Characterization of Radiolabeled Lipid Nanoparticles

PLN’s size and size distribution were determined by dynamic light scattering (DLS) measurements using a Malvern instrument (NANO ZS, Malvern Instruments, CA, USA). The Z-average particle size was measured in triplicate. The integrity of the radiolabeled PLN was determined by several analytical methods. The samples were assessed by size exclusion LPLC equipped with a size exclusion Sepharose CL 6B column (25 × 300 mm, GE healthcare, 1.5% NaCl, pH 6.8;0.8mL/min)(modified for pressure pump use), an UV monitor, a fluorescent monitor and an on-line flow radioactivity detector (Bioscan Inc., Washington, DC, USA)(Lee et al., 2013b (link)). The radiochemical purity of ^99mTc-PLN was also evaluated by ascending ITLC (Gelman Sciences, Inc., Ann Arbor, MI, USA) using 100% acetone as the solvent phase (Arulsudar et al., 2003 (link)). Calcein entrapment efficiency was determined by fluorescent intensity change at 495nm Excitation (Ex)/ 515nm Emission (Em), using a fluorescence microplate reader (SpectraMax M2, Molecular Devices) after adding the detergent Triton X 100 (TX100, 0.02% final concentration). The drug encapsulation efficiency was calculated using the following formula: F_t/F₀ where F_t is the fully dequenched drug fluorescence intensity after the addition of TX100 and F₀ is the fluorescence intensity of drug before the addition of TX100.