Abstract
Reactive oxygen species (ROS) and dissolved oxygen play key roles across many biological processes, and fluorescent stains and dyes are the primary tools used to quantify these species in vitro. However, spatio-temporal monitoring of ROS and dissolved oxygen in biological systems are challenging due to issues including poor photostability, lack of reversibility, and rapid off-site diffusion. In particular, ROS monitoring is hindered by the short lifetime of ROS molecules and their low abundance. The combination of nanomaterials and fluorescent detection has led to new opportunities for development of imaging probes, sensors, and theranostic products, because the scaffolds lead to improved optical properties, tuneable interactions with cells and media, and ratiometric sensing robust to environmental drift. In this review, we aim to critically assess and highlight recent development in nanosensors and nanomaterials used for the detection of oxygen and ROS in biological systems, and their future potential use as diagnosis tools.
Highlights
Molecular oxygen has an important impact upon a broad range of biological processes, ranging from its central roles in cellular respiration (Gnaiger et al, 1995; Bartz and Piantadosi, 2010) and enzymatic processes in aerobic organisms (Adeva-Andany et al, 2014) to its activity as a poison to anaerobes (Lungu et al, 2009; Botheju and Bakke, 2011)
We aim to provide a summary of current optical techniques for both oxygen and Reactive oxygen species (ROS) detection and their current limitations, before discussing recent advances in optical oxygen and ROS nanosensors in 2D and 3D systems, and discussing potential alternative methods for dynamic and deep-tissue imaging of ROS
This study demonstrated the key sensor characteristics ideal for biosensing applications: good reversibility and dynamic range, while displaying minimal dye leaching and photobleaching and is an approach that could be further used to provide valuable information on key biological processes related to intracellular oxygen
Summary
Molecular oxygen has an important impact upon a broad range of biological processes, ranging from its central roles in cellular respiration (Gnaiger et al, 1995; Bartz and Piantadosi, 2010) and enzymatic processes in aerobic organisms (Adeva-Andany et al, 2014) to its activity as a poison to anaerobes (Lungu et al, 2009; Botheju and Bakke, 2011). Gold nanoclusters can be directly oxidised by reactive oxygen species, including ClO−, ONOO− and OH, yielding a change in fluorescence signal, the reaction is not specific to hydroxyl radicals, preventing its use as a highly selective ROS nanoprobe (Li et al, 2017). The Han group has developed a wide range of probes to dynamically monitor ROS in vitro In their initial work, Yu et al (2011) developed a near-infrared fluorescence probe to detect peroxynitrite (Figure 6A). Koide et al (2012) developed a near-infrared fluorescence stain for monitoring ROS by synthesizing 2-Me TeR, a rhodamine-based dye modified with a tellurium group, which showed reversible fluorescence in the presence of OH, ONOO−, and OCl−. Lifetime imaging enabled quantification of ONOO− levels up to a 5 cm tissue penetration depth, highlighting the possibilities of non-invasive imaging with minimal signal attenuation
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