Preparation of DiR-Loaded BSA Nanoparticles

DiR (1, 1-dioctadecyl-3, 3, 3, 3-tetramethylindotricarbocyanine iodide) (PromoCell GmbH, Heidelberg, Germany) loaded BSA (Seracare, Milford, MA) nanoparticles were prepared by a similar method as described previously [3 (link),6 (link)]. Briefly, bovine serum albumin, BSA (250 mg) was dissolved in DI water (4 mL) and then DiR dye (25 mg suspended in acetone) was added to BSA solution and stirred for one hour following the addition of glutaraldehyde (EM grade 70%, EMS, PA, USA) at a concentration of 42 μg/mg BSA. The mixture was added dropwise to 24 mL of ethanol under sonication (Omni Ruptor 400 Ultrasonic Homogenizer, Omni International Inc, Kennesaw, GA) on ice for 30 minutes.