Figure 2.

Fluorescence imaging based on EPR effect. The EPR effect-based uptake of a fluorescent imaging nanoprobe in the tumor was compared with uptake of the parental low molecular weight (LMW) fluorescent probe in vivo. A) 24 h after intravenous injection of the LMW fluorescent probe, rhodamine B into S-180 tumor-bearing mice, no distinct tumor is visible. B) Injection of TRITC-BSA (67 kDa) resulting in highly tumor selective fluorescence under the same experimental conditions. C) At 24 h, S-180 tumor-bearing mice were dissected, and each organ was imaged with an IVIS imaging system. Results showed that only tumor tissues showed significant fluorescence. D) Same as (C) except that nitroglycerin (NG) ointment was applied to the skin, and then the EPR effect and tumor targeting were evaluated. In (D), the cut surface of tumor tissues shows a more homogeneous tumor uptake of TRIT-BAS probe, and also more TRIT-BAS remained in the blood, which indicates that the EPR effect depends on time and would increase progressively. In (C) and (D), fluorescence is only seen in the tumor tissue. (S, spleen; T, tumor; Lu, lung; Li, liver; H, heart; P, plasma). Reproduced with permission.^[17] Copyright 2013, Elsevier.