Professional Education

  • Ph.D., National University of Singapore, Fluorescent Biomaterials (2011)
  • M. S., Fudan University, Polymer Physics and Chemistry (2007)
  • B. E., East China University of Science and Technology, Materials Physics (2004)

Stanford Advisors


Journal Articles

  • Real-time imaging of oxidative and nitrosative stress in the liver of live animals for drug-toxicity testing. Nature biotechnology Shuhendler, A. J., Pu, K., Cui, L., Uetrecht, J. P., Rao, J. 2014; 32 (4): 373-380


    Current drug-safety assays for hepatotoxicity rely on biomarkers with low predictive power. The production of radical species, specifically reactive oxygen species (ROS) and reactive nitrogen species (RNS), has been proposed as an early unifying event linking the bioactivation of drugs to hepatotoxicity and as a more direct and mechanistic indicator of hepatotoxic potential. Here we present a nanosensor for rapid, real-time in vivo imaging of drug-induced ROS and RNS for direct evaluation of acute hepatotoxicity. By combining fluorescence resonance energy transfer (FRET) and chemiluminescence resonance energy transfer (CRET), our semiconducting polymer-based nanosensor simultaneously and differentially detects RNS and ROS using two optically independent channels. We imaged drug-induced hepatotoxicity and its remediation longitudinally in mice after systemic challenge with acetaminophen or isoniazid. We detected dose-dependent ROS and RNS activity in the liver within minutes of drug challenge, which preceded histological changes, protein nitration and DNA double-strand-break induction.

    View details for DOI 10.1038/nbt.2838

    View details for PubMedID 24658645

  • Semiconducting polymer nanoparticles as photoacoustic molecular imaging probes in living mice NATURE NANOTECHNOLOGY Pu, K., Shuhendler, A. J., Jokerst, J. V., Mei, J., Gambhir, S. S., Bao, Z., Rao, J. 2014; 9 (3): 233-239


    Photoacoustic imaging holds great promise for the visualization of physiology and pathology at the molecular level with deep tissue penetration and fine spatial resolution. To fully utilize this potential, photoacoustic molecular imaging probes have to be developed. Here, we introduce near-infrared light absorbing semiconducting polymer nanoparticles as a new class of contrast agents for photoacoustic molecular imaging. These nanoparticles can produce a stronger signal than the commonly used single-walled carbon nanotubes and gold nanorods on a per mass basis, permitting whole-body lymph-node photoacoustic mapping in living mice at a low systemic injection mass. Furthermore, the semiconducting polymer nanoparticles possess high structural flexibility, narrow photoacoustic spectral profiles and strong resistance to photodegradation and oxidation, enabling the development of the first near-infrared ratiometric photoacoustic probe for in vivo real-time imaging of reactive oxygen species-vital chemical mediators of many diseases. These results demonstrate semiconducting polymer nanoparticles to be an ideal nanoplatform for developing photoacoustic molecular probes.

    View details for DOI 10.1038/NNANO.2013.302

    View details for Web of Science ID 000332637200018

  • Semiconducting Polymer Nanoprobe for In Vivo Imaging of Reactive Oxygen and Nitrogen Species ANGEWANDTE CHEMIE-INTERNATIONAL EDITION Pu, K., Shuhendler, A. J., Rao, J. 2013; 52 (39): 10325-10329


    Semiconducting polymer nanoparticles are used as a free-radical inert and light-harvesting nanoplatform for in vivo molecular imaging of reactive oxygen and nitrogen species (RONS). This nanoprobe permits detection of RONS in the microenvironment of spontaneous bacterial infection (see picture; FRET=fluorescence resonance energy transfer).

    View details for DOI 10.1002/anie.201303420

    View details for Web of Science ID 000329141800033

    View details for PubMedID 23943508

  • Conjugated Oligoelectrolyte Harnessed Polyhedral Oligomeric Silsesquioxane as Light-Up Hybrid Nanodot for Two-Photon Fluorescence Imaging of Cellular Nucleus ADVANCED MATERIALS Pu, K., Li, K., Zhang, X., Liu, B. 2010; 22 (37): 4186-?


    A water-soluble organic/inorganic hybrid nanodot based on polyhedral oligomeric silsesquioxane (POSS) and conjugated oligoelectrolyte is designed and synthesized for two-photon fluorescence imaging of cellular nucleus, which takes advantage of its small size (?3.3 nm) that imparts nucleus permeability and substantial DNA-enhanced two-photon excited fluorescence that allows illuminating the nucleus with a high contrast.

    View details for DOI 10.1002/adma.201001544

    View details for Web of Science ID 000283392000013

    View details for PubMedID 20589775

  • Cationic Oligofluorene-Substituted Polyhedral Oligomeric Silsesquioxane as Light-Harvesting Unimolecular Nanoparticle for Fluorescence Amplification in Cellular Imaging ADVANCED MATERIALS Pu, K., Li, K., Liu, B. 2010; 22 (5): 643-?

    View details for DOI 10.1002/adma.200902409

    View details for Web of Science ID 000274615600015

    View details for PubMedID 20217765

  • A Graphene-Conjugated Oligomer Hybrid Probe for Light-Up Sensing of Lectin and Escherichia Coli ADVANCED MATERIALS Wang, L., Pu, K., Li, J., Qi, X., Li, H., Zhang, H., Fan, C., Liu, B. 2011; 23 (38): 4386-?

    View details for DOI 10.1002/adma.201102227

    View details for Web of Science ID 000297007000006

    View details for PubMedID 21960474

  • Affibody-Attached Hyperbranched Conjugated Polyelectrolyte for Targeted Fluorescence Imaging of HER2-Positive Cancer Cell BIOMACROMOLECULES Pu, K., Shi, J., Cai, L., Li, K., Liu, B. 2011; 12 (8): 2966-2974


    A hyperbranched conjugated polyelectrolyte (HCPE) with a core-shell structure is designed and synthesized via alkyne polycyclotrimerization and click chemistry. The HCPE has an emission maximum at 565 nm with a quantum yield of 12% and a large Stokes shift of 143 nm in water. By virtue of its poly(ethylene glycol) shell, this polymer naturally forms spherical nanoparticles that minimize nonspecific interaction with biomolecules in aqueous solution, consequently allowing for efficient bioconjugation with anti-HER2 affibody via carbodiimide-activated coupling reaction. The resulting affibody-attached HCPE can be utilized as a reliable fluorescent probe for targeted cellular imaging of HER2-overexpressed cancer cells such as SKBR-3. Considering its low cytotoxicity and good photostability, the HCPE nanoprobe holds great promise in practical imaging tasks. This study also provides a molecular engineering strategy to overcome the intrinsic limitations of traditional fluorescent polymers (e.g., chromophore-tethered polymers and linear conjugated polyelectrolytes) for bioconjugation and applications.

    View details for DOI 10.1021/bm200563a

    View details for Web of Science ID 000293488200014

    View details for PubMedID 21710990

  • Conjugated polyelectrolyte blend as perturbable energy donor-acceptor assembly with multicolor fluorescence response to proteins CHEMICAL COMMUNICATIONS Pu, K., Zhan, R., Liu, B. 2010; 46 (9): 1470-1472


    Blending conjugated polyelectrolytes is demonstrated to be a convenient yet effective method to create a perturbable energy transfer systems with multicolor fluorescence response toward both nonmetalloproteins and metalloproteins, which holds great promise in visual protein sensing.

    View details for DOI 10.1039/b915984c

    View details for Web of Science ID 000274580700025

    View details for PubMedID 20162151

  • A molecular brush approach to enhance quantum yield and suppress nonspecific interactions of conjugated polyelectrolyte for far-red/near-infrared fluorescence targeted cell imaging Advanced Functional Materials Pu KY, Li K, Liu B 2010; 20: 2770
  • Fluorescent single-molecular core-shell nanospheres of hyperbranched conjugated polyelectrolyte for live-cell imaging Chemistry of Materials Pu KY, Li K, Shi JB, Liu B 2009; 21: 3816
  • Conjugated polyelectrolytes as light-up macromolecular probes for heparin sensing Advanced Functional Materilas Pu KY, Liu B 2009; 19: 277
  • Intercalating dye harnessed cationic conjugated polymer for real-time naked-eye recognition of double-stranded DNA in serum Advanced Functional Materials Pu KY, Liu B 2009; 19: 1371
  • Optimizing the cationic conjugated polymer-sensitized fluorescent signal of dye labeled oligonucleotide for biosensor applications BIOSENSORS & BIOELECTRONICS Pu, K., Liu, B. 2009; 24 (5): 1067-1073


    Methods for real time, highly selective and sensitive polynucleotide detection are of vast scientific and economic importance. Fluorescence resonance energy transfer (FRET)-based assays which take advantage of the collective response of water-soluble conjugated polymers (CPs) and the self-assembly characteristic of aqueous polyelectrolytes have been widely used for the detection of DNA, RNA, protein and small molecules. The detection sensitivity of CP-based biosensor is dependent on the signal amplification of dye emission upon excitation of CP relative to that upon direct excitation of the dye. Using cationic polyfluorene derivatives and chromophore (fluorescein or Texas Red) labeled single-stranded DNA molecules (ssDNA-C*) as donor/acceptor pairs, we show that in addition to the spectral overlap, orientation and distance between the donor and the acceptor, the energy levels and fluorescence quenching of the donor/acceptor within the polymer/DNA-C* complexes are also important factors that affect the signal output of dye emission.

    View details for DOI 10.1016/j.bios.2008.07.029

    View details for Web of Science ID 000263199800002

    View details for PubMedID 18760913

  • Effect of charge density on energy-transfer properties of cationic conjugated polymers Advanced Functional Materials Pu KY, Fang Zhen, Liu B 2008; 18: 1321
  • A multicolor cationic conjugated polymer for naked-eye detection and quantification of heparin Macromolecules Pu KY, Liu B 2008; 41: 6636

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