High-resolution, serial intravital microscopic imaging of nanoparticle delivery and targeting in a small animal tumor model

Abstract

Nanoparticles are under active investigation for the detection and treatment of cancer. Yet our understanding of nanoparticle delivery to tumors is limited by our ability to observe the uptake process on its own scale in living subjects. We chose to study single-walled carbon nanotubes (SWNTs) because they exhibit among the highest levels of tumor uptake across the wide variety of available nanoparticles. We target them using RGD (arginine-glycine-aspartic acid) peptide which directs them to integrins overexpressed on tumor vasculature and on the surface of some tumor cells (e.g., U87MG as used here). We employ intravital microscopy (IVM) to quantitatively examine the spatiotemporal framework of targeted SWNT uptake in a murine tumor model. IVM provided a dynamic microscale window into nanoparticle circulation, binding to tumor blood vessels, extravasation, binding to tumor cells, and tumor retention. RGD-SWNTs bound to tumor vasculature significantly more than controls (P<0.0001). RGD-SWNTs extravasated similarly compared to control RAD-SWNTs, but post-extravasation we observed as RGD-SWNTs eventually bound to individual tumor cells significantly more than RAD-SWNTs (p<0.0001) over time. RGD-SWNTs and RAD-SWNTs displayed similar signal in tumor for a week, but over time their curves significantly diverged (p<0.001) showing increasing RGD-SWNTs relative to untargeted SWNTs. We uncovered the complex spatiotemporal interplay between these competing uptake mechanisms. Specific uptake was delimited to early (1–6 hours) and late (1–4 weeks) time-points, while non-specific uptake dominated from 6 hours to 1 week. Our analysis revealed critical, quantitative insights into the dynamic, multifaceted mechanisms implicated in ligand-targeted SWNT accumulation in tumor using real-time observation.

Imaging the pharmacology of nanomaterials by intravital microscopy: Toward understanding their biological behavior

“…Perhaps unsurprisingly, the targeted NP exhibited greater tumor accumulation at early time points within six hours of administration, while passive tumor penetration and EPR effects dominated accumulation at later time points. Unexpectedly however, NP targeting again led to enhanced tumor retention at very late time points (>1 week post-administration), while non-targeted NPs were no longer detectable [72]. These results are somewhat consistent with another study that found RGD-liposomes could transiently saturate binding sites on vasculature.…”

Biotransport kinetics and intratumoral biodistribution of malonodiserinolamide-derivatized [60]fullerene in a murine model of breast adenocarcinoma

“…Intratumoral extravasation and extravascular transport dynamics of c 60 -serPF While NP vascular delivery, extravasation and changes in intravascular and extravascular NP concentration have been quantified over various time scales from minutes 31,34,39 to days 35 using time lapse imaging, this article presents time lapse imaging with continuous quantification of NP extravasation on a second-to-second timescale in select and global ROIs, representing water-soluble fullerene derivative biotransport dynamics. At the tumor periphery, where IVM imaging has captured these transport dynamics, convective forces play a role in microvascular delivery, 32 while both convection and diffusion contribute to extravascular transport.…”

“…Furthermore, while many IVM studies quantitatively monitor drug or NP kinetics with temporal resolution on the order of minutes to hours [34][35][36][37] and even days, 35 no study has quantitatively tracked initial NP or drug delivery influx dynamics in the tumor microenvironment at a resolution on the timescale of seconds. As C 60 -serPF clears rapidly from the blood stream (as evidenced by the color change of mouse urine occurring within 15 min of C 60 -serPF injection 21 ), capture of C 60 -serPF …”

Intravital Microscopy Imaging Approaches for Image-Guided Drug Delivery Systems

“…5) [28]. Other research efforts have exploited IVM imaging to examine the effectiveness of arginine-glycine-aspartic acid (RGD) peptide conjugated to quantum dots [77], carbon single-wall nano-tubes [78], and liposomal nanoparticles [79]. …”