Ratiometric reactive oxygen species nanoprobe for noninvasive in vivo imaging of subcutaneous inflammation/infection.

Release of reactive oxygen species (ROS) accompanied with acute inflammation and infection often results in cell death and tissue injury. Several ROS-reactive bioluminescent probes have been investigated in recent years to detect ROS activity in vivo. Unfortunately, these probes cannot be used to quantify the degree of ROS activity and inflammatory responses due to the fact that the extent of the bioluminescent signals is also probe-concentration dependent. To address this challenge, we fabricated a ratiometric ROS probe in which both ROS-sensitive chemiluminescent agents and ROS-insensitive fluorescent reference dye were conjugated to particle carriers. The bioluminescence/reference fluorescence intensity ratios was calculated to reflect the extent of localized ROS activities while circumventing the variations in bioluminescent intensities associated with the ROS probe concentrations. The physical and chemical properties of the ratiometric probes were characterized. Furthermore, we assessed the accuracy and reproducibility of the probe in detecting ROS in vitro. The ability of the ratiometric probes to detect ROS production in inflamed/infected tissues was also examined using animal models of inflammation and infection. The overall results imply that ratiometric ROS probes can rapidly and non-invasively detect and quantify the extent of inflammatory responses and bacterial infection on wounds in real time.