NanoSOSG: A Nanostructured Fluorescent Probe for the Detection of Intracellular Singlet Oxygen.

Rubén Ruiz‐González,Francesca Giuntini,Santi Nonell,Òscar Gulías,Huguette Savoie,Roger Bresolí‐Obach,Montserrat Agut,Ross W Boyle

doi:10.1002/anie.201609050

Abstract

A biocompatible fluorescent nanoprobe for singlet oxygen (1 O2 ) detection in biological systems was designed, synthesized, and characterized, that circumvents many of the limitations of the molecular probe Singlet Oxygen Sensor Green® (SOSG). This widely used commercial singlet oxygen probe was covalently linked to a polyacrylamide nanoparticle core using different architectures to optimize the response to 1 O2 . In contrast to its molecular counterpart, the optimum SOSG-based nanoprobe, which we call NanoSOSG, is readily internalized by E. coli cells and does not interact with bovine serum albumin. Furthermore, the spectral characteristics do not change inside cells, and the probe responds to intracellularly generated 1 O2 with an increase in fluorescence.

Highlights

A biocompatible fluorescent nanoprobe for singlet oxygen (1O2) detection in biological systems has been designed, synthesised and characterized, that circumvents many of the limitations of the molecular probe Singlet Oxygen Sensor Green®
The presence of bovine serum albumin (BSA) resulted in red-shifted fluorescence and lower responsiveness to 1O2, which the authors attributed to the protein kinetically competing with Singlet Oxygen Sensor Green® (SOSG) for 1O2 molecules. They were able to show that SOSG could be internalised by HeLa cells in protein-free medium.[4b]. Yet, intracellular SOSG showed additional problems that further detract from its use as a 1O2 reporter: its fluorescence spectrum was still red-shifted compared to aqueous solutions, intense fluorescence was still observed prior to 1O2 exposure, and it was difficult to obtain systematic and reproducible results. [4b] As shown below, the performance of NanoSOSG probes is not affected by such shortcomings
We show in the Supplementary Information that SOSG forms 1:1 and 2:1 complexes with BSA, each with distinct spectra and binding constants (Figure S4)

Summary

Introduction

A biocompatible fluorescent nanoprobe for singlet oxygen (1O2) detection in biological systems has been designed, synthesised and characterized, that circumvents many of the limitations of the molecular probe Singlet Oxygen Sensor Green®. The response of the nanoprobe was poor when compared to the free probe, i.e., only a modest 10% fluorescence increase was observed (Figure S1, panels B and D).

Results

Conclusion