Dual-emission hydrogel nanoparticles with linear and reversible luminescence-response to pH for intracellular...

A type of dual-emission probe with highly recognizable luminescence-response to pH has been designed. For the prepared core-shell polymeric hydrogel nanoparticles probe (Eu(DBM)₃Phen doped polystyrene (PS)-co-poly(N-isopropylacrylamide)(PNIPAM)/FITC), the red emission of inner encapsulated europium complexes Eu(DBM)₃Phen is remained in the hydrophobic PS core and used as a stable reference signal. Comparingly, the green emission of outer electrostatic bonded fluorescent isothiocyanate (FITC) moieties on the hydrophilic PNIPAM shell is adjusted and acted linear and reversible luminescence-response to pH between 5.8 and 7.4 with an exact resolution of 0.1 units. As a remarkable and smart pH probe, the hydrogel nanoparticles show low biological toxicity and prolonged resistance to ions and photobleaching. Also, the probes have successfully discriminated the fluorescent imaging for cytoplasmic matrix based on different pH with minimum biologic background fluorescence. These dual-emission pH-sensitive hydrogel nanoparticles suggest potential applications in clinical medicine, such as cell imaging and disease diagnosis.