Nanoparticle structure transformation of mPEG grafted chitosan with rigid backbone induced by α -cyclodextrin

Abstract This paper presented an interesting nanoparticle-based drug delivery system with morphology transition behavior depending on the content of exposed PEG chain on the particle surface, which is adjustable by addition of different amount of cyclodextrin ( α -CD). The effect of α -CD inclusion to the self-assembly behavior of methoxy polyethylene glycol (mPEG) grafted chitosan (CS) was studied. The results showed that the mPEG grafted chitosan (mPEG- g -CS) forms self-assembled nanoparticles with either micelle or hollow sphere morphology depending on the ratio of α -CD to mPEG, as characterized by atomic force microscopy (AFM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). Their sizes and zeta potential increased from 257.6 nmto 768.2 nm and from +4.5 mV to +11.6 mV, respectively, with the increasing amount of α -CD. The correlation between zeta potential and particle size of α -CD/mPEG- g -CS nanoparticles indicated varied PEG density on surface of nanoparticles. Based on the above experimental observations, a likely mechanism for the morphological transition of the rod-coil graft copolymer mPEG- g -CS was proposed.