4.16. Biodistribution Study

The biodistribution pattern of the nanoconjugates was monitored by the noninvasive imaging method. Dil (25 μg; a near-infrared dye) was added to 320 μL of the Au-CGKRK nanoconjugate (containing 143 μg of gold). The solution was centrifuged at 20 000 rpm and 4 °C for 1 h to obtain the NIR-dye-labeled nanoconjugates. The resulting 320 μL of NIR-dye-labeled Au-CGKRK nanoconjugates was divided into two equal parts. Two B16F10 tumor-bearing 6–8 week old female C57BL/6J (each weighing 20–22 g) mice were i.p. administered with NIR-labeled nanoconjugates (each mouse received 160 μL of NIR-labeled nanoconjugates). Animals were anesthetized with ketamine–xylazine 2 h post i.p. treatment of NIR-labeled nanconjugates, and the biodistribution profile of the NIR dye in mice was monitored using a PerkinElmer IVIS spectrum animal imager. Such biodistribution profile was also measured 24 h post i.p. treatment. With a view to further confirm the biodistribution patterns, mice were sacrificed after the completion of noninvasive imaging 24 h post i.p. treatment, vital organs (including brain, heart, lungs, liver, kidney, spleen, and tumor tissue) were collected, and ex vivo imaged with the same imager. In addition, with a view to confirm accumulation of i.p. administered fluorescently labeled Au-CGKRK + Cy5siRNA nanoconjugates in melanoma-bearing mice, tumor tissues were cryosectioned (10 μm) at 24 h post i.p. treatment and observed under a confocal microscope at 60× magnification using DAPI for nucleus staining.