Photoswitchable polyurethane based nanoaggregates for on-command release of noncovalent guest molecules

Abstract

The self-assembly of light responsive amphiphilic polymers has been of great interest in spatially and temporally controlled drug delivery applications. In this article, we report the design, synthesis and characterization of amphiphilic main chain azobenzene polyurethane as well as its self-assembly in aqueous milieu. This polymer self-assembles into micellar nanostructure (investigated by dynamic light scattering and scanning electron microscopy imaging) and shows hydrophobic guest sequestration with high encapsulation stability (probed by FRET experiment). The photoswitching (trans-to-cis) of these nanoaggregates has been investigated by irradiation with UV light (λ = 365 nm), which results significant change in the hydrophobic environment and molecular arrangement in the micellar core. This leads to encapsulated guest release in a controlled manner as probed by UV-vis spectroscopy. Furthermore, we demonstrated tumor-relevant pH (∼6.5-6.8) induced surface charge modulation (neutral to positive) by zeta potential measurements. The light responsive guest release and pH-specific charge modulation, we believe, will have significant impact in development of delivery systems for targeted and controlled delivery of drug molecules.