Micro-flow assisted synthesis of fluorescent polymer nanoparticles with tuned size and surface properties

Abstract

Numerous different photonics and biomedical applications depend on the fluorescent polymer micro- and nanoparticles. Besides optical or spectroscopic properties, the performance of the polymer nanoparticles is determined by their size, size distribution, and surface charge. Moreover, in order to realize a very uniform performance, the functional polymer nanoparticles should be of high homogeneity and demand for the preparation in a minimum number of synthesis steps. Here, we present a microfluidic-assisted synthesis of different types of reproducible fluorescent polymer nanoparticles with tuned size (40 nm up to 600 nm) and surface charge (ζ potential=-52 mV up to +45 mV). Four different preparation strategies were introduced for fluorophore-functionalized nanoparticles: (a) noncovalent binding of fluorophores with high loading, (b) covalent linking of fluorophores with enhanced stability, (c) surface-anchored fluorophores by hydrophobic interactions for triple function at the same time, and (d) surface immobilization of biomolecules and fluorophore by ionic as well as secondary interactions. In this way, four different classes of nanoparticles suited for different applications were prepared with a spherical shape as a model system. Moreover, the principle has been extended to the different types of nonspherical and composite polymer nanoparticles.