Near-infrared light sensitive polypeptide block copolymer micelles for drug delivery

A new biocompatible block copolymer (BCP) composed of poly(ethylene oxide) (PEO) and poly(L-glutamic acid) bearing a number of 6-bromo-7-hydroxycoumarin-4-ylmethyl groups, PEO114-b-P(LGA(0.62)-co-COU0.38)(34), was prepared for near-infrared (NIR) light-induced drug delivery. We demonstrate that micelles of PEO114-b-P(LGA(0.62)-co-COU0.38)(34) could be disrupted by 794 nm NIR light excitation via two-photon absorption. This was linked to the high two-photon absorption cross-section of the coumarin moiety. Disruption followed from the NIR light-induced removal of coumarin groups from the polypeptide block that shifted the hydrophilic-hydrophobic balance toward the destabilization of the micelles in aqueous solution. Using NIR light-triggered disruption of BCP micelles, we investigated the release of an antibacterial drug (Rifampicin) and an anticancer drug (Paclitaxel) loaded into the photosensitive BCP micelles. We found that the two drugs could be released effectively upon NIR light exposure of the micellar solution. To our knowledge, this is the first study of NIR light-triggered disruption of biocompatible polypeptide BCP micelles and its use for drug release. This is a step forward towards light-controllable drug delivery applications.