In vivo biodistribution and clearance studies using multimodal organically modified silica nanoparticles

Abstract

Successful translation of the use of nanoparticles from laboratories to clinics requires exhaustive and elaborate studies involving the biodistribution, clearance, and biocompatibility of nanoparticles for in vivo biomedical applications. We report here the use of multimodal organically modified silica (ORMOSIL) nanoparticles for in vivo bioimaging, biodistribution, clearance, and toxicity studies. We have synthesized ORMOSIL nanoparticles with diameters of 20-25 nm, conjugated with near-infrared (NIR) fluorophores and radiolabeled them with (124)I, for optical and PET imaging in vivo. The biodistribution of the nontargeted nanoparticles was studied in nontumored nude mice by optical fluorescence imaging, as well by measuring the radioactivity from harvested organs. Biodistribution studies showed a greater accumulation of nanoparticles in liver, spleen, and stomach than in kidney, heart, and lungs. The clearance studies carried out over a period of 15 days indicated hepatobiliary excretion of the nanoparticles. Selected tissues were analyzed for any potential toxicity by histological analysis, which confirmed the absence of any adverse effect or any other abnormalities in the tissues. The results demonstrate that these multimodal nanoparticles have potentially ideal attributes for use as biocompatible probes for in vivo imaging.

Figure 1

Showing the basic characterization of the DY776 conjugated ORMOSIL nanoparticles: (1a) Nanoparticles size distribution profile as measured by DLS, (1b) representative TEM image, (1c) Absorption and emission spectra, (1d) fluorescence life time decay curves of the DY776, either free or conjugated with ORMOSIL nanoparticles.

Figure 2

Biodistribution of OMROSIL nanoparticles by the measurement of the fluorescence (a, b, c) and radioactivity (d, e, f) from different organs of the mice injected with DY776 conjugated and ¹²⁴I labeled ORMOSIL nanoparticles respectively. (a) fluorescence acquired from the individual organs, (b) whole body fluorescence imaging of the mice 24hrs post injection, (c) quantitative estimation of fluorescence acquired from different organs of the mice, (d & e) PET images of the mice injected with ¹²⁴I-ORMOSIL nanoparticles 2 and 24hrs post injection, respectively, and (f) quantitative radioactivity measurements from the individual organs of the mice.

Figure 3

Clearance of the DY776 conjugated ORMOSIL nanoparticles injected intravenously into the mice (upper panel) and a comparison with the free DY776 injected mice as control (lower panel). Same acquisition time was maintained for all the time points of imaging.

Figure 4

Quantitative estimation of fluorescence acquired from various organs of the mice injected with (a) the DY776 conjugated ORMOSIL nanoparticles and (b) free DY776, at 24, 120 and 360 hrs.

Figure 5

Fluorescence images of the organs as well as dissected mice injected with the DY776 conjugated ORMOSIL nanoparticles (upper panel) and free DY776 (lower panel) at 24, 120 and 360 hrs post-injection. A gradual reduction in the fluorescence intensity indicates excretion of the nanoparticles by the hepatobiliary route.

Figure 6

Histological sections of liver, kidney, spleen, lungs and skin samples, collected after 15 days post injections of the free DY776 (left) and DY776 conjugated ORMOSIL nanoparticles (right). Sections were stained with H&E and observed under a light microscope at 10× and 40× magnification.

Scheme 1

Coupling of silane precursor, 3-aminopropyltriethoxy silane, to DY776 NHS ester to form DY776 silane precursor.

Scheme 2

Synthesis of ¹²⁴I labeled DY776-conjugated ORMOSIL nanoparticles via the Bolton Hunter method.