Ultrabright Fluorescent Silica Nanoparticles for Dual pH and Temperature Measurements.

Saquib Ahmed M A Peerzade,Igor Sokolov,Nadezhda Makarova

doi:10.3390/nano11061524

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.

Highlights

Knowledge of temperature and acidity at the nanoscale is of interest from both applied and fundamental points of view
The previously reported procedure [13,16] was modified to assemble the presented pH and temperature sensor based on mesoporous silica particles
We demonstrate to the change in Förster’s resonance energy transfer (FRET) efficiency

Summary

Introduction

Knowledge of temperature and acidity at the nanoscale is of interest from both applied and fundamental points of view. Understanding the distribution of those parameters inside of the biological cell is key to understanding complex biochemical processes that are occurring in a highly heterogeneous environment of the cell. Cellular functions like gene and protein expression and protein stability are strongly temperaturedependent [1]. It is known that cell migration, cell proliferation, wound healing [2], protein denaturation, protein folding and protein stability [3] are strongly pH-dependent. From a fundamental point of view, physical and chemical processes in the nanoscale are still not well understood in general because temperature and acidity were not measured at that scale.

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Discussion

Conclusion