Kuo-Yen Huang

Efficient electron transfer in carbon nanodot–graphene oxide nanocomposites

Carbon nanodots (CNDs) have emerged as fascinating materials with exceptional electronic and optical properties, and thus they offer many promising applications in photovoltaics and photocatalysis. In this paper we investigate electron transfer in nanocomposites of CNDs–graphene oxide (GO), –multi-walled carbon nanotubes (MWNTs) and –TiO2 nanoparticles without linker molecules, using steady state and time-resolved spectroscopy. Significant fluorescence quenching was observed in the CND–GO system, and it is attributed to the ultrafast electron transfer from CNDs to GO with a time constant of 400 fs. In comparison, carbon nanotubes result in static quenching of fluorescence in CNDs. No charge transfer was observed in both CND–MWNT and CND–TiO2 nanocomposites. This finding suggests that the CND–GO nanocomposite can be an excellent candidate for hot carrier solar cells due to the effective carrier extraction, broad spectral absorption, weak electron–phonon scattering, and thus a slow cooling rate for hot carriers.

Ultrafast electron transfer in the nanocomposite of the graphene oxide–Au nanocluster with graphene oxide as a donor

Graphene oxide has been extensively investigated as an electron acceptor due to its exceptional electronic and optical properties. Here we report an unusual ultrafast electron transfer occurring in the nanocomposites of Au nanocluster (Au NC)–graphene oxide (GO) in which GO acts as an electron donor. An ultrafast electron transfer is corroborated from the excited states of graphene oxide into the highest occupied molecular orbital (HOMO) of Au NCs. It is found that the electron transfer rate is significantly higher in Au10–GO nanocomposites (4.17 × 1012 s−1) than that in Au25–GO (0.49 × 1012 s−1) due to a larger energy difference and smaller sized ligands. This finding suggests that graphene oxide–Au nanocluster nanocomposites can be very useful to construct novel nanostructures with enhanced visible light photovoltaic, photonic and photo-catalytic activities.

High-efficiency cascade CdS/CdSe quantum dot-sensitized solar cells based on hierarchical tetrapod-like ZnO nanoparticles

Quantum dot-sensitized solar cells (QDSCs) constructed using cascade CdS/CdSe sensitizers and the novel tetrapod-like ZnO nanoparticles have been fabricated. The cascade co-sensitized QDSCs manifested good electron transfer dynamics and overall power conversion efficiency, compared to single CdS- or CdSe-sensitized cells. The preliminary CdS layer is not only energetically favorable to electron transfer but behaves as a passivation layer to diminish the formation of interfacial defects during CdSe synthesis. On the other hand, the anisotropic tetrapod-like ZnO nanoparticles, with a high electron diffusion coefficient, can afford a better carrier transport than traditional ZnO nanoparticles. The resultant solar cell yielded an excellent performance with a solar power conversion efficiency of 4.24% under simulated one sun (AM1.5G, 100 mW cm(-2)) illumination.

Single-particle studies of band alignment effects on electron transfer dynamics from semiconductor hetero-nanostructures to single-walled carbon nanotubes.

We utilize single-molecule spectroscopy combined with time-correlated single-photon counting to probe the electron transfer (ET) rates from various types of semiconductor hetero-nanocrystals, having either type-I or type-II band alignment, to single-walled carbon nanotubes. A significantly larger ET rate was observed for type-II ZnSe/CdS dot-in-rod nanostructures as compared to type-I spherical CdSe/ZnS core/shell quantum dots and to CdSe/CdS dot-in-rod structures. Furthermore, such rapid ET dynamics can compete with both Auger and radiative recombination processes, with significance for effective photovoltaic operation.

Advanced glycation end products induce T cell apoptosis: Involvement of oxidative stress, caspase and the mitochondrial pathway

Accumulation of advanced glycation end products (AGEs) is a hallmark in aged people. T cells play important roles in maintaining homeostasis of immune function. This study investigated the effects of AGEs-bovine serum albumin (AGEs) in human T cells. Incubation of Jurkat and several immortalized T cell lines with AGEs resulted in cell death dose-dependently. AGEs-induced cell death was partially but significantly blocked by neutralizing antibodies recognizing receptor of AGEs. In addition to detecting DNA nick, simultaneous stainings of annexin V with 7-amino-actinomycin D further confirmed the apoptotic nature of cell death. AGEs also caused apoptosis in purified T cells. Although AGEs-induced apoptosis could be blocked by the pan-caspase inhibitor, Ala-Asp-fluomethyl ketone (Z-VAD-fmk), there was no activation of caspase-3, -5, -8 and -9. AGEs caused mitochondrial outer membrane permeabilization and this process was prevented by an antioxidant or Z-VAD-fmk. Furthermore, AGEs treatment led to translocation of apoptosis inducing factor (AIF) from the mitochondria into the nucleus. Altogether, this report demonstrated that AGEs induced T cell apoptosis in an oxidative stress-associated and caspase-dependent manner with involvement of the mitochondrial pathway. It is likely that AGEs-induced T cell apoptosis may play a role in T cell homeostasis in ageing.

Dynamic study on the transformation process of gold nanoclusters

In this paper, the transformation process from Au8 to Au25 nanoclusters (NCs) is investigated with steady state fluorescence spectroscopy and time-resolved fluorescence spectroscopy at various reaction temperatures and solvent diffusivities. Results demonstrate that Au8 NCs, protected by bovine serum albumin, transform into Au25 NCs under controlled pH values through an endothermic reaction with the activation energy of 74 kJ mol(-1). Meanwhile, the characteristic s-shaped curves describing the formation of Au25 NCs suggest this process involves a diffusion controlled growth mechanism.

Magnetically Guided Viral Transduction of Gene-Based Sensitization for Localized Photodynamic Therapy To Overcome Multidrug Resistance in Breast Cancer Cells

Chemotherapy represents a conventional treatment for many cancers at different stages and is either solely prescribed or concomitant to surgery, radiotherapy, or both. However, treatment is tempered in instances of acquired drug resistance in response to either chemotherapy or targeted therapy, leading to therapeutic failure. To overcome this challenge, many studies focus on how cancer cells manipulate their genomes and metabolism to prevent drug influx and facilitate the efflux of accumulated chemotherapy drugs. Herein, we demonstrate magnetic adeno-associated virus serotype 2 (ironized AAV2) has an ability to be magnetically guided and transduce the photosensitive KillerRed protein to enable photodynamic therapy irrespective of drug resistance.

Light-triggered methylcellulose gold nanoparticle hydrogels for leptin release to inhibit fat stores in adipocytes

Leptin is released in response to increased triglyceride storage in adipocytes and impacts body weight, but has drawbacks such as poor therapeutic effect and side effects when delivered systemically. Leptin also modifies adipocyte sensitivity to insulin to inhibit lipid accumulation. Here, light-triggered degradation of hydrogels was used to improve accuracy and effectiveness for sustained and controllable release. In our approach, leptin was entrapped within methylcellulose (MC)-based hydrogels, with incorporation of gold nanoparticles (NP). The incorporation of gold NP into MC hydrogels led to a tunable light irradiation response that dictated the hydrogel release rate of leptin. This manuscript demonstrates feasibility in designing tunable thermosensitive hydrogels for loading multimodality therapeutic agents to enhance the bioactivity of leptin for obesity therapy.

Abstract 4401: A novel drug suppresses proliferation of lung cancer cells via increasing the CBL activity and down-regulating epidermal growth factor receptor

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA Aberrant epidermal growth factor receptor (EGFR) signaling is one of the most critical oncogenic pathways in NSCLC that may trigger the tumor progression. Thus, how to suppress the EGFR downstream signaling cascade or to reduce the EGFR expression level has long been considered an important therapeutic approach for cancer interventions. Here, we found a regulatory mechanism by which the degradation of EGFR is enhanced by a novel promising drug, compound 22. First, the exposure to compound 22 induced cell death via apoptosis in lung cancer cell lines, including EGFR wild type A549 as well as EGFR mutant PC9 and H1975 cells. Compound 22 decreased the EGFR protein level in a dose-dependent manner and facilitated dephosphorylation of its downstream targets, including AKT and ERK, both of which play a critical role for cancer cell survival. Second, we observed that compound 22 induced EGFR degradation through proteasome degradation in the cycloheximide chase plus MG132 assay. Additionally, compound 22 increased the CBL (the ubiquitin E3 ligase)-mediated ubiquitination of EGFR, which was accompanied by the enhancement of Y1045 phosphorylation in the EGFR kinase domain. Overall, these pieces of evidence suggest that compound 22 is a novel class of anticancer drug which is able to inhibit the TKI-resistant NSCLC cells by inducing the degradation of EGFR. Citation Format: Kuo-Yen Huang, Szu-Hua Pan, Wen-Lung Wang, Ching-Shih Chen, Tse-Ming Hong, Pan-Chyr Yang. A novel drug suppresses proliferation of lung cancer cells via increasing the CBL activity and down-regulating epidermal growth factor receptor. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4401. doi:10.1158/1538-7445.AM2014-4401

Investigation of temperature dependence on heterojunction bipolar light-emitting transistors embedded InGaAs/GaAs quantum wells

In this work, an analytical study of the temperature dependence of current gain and ideality factor (η) has been performed for the heterojunction bipolar light emitting transistor (HBLET). In order to utilize the radiative recombination, the structure of HBT embedded two quantum wells in the base region which can improve the radiation efficiency. Compare with the convention HBT, the temperature dependence of current gain increases 42.5% with increasing temperature from 350K followed by a decrease towards 300K. Variation of gain with temperature is different from that the characteristic of HBT adding another advantage in favor of the HBLET. The ηB of these devices are similar, revealing that the space-charge recombination dominates the overall base current. The high output power of HBLET is 962 μW at 88 mA. These results reveal that the HBLET which combine electrical and optical characteristic device.