Imaging of radicals following injury or acute stress in peripheral nerves with activatable fluorescent probes

Abstract

Peripheral nerve injury evokes a complex cascade of chemical reactions including generation of molecular radicals. Conversely, the reactions within nerve induced by stress are difficult to directly detect or measure to establish causality. Monitoring these reactions in vivo would enable deeper understanding of the nature of the injury and healing processes. Here, we utilized near-infrared fluorescence molecular probes delivered via intra-neural injection technique to enable live, in vivo imaging of tissue response associated with nerve injury and stress. These initially quenched fluorescent probes featured specific sensitivity to hydroxyl radicals and become fluorescent upon encountering reactive oxygen species (ROS). Intraneurally delivered probes demonstrated rapid activation in injured rat sciatic nerve but minimal activation in normal, uninjured nerve. In addition, these probes reported activation within sciatic nerves of living rats after a stress caused by a pinprick stimulus to the abdomen. This imaging approach was more sensitive to detecting changes within nerves due to the induced stress than other techniques to evaluate cellular and molecular changes. Specifically, neither histological analysis of the sciatic nerves, nor the expression of pain and stress associated genes in dorsal root ganglia could provide statistically significant differences between the control and stressed groups. Overall, the results demonstrate a novel imaging approach to measure ROS in addition to the impact of ROS within nerve in live animals.

Near-infrared fluorescence image-guidance in plastic surgery: A systematic review

“…There were four different hand-held systems (PDE n = 13, Visionsense n = 1, Fluobeam n = 2, and HyperEye n = 1) [ 7 – 19 , 44 – 46 , 49 ], one non-hand-held system (FLARE n = 8) [ 36 – 43 ], and three types of microscopes with an integrated NIRF (SPY n = 16, LEICA n = 2, and Pentero n = 1) [ 20 – 35 , 47 , 48 ] suitable for fluorescence image guidance. In one study, a prototype was used which was not further specified [ 51 ]; three articles unfortunately did not state what kind of imaging system was used [ 52 – 54 ].…”

“…Five different preclinical dyes were tested in animal studies in order to detect nerve injury by intraneural injection of the dye [ 53 , 54 ]. One study labeled fat cells with a specific fluorescent dye to enable the investigation of the amount of fat cells, which survived after autologous fat cell transportation [ 52 ].…”

“…Three articles [ 18 , 53 , 54 ] injected a preclinical dye intraneurally to check for nerve injury (see Table 6 ).…”

Recent Advances in Intraoperative Nerve Bioimaging: Fluorescence‐Guided Surgery for Nerve Preservation

“…By utilizing optical imaging techniques, earlier nerve inflammation can be detected noninvasively. [53] Last but not least, nerve density visualization in tumors will help in the assessment of cancer aggressiveness and prognosis, due to the nerve-cancer cell cross-talk during cancer progression. [25 d,46,54] Fluorescence imaging has tremendous clinical potential for image-guided surgery because it is typically much easier to be visually interpreted than MRI or US.…”

“…For example, an ROS-activatable probe can be utilized for in vivo visualization of an inflamed nerve. [53] Another factor to be considered for fluorescent tags is the hydrophobicity. It has previously been shown that hydrophobic fluorophores have higher affinity to the myelin sheath in both the PNS and CNS; however, this commonly resulted in nonspecific accumulations in adipose tissue and may affect the migration of targeted agents along nerve fibers.…”