Synthesis of poly(ethylene glycol)-polydiacetylene conjugates and their micellar and chromic characteristics.

In this report, novel polymer-lipid conjugates were synthesized and their unique micellar and chromic properties were studied. The conjugates were synthesized by the liquid-phase peptide synthesis method using methoxy(polyethylene glycol)-amine (mPEG-NH2, MW2000) as a supporting material. One and two 10,12-pentacosadiynoic acid (PCDA) groups were conjugated to mPEG-NH2 to prepare mPEG-PCDA and mPEG-PCDA2, respectively. The polymer conjugates could form nanometer-sized micelles in aqueous media and be further polymerized under the exposure of UV 254 nm due to the UV sensitive nature of PCDA. It was observed that mPEG-PCDA2 micelle showed very distinctive photochromism and thermochromism in response to UV or heat, whereas mPEG-PCDA did not display any chromic properties. Moreover, a distinctive chromic property change was observed by adding alpha-cyclodextrin as a model biological molecule to the micelle solution. Due to their unique properties such as high water-solubility, cross-linkable micelle formation with a nano-scaled size, and stimuli-responsive chromic nature, the polymer-lipid conjugates would be useful for various biomedical applications, in particular as a nano-carrier for drug delivery and biosensor.