High-Shear-Imparted Tunable Fluorescence in Polyethylenimines

In general, fluorescent polyethylenimine (PEI) nanoparticles absorb primarily UV light, with the fluorophores typically having extended conjugated structures. In this work, PEI nanoparticles of circa 10 nm in diameter, devoid of such structural features and with tunable fluorescence, were generated in a microfluidic platform. Tunability of the fluorescence was achieved by varying the flow rate of liquid entering the rapidly rotating tube in a vortex fluidic device (VFD), without the need for additional reagents. Chemical incorporation of amide functional groups triggered enhanced fluorescence intensity and auto-fluorescence over a wide range, and the resulting nanoparticles showed significantly reduced cytotoxicity compared to as-received polymers.