You are here

Toxicity and Biodistribution of Gold Nanoparticle-based Photo Immuno-Nanotherapy for Bladder Cancer

We developed a novel treatment for localized and metastatic bladder cancer (BC) consisting of a combination of gold nanoparticle-based photothermal therapy and immunotherapy called SYMPHONY. We have previously found that SYMPHONY effectively ablates primary tumors, induces potent anti-tumor immunity, and consequently destroys distant metastases via abscopal mechanisms. Here we analyzed the biodistribution and toxicity of the gold nanostars used in SYMPHONY in murine BC models.

Methods

MB49 syngeneic bladder tumors were grown in C57BL/6 mice until size was 100 mm2. Tumors were then treated with SYMPHONY and tissue samples obtained from lung, liver, brain, spleen, kidney, heart, and intestine at selected post-treatment timepoints ranging from minutes to months post-therapy. Gold nanostars were dosed at 20mg/kg or 80 mg/kg and given via tail vein injection. Toxicity was assessed in several ways. First, histopathology was performed on necropsied tissue sections to assess for organ injury. Second, blood chemistries and body weight were measured longitudinally. Third, F4/80 immunohistochemistry staining for macrophages was performed in spleen and liver. Fourth, harvested tissues were digested with aqua regia for inductively coupled plasma mass spectrometry (ICP-MS) to quantify gold mass within organ sites. GNS uptake was then calculated as % injection dose (ID)/g tissue. Lastly, we labelled GNS with I-124, injected these radiolabeled nanoparticles with tail vein at 20mg/kg, and obtained positron emission tomography (PET) images at 0h, 4h, 24h, 48h, and 120h with an animal microPET scanner.

Results

Figure 1: microPET imaging of I-124 labeled gold nanostars at sequential time pointsH&E examination was unremarkable and demonstrated healthy and intact tissue. There was no significant difference between control animals and GNS-treated animal on pathology. Similarly, there was no significant difference in blood chemistry results among the control and GNS-treated groups, and no evidence of biochemical toxicity. F4/80 IHC staining showed GNS nanoparticles accumulated within macrophages but did not demonstrate a noticeable inflammatory response triggered by the GNS nanoparticles. GNS uptake (% ID/g) was highest in the spleen (median 105%), followed by liver (40%), with the remaining organs all <20%. No uptake was noted in the brain. Importantly, I-124 labeled GNS PET imaging showed that GNS travelled to the the liver and spleen after 24 hours, and that free I-124 leached into the thyroid (Figure).

Figure 2: Gold nanostar tissue biodistribution with the use of inductively-coupled plasma mass spectrometry (ICP-MS) to measure gold mass content, reported in % injection dose per gram of tissue (% ID/g)Figure 3: a) longitudinal average mice bodyweights for control (black) and gold nanostar injection groups (20 mg/kg (red) or 80 mg/kg (blue)). b) blood chemistry test results. C) & D) F4/80 IHC staining for spleen (c) and liver (d) to show macrophages, without a significant inflammatory response seenFigure 4: H&E staining of necropsied mice tissue after treatment with control (PBS) and gold nanostar injection groups (20 mg/kg & 80 mg/kg)

Conclusions

SYMPHONY treatment using gold nanostars shows no evidence of significant toxicity in BC models, suggesting that this therapy should be safe to translate to humans. Biodistribution studies demonstrate gold metabolism with the splenic and hepatic reticuloendothelial system as the primary method of disposal. This novel therapy, which provides local and distant bladder cancer control, is an exciting new therapy for BC.

Video

Contact

For more information on this presentation, please contact:

Gregory Barton, MD
Twitter: @GbartonUro
Email: gregory.barton@duke.edu