Preparation of a novel fluorescence nanosensor based on calcein-doped silica nanoparticles, and its application to the determination of calcium in blood serum

A fluorescent nanosensor based on the use of calcein-doped silica nanoparticles (CDSNPs) for the determination of calcium in blood serum is detailed. Calcein is entrapped within silica nanoparticles by the inverse microemulsion polymerisation process that produces spherical sensors in the size region of 48 +/- 4 nm. Calcein encapsulation reduces calcein leaching from the silica matrix when immersed in water and photobleaching which will affect the emission intensity from the irradiation of light. The calcein-doped silica nanoparticles (CDSNPs) have excellent stability to leaching and photobleaching, as well as the selectivity towards calcium over other substances such as K+, Al3+ and Mg2+. The dynamic range of these CDSNPs was found to be 0.003-2 mu g mL(-1)calcium with a linear range from 0.01 to 2 mu g mL(-1). The application of CDSNPs for the determination of calcium in the blood serum is demonstrated. We also explored the application of fluorescence microscopy imaging of calcium in serum with the CDSNPs. The results demonstrate that CDSNPs are insensitive to interferences and capable of determining calcium in serum.