ABSTRACT
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.
ABSTRACT
Objective To filter the noises in the experimental data of parallel plate flow chamber for observing more clearly the events occurring in the process of cell rolling adhesion and develop a new method to measure the elasticity of microvillus on cells based on the flow chamber experiment. Method The experiment of E-selectin regulated HL-60 cell rolling was performed by flow chamber system, and the data were denoised by wavelet analysis so that the high frequency thermal response signals were extracted from the data. Based on the equipartition theorem and equilibrium equations of tethered cell, the relationship between the cell microvillus spring constant and thermal fluctuations was constructed. Results Filtering noises from cell rolling time course by wavelet analysis, the events such as free rolling, slowing down, stopping and speeding up of rolling cell could be observed more easily; almost 80% of fluctuating energy of a rolling cell was involved in its high frequency fluctuation which was regarded as the thermal response of the cell to the Brown movement of water molecules, and the spring constant of microvillus on HL-60 cell was measured to be (13.7±7.4) μN/m at wall shear stress from 0.01～0.06 Pa. Conclusions The wavelet analysis can filter the thermal noises in cell rolling data of flow chamber experiment, and since the rigidity information of cell microvillus is involved in and can be extracted from the high frequency thermal fluctuation of the rolling cell, the parallel plate flow chamber experimental technique can be extended to measure the elasticity of microvillus on cells.