In Vivo Bioimaging and Biodistribution of DiR-Labeled Solid SNEDDS of Black Sticky Rice Extract Using Neusilin® US2 as Solid Carrier

Abstract

Black Sticky Rice Extract (BSRE; Oryza sativa var. glutinosa Blanco) is rich in anthocyanins and flavonoids with well-documented antioxidant and hepatoprotective activities. Nevertheless, its clinical translation is hindered by poor aqueous solubility and limited stability under physiological conditions, resulting in low oral bioavailability. To overcome these limitations, a Self-Nanoemulsifying Drug Delivery System (SNEDDS) was developed to enhance BSRE solubilization, stability, and hepatic targeting efficiency. A 1,1'-dioctadecyl-3,3,3',3'-tetramethylindotricarbocyanine iodide (DiR)-labeled SNEDDS was formulated using corn oil, Tween 80, and propylene glycol, followed by solidification onto Neusilin® US2 to obtain solid SNEDDS (S-SNEDDS). Physicochemical properties, including flowability, bulk and tapped density, and residual moisture content, were evaluated to assess processability and stability. In vivo biodistribution and hepatic targeting were investigated in mice using IVIS Spectrum fluorescence imaging (700-900 nm) after oral administration of three formulations: BSRE + corn oil + DiR, blank SNEDDS + DiR, and SNEDDS-BSRE + DiR. Quantitative region-of-interest (ROI) analysis was performed using Living Image® software, and statistical differences were analyzed by one-way ANOVA followed by Tukey's post-hoc test. The S-SNEDDS granules exhibited excellent flow properties (angle of repose = 27°, Carr's index = 13.5%, Hausner's ratio = 1.16) and optimal residual moisture (3.20%), confirming good solid-state stability and reconstitution performance. IVIS imaging revealed formulation-dependent biodistribution profiles: BSRE + corn oil produced diffuse systemic fluorescence, blank SNEDDS + DiR showed weak and transient signals, whereas SNEDDS-BSRE + DiR demonstrated moderate but sustained hepatic fluorescence. Quantitative ROI analysis confirmed significant intergroup differences (p < 0.001). Overall, incorporation of BSRE into the SNEDDS matrix enhanced nanocarrier stability and hepatic localization, highlighting the potential of SNEDDS-BSRE as a bioimaging-guided oral nutraceutical platform for liver-targeted delivery.

Keywords: Black Sticky Rice Extract; IVIS imaging; SNEDDS; anthocyanins; biodistribution; hepatoprotective; polyphenols; radiant efficiency.