Improving the Photostability of Semiconducting Polymer Dots Using Buffers

The photostability of fluorescent probes is critical in biological imaging, especially for long-term observational analyses. Here, we describe a simple and universal method to improve the photostability of semiconducting polymer dots (Pdots) and other fluorescent probes by using buffers. Using Pdots as a model system, we found that HEPES or MES buffer can improve the photostability of Pdots by a factor of 20. Through a systematic study, we show that Pdot photobleaching is dominated by photoinduced radicals which can be quenched by the piperazine or morpholine structures of these buffers, which act as radical scavengers. For conditions where choice of buffer is limited, we designed fluorescent polymers conjugated with radical scavengers to improve Pdot photostability. We then demonstrate a practical application in which HEPES buffer is used to improve the photostability of Pdots during cell imaging.