Jem Kun Chen

Hot-injection synthesis of monodispersed Cu2ZnSn(SxSe1−x)4 nanocrystals: tunable composition and optical properties

In this study, we demonstrate that Cu2ZnSn(SxSe1−x)4 nanocrystals with a tunable bandgap could be synthesized by a “hot-injection” protocol. In this protocol, metal stearates dissolved in oleylamine were injected into a hot solution of anion precursors in 1-octadecene (ODE) at a given reaction temperature. ODE, which is a low-cost, low-hazard, and air-stable liquid, was used as the solvent. Oleylamine was chosen as both the reagent to activate the precursors and as the capping agent for the nanocrystals. The composition of the Cu2ZnSn(SxSe1−x)4 nanocrystals could be adjusted across the x range from 0 to 1 by varying the S/Se reactant ratio. The lattice parameters (a and c) measured from X-ray diffraction patterns decreased linearly with increasing Se content. This trend was consistent with Vegards law, which confirmed the formation of homogeneous Cu2ZnSn(SxSe1−x)4 nanocrystals. The A1 symmetry modes of the Cu2ZnSn(SxSe1−x)4 nanocrystals seen by Raman spectroscopy gradually shifted with decreasing x (S content) to the lower frequency side and completely disappeared when x = 0. The absorption spectra of the Cu2ZnSn(SxSe1−x)4 nanocrystals revealed that the bandgaps of the nanocrystals could be adjusted over the range 1.0–1.5 eV by decreasing the S content. The relatively small value for the bowing parameter indicated that the synthesized Cu2ZnSn(SxSe1−x)4 nanocrystals had good miscibility.

Gadolinium-based CuInS2/ZnS nanoprobe for dual-modality magnetic resonance/optical imaging.

A new magnetic resonance/optical nanoprobe with specific cellular targeting capabilities based on nontoxic CuInS2/ZnS quantum dots (QDs) with direct covalent attachment of a Gd(III)-complex for tumor-specific imaging is reported. We introduce amphiphilic poly(maleic anhydride-alt-1-octadecene) to interdigitate with hydrophobic, protective agents on the surface of CuInS2/ZnS QDs that allows phase transfer of hydrophobic QDs from the organic into aqueous phase. Carbodiimide chemistry is used to covalently couple the Gd(III) complex on the surface of CuInS2/ZnS QDs, and then folic acid is further utilized to functionalize this dual-modality nanoprobe for active tumor targeting based on the fact that the membrane-associated folate receptor is overexpressed in many tumor cells. The longitudinal relaxivity value is 3.72 mM(-1) s(-1) for the dual-modality nanoprobe and a clear, positive, and increasing contrast enhancement of magnetic resonance signals concurrently with increasing Gd(III) concentration is observed. The dual-modality nanoprobe exhibits negligible cytotoxicity with >80% cell viability at a concentration of up to 100 μg/mL in human cervical (HeLa), human liver carcinoma (HepG2), and human breast (MCF-7) cells after 24 h. The specificity of folic-acid-conjugated nanoprobe cellular uptake has been investigated by confocal scanning laser imaging, which revealed that HeLa cells, expressing the folate receptor, internalized a higher level of dual-modality nanoprobes than HepG2 and MCF-7 cells.

Silica nanohybrids integrated with CuInS2/ZnS quantum dots and magnetite nanocrystals: Multifunctional agents for dual-modality imaging and drug delivery

A strategy is presented for the synthesis of dual-modality and theranostic silica (SiO2) nanohybrids that exert excellent properties for drug delivery vehicles as well as optical and magnetic resonance imaging. SiO2 nanohybrids are composed of CuInS2/ZnS quantum dots and magnetite nanocrystals, with an outside SiO2 shell grafted with poly(ethyleneglycol) and amine groups to provide better biocompatibility and allow subsequent bioconjugation, respectively. The synthesized nanohybrids are of ultra-small size (diameter < 30 nm) and highly monodispersed and stable in aqueous suspension. In vitro results showed that the SiO2 nanohybrids were efficiently taken up by the cells and localized in the intracellular vesicles, emitting strong fluorescence from the cytoplasm and nearby nucleus. It was also demonstrated that SiO2 nanohybrids could be used as a new class of magnetic resonance imaging probes, demonstrating a high spin–spin (T2) relaxivity (r2 = 214 mM−1 s−1). The Pt(IV) anticancer drug, c,c,t-[Pt(NH3)2Cl2(O2CCH2CH2CO2H)2], was used as a model drug to attach to the surface of dual-modality SiO2 nanohybrids by using n-ethyl-N′-(3-dimethylaminopropyl)carbodiimide and hydroxysuccinimide as the activating agents. The drug readily formed amide linkages with amines on the surface of the SiO2 nanohybrids, resulting in Pt(IV)-conjugated SiO2 nanohybrids. The results reveal that the Pt(IV)-conjugated SiO2 nanohybrids show higher cytotoxicity than the free Pt(IV) anticancer drug, indicating the potential for using the obtained multifunctional SiO2 nanohybrids simultaneously as highly effective dual-modality imaging probes for cancer diagnosis and chemotherapy.

Rapid fabrication of carbon quantum dots as multifunctional nanovehicles for dual-modal targeted imaging and chemotherapy

Herein, we synthesized an S, N, and Gd tri-element doped magnetofluorescent carbon quantum dots (GdNS@CQDs) within 10min by using a one-pot microwave method. Our results showed that these magnetofluorescent GdNS@CQDs have excellent fluorescent and magnetic properties. Moreover, GdNS@CQDs exhibited high stability at physiological conditions and ionic strength. These magnetofluorescent GdNS@CQDs were conjugated with a folic acid, denoted as FA-GdNS@CQDs, for targeting dual modal fluorescence/magnetic resonance (MR) imaging. The in vitro and in vivo studies confirmed the high biocompatibility and low toxicity of FA-GdNS@CQDs. FA-GdNS@CQDs enhanced the MR response as compared to that for commercial Gd-DTPA. The targeting capabilities of FA-GdNS@CQDs were confirmed in HeLa and HepG2 cells using in vitro fluorescence and MR dual modality imaging. Additionally, an anticancer drug, doxorubicin, was incorporated into the FA-GdNS@CQDs forming FA-GdNS@CQDs-DOX, which enables targeted drug delivery. Importantly, the prepared FA-GdNS@CQDs-DOX showed a high quantity of doxorubicin loading capacity (about 80%) and pH-sensitive drug release. The uptake into cancer cells and the intracellular location of the FA-GdNS@CQDs were observed by confocal laser scanning microscopy. We also successfully demonstrated in vivo fluorescence bio imaging of the FA-GdNS@CQDs, using zebrafish as an animal model.nnnSTATEMENT OF SIGNIFICANCEnIn this manuscript, we reported a facial, rapid, and environmental friendly method to fabricate hetero atoms including gadolinium, nitrogen, and sulfur doped multi-functional magnetofluorescent carbon quantum dots (GdNS@CQDs) nanocomposite. These multifunctional GdNS@CQDs were conjugated with a folic acid for targeting dual modal fluorescence/magnetic resonance imaging. Additionally, an anticancer drug, doxorubicin, was incorporated into the nanocomposite forming FA-GdNS@CQDs-DOX, which enables targeted drug delivery. We have developed GdNS@CQDs with integrated functions for simultaneous in vitro cell imaging, targeting, and pH-sensitive controlled drug release in HeLa cells. Furthermore, we successfully demonstrated the use of this material for in vivo fluorescence imaging, using zebrafish as an animal model.

Label-free DNA detection using two-dimensional periodic relief grating as a visualized platform for diagnosis of breast cancer recurrence after surgery.

In this study we fabricated a nanopillar array of silicon oxide, involving very-large-scale integration (VLSI) and reactive ion etching (RIE), as two-dimensional periodic relief gratings (2DPRGs) on Si surfaces. Thiolated oligonucleotide was successively immobilized on the thiol functionalized surfaces of 2DPRGs by disulfide bond as an optical probe to detect a human genomic DNA (hgDNA584), related to breast cancer recurrence after surgery, from a biological specimen. The oligonucleotide-bound 2DPRG alone produces insignificant structure change, but upon hybridization with hgDNA584 leads to a dramatic change of the pillar scale due to hgDNA584 filling inside the 2DPRG layers. The performance of the sensor was evaluated by capturing hgDNA584 on the oligonucleotide-bound 2DPRGs and measuring the effective refractive index (neff), resulting of color change from pure blue to red, observed by naked eyes along an incident angle of 20-30°. The surface-bound 2DPRG based assay with the chemoresponsive diffraction grating signal transduction scheme results in an experimentally simple DNA detection protocol, displaying attributes of both detection methodologies: the high sensitivity and selectivity afforded by 2DPRG probes and the experimental simplicity, and miniaturization potential provided by the diffraction-based sensing technology.

Development of bovine serum albumin-modified hybrid nanoclusters for magnetofluorescence imaging and drug delivery

In this study, bovine serum albumin (BSA) was used for simultaneously clustering and phase-transferring both oil-soluble AgInS2–ZnS quantum dots (QDs) and MnFe2O4 magnetic nanoparticles (MNPs) under ultrasonication. The hybrid nanoclusters, BSA(QMs), thus produced were conjugated with folic acid (FA) and doxorubicin (DOX) to improve their target specificity and drug delivery to HeLa cancer cells. The resulting nanoclusters were characterized by employing different analytical techniques, and the results showed the nanocluster magnetofluorescence property derived from the clustering process. It was also found that the hybrid nanoclusters were biocompatible, non-toxic, and considerably stable over a wide range of pH values and at high ionic strengths. In addition, the in vitro confocal microscopy and MR relaxation studies revealed the yellow fluorescence and T2 contrast-enhancing property of FA–BSA(QMs), as well as their cellular pathway to enter HeLa cells via folate receptor-mediated endocytosis. Furthermore, the cell viability data and flow cytometry results demonstrated the selective uptake of DOX–FA–BSA(QMs) by the HeLa cells, which significantly enhanced cell cytotoxicity. These results suggest that the proposed nanoclusters can be used as an effective and efficient strategy for magnetofluorescent probing and cancer drug delivery.

Visualization platform of one-dimensional gratings of tethered polyvinyltetrazole brushes on silicon surfaces for sensing of Cr(III)

AbstractPolyacrylonitrile (PAN) was grafted on silica (Si) surfaces in the form of one-dimensional (1D) gratings to form well-defined line patterns. The tethered PAN 1D gratings were then subjected to a cyano-to-tetrazole conversion reaction to generate a tethered polyvinyltetrazole (PVT) 1D grating. This results in different properties for the transverse magnetic (TM) and transverse electric (TE) polarizations, i.e. perpendicular and parallel to the line patterns, respectively. After adsorption of Cr(III), the negative charges of PVT chains were neutralized, and this results in a collapse of the polymer brushes. As a result, the effective refractive indices vary with the concentration of Cr(III). This causes a gradual color change from yellow via green to blue at incident angles of 30–40°. The adsorption of the ions Na+, Ag+, Ca2+, Cd2+, Fe3+, Zn2+ and Cr6+ ions, in contrast, does not cause significant changes in the effective refractive index. The Cr(III)-induced deswelling transitions can be reversed by treatment with acid. The assay has a limit of detection (LOD) as low as 20xa0μg·L−1 of Cr(III). The ions Pb(II), Cu(II) and Cr(VI) are also adsorbed by the PVT grating, but the respective LODs are higher (80, 100 and 40xa0μg·L−1).n Graphical abstractPolyvinyltetrazole (PVT) is exploited to graft on silica surfaces as one-dimensional (1D) gratings. The grating-based assay exhibited high sensitivity and selectivity due to significant change of effective refractive indices in an experimentally simple setup for visualization of Cr3+.

Fabrication of metamaterial absorber using polymer brush-gold nanoassemblies for visualizing the reversible pH-responsiveness

Poly(2-dimethylaminoethyl methacrylate) was grafted onto flat silicon substrates via atom transfer radical polymerization to form bottom layers. Two fabrication processes, very-large-scale integration and reactive ion etching, were applied in sequence to generate 400 nm-scale hole arrays of tethered poly(2-dimethylaminoethyl methacrylate) layers as sub-wavelength hole array on the Si surfaces, followed by the immobilization of surface functionalized gold nanoparticles by means of physical interaction (electrostatic attraction, entanglement, and hydrogen bonding) to generate a metamaterial absorber. Hole dimensions of the metamaterial absorber shrank reversibly and significantly upon changing the pH from 10.7 and 3.3 due to swelling behavior, leading to a significant change in surface plasmon resonance. We found that the change in the surface plasmon resonance of the metamaterial absorber, related to the dimensions of its holes upon pH treatment, resulted in a color change from purple to orange, observable by the naked eye at a fixed angle of 10°. The maximum shift of the absorptive peak position was greater than 300 nm, and these shifts corresponded to the color changes in the solutions at various values of pH.

Polyacrylonitrile microscaffolds assembled from mesh structures of aligned electrospun nanofibers as high-efficiency particulate air filters

ABSTRACT Electrospun polyacrylonitrile (PAN) fibers of very small diameters have potential for integration into filters capable of increasing the particle filtration efficiency. To fulfill the requirements for high-efficiency particulate air (HEPA) filters with a reasonable pressure drop, we generated aligned electrospun PAN fibers through pre-alignment at various rotation rates and subsequent solvent vapor annealing (SVA) under a loading. We evaluated the properties of microscaffold filters assembled from aligned electrospun PAN fibers in the form of linear, square, and triangular multiple meshes. The microscaffolds featuring multiple square meshes exhibited dramatically increased filtration efficiency without a significant pressure drop. A nine-layer cross-ply structure provided a filtration efficiency of 99.98% for 0.25-μm particles at a face velocity of 10 cm s−1; its filtration quality factor was the highest among all of the tested microscaffolds. Thus, HEPA filters featuring a low packing density can be achieved using PAN fibers.

Preparation of poly(ethylene glycol) methacrylate coated CuInS2/ZnS quantum dots and their use in cell staining

A simple synthesis of poly(ethylene glycol) methacrylate (PEGMA) coated CuInS2/ZnS quantum dots (QDs) has been developed. X-ray diffraction, transmission electron microscopy, and atomic force microscopy observations demonstrated that uniform CuInS2/ZnS QDs were successfully prepared. Fourier transform infrared spectroscopy indicated no new peak after the coating process, indicating that only physical interactions occurred during coating and that PEGMA did not disturb the crystal structure of the CuInS2/ZnS QDs. After PEGMA coating, the photoluminescence spectra of the CuInS2/ZnS QDs red shifted (from 566 nm to 589 nm) and the QD particle size increased. The concentration and molecular weight of PEGMA play important roles in the water solubility and hydrodynamics of the particles. The PEGMA-coated CuInS2/ZnS QDs showed stable emissions for up to 3 weeks. As a demonstration of a potential biomedical application, PEGMA-coated CuInS2-ZnS QDs were used in labeling human liver carcinoma (HepG2) tumor cells.