Fig. 2

Mechanical stimulus-evoked pain-like hypersensitivity testing and live animal NIRF imaging. The manual up-down Von Frey test is performed on the days outlined in Fig. 1a to evaluate mechanical allodynia. Panel a shows results from daily testing, and panel b summarizes 50% withdrawal thresholds at day-8, day-12, and day-18. At day-8, both CCI animal groups are significantly more hypersensitive than sham CCI animals (a and b). Nanomedicine is injected after behavioral testing is completed on day-8. The CCI animals given CXB-NE show a significant reversal in withdrawal thresholds at day-12, a level similar to the sham CCI group (a and b). The reversal in pain-like hypersensitivity lasts for approximately 6 days (shown in a, day-9 to 14; ****p < .0001, *p = 0.0257, two-way ANOVA with Tukey’s posthoc test) and by day-18 the withdrawal threshold lowers back to a level indicative of a chronic pain state (a and b). All associated data analysis can be found here [57]: https://doi.org/10.6084/m9.figshare.8287823.v1. Whole-body live-animal NIRF imaging is performed on day 11 and day 17, the evening before day-12 and day-18 animals respectively are euthanized, and perfusion fixed. In the live animals at day-11, there is a significant decrease in NIRF signal in CCI animals given CXB-NE (c and f) compared to animals administered with DF-NE (c and e). The animals show no fluorescence at day-8, prior to injection (d). At day-17, NIRF signal at the site of the ipsilateral sciatic nerve is significantly decreased in the CCI group given DF-NE (g). A similar level of NIRF signal is observed at day-17 in the CCI group given CXB-NE (h). Pain behavior data is represented as mean ± SD (n = 7–29 animals; *p < .05, ****p < .0001, one-way ANOVA with Tukey’s posthoc test). In vivo imaging data is represented as mean ± SEM (n = 7 animals; *p < .05, **p < .01, one-way ANOVA with Tukey’s post hoc test)