Supramolecular polymer micelles prepared by steric effect tuned self-assembly: a new strategy for self-assembly

Low molecular weight poly(3-caprolactone) (PCL) and alpha-cyclodextrin (alpha-CD) favor forming crystallized peseudopolyrotaxanes in most of solvents, which impedes their biomedical application. This work provides an example of site-specific polymer functionalization of PCL to control the hierachical assembly with CDs to form novel supramolecular polymer micelles (SMPMs). The unique design of functional PCL includes the introduction of anticancer drug doxorubicin (Dox) with a larger molecular volume as the steric group into the backbone of PCL to realize the partial inclusion complex of PCL with alpha-CD. This inclusion complex can then self assemble into SMPMs with an average size of around 20 nm in aqueous solution due to the hydrophobic-hydrophilic interaction. The structure and morphology of the SMPMs were investigated and revealed by comprehensive characterizations including 1 HNMR, XRD and TEM, TGA etc., their controlled drug release and cell internalization behavior were also explored. The above proof of concept paves the way for a new strategy for selfassembly and overcomes the dispersion of pseudopolyrotaxanes, also, the micelles formed show great promise in biomedical applications, especially in controlled drug release.