Amphiphilic conjugated block copolymers as NIR-bioimaging probes

Although semiconducting polymer nanoparticles (SPN) are emerging as versatile theragnostic platforms for drug delivery and near infrared (NIR)-imaging, their synthesis remains restricted to nanoprecipatation or graft polymers. Here we present a novel method for creating an SPN of the donor-acceptor conjugated polymer p(IDT-NDI) containing indacenodithienothiophene (IDT) and naphthalene diimide (NDI) units. The conjugated polymer is functionalised with a styryl endgroup which is used to introduce a RAFT-agent via a 1,2-radical insertion reaction. This results in a conjugated macroinitiator which can be chain extended using classical RAFT polymerization with methyl acrylate resulting in an amphiphillic triblock copolymer. The amphiphile showed excellent self-assembly with stable particles of 80-110 nm diameter and absorption and emission in the NIR-region. The micelles are taken up efficiently by cells and can deliver a payload proving this method to be a new and powerful tool for the future of SPN in bioimaging.