Research Interests

Nanomaterials Engineering

  • Hybrid nanomaterials for solar fuel applications

  • Graphene-nanocrystal composite-based on flexible electronics

  • Polymer-inorganic nanocrystal hybrid materials built upon supramolecular interactions

  • Functional films based on directed self-assembly of nanocrystals at oil/water interfaces

  • Fluorescent metal nanoclusters


Highlights

  • Plasmonic Vesicles of Amphiphilic Gold Nanocrystals: Self-Assembly and External-Stimuli-Triggered Destruction

    We report a versatile strategy based on the use of multifunctional mussel-inspired polydopamine for constructing well-defined single-nanoparticle@metal-organic framework (MOF) core-shell nanohybrids. The capability of polydopamine to form a robust conformal coating on colloidal substrates of any composition and to direct the heterogeneous nucleation and growth of MOFs makes it possible for customized structural integration of a broad range of inorganic/organic nanoparticles and functional MOFs. Furthermore, the unique redox activity of polydopamine adds additional possibilities to tailor the functionalities of the nanohybrids by sandwiching plasmonic/catalytic metal nanostructures between the core and shell via localized reduction. The core-shell nanohybrids, with the molecular sieving effect of the MOF shell complementing the intrinsic properties of nanoparticle cores, represent a unique class of nanomaterials of considerable current interest for catalysis, sensing, and nanomedicine.

  • Coating Graphene Paper with 2D-Assembly of Electrocatalytic Nanoparticles: A Modular Approach toward High-Performance Flexible Electrodes

    We present a new strategy, built upon the use of mussel-inspired polydopamine (PDA), for constructing multifunctional nanochains of magnetic nanoparticles. One key finding is that self-polymerization of PDA around magnetically aligned nanoparticles affords robust rigid magnetic nanochains with versatile reactivity imparted by PDA. In particular, we have shown that loading of metal nanoparticles on the nanochains via localized reduction by PDA gave rise to magnetically recyclable, self-mixing nanocatalysts. Surface coupling of PDA with nucleophilic thiol and amine groups via Michael addition and/or Schiff base reactions, on the other hand, enabled easy bioconjugation of targeting ligands such as DNA aptamer for specific recognition of the nanochains to cancer cells, which led to magnetolysis of the cancer cells in a spinning magnetic field. The PDA-enabled strategy allows for flexible selection of magnetic building blocks and postsynthesis functionalization, which are of considerable interest for a wide spectrum of chemical and biomedical applications.

  • Responsive Plasmonic Assemblies of Amphiphilic Nanocrystals at Oil Water Interfaces

    We report a new strategy to synthesize core-shell metal nanoparticles with an interior, Raman tag-encoded nanogap by taking advantage of nanoparticle-templated self-assembly of amphiphilic block copolymers and localized metal precursor reduction by redox-active polymer brushes. Of particular interest for surface-enhanced Raman scattering (SERS) is that the nanogap size can be tailored flexibly, with the sub-2 nm nanogap leading to the highest SERS enhancement. Our results have further demonstrated that surface functionalization of the nanogapped Au nanoparticles with aptamer targeting ligands allows for specific recognition and ultrasensitive detection of cancer cells. The general applicability of this new synthetic strategy, coupled with recent advances in controlled wet-chemical synthesis of functional nanocrystals, opens new avenues to multifunctional core-shell nanoparticles with integrated optical, electronic, and magnetic properties.

Biomedical Nanotechnology

  • Plasmonic nanostructures for biosensing and bioimaging

  • Semiconductor quantum dots for live cell imaging and biomarker profiling

  • Multi-functional nanoparticles for integrated cancer imaging and therapy

  • Self-assembled nanostructures for disease-targeted drug/gene delivery


Highlights

  • Self-Assembled Plasmonic Vesicles of SERS-Encoded Amphiphilic Gold Nanoparticles for Cancer Cell Targeting and Traceable Intracellular Drug Delivery

    We report the development of bioconjugated plasmonic vesicles assembled from SERS-encoded amphiphilic gold nanoparticles for cancer-targeted drug delivery. This new type of plasmonic assemblies with a hollow cavity can play multifunctional roles as delivery carriers for anticancer drugs and SERS-active plasmonic imaging probes to specifically label targeted cancer cells and monitor intracellular drug delivery. We have shown that the pH-responsive disassembly of the plasmonic vesicle, stimulated by the hydrophobic-to-hydrophilic transition of the hydrophobic brushes in acidic intracellular compartments, allows for triggered intracellular drug release. Because self-assembled plasmonic vesicles exhibit significantly different plasmonic properties and greatly enhanced SERS intensity in comparison with single gold nanoparticles due to strong interparticle plasmonic coupling, disassembly of the vesicles in endocytic compartments leads to dramatic changes in scattering properties and SERS signals, which can serve as independent feedback mechanisms to signal cargo release from the vesicles. The unique structural and optical properties of the plasmonic vesicle have made it a promising platform for targeted combination therapy and theranostic applications by taking advantage of recent advances in gold nanostructure based in vivo bioimaging and photothermal therapy and their loading capacity for both hydrophilic (nucleic acids and proteins) and hydrophobic (small molecules) therapeutic agents.

  • Quantum Dots with Phenylboronic Acid Tags for Specific Labeling of Sialic Acids on Living Cells

    Sialic acids with a nine-carbon backbone are commonly found at the terminal position of the glycans structures on cell membranes. The unique distribution and ubiquitous existence of sialic acid on the cell membrane make them important mediators in various biological and pathological processes. We report a new class of imaging probes based on semiconductor quantum dots with small molecular phenylboronic acid tags for highly specific and efficient labeling of sialic acid on living cells. Our results have shown that the use of these probes enables one-step labeling and continuous tracking of the cell surface sialic acid moieties without any pretreatment of living cells. The one-step procedure with fast binding kinetics and the biocompatibility of these probes make it an ideal noninvasive technology for living cell imaging. We also find that the labeled sialic acids undergo quick internalization shortly after surface binding via endocytosis and eventually distribute in the perinuclear region. This distribution pattern is consistent with the notion that sialylated glycoproteins are populated on cell membranes and recycled through the vesicular exocytotic and endocytic pathways. The superior photostability and brightness of quantum dots enable quantitative analysis of the diffusion dynamics of sialic acids, which has been a significant challenge for glycan imaging.

  • Quantum Dots with Multivalent and Compact Polymer Coatings for Efficient Fluorescence Resonance Energy Transfer and Self-Assembled Biotagging

    Multicolor quantum dot (QD) probes with compact sizes, excellent colloidal stability, and high quantum yields were developed by using a new class of multivalent polymer ligands based on poly(maleic anhydride) homopolymer. These size-minimized QDs allow facile construct of bioconjugated QDs through metal-affinity chelating between polyhistidine (His) tags of recombinant proteins and QD surfaces. Our results have shown that fluorescent protein, for example, mCherry with His-tag, is able to assemble on the QD surface and give rise to highly efficient fluorescence resonance energy transfer (FRET) between the QD donor and the fluorescent protein acceptor. Our results suggest that using this new class of compact QD probes leads to significant enhancement of FRET efficiency in comparison with the bulky amphiphilic polymer encapsulated QDs. We have also found that self-assembled QD probes can be successfully used for immunofluorescence cell staining, indicating that this self-assembled biotagging strategy is both versatile and robust in nature.

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