All Publications

  • Invivo bioluminescence imaging of granzyme B activity in tumor response to cancer immunotherapy. Cell chemical biology Chen, M., Zhou, K., Dai, S., Tadepalli, S., Balakrishnan, P. B., Xie, J., Rami, F. E., Dai, T., Cui, L., Idoyaga, J., Rao, J. 2022


    Cancer immunotherapy has revolutionized the treatment of cancer, but only a small subset of patients benefits from this new treatment regime. Imaging tools are useful for early detection of tumor response to immunotherapy and probing the dynamic and complex immune system. Here, we report a bioluminescence probe (GBLI-2) for non-invasive, real-time, longitudinal imaging of granzyme B activity in tumors receiving immune checkpoint inhibitors. GBLI-2 is made of the mouse granzyme B tetrapeptide IEFD substrate conjugated to D-luciferin through a self-immolative group. GBLI-2 was evaluated for imaging the dynamics of the granzyme B activity and predicting therapeutic efficacy in a syngeneic mouse model of CT26 murine colorectal carcinoma. The GBLI-2 signal correlated with the change in the population of PD-1- and granzyme B-expressing CD8+ Tcells in tumors.

    View details for DOI 10.1016/j.chembiol.2022.08.006

    View details for PubMedID 36103874

  • Reversibly Photoswitching Upconversion Nanoparticles for Super-sensitive Photoacoustic Molecular Imaging. Angewandte Chemie (International ed. in English) Rao, J., Liu, C., Zheng, X., Dai, T., Wang, H., Chen, X., Chen, B., Sun, T., Wang, F., Chu, S. 2022


    Photoacoustic (PA) imaging uses light excitation to generate the acoustic signal for detection and improves tissue penetration depth and spatial resolution in the clinically relevant depth of living subjects. However, strong background signals from blood and pigments have significantly compromised the sensitivity of PA imaging with exogenous contrast agents. Here we report a nanoparticle-based probe design that uses light to reversibly modulate the PA emission to enable photoacoustic photoswitching imaging (PAPSI) in living mice. Such a nanoprobe is built with upconverting nanocrystals and photoswitchable small molecules and can be switched on by NIR light through upconversion to UV energy. Reversibly photoswitching of the nanoprobe reliably removed strong tissue background, increased the contrast-to-noise ratio, and thus improved imaging sensitivity. We have shown that PAPSI can image 0.05 nM of the nanoprobe in hemoglobin solution and 10 4 labeled cancer cells after implantation in living mice using a commercial PA imager.

    View details for DOI 10.1002/anie.202116802

    View details for PubMedID 35139242

  • A Fluorogenic Trehalose Probe for Tracking Phagocytosed Mycobacterium tuberculosis. Journal of the American Chemical Society Dai, T. n., Xie, J. n., Zhu, Q. n., Kamariza, M. n., Jiang, K. n., Bertozzi, C. R., Rao, J. n. 2020


    Tuberculosis (TB) disease is a global epidemic caused by the pathogenic Mycobacterium tuberculosis (Mtb). Tools that can track the replication status of viable Mtb cells within macrophages are vital for the elucidation of host-pathogen interactions. Here, we present a cephalosphorinase-dependent green trehalose (CDG-Tre) fluorogenic probe that enables fluorescence labeling of single live Bacille Calmette-Guérin (BCG) cells within macrophages at concentrations as low as 2 µM. CDG-Tre fluoresces upon activation by BlaC, the β-lactamase uniquely expressed by Mtb, and the fluorescent product is subsequently incorporated within the bacterial cell wall via trehalose metabolic pathway. CDG-Tre showed high selectivity for mycobacteria over other clinically prevalent species in the Corynebacterineae suborder. The unique labeling strategy of BCG by CDG-Tre provides a versatile tool for tracking Mtb in both pre- and post-phagocytosis and elucidating fundamental physiological and pathological processes related to the mycomembrane.

    View details for DOI 10.1021/jacs.0c07700

    View details for PubMedID 32813512

  • Targeting MMP-14 for dual PET and fluorescence imaging of glioma in preclinical models. European journal of nuclear medicine and molecular imaging Kasten, B. B., Jiang, K., Cole, D., Jani, A., Udayakumar, N., Gillespie, G. Y., Lu, G., Dai, T., Rosenthal, E. L., Markert, J. M., Rao, J., Warram, J. M. 2019


    PURPOSE: There is a clinical need for agents that target glioma cells for non-invasive and intraoperative imaging to guide therapeutic intervention and improve the prognosis of glioma. Matrix metalloproteinase (MMP)-14 is overexpressed in glioma with negligible expression in normal brain, presenting MMP-14 as an attractive biomarker for imaging glioma. In this study, we designed a peptide probe containing a near-infrared fluorescence (NIRF) dye/quencher pair, a positron emission tomography (PET) radionuclide, and a moiety with high affinity to MMP-14. This novel substrate-binding peptide allows dual modality imaging of glioma only after cleavage by MMP-14 to activate the quenched NIRF signal, enhancing probe specificity and imaging contrast.METHODS: MMP-14 expression and activity in human glioma tissues and cells were measured in vitro by immunofluorescence and gel zymography. Cleavage of the novel substrate and substrate-binding peptides by glioma cells in vitro and glioma xenograft tumors in vivo was determined by NIRF imaging. Biodistribution of the radiolabeled MMP-14-binding peptide or substrate-binding peptide was determined in mice bearing orthotopic patient-derived xenograft (PDX) glioma tumors by PET imaging.RESULTS: Glioma cells with MMP-14 activity showed activation and retention of NIRF signal from the cleaved peptides. Resected mouse brains with PDX glioma tumors showed tumor-to-background NIRF ratios of 7.6-11.1 at 4 h after i.v. injection of the peptides. PET/CT images showed localization of activity in orthotopic PDX tumors after i.v. injection of 68Ga-binding peptide or 64Cu-substrate-binding peptide; uptake of the radiolabeled peptides in tumors was significantly reduced (p < 0.05) by blocking with the non-labeled-binding peptide. PET and NIRF signals correlated linearly in the orthotopic PDX tumors. Immunohistochemistry showed co-localization of MMP-14 expression and NIRF signal in the resected tumors.CONCLUSIONS: The novel MMP-14 substrate-binding peptide enabled PET/NIRF imaging of glioma models in mice, warranting future image-guided resection studies with the probe in preclinical glioma models.

    View details for DOI 10.1007/s00259-019-04607-x

    View details for PubMedID 31773232

  • Rapid and specific labeling of single live Mycobacterium tuberculosis with a dual-targeting fluorogenic probe SCIENCE TRANSLATIONAL MEDICINE Cheng, Y., Xie, J., Lee, K., Gaur, R. L., Song, A., Dai, T., Ren, H., Wu, J., Sun, Z., Banaei, N., Akin, D., Rao, J. 2018; 10 (454)


    Tuberculosis (TB) remains a public health crisis and a leading cause of infection-related death globally. Although in high demand, imaging technologies that enable rapid, specific, and nongenetic labeling of live Mycobacterium tuberculosis (Mtb) remain underdeveloped. We report a dual-targeting strategy to develop a small molecular probe (CDG-DNB3) that can fluorescently label single bacilli within 1 hour. CDG-DNB3 fluoresces upon activation of the β-lactamase BlaC, a hydrolase naturally expressed in Mtb, and the fluorescent product is retained through covalent modification of the Mtb essential enzyme decaprenylphosphoryl-β-d-ribose 2'-epimerase (DprE1). This dual-targeting probe not only discriminates live from dead Bacillus Calmette-Guérin (BCG) but also shows specificity for Mtb over other bacterial species including 43 nontuberculosis mycobacteria (NTM). In addition, CDG-DNB3 can image BCG phagocytosis in real time, as well as Mtb in patients' sputum. Together with a low-cost, self-driven microfluidic chip, we have achieved rapid labeling and automated quantification of live BCG. This labeling approach should find many potential applications for research toward TB pathogenesis, treatment efficacy assessment, and diagnosis.

    View details for PubMedID 30111644