. The resulting targeted microbubbles were able to bind with TNF-α-stimulated lymphocytes, which could also adhere to murine endothelial bEnd.3 cells at same time. The number of adhered microbubbles increased in concomitant with elevation of TNF-α concentration, with mean 4 ± 4, 7 ± 4, 21 ± 9 and 103 ± 13 microbubbles per view field (200 ×) for 0.4, 2, 10 and 50 ng/ml of TNF-α stimulation, respectively. In contrast, fewer targeted microbubbles adhered to the TNF-α-stimulated endothelial cells without assistance of lymphocytes. These findings suggested that lymphocytes might be useful as a vehicle of targeted microbubbles to increase the site-specific accumulation of targeted ultrasound contrast agent and have potential application to ultrasound molecular imaging of cardiovascular diseases.