To evaluate the application of endothelial cell-specific CD31 antibody-targeted fluorescence imaging in liver segment labeling.

The endothelial cell-specific antibody CD31 with rapid binding property was selected by immunofluorescence. The binding characteristics of CD31 antibody were qualitatively and quantitatively evaluated with coupling fluorescent dye Alexa Fluor 647 (AF647). The localization, half-life and cytotoxicity of CD31 fluorescent antibody were analyzed by endothelial cell staining in vitro. The capture efficiency of CD31 antibody was analyzed by single cell suspension model. The relationship between the perfusion dose and capture efficiency of CD31 antibody was assessed in liver perfusion model in vitro. The difference between perfused and non-perfused liver segments was analyzed under fluorescence microscope, and the fluorescence contrast was quantitatively analyzed. The concentration for 50% of maximal effect (EC₅₀) of immunofluorescence staining of CD31 antibody were compared by t test between two groups.

Anti-mouse CD31 antibody could rapidly and specifically bind to endothelial cells within 10 s. Quantitative analysis showed that AF647 labeled-CD31 antibody still possessed rapid binding characteristics. After AF647-labeled CD31 antibody was incubated for 10 s and 15 min, the EC₅₀ were (4.23±0.86) and (0.72±0.10) μg/ml respectively, which were significantly higher than (1.21±0.24) and (0.32±0.07) μg/ml of the pure CD31 antibody (t=5.877, 5.928; P<0.05). Cell staining showed that CD31 fluorescent antibody was localized on cell membrane and in cytoplasm with a half-life of 5 h and no cytotoxicity. Single cell suspension binding model revealed that the antibody capture efficiency reached up to 80%. In vitro perfusion model showed that CD31 fluorescent antibody could be effectively captured by vascular endothelial cells, and the capture efficiency was slightly decreased with the increase of antibody concentration. The capture efficiency reached (47±8)% when the perfusion volume was 200 ng, and the fluorescence intensity in the perfused area was (2.4±0.5) times of that in the non-perfused area.

Endothelial cell-specific CD31 antibody-targeted fluorescence imaging is a safe, effective, rapid and specific labeling tool, which is a potential approach for liver segment labeling.