Magntic-fluorescent PEG-PCL Polymeric Micelles: Preparation, Characterization And Their Application For Dual-Modal Imaging Of Cells

Polymeric micelles have been emerged as an excellent nano-carrier for hydrophobicmolecules or nanoparticles owing to their special properties of small and controllable size,good stability, modification ability and so on. Magnetic-fluorescent polymeric micelleswhich combining the advantages of polymeric micelles, have double functions offluorescence and magnetic response and attract extensive interest of researchers owing totheir great potential for biomedical applications. The objective of the project was toconstruct the magnetic-fluorescent polymeric micelles with cancer cell targeting abilitywhich could be used as a multimodal imaging probe for MRI and fluorescent imaging.Based on the block copolymer PEG-PCL as a carrier, and SPIO as an MRI T2contrastagent, the following work was carried out:（1） Solvent-evaporation method was used to prepare SPIO-loaded mPEG5000-PCL5000micelles. The average size of the micelles was100±15nm and the PDI was0.166±0.021detected by a Malvern Zatasizer. Moreover, the morphology of the micelles wasinvestigated by transmission electron microscopy （TEM）. The result showed that themicelles were spherical in shape with inner core and outer shell. No obvious aggregationwas observed.（2） The T2relaxivity of the mPEG5000-PCL5000micelles was86mM^-1s^-1detected byMRI system. The micelles had significant enhancing effect of MRI T2-weight imagecontrast. Cell uptake experiment indicated that the micelles which had some magneticresponse could be internalized by Hela cells.（3） mPEG₅₈₀₀-PCL₁₅₀₀₀and NH₂-PEG5800-PCL19000were used as carrier materials forSPIO-loaded micelles preparation according to the same method mentioned before. ThenCy5.5and transferrin were conjugated to the micelles. The average size of the modifiedmicelles was about255nm and the PDI was0.042detected by a Malvern Zatasizer. TEMimages of the micelles showed that the single micelle was isolated clusters of SPIOparticles. Cy5.5and transferrin modification were characterized by FTIR andNative-PAGE. The critical micelle concentration was2.5mg/l using pyrene as afluorescence probe. The T2relaxivity of the modified micelles was154mM^-1s^-1detected by MRI system. The saturation magnetization of the modified micelles was13emu g^-1.（4） Cell labelling experiment indicated that the modified micelles could be labelledby MRI and fluorescent imaging which had transferrin-receptor targeting ability to acertain extent. Moreover, RT-PCR was used to confirm that the TfR1expressing of HepG2cells was significant higher than that of HL7702cells.