Cross-linkage induced fluorescence: Fabrication of fluorescent organic particles via reaction between polyethyleneimine and dopamine-containing copolymers

Dopamine is the most abundant catecholamine neurotransmitter in the brain and has extensive applications in biomedicine and materials science. Here, novel metal-free fluorescent organic particles (FOPs) with excellent biocompatibility and high photostability, namely DA-PEG-PEI, were successfully synthesized through combination of ring-opening reaction and crosslinking reaction between polyethyleneimine (PEI) and dopamine-containing copolymers (DA-PEGDGE). Because of the crosslink-enhanced emission (CEE) effect of PEI and a quantity of functional groups such as catechol and amines on the surface of the particles, DA-PEG-PEI FOPs possessed high water dispersibility and superior optical properties , making them highly potential for biological imaging applications. Moreover, owing to the existence of functional components/groups, such as amines, catechol groups, the resultant DA-PEG-PEI FOPs can be potentially applied for loading or carrying different bioactive molecules , such as anticancer agent bortezomib, siRNA and CPG oligodeoxynucleotide through formation of dynamic bonds or electrostatic interaction . Furthermore, this reaction can occur under ambient environment, room temperature, in the present of oxygen and without catalysts. Therefore, we believe that this work could not only provide a simple and elegant route for preparation of FOPs, but also have great potential for construction of multifunctional theranostic platforms.