George Huang

Differential Uptake of Carbon Nanoparticles by Plant and Mammalian Cells

Consequently, a body of literature over the past decade hasbeen centered on cytotoxicity, genotoxicity, and ecotoxicity ofnanomaterials, pointing to the general understanding thatnanotoxicity is often derived from the physiochemicalproperties of the nanomaterials and their interplay with thehost environment.

Anticarcinogenic Activity of Strawberry, Blueberry, and Raspberry Extracts to Breast and Cervical Cancer Cells

Freeze-dried fruits of two strawberry cultivars, Sweet Charlie and Carlsbad, and two blueberry cultivars, Tifblue and Premier were sequentially extracted with hexane, 50% hexane/ethyl acetate, ethyl acetate, ethanol, and 70% acetone/water at ambient temperature. Each extract was tested separately for in vitro anticancer activity on cervical and breast cancer cell lines. Ethanol extracts from all four fruits strongly inhibited CaSki and SiHa cervical cancer cell lines and MCF-7 and T47-D breast cancer cell lines. An unfractionated aqueous extract of raspberry and the ethanol extract of Premier blueberry significantly inhibited mutagenesis by both direct-acting and metabolically activated carcinogens.

Measurement of particle size distribution in mammalian cells in vitro by use of polarized light spectroscopy

We demonstrate the feasibility of measuring the particle size distribution (PSD) of internal cell structures in vitro. We use polarized light spectroscopy to probe the internal morphology of mammalian breast cancer (MCF7) and cervical cancer (Siha) cells. We find that graphing the least-squared error versus the scatterer size provides insight into cell scattering. A nonlinear optimization scheme is used to determine the PSD iteratively. The results suggest that 2-microm particles (possibly the mitochondria) contribute most to the scattering. Other subcellular structures, such as the nucleoli and the nucleus, may also contribute significantly. We reconstruct the PSD of the mitochondria, as verified by optical microscopy. We also demonstrate the angle dependence of the PSD.

Cytochrome P450 1 enzyme inhibition and anticancer potential of chromene amides from Amyris plumieri.

Cytochrome P450 (CYP) enzyme inhibitory properties of six chromenylated amide compounds (CAs) from Amyris plumieri are described. Inhibition of CYP microsomes (CYP1A1, CYP1A2, CYP1B1, CYP2D6, CYP3A4 and CYP2C19) was monitored using a fluorescent assay. Potent inhibition was found against CYP1A1 with IC(50) and K(i) for CA1 (acetamide), being the lowest at 1.547 ± 1.0 μM and 0.37 μM respectively, displaying non-competitive kinetics. The selectivity for CYP1A1 was increased in CA3 (butanamide), which also exhibited cytotoxicity against breast cancer cells, MCF7 with an IC(50) of 47.46 ± 1.62 μM. Structure-activity relationship studies provide insight at a molecular level for CAs with implications in chemoprevention and chemotherapy.

Calcium-enhanced exocytosis of gold nanoparticles

This paper examines the exocytosis of nanoparticles, an important but rarely documented aspect of cell responses to engineered nanomaterials. Specifically, HT-29 mammalian cells were labeled with a lipophilic Laurdan dye, and the membrane fluidity in the presence of goldnanoparticles was evaluated by the generalized polarization (GP) values derived from the fluorescence spectra of the dye. The concentration of excreted goldnanoparticles increased with increasing extracellular calcium, directly demonstrating exocytosis of nanoparticles and corroborating the inference made from the GP values of the Laurdan dye. This study provides additional information for understanding the fate of nanomaterials in biological systems.

Cytotoxic and potent CYP1 inhibitors from the marine algae Cymopolia barbata

Background Extracts from the marine algae Cymopolia barbata have previously shown promising pharmacological activity including antifungal, antitumor, antimicrobial, and antimutagenic properties. Even though extracts have demonstrated such bioactivity, isolated ingredients responsible for such bioactivity remain unspecified. In this study, we describe chemical characterization and evaluations of biological activity of prenylated bromohydroquinones (PBQ) isolated from the marine algae C. barbata for their cytotoxic and chemopreventive potential. Methods The impact of PBQs on the viability of cell lines (MCF-7, HT29, HepG, and CCD18 Co) was evaluated using the MTS assay. In addition, their inhibitory impact on the activities of heterologously expressed cytochrome P450 (CYP) enzymes (CYP1A1, CYP1A2, CYP1B1, CYP2C19, CYP2D6, and CYP3A4) was evaluated using a fluorescent assay. Results 7-Hydroxycymopochromanone (PBQ1) and 7-hydroxycymopolone (PBQ2) were isolated using liquid and column chromatography, identified using 1 H and 13 C NMR spectra and compared with the spectra of previously isolated PBQs. PBQ2 selectively impacted the viability of HT29, colon cancer cells with similar potency to the known chemotherapeutic drug, fluorouracil (IC50, 19.82 ± 0.46 μM compared to 23.50 ± 1.12 μM, respectively) with impact toward normal colon cells also being comparable (55.65 ± 3.28 compared to 55.51 ± 3.71 μM, respectively), while PBQ1 had no impact on these cells. Both PBQs had potent inhibition against the activities of CYP1A1 and CYP1B1, the latter which is known to be a universal marker for cancer and a target for drug discovery. Inhibitors of CYP1 enzymes by virtue of the prevention of activation of carcinogens such as benzo-a-pyrene have drawn attention as potential chemopreventors. PBQ2 potently inhibited the activity of CYP1B1 (IC50 0.14 ± 0.04 μM), while both PBQ1 and PBQ2 potently inhibited the activity of CYP1A1 (IC50s of 0.39 ± 0.05 μM and 0.93 ± 0.26 μM, respectively). Further characterizations showed partial noncompetitive enzyme kinetics for PBQ2 with CYP1B1 with a Ki of 4.7 × 10–3 ± 5.1 × 10–4 μM and uncompetitive kinetics with CYP1A1 (Ki = 0.84 ± 0.07 μM); while PBQ1 displayed partial non competitive enzyme kinetics with CYP1A1 (Ki of 3.07 ± 0.69 μM), noncompetitive kinetics with CYP1A2 (Ki = 9.16 ± 4.68 μM) and uncompetitive kinetics with CYP1B1 (Ki = 0.26 ± 0.03 μM) . Conclusions We report for the first time, two isolated ingredients from C. barbata, PBQ1 and PBQ2, that show potential as valuable chemotherapeutic compounds. A hydroxyl moiety resident in PBQ2 appears to be critical for selectivity and potency against the cancer colon cells, HT29, in comparison to the three other malignant cell lines studied. PBQs also show potency against the activities of CYP1 enzyme which may be a lead in chemoprevention. This study, the first on isolates from these marine algae, exemplifies the value of searching within nature for unique structural motifs that can display multiple biological activities.

Diffusion of carbon nanotubes with single-molecule fluorescence microscopy

Single walled carbon nanotubes (SWNTs) are a promising gene and drug delivery system since their physical dimensions mimic nucleic acids. Towards this aim, the hydrophobicity of SWNTs was averted by coating with ribonucleic acid (RNA) polymer [poly(rU)] or bovine serum albumin (BSA) and the consequent diffusion of these synthetic-biomolecular hybrids was studied by single-molecule fluorescence microscopy. The diffusion coefficient for SWNT-poly(rU) was measured at 0.374±0.045μm2∕s and for SWNT-BSA it was 0.442±0.046μm2∕s. Our diffusion study provides a fundamental guidance to gene delivery using SWNT as transporters.

Cytoprotective properties of a fullerene derivative against copper

To delineate the complexity of the response of cells to nanoparticles we have performed a study on HT-29 human colon carcinoma cells exposed first to a fullerene derivative C(60)(OH)(20) and then to physiological copper ions. Our cell viability, proliferation, and intracellular reactive oxygen species (ROS) production assays clearly indicated that C(60)(OH)(20) suppressed cell damage as well as ROS production induced by copper, probably through neutralization of the metal ions by C(60)(OH)(20) in the extracellular space, as well as by adsorption and uptake of the nanoparticles surface-modified by the biomolecular species in the cell medium. This double-exposure study provides new data on the effects of nanoparticles on cell metabolism and may aid the treatment of oxidant-mediated diseases using nanomedicine.

Glaucarubulone glucoside from Castela macrophylla suppresses MCF-7 breast cancer cell growth and attenuates benzo[a]pyrene-mediated CYP1A gene induction.

Quassinoids often exhibit antioxidant and antiproliferative activity. Emerging evidence suggests that these natural metabolites also display chemopreventive actions. In this study, we investigated the potential for the quassinoid glaucarubulone glucoside (Gg), isolated from the endemic Jamaican plant Castela macrophylla (Simaroubaceae), to display potent cytotoxicity and inhibit human cytochrome P450s (CYPs), particularly CYP1A enzymes, known to convert polyaromatic hydrocarbons into carcinogenic metabolites. Gg reduced the viability of MCF‐7 breast adenocarcinoma cells (IC50 = 121 nm) to a greater extent than standard of care anticancer agents 5‐fluorouracil, tamoxifen (IC50 >10 μm) and the tamoxifen metabolite 4‐hydroxytamoxifen (IC50 = 2.6 μm), yet was not cytotoxic to non‐tumorigenic MCF‐10A breast epithelial cells. Additionally, Gg induced MCF‐7 breast cancer cell death. Gg blocked increases in reactive oxygen species in MCF‐10A cells mediated by the polyaromatic hydrocarbon benzo[a]pyrene (B[a]P) metabolite B[a]P 1,6‐quinone, yet downregulated the expression of genes that promote antioxidant activity in MCF‐7 cells. This implies that Gg exhibits antioxidant and cytoprotective actions in non‐tumorigenic breast epithelial cells and pro‐oxidant, cytotoxic actions in breast cancer cells. Furthermore, Gg inhibited the activities of human CYP1A according to non‐competitive kinetics and attenuated the ability of B[a]P to induce CYP1A gene expression in MCF‐7 cells. These data indicate that Gg selectively suppresses MCF‐7 breast cancer cell growth without impacting non‐tumorigenic breast epithelial cells and blocks B[a]P‐mediated CYP1A induction. Taken together, our data provide a rationale for further investigations of Gg and similar plant isolates as potential agents to treat and prevent breast cancer. Copyright