Adhesive behavior of dual-targeted microbubbles carrying both Sialyl Lewisx and anti-ICAM-1 monoclonal antibody in vitro / 中华超声影像学杂志

Objective To assess the adhesive behavior of dual-targeted microbubbles carrying both Sialyl Lewisx and anti-ICAM-1 monoclonal antibodies in vitro. Methods Selectin-targeted (with Sialyl Lewisx) microbubbles (MB-S),ICAM-1-targeted (with anti-ICAM-1 monoclonal antibodies) microbubbles (MB-Ⅰ),and dual-targeted (with both ligands) microbubbles(MB-D) were prepared by attaching the ligands to the biotinylated lipid-microbubbles via multi-step avidin biotin bridging chemistry. A parallel plate flow chamber combined with a novel automated tracking algorithm,were used to analyze the transient velocities,rolling and firmly adherent numbers of microbubbles at various shear stress (0. 6,2.0 and 4.0 dyn/cm2)over 6 min. Microbubbles detachments were tested by ramping up the shear stress at 30 s intervals. Results At 0.6 dyn/cm2 shear stress, the rolling numbers of MB-S and MB-D were remarkably more than that of MB-I( P＜0.05), while at 2.0 and 4.0 dyn/cm2 MB-S performed higher rolling efficiency as compared with either MB-I and MB-D ( P＜ 0.05). In all flow conditions, the adhesive numbers of MB-D to the targets were obviously greater than those of MB-S and MB-I ( P＜ 0.05). Half-maximal detachment decreased gradually in MB-I, MB-D and MB-S by turns ( P＜ 0.05). Conclusions MB-I, MB-S and MB-D have different adhesive behaviors. MB-I exhibites primarily firm adhesion with low rolling efficiency, while MB-S reveales unstable or transient adhesion with high rolling efficiency,and MB-D exhibites firm adhesion with high rolling efficiency. MB-D may be suitable for molecular imaging in high-flow vessels.

Preparation and evaluation of nanometer-scale bubbles with surfaces of N-palmitoyl chitosan / 中华超声影像学杂志

Objective To develop nanometer-scale bubbles with surfaces of N-palmitoyl chitosan(PLCS) as ultrasound contrast agent and evaluate its characteristics and acoustic effects in vivo. Methods The PLCS nanobubbles were prepared using a cutting technique at differential high-frequency of shear speed. Both optical and transmission electron micrography were performed to determine the nanobubble size and morphology. Concentration, size-distribution and zeta potential of the PLCS nanobubbles were measured by cell counting chamber, Malvern lazer particle analyzer and zeta-sizer at 1-day, 45-day and 90-day. The acoustic effects of the PLCS nanobubbles on myocardium and renal tissue in 6 normal rats were observed using bolus infusion of the nanobubbles intravenously. The maximum video intensity(VI) was measured.Results The PLCS nanobubbles with nice round-shape and uniform site-distribution were demonstrated.The mean diameter,concentration and zeta potential of the PLCS nanobubbles were (617 ± 12) nm, (7.2 ±0.6) × 109/ml and (52.9 ± 1.3)mV at the 1-day,and all of parameters did not change significantly in 45-day and 90-day ( P ＞ 0. 05). A significant contrast-enhancement was noted on myocardium and renal tissue during infusion of the nanobubbles. VI on both tissues was (15.6 ± 1.1)GU and (27.3 ± 2.5)GU,respectively. The visual contrast-enhancement last up to (10 ± 2)min. Conclusions The PLCS nanometerscale bubbles have excellent physical-features and contrast-enhanced ultrasound effects in vivo. It may develop as a novel contrast ultrasound agent which could cross endothelial cell membrances.

Binding capability of microbubbles targeted to VCAM-1 under pulsatile high-shear flow conditions / 中华超声影像学杂志

Objective To assess the binding capability of microbubbles targeted to VCAM-1 using the parallel plate flow chamber mimic the pulsatile high-shear flow conditions of artery. Methods Targeted microbubbles were designed by conjugating monoclonal antibodies against mouse VCAM-1 to the lipid shell of the microbubbles via an "avidin-biotin" bridge. The binding and retention of targeted microbubbles to VCAM-1 (MBv) immobilized on a culture dish were assessed in a flow chamber at variable shear stress (0.5～ 16.0 dynes/cm2 ). The pulsatile flow conditions were generated and compared to the continuous flow conditions. The retentive ability of MBv was evaluated by the detachment test. Results The marked binding of MBv were seen in pulsatile and continuous flow conditions at low-shear flow conditions of 0.5 ～ 2dyn/cm2 ,but the binding rate in the pulsatile flow group was higher ( P ＜0. 05) than that in the continuous flow conditions. Furthermore,the marked binding of MBv was still noted at the highest shear rates (4～8dyn/cm2) under pulsatile flow conditions, while it was not observed under continuous flow conditions. The half detachment rate of MBv was high up to (20.7 ± 3. 1)dyn/cm2. Conclusions The targeted microbubbles binding to VCAM-1 specific and effective at high-shear stress under pulsatile flow conditions. The molecular ultrasound imaging can be potentially used in the high-shear conditions artery system.