Maixian Liu

Au-Cu2- xSe heterodimer nanoparticles with broad localized surface plasmon resonance as contrast agents for deep tissue imaging

We report a new type of heterogeneous nanoparticles (NPs) composed of a heavily doped semiconductor domain (Cu2-xSe) and a metal domain (Au), which exhibit a broad localized surface plasmon resonance (LSPR) across visible and near-infrared (NIR) wavelengths, arising from interactions between the two nanocrystal domains. We demonstrate both in vivo photoacoustic imaging and in vitro dark field imaging, using the broad LSPR in Cu2-xSe-Au hybrid NPs to achieve contrast at different wavelengths. The high photoacoustic imaging depth achieved, up to 17 mm, shows that these novel contrast agents could be clinically relevant. More broadly, this work demonstrates a new strategy for tuning LSPR absorbance by engineering the density of free charge carriers in two interacting domains.

Cu2–xSe Nanocrystals with Localized Surface Plasmon Resonance as Sensitive Contrast Agents for In Vivo Photoacoustic Imaging: Demonstration of Sentinel Lymph Node Mapping

Abstract The promise of a new nanomaterial, Cu(2-x) Se nanocrystals, as a contrast agent for photoacoustic imaging is demonstrated. The Cu(2-x) Se nanocrystals exhibit strong optical absorption at near infrared wavelengths that can efficiently penetrate tissue. In vivo photoacoustic tomography using this nanomaterial as the contrast agent provides clear three-dimensional resolution of a sentinel lymph node in a rat model.

Synthesis and Characterization of Mn:ZnSe/ZnS/ZnMnS Sandwiched QDs for Multimodal Imaging and Theranostic Applications

In this work, a facile aqueous synthesis method is optimized to produce Mn:ZnSe/ZnS/ZnMnS sandwiched quantum dots (SQDs). In this core-shell co-doped system, paramagnetic Mn(2+) ions are introduced as core and shell dopants to generate Mn phosphorescence and enhance the magnetic resonance imaging signal, respectively. T1 relaxivity of the nanoparticles can be improved and manipulated by raising the shell doping level. Steady state and time-resolved optical measurements suggest that, after high level shell doping, Mn phosphorescence of the core can be sustained by the sandwiched ZnS shell. Because the SQDs are free of toxic heavy metal compositions, excellent biocompatibility of the prepared nanocrystals is verified by in vitro MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. To explore the theranostic applications of SQDs, liposome-SQD assemblies are prepared and used for ex vivo optical and magnetic resonance imaging. In addition, these engineered SQDs as nanocarrier for gene delivery in therapy of Panc-1 cancer cells are employed. The therapeutic effects of the nanocrystals formulation are confirmed by gene expression analysis and cell viability assay.

Au–Cu2−xSe heterogeneous nanocrystals for efficient photothermal heating for cancer therapy

In this study, we show that Au-Cu2-xSe heterogeneous nanocrystals have great promise for use in photothermal therapy (PTT). Ligand-stabilized heterogeneous gold-copper selenide (Au-Cu2-xSe) hybrid nanocrystals were synthesized by a colloidal gold seed-mediated method. The nanocrystals exhibit broad localized surface plasmon resonance (LSPR) across visible and near-infrared (NIR) wavelengths, arising from interactions between the two nanocrystal domains. After a ligand-exchange process, the NCs readily disperse in water while retaining their LSPR absorbance. Upon illumination with a 980 nm laser, the Au-Cu2-xSe nanocrystals produced significant photothermal heating with a photothermal transduction efficiency comparable to that of larger gold nanostructures that have been widely studied for PTT. In vitro photothermal heating of Au-Cu2-xSe nanocrystals in the presence of human cervical cancer cells caused cell ablation after 10 min laser irradiation. Cell viability assays demonstrated that the hybrid nanocrystals are biocompatible at doses needed for photothermal therapy. Overall, these heterogeneous nanocrystals provide the NIR PTT efficacy of larger gold nanorods in a much smaller overall nanostructure that may have advantages with respect to biodistribution and clearance.

Shape Evolution of Biconcave Djurleite Cu1.94S Nanoplatelets Produced from CuInS2 Nanoplatelets by Cation Exchange

Development of nanomaterials of previously unavailable shapes and compositions continues to be a key need and interest in nanotechnology. Here, we report the preparation of unique biconcave djurleite Cu1.94S nanoplatelets (NPls) from template CuInS2 (copper indium sulfide, CIS) NPls via a cation exchange (CE) reaction. Upon initiation of the CE reaction, the In3+ ions diffuse out of the CIS crystal lattice, and the remaining copper sulfide adopts the djurleite phase almost instantly. This rapid phase transition produces numerous vacancies and defects before Cu+ ions can diffuse into the nanostructures. The formation of a biconcave shape is attributed to the assembly and migration of these defects. The flat surfaces of the NPls are ultimately restored through a ripening process that produces single-crystalline NPls much thicker than the starting templates. Striped NPls were observed in the final products, due to stacking faults at the boundary between newly deposited and residual layers of djurleite. These studies not only provide a better understanding of the relationships among composition, morphology, and crystal structure for copper sulfide-based nanocrystals, but also provide a pathway to a previously inaccessible morphology.

Galectin-1 Reduces Neuroinflammation via Modulation of Nitric Oxide-Arginase Signaling in HIV-1 Transfected Microglia: a Gold Nanoparticle-Galectin-1 “Nanoplex” a Possible Neurotherapeutic?

Galectins are a family of β-galactoside-binding lectins that are important modulators of homeostasis in the central nervous system (CNS). Galectin-1 is a pivotal regulator of microglia activation that alters the immune balance from neurodegeneration to neuroprotection and could have therapeutic relevance in HIV associated neurocognitive disorders (HAND). We have previously shown that galectin-1 treatment decreased oxidative stress in microglia and hypothesize that the mechanism underlying this phenomenon is the cross regulatory interactions between Nitric oxide (NO) and Arginase I activity in microglia. We induced microglial activation and examined the effect of galectin-1 on the expression of various M1/M2 microglial phenotypic markers. Since, TNF-α is associated with activation of microglial cells involved in pathogenesis of neurodegenerative diseases, we treated HIV transfected human microglial cell cultures (CHME-5/HIV) with TNF-α followed by treatment with galectin-1, to examine the galectin-1 mediated neuro-modulatory response. Our results show that treatment of CHME-5/HIV microglia with galectin-1 reduced TNF-α induced oxidative stress by ~40%, and also significantly reduced iNOS gene expression and NO production while correspondingly increasing arginase-1, cationic amino acid transporter (CAT-1) gene expression and arginase activity. Galectin-1 treatment results in shifting microglia polarization from M1 toward the beneficial M2 phenotype which may prevent neurodegeneration and promote neuroprotection. Thus, our data suggests that galectin-1 treatment reduces neuroinflammation in the CNS microenvironment via the modulation of the NO-arginase network in microglia and thus could play a neuroprotective role in HAND. Further, the therapeutic potential of galectin-1 could be enhanced by conjugation of galectin-1 onto gold nanoparticles (Au-NP), resulting in a nanogold-galectin-1 (Au-Gal-1) multivalent complex that will have more clinical translational efficacy than free galectin-1 by virtue of increasing the payload influx.

TiO2-coated fluoride nanoparticles for dental multimodal optical imaging

Core-shell nanostructures associated with photonics techniques have found innumerous applications in diagnostics and therapy. In this work, we introduce a novel core-shell nanostructure design that serves as a multimodal optical imaging contrast agent for dental adhesion evaluation. This nanostructure consists of a rare-earth-doped (NaYF4 :Yb 60%, Tm 0.5%)/NaYF4 particle as the core (hexagonal prism, ~51 nm base side length) and the highly refractive TiO2 material as the shell (~thickness of 15 nm). We show that the TiO2 shell provides enhanced contrast for optical coherence tomography (OCT), while the rare-earth-doped core upconverts excitation light from 975 nm to an emission peaked at 800 nm for photoluminescence imaging. The OCT and the photoluminescence wide-field images of human tooth were demonstrated with this nanoparticle core-shell contrast agent. In addition, the described core-shell nanoparticles (CSNps) were dispersed in the primer of a commercially available dental bonding system, allowing clear identification of dental adhesive layers with OCT. We evaluated that the presence of the CSNp in the adhesive induced an enhancement of 67% scattering coefficient to significantly increase the OCT contrast. Moreover, our results highlight that the upconversion photoluminescence in the near-infrared spectrum region is suitable for image of deep dental tissue.

Selective Cation Incorporation into Copper Sulfide Based Nanoheterostructures

Heterogeneous copper sulfide based nanostructures have attracted intense attention based on their potential to combine the plasmonic properties of copper-deficient copper sulfides with properties of other semiconductors and metals. In general, copper sulfides are versatile platforms for production of other materials by cation incorporation and exchange processes. However, the outcomes of subsequent cation exchange (CE) or incorporation processes involving nanoheterostructure (NH) templates have not been explored. In this work, we incorporate indium and tin into Cu1.81S-ZnS NHs. We demonstrate that the outcomes of cation incorporation are strongly influenced by heterocation identity and valence and by the presence of a Cu-extracting agent. The selectivity of cation incorporation depends upon both the cation itself and the heterodomains in which CE reactions take place. The final nanocrystals (NCs) emerge in many forms including homogeneous NCs, heterodimers, core@shell NHs and NHs with three different domains. This selective cation incorporation not only facilitates the preparation of previously unavailable metal sulfide NHs but also provides insight into mechanisms of CE reactions.

Strong Stimulated Mie Scattering From Plasmonic CuS Nanocrystals in Toluene or Pentane

We report here strong stimulated Mie scattering (SMS) from a grating formed by optically redistributed plasmonic CuS nanocrystals (NCs), which exhibit a strong near-infrared localized surface plasmon resonance. We demonstrate that CuS NCs dispersed in a solvent, such as toluene or pentane, interact strongly with light due to their large polarizability that arises from their high concentration of free charge carriers. The NCs redistribute in the intensity grating that is formed by the interference of forward pump light with backward Mie scattered light. This alignment generates a Bragg grating of CuS NCs, which produces efficient reflection to the plasmonically enhanced backward Mie scattering. We report SMS from CuS NCs suspended in toluene at varying concentrations, pumped by ∼816-nm and ∼10-ns laser pulses. At the optimum concentration and for a 2-cm cuvette length, the reflectivity (energy transfer efficiency from the input pump to the backward SMS) reached 29%, and the pump energy threshold was 4.8 times lower than that of stimulated Brillouin scattering in pure toluene. The time delay of the backward SMS pulse observed at lower pump energy levels is consistent with reflection from a grating formed by spatial redistribution due to drift mobility of nanoparticles. Changing the solvent from toluene to pentane that has lower viscosity, reduced the delay time, which is also consistent with the nanoparticle redistribution model. The temporal behavior, spectral line shape, and far-field distribution of the backward SMS are presented.