In vivo tumor imaging

In vivo tumor imaging with MM-OCT

Magnetomotive optical coherence tomography (MM-OCT) detects the presence of magnetic nanoparticles (MNPs) within biological tissues based on the magnetomotions induced. Functionalized MNPs can allow for in vivo tumor targeting. For example, antibody-conjugated MNPs can detect mammary tumors, which can be sensed with MM-OCT.  In addition, MNPs are well-known image contrast agents for MRI imaging, where a shortened T2* relaxation time can be induced thereby providing negative contrast. Therefore, the same MNPs delivered to the targeted tumors can function as MM-OCT/MRI dual-modality contrast agents. 

  • John R, Rezaeipoor R, Adie SG, Chaney EJ, Oldenburg AL, Marjanovic M, Halder JP, Sutton B, Boppart SA. In vivo magnetomotive optical molecular imaging using targeted magnetic nanoprobes.   PNAS, 107:8085-8090. 2010.

MM-OCT images are shown as an overlay of the magnetomotion (green) and the structural OCT (red). The MNPs, conjugated with antibody, can target human epidermal growth factor receptor 2 (HER2 neu) protein, and hence allow for in vivo mammary tumor targeting. (A) MM-OCT signal can only be detected from the tumor laden (I) with targeted MNPs.  In contrast, the tumors laden (II) with non-targeting MNPs or (III) without any MNP exhibit almost no MM-OCT signal. This is validated with (C-D) iron-oxide staining, where MNPs are only found in case (I).  

In vivo MM-OCE for magnetic hyperthermia dosimetry

MNPs delivered into tumors can be leveraged to also function as dosmetric agentsIn fact, the MNPs can serve as internal heating sources in a magnetic hyperthermia (MH) treatment, where the MNP-laden malignancy can be thermally damaged, and the biomechanical propertied can be altered.  Based on the heat-induced changes in tissue viscoelasticity, thermal dosage can be inferred.  Magnetomotive optical coherence elastography (MM-OCE) can extract the temporal characteristics of the magnetomotions and infer the biomechanical properties of the tumors.  Therefore, a novel MH dosimetry can be allowed by MM-OCE-based stiffness sensing. 

  • Huang P.C., Chaney E.J., Aksamitiene E, Barkalifa R., Spillman D.R., Bogan B.J., and Boppart S.A.  Biomechanical sensing of in vivo magnetic nanoparticle hyperthermia-treated melanoma using magnetomotive optical coherence elastography. Theranostics 11(12):5620-5633, 2021.

Living melanoma-bearing mouse injected with MNPs, treated with magnetic hyperthermia, and imaged with MM-OCT and MM-OCE. Successful intratumoral injection of MNPs is validated with in vivo MM-OCT.  Based on the biomechanical response probed by MM-OCE, the impact of thermal dosage on tumor elasticity can depend on tumor cellularity, protein conformation, and the temperature achieved.    

Intravital SLAM imaging of the tumor microenvironment 

Simultaneous label-free autofluorescence-multiharmonic (SLAM) microscopy is a powerful tool that elucidates pathways in biological processes, which gives major advantages to intravital imaging as no extrinsic agents are involved.  SLAM is a single-excitation source nonlinear imaging platform using a custom-designed excitation window at 1110 nm and shaped ultrafast pulses at 10 MHz to enable fast, simultaneous, and efficient acquisition of autofluorescence (FAD and NADH) and second/third-harmonic generation from a wide range of cellular and extracellular components (e.g., tumor cells, immune cells, vesicles, and vessels) in living tissues. In addition, in vivo tracking of cellular events can also be allowed.  

One of the fascinating applications of SLAM is that it can be used for cancer prognosis. SLAM can see the morphological and metastatic alternations in tumor microenvironment during the chemotherapy. In vivo study with PDX mice showed that SLAM can find the effective chemotherapy regimen leading to personalized therapy. 

  • You S, Tu H, Chaney EJ, Sun Y, Zhao Y, Bower AJ, Liu Y-Z, Marjanovic M, Sinha S, Pu Y, Boppart SA. Intravital imaging by simultaneous label-free autofluorescence multiharmonic microscopy. Nature Communications, 9:2125. 2018.
  • Park, J., Chaney, E., You, S., Abdelrahman, A.M., Leiting, J.L., Yonkus, J.A., Groves, P.D., Harrington, J.J., Spillman, D.R., Lynch, I.T. and Marjanovic, M., 2020, April. Characterizing Treatment Response of Pancreatic Tumor Patient-Derived Xenografts in Mice by Simultaneous Label-Free Autofluorescence Multi-Harmonic (SLAM) Microscopy. In Clinical and Translational Biophotonics (pp. TM2B-4). Optical Society of America. 

Leukocyte-swarming visualized and characterized by SLAM microscopy. Images acquired at (a) the beginning and (b) the end of the swarming. Collagen rearrangement was marked by the white boundary (Cluster 1, C1) while lipid interaction was marked by cyan boundary (Cluster 2, C2). (c)(e) Zoomed-in images of multi-nucleated neutrophils. (f) Traces of Cells 1–14, which were tracked to travel via similar routes to the same cluster at different time points, as shown in the velocity map (j)(g) Traces of Cells 15–16, which were both tracked for > 30 min and exhibited different behavior, with Cell 15 migrating towards the cluster with high speed and high directionality throughout the entire time course and Cell 11 mostly making random walk, as shown in the corresponding velocity map (k)(h) Leukocytes leaving the site (Cells 17–18 in Video). The series of snapshots were taken every 2 s and shown for every 20 s. The first three snapshots showed the deformation of the leukocyte, changing from a round shape to a stretched cell elongated along the direction of travel, which typically precedes the acceleration process shown in the last three snapshots. (i) Quantification of collagen clearance, cell accumulation, and lipid deformation within the marked clusters in a and b (C1 and C2). (j)(k) Velocity and directionality map of Cells 1–16. The color of the curves matches the color of the traces in (f) and (g) and the Video. D directionality. Scale bar: 50 µm 

SLAM image of an in vivo tissue after drug treatment. (a) Representative image of tumor tissue in channel of (a) 2PF, (b) 3PF, (c) SHG, (d) THG, (e) merged. Different aspects of THG/3PAF compared between (f) chemotherapy treated and (g) control mice.