Figure 3.

MPO fluorescence and CT imaging of paw inflammation. (A) Mice were treated with PMA to induce inflammation on the right hindpaw, and vehicle as negative control on the left hindpaw, and fluorescence reflectance imaging (FRI) was performed. Yellow circles outline sites of topical administration of PMA or vehicle. Brightfield images are presented to outline anatomy (left column). Fluorescence images of MPO activity demonstrate increased fluorescence signal in the PMA-treated right hindpaw in a wildtype mouse injected with MPO activatable biotinylated sensor (MABS) (top row). In an MPO-KO mouse injected with MABS (second row), a wildtype mouse injected with non-specific analogue (third row), and an MPO-KO mouse injected with non-specific analogue (bottom row) no fluorescence signal over background was detected in either hindpaw. (B) Mice were treated with Complete Freud's Adjuvant (CFA) to induce inflammation on the right hindpaw, and saline as negative control on the left hindpaw. 24 hours later, CT imaging before and at 15, 30 and 60 minutes after intravenous injection of streptavidin-gold conjugated nanoparticles was performed. Yellow circles outline sites of CFA or saline administration. A wildtype mouse injected with CFA in the left hindpaw demonstrates contrast enhancement at the injection site over time (top row). No contrast enhancement is seen in an MPO-KO mouse injected with CFA in the left paw (middle row), or in a wildtype mouse with CFA in the left paw injected with streptavidin-conjugated GNPs only without MABS (bottom row). (C) Quantification of fluorescence signal in the hindpaws of PMA and vehicle-treated mice (** p < 0.01, n.s. not significant, N=3 mice per group, student's t-test, experiment was replicated twice). (D) Quantification of contrast enhancement in the hindpaws with CFA in wildtype and MPO-KO mice with MABS and wildtype mice with CFA with gold nanoparticles only, respectively. (* p < 0.05, N=3 mice per group, student's t-test experiment was performed once).