Fluorescent Magnetic Nanoparticles for Magnetically Enhanced Cancer Imaging and Targeting in Living Subjects

Early detection and targeted therapy are two major challenges in the battle against cancer. Novel imaging contrast agents and targeting approaches are greatly needed to improve the sensitivity and specificity of cancer theranostic agents. Here, we implemented a novel approach using a magnetic micromesh and biocompatible fluorescent magnetic nanoparticles (FMN) to magnetically enhance cancer targeting in living subjects. This approach enables magnetic targeting of systemically administered individual FMN, containing a single 8 nm superparamagnetic iron oxide core. Using a human glioblastoma mouse model, we show that nanoparticles can be magnetically retained in both the tumor neovasculature and surrounding tumor tissues. Magnetic accumulation of nanoparticles within the neovasculature was observable by fluorescence intravital microscopy in real time. Finally, we demonstrate that such magnetically enhanced cancer targeting augments the biological functions of molecules linked to the nanoparticle surface

Fluorescent Magnetic Nanoparticles for Magnetically Enhanced Cancer Imaging and Targeting in Living Subjects

Early detection and targeted therapy are two major challenges in the battle against cancer. Novel imaging contrast agents and targeting approaches are greatly needed to improve the sensitivity and specificity of cancer theranostic agents. Here, we implemented a novel approach using a magnetic micromesh and biocompatible fluorescent magnetic nanoparticles (FMN) to magnetically enhance cancer targeting in living subjects. This approach enables magnetic targeting of systemically administered individual FMN, containing a single 8 nm superparamagnetic iron oxide core. Using a human glioblastoma mouse model, we show that nanoparticles can be magnetically retained in both the tumor neovasculature and surrounding tumor tissues. Magnetic accumulation of nanoparticles within the neovasculature was observable by fluorescence intravital microscopy in real time. Finally, we demonstrate that such magnetically enhanced cancer targeting augments the biological functions of molecules linked to the nanoparticle surface

Fluorescent Magnetic Nanoparticles for Magnetically Enhanced Cancer Imaging and Targeting in Living Subjects

Early detection and targeted therapy are two major challenges in the battle against cancer. Novel imaging contrast agents and targeting approaches are greatly needed to improve the sensitivity and specificity of cancer theranostic agents. Here, we implemented a novel approach using a magnetic micromesh and biocompatible fluorescent magnetic nanoparticles (FMN) to magnetically enhance cancer targeting in living subjects. This approach enables magnetic targeting of systemically administered individual FMN, containing a single 8 nm superparamagnetic iron oxide core. Using a human glioblastoma mouse model, we show that nanoparticles can be magnetically retained in both the tumor neovasculature and surrounding tumor tissues. Magnetic accumulation of nanoparticles within the neovasculature was observable by fluorescence intravital microscopy in real time. Finally, we demonstrate that such magnetically enhanced cancer targeting augments the biological functions of molecules linked to the nanoparticle surface

Choroidal flatmounts showing accumulation of rhodamine labeled NP and expression of GFP plasmid in the CNV.

<p>The CNV lesions are delineated by arrowheads in bright field images with false blue color (A and E). FITC-filtered images highlight the GFP expression one day after systemic injection of Rd-NP-GFPg (B) whereas non-targeted NP (Rd-ntNP-GFPg) does not induce GFP expression in CNV (F). Cy3-filtered images highlight that rhodamine-labeled NP (Rd-NP-GFPg) accumulates in the CNV (C), while rhodamine-labeled non-targeted NP (Rd-ntNP-GFPg) does not (G). Some particles can be visualized circulating in the choroidal vessels. Overlay of images A–C is presented in panel D and overlay of E–G is shown in H.</p

Bioimaging with NP-angiography showing GFP expression using the Topcon camera with fluorescein angiography filter settings.

<p>Late phase FAs (A and D) show the CNV lesions prior to injection of NP. Autofluorescent images taken prior to injection of NP reveal minimal background fluorescence of the CNV lesions (B and E). Injection of targeted NP carrying a GFP plasmid (NP-GFPg) causes increased fluorescence of the CNV lesions from GFP expression (C) whereas non-targeted NP carrying a GFP plasmid (ntNP-GFPg) does not cause any increase in the intensity of fluorescence of the CNV over background autofluorescence (F).</p

Late phase fluorescein angiography (FA) and choroidal flatmounts (<i>x10</i>) two weeks after laser photocoagulation.

<p>Representative lesions are from the control group (A–D) and the NP-ATPμ-Raf treated group (E and F). Group (A) received no treatment; (B) received intravenous injection of non-targeted NP containing ATPμ-Raf on days 1, 3, and 5 after laser CNV creation; (C) received intravenous injection of α_νβ₃ targeted-NP without ATPμ-Raf gene on days 1,3, and 5; (D) received injection of ATPμ-Raf gene without NP on days 1, 3, and 5; (E) received injection of α_νβ₃ targeted-NP containing ATPμ-Raf (NP-ATPμ-Raf) on days 1, 3, and 5; and (F) received injection of NP-ATPμ-Raf on days 3, 5, and 7. NP-ATPμ-Raf treated groups (E and F) had significantly lower grade CNV lesions on FA grading and smaller CNV size compared to the control group (A–D). No statistically significant difference in size was noted between the control groups A–D. Quantification of the CNV size on choroidal flat mounts is shown in (G). *P<0.01. Data are expressed as the mean ± SE.</p

Increased macrophage infiltration at the site of treated CNV.

<p>Macrophage infiltration was highest on day 3 with gradual decrease on days 5 and 7. Significantly higher number of macrophages were observed with the NP-ATPμ-Raf treated group compared to the control group on days 5 and 7 (A and B). There was a statistically significant reduction of CNV size noted on day 7(C). Immunofluorescent staining of representative frozen sections (<i>x20</i>) obtained at 3, 5, and 7 days after laser photocoagulation for ED 1, a marker for macrophage (D). *P<0.01. Data are expressed as the mean ± SE.</p

Evaluation of endothelial cell apoptosis with TUNEL staining in frozen sections.

<p>Quantification of TUNEL positive cells showed significantly more TUNEL(+) cells/lesion (A) and TUNEL (+) cells/mm² (B) with treatment of NP-ATPμ-Raf compared to the control group on day 3 and 5 after laser injury. There was a statistically significant reduction of CNV size noted on day 7(C). Double-immunofluorescent staining of frozen sections (<i>x20</i>) obtained at 3, 5 and 7 days after laser photocoagulation for the endothelial cell marker CD31 and TUNEL stain (D). *P<0.01. Data are expressed as the mean ± SE.</p

<i>In vivo</i> evaluation of CNV utilizing SD-OCT.

<p>Quantification of CNV size using SD-OCT (A) reveals a decrease in CNV size, reaching statistical significance on day 7 (Mann- Whitney U test, p = 0.001) in the NP-ATPμ-Raf treated group compared to the control group. A hyper-reflective subretinal lesion is seen as delineated by the red dotted line (B). This lesion corresponds to the hyporeflective area on fundus reconstruction (red dotted circle, C). *P<0.01. Data are expressed as the mean ± SE.</p