<p>This study aims to develop core–shell nanoparticles using biodegradable polycaprolactone (PCL) and a fluorescent dye, and to investigate their biodistribution to evaluate the drug-release mechanism. PCL was electrosprayed coaxially with two types of dye: N-hydroxysuccinimide (NHS) and Dextran Texas Red in two separate experiments. The PCL solution was prepared by dissolving PCL in a combination of acetic acid, formic acid, and trifluoroethanol. The IRDye solutions were prepared by dissolving the dye in dimethylformamide. The parameters for electrospraying include a voltage range of 15–45 kV, a core flow rate of 0.5 mL/h, a sheath flow rate of 0.7 mL/h, a tip-to-collector distance of 160 mm, and a humidity level between 45 and 55%. Ultraviolet–visible (UV–VIS) spectrophotometry was employed to identify the presence of the molecules before and after the electrospray process. UV–VIS detected the presence of the polymer-encapsulated Dextran Texas Red after electrospraying at 15 kV within a wavelength range of 700–720 nm. A scanning electron microscope was utilized to observe the morphology of the nanoparticles. The PCL and NHS nanoparticles showed randomly formed particle shapes. However, the morphology of the Dextran and PCL nanoparticles showed uniform surface features and did not exhibit large beads or bundles of particles. In vivo biodistribution and fluorescent imaging of the nanoparticles were conducted after they were injected into mice. Dextran Texas Red did not show any fluorescent activities in the body; however, NHS IRDye nanoparticles showed distribution at different organs with clearance through the kidneys and increased activity in the urinary bladder.</p>