A series of biodegradable PCL-PEG-PCL block copolymers were successfully synthesized by ring-opening polymerization of epsilon-caprolactone initiated by poly(ethylene glycol) (PEG), which were characterized by (1)H NMR, (13)C NMR, and FTIR. Their aqueous solution displayed special gel-sol transition behavior with temperature increasing from 4 to 100 degrees C, when the polymer concentration was above corresponding critical gel concentration (CGC). The gel-sol phase diagram was recorded using test tube inverting method and DSC method, which depended not only on chemical composition of copolymers, but also on heating history of copolymer's aqueous solution. As a result, the gel-sol transition temperature could be adjusted, which might be very useful for its application in biomedical fields such as injectable drug delivery system. And the typical shell-core structure of PCL-PEG-PCL micelles was introduced. The micelle-packing and partial crystallization might be the key gelation machanism for this gel-sol transition behavior of PCL-PEG-PCL aqueous solution.
The magnetic bovine serum albumin (BSA) microspheres (MS) were prepared by emulsification/solidification method. In this experiment, two kinds of magnetic MS, e.g. BSA MS and PEG-incorporated BSA microspheres (PMS) were prepared. The obtained MS were characterized by Malvern laser particle sizer and scanning electron microscopy (SEM). The obtained MS were spherical and about 1.3 microm in size. The magnetic responsivity and in vitro release behavior of these MS were studied in detail. The in vivo distribution and targeting delivery of 5-fluorouracil (5-Fu) magnetic MS after artery administration were studied in rat. The results showed that PMS could efficiently delivery 5-Fu to the targeted site compared with BSA MS without PEG MS and free drug.
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