Biodistribution of Polymeric Micelles

The blood circulating nature of polymeric micelles could be affected by a number of factors such as the sizes, size distribution, core-shell segregation, length of core- and shell-forming blocks, aggregation number, and critical association concentration (c.a.c). We have so far demonstrated that polymeric micelles with a diameter of several tens nanometer, a fairly narrow size distribution and a segregated core-shell structure were able to circulate stably in bloodstream. For example, remarkably prolonged blood circulation was observed for the micelles formed from PEG-PAsp(Dox)7' 8, PEG-PBLA 38 and PEG-PAsp(CDDP) block copolymers 9. Since tumor accumulation of macromolecules based on the EPR effect occurs in a passive manner (passive targeting), such prolonged blood circulation of polymeric micelles should be primarily needed for successful tumor targeting.

Figure 1. Weight and number-averaged distribution of Dox-loaded PEG-PBLA micelle measured by dyiuimic light scattering (DLS) in histogram mode (in distilled water, 25'C, polymer concentration: 0.1 wt%). Solid line: weight-averaged distribution; dashed-line: number-averaged distribution. (Reprinted with permission from Ref. [38). Copyright 2000 Elsevier Science.)

Figure 1. Weight and number-averaged distribution of Dox-loaded PEG-PBLA micelle measured by dyiuimic light scattering (DLS) in histogram mode (in distilled water, 25'C, polymer concentration: 0.1 wt%). Solid line: weight-averaged distribution; dashed-line: number-averaged distribution. (Reprinted with permission from Ref. [38). Copyright 2000 Elsevier Science.)

Regarding basic biodistribution study of polymeric micelles, we recently reported long-circulating polymeric micelles formed from PEG-PDLLA

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