Ultrabright Fluorescent Silica Nanoparticles for Dual pH and Temperature Measurements

Abstract

The mesoporous nature of silica nanoparticles provides a novel platform for the development of ultrabright fluorescent particles, which have organic molecular fluorescent dyes physically encapsulated inside the silica pores. The close proximity of the dye molecules, which is possible without fluorescence quenching, gives an advantage of building sensors using FRET coupling between the encapsulated dye molecules. Here we present the use of this approach to demonstrate the assembly of ultrabright fluorescent ratiometric sensors capable of simultaneous acidity (pH) and temperature measurements. FRET pairs of the temperature-responsive, pH-sensitive and reference dyes are physically encapsulated inside the silica matrix of ~50 nm particles. We demonstrate that the particles can be used to measure both the temperature in the biologically relevant range (20 to 50 °C) and pH within 4 to 7 range with the error (mean absolute deviation) of 0.54 °C and 0.09, respectively. Stability of the sensor is demonstrated. The sensitivity of the sensor ranges within 0.2–3% °C−1 for the measurements of temperature and 2–6% pH−1 for acidity.

Towards the Use of Individual Fluorescent Nanoparticles as Ratiometric Sensors: Spectral Robustness of Ultrabright Nanoporous Silica Nanoparticles

“…It should lead to a variation of fluorescence spectra between different particles [ 1 , 2 , 3 , 4 ]. The majority of ratiometric sensors deal with two fluorescent dyes (one as a reference and the other dye as the sensing one) [ 5 , 7 , 9 , 11 ]. Encapsulation of both dyes within one nanoparticle is technically impossible at precisely the same dye ratio.…”

“…Measurements of temperature at the submicron scale were limited too. Sensors working at the nanoscale (nanosensors) can address this challenge, in particular, fluorescence-based nanosensors [ 4 , 5 , 6 , 7 , 8 , 9 ]. Nanosensors demonstrate high stability and brightness compared to other methods [ 10 , 11 , 12 , 13 ].…”

“…The approach used to create ultrabright fluorescent nanoparticles can be used to create complex fluorescent spectra of particles, beneficial in multiplexed biomedical imaging, flow cytometry, and sensors [ 11 , 26 , 30 ]. The ability to create sensors of temperature and acidity has been recently demonstrated [ 7 ].…”

Microrobotic Swarms for Intracellular Measurement with Enhanced Signal-to-Noise Ratio

“…For instance, temperature-sensitive-dye-coated nanoparticles and pH-dye-coated nanoparticles can be used together to form swarms for simultaneous measurement of pH and temperature. Future work can investigate the intracellular synthesis of magnetic nanoparticles as inspired by ref and colabel with fluorescent ion sensors . Such in situ capability can further improve the biocompatibility of nanoparticles and also circumvent the need for nanoparticle delivery.…”

“…Future work can investigate the intracellular synthesis of magnetic nanoparticles as inspired by ref 18 and colabel with fluorescent ion sensors. 88 Such in situ capability can further improve the biocompatibility of nanoparticles and also circumvent the need for nanoparticle delivery.…”