Evaluation of superparamagnetic iron oxide nanoparticles (Endorem®) as a photoacoustic contrast agent for intra‐operative nodal staging

Abstract

Detection of tumor metastases in the lymphatic system is essential for accurate staging of malignancies. Commercially available superparagmagnetic nanoparticles (SPIOs) accumulate in normal lymph tissue after injection at a tumor site, whereas less or no accumulation takes place in metastatic nodes, thus enabling lymphatic staging using MRI. We verify for the first time the potential of SPIOs, such as Endorem(®) as a novel photoacoustic (PA) contrast agent in biological tissue. We injected five Wistar rats subcutaneously with variable amounts of Endorem(®) and scanned the resected lymph nodes using a tomographic PA setup. Findings were compared using histology, vibrating sample magnetometry (VSM) and 14 T MR-imaging. Our PA setup was able to detect the iron oxide accumulations in all the nodes containing the nanoparticles. The distribution inside the nodes corresponded with both MRI and histological findings. VSM revealed that iron quantities inside the nodes varied between 51 ± 4 and 11 ± 1 µg. Nodes without SPIO enhancement did not show up in any of the PA scans. Iron oxide nanoparticles (Endorem(®)) can be used as a PA contrast agent for lymph node analysis and a distinction can be made between nodes with and nodes without the agent. This opens up possibilities for intra-operative nodal staging for patients undergoing nodal resections for metastatic malignancies.

Synthesis, Functionalization, and Design of Magnetic Nanoparticles for Theranostic Applications

“…Since a series of anatomical size Reproduced with permission. [25] www.advancedsciencenews.com www.advhealthmat.de…”

“…Specifically, images are produced depending on the absorption magnitude of short pulsed illumination by biological chromophores like melanin and hemoglobin. [25] Biological chromophores with strong optical absorbing such as melanin and hemoglobin can be exploited as endogenous contrast agents to provide a noninvasive PAI of these chromophores in vivo. [832] Although this strategy is practical for visualization of the vasculature tissues, other biological processes with shortage of intrinsic chromophores need additional exogenous contrast for performing PAI.…”

“…In another study, the feasibility of iron oxide nanoparticle itself to be exploited for dual PAI/MRI imaging was shown. [25] The group subcutaneously injected commercial available Endorem MNPs into five Wistar rats and scanned the resected lymph nodes using a tomographic PA setup. PAI detected the iron oxide accumulations in the nodes containing MNPs and the PA response pattern was comparable with the location of MRI signal decrease (Figure 51).…”

“…[4] In the matter of diagnostic applications, MNPs can serve as potential contrast agents for MRI, [19] as well as novel tracers for magnetic particle imaging (MPI). [20] Furthermore, MNPs enable a successful dual/three-modal imaging by serving as workhorses to load other imaging modalities, such as positron emission tomography (PET), [21] optical, [22] single photon emission tomography (SPECT), [23] computed tomography (CT), [24] and photoacoustic [25] imaging techniques. On the other hand, numerous therapeutic applications of MNPs have been widely investigated during the last decades.…”

Nanotechnology Advances in Drug Delivery

“…Only a few of them are currently on the market (e.g. the already mentioned Abraxane® [20] and Endorem® [65]). A few reasons are that many nanomaterials have poor drug loading efficiency (< 5%, weight of the drug respect to the nanocarrier) or too rapid a release profile after administration ("burst release").…”