Quantum Diamonds at the Beach: Chemical Insights into Silica Growth on Nanoscale Diamond using Multimodal Characterization and Simulation.

Surface chemistry of materials that host quantum bits such as diamond is an important avenue of exploration as quantum computation and quantum sensing platforms mature. Interfacing diamond in general and nanoscale diamond (ND) in particular with silica is a potential route to integrate room temperature quantum bits into photonic devices, fiber optics, cells, or tissues with flexible functionalization chemistry. While silica growth on ND cores has been used successfully for quantum sensing and biolabeling, the surface mechanism to initiate growth was unknown. This report describes the surface chemistry responsible for silica bond formation on diamond and uses X-ray absorption spectroscopy (XAS) to probe the diamond surface chemistry and its electronic structure with increasing silica thickness. A modified Stöber (Cigler) method was used to synthesize 2-35 nm thick shells of SiO2 onto carboxylic acid-rich ND cores. The diamond morphology, surface, and electronic structure were characterized by overlapping techniques including electron microscopy. Importantly, we discovered that SiO2 growth on carboxylated NDs eliminates the presence of carboxylic acids and that basic ethanolic solutions convert the ND surface to an alcohol-rich surface prior to silica growth. The data supports a mechanism that alcohols on the ND surface generate silyl-ether (ND-O-Si-(OH)3) bonds due to rehydroxylation by ammonium hydroxide in ethanol. The suppression of the diamond electronic structure as a function of SiO2 thickness was observed for the first time, and a maximum probing depth of ∼14 nm was calculated. XAS spectra based on the Auger electron escape depth was modeled using the NIST database for the Simulation of Electron Spectra for Surface Analysis (SESSA) to support our experimental results. Additionally, resonant inelastic X-ray scattering (RIXS) maps produced by the transition edge sensor reinforces the chemical analysis provided by XAS. Researchers using diamond or high-pressure high temperature (HPHT) NDs and other exotic materials (e.g., silicon carbide or cubic-boron nitride) for quantum sensing applications may exploit these results to design new layered or core-shell quantum sensors by forming covalent bonds via surface alcohol groups.

Selective analysis of the okadaic acid group in shellfish samples using fluorous derivatization coupled with liquid chromatography-tandem mass spectrometry.

Okadaic acid (OA) group are diarrheal shellfish poison that accumulates in the midgut glands of shellfish. It is difficult to remove these poisons by normal cooking because they are thermally stable and hydrophobicity. Therefore, in order to prevent foodborne disease due to shellfish poison, analysis by liquid chromatography (LC)-tandem mass spectrometry (MS/MS) before shipment is necessary. Herein the selective analytical method for OA group in shellfish sample using fluorous derivatization coupled with LC-MS/MS was developed. OA group were derivatized with the fluorous alkylamine reagent by condensing agent, and the obtained derivatives were separated with fluorous LC column (Fluofix-II 120E, 250 × 2.0 mm i.d., 5 µm, Fujifilm Wako Pure Chemical). The derivatized OA group were selective retained by fluorous LC column and accurate analysis was enabled. The present method was applied to the analysis of OA and dinophysistoxin-1 (DTX-1) in scallop midgut gland which is the certified reference material provided by national metrology institute of Japan. As a result of analysis using the present method with DTX-2 as the internal standard, the quantitative value were in agreement with the certified value.

Sulindac enhances the proteasome inhibitor bortezomib-mediated oxidative stress and anticancer activity.

PURPOSE: The nonsteroidal antiinflammatory drug sulindac is a promising chemopreventive agent against colon cancer. Here, we address whether sulindac enhances the anticancer effects of the proteasome inhibitor bortezomib (PS-341) in colon cancer cells. EXPERIMENTAL DESIGN: The synergistic effects of sulindac with bortezomib were evaluated by cell death, colony formation assay, DNA fragmentation, and tumor progression of DLD-1 xenografts. Reactive oxygen species (ROS) generation was detected using carboxy-H2DCFDA or dihydroethidium. Oxidative stress was evaluated by heme oxygenase-1 induction and stress-activated mitogen-activated protein kinases p38 and c-Jun-NH2-kinase phosphorylation. Oxidative DNA damage was evaluated by histone H2AX phosphorylation and accumulation of 8-hydroxy-2'-deoxyguanosine. RESULTS: Sulindac and its metabolites enhanced the anticancer effects of bortezomib in DLD-1 and BM314 colon cancer cells. Sulindac induced ROS generation and enhanced bortezomib-mediated oxidative stress and subsequent DNA damage. Their combined effects were highly sensitive to free radical scavengers L-N-acetylcysteine and alpha-tocopherol, but were much less sensitive to a p38 inhibitor SB203580. CONCLUSION: Sulindac synergistically augments the anticancer effects of bortezomib primarily through cooperative ROS generation and oxidative DNA damage, thereby representing a novel combination therapy against colon cancer.

Synergistic effect of histone deacetylase inhibitors FK228 and m-carboxycinnamic acid bis-hydroxamide with proteasome inhibitors PSI and PS-341 against gastrointestinal adenocarcinoma cells.

PURPOSE: We investigated whether the histone deacetylase inhibitors m-carboxycinnamic acid bis-hydroxamide (CBHA) and a bicyclic depsipeptide, FK228, can enhance the anticancer effect of the proteasome inhibitors PSI and PS-341 in gastrointestinal carcinoma cells. EXPERIMENTAL DESIGN: The anticancer effect of CBHA or FK228 and PSI or PS-341 was evaluated by cell death, caspase-3 activity, externalization of phosphatidylserine and DNA fragmentation, and colony formation assay. Expression of apoptosis-related molecules and cell cycle regulatory molecules, as well as phosphorylation of p38 were investigated by immunoblots. Generation of reactive oxygen species (ROS) was detected by intracellular oxidation of 5- (and-6)-carboxy-2',7'-dichlorodihydrofluorescein diacetate. RESULTS: CBHA or FK228 plus PSI or PS-341 synergistically induced apoptosis in human colonic DLD-1 and gastric MKN45 carcinoma cell lines. CBHA or FK228, but not 5-fluorouracil, plus PS-341 strongly decreased plating efficiency of DLD-1 cells. FK228 elicited ROS generation, and the free radical scavenger l-N-acetylcysteine inhibited the synergistic anticancer effect of combined therapy. In addition, l-N-acetylcysteine inhibited the combined therapy-mediated elevation of a proapoptotic BH3-only protein Bim expression, phosphorylation of H2AX, and accumulation of 8-hydroxydeoxyguanosine. CONCLUSIONS: FK228 or CBHA and PSI or PS-341 synergistically induce apoptosis in DLD-1 and MKN45 cells depending on ROS-mediated signals. Our data suggest that a combination of FK228 or CBHA with PSI or PS-341 may be a valuable therapy against gastrointestinal adenocarcinoma cells.

Parthenolide-induced apoptosis in multiple myeloma cells involves reactive oxygen species generation and cell sensitivity depends on catalase activity.

The sesquiterpene lactone, parthenolide (PTL), possesses strong anticancer activity against various cancer cells. We report that PTL strongly induced apoptosis in 4 multiple myeloma (MM) cell lines and primary MM cells (CD38(+) high), but barely induced death in normal lymphocytes (CD38(-/+)low). PTL-mediated apoptosis correlated well with ROS generation and was almost completely inhibited by L-N-acetylcysteine (L-NAC), indicating the crucial role of oxidative stress in the mechanism. Among 4 MM cell lines, there is considerable difference in susceptibility to PTL. KMM-1 and MM1S cells sensitive to PTL possess less catalase activity than the less sensitive KMS-5 and NCI-H929 cells as well as normal lymphocytes. A catalase inhibitor 3-amino-1,2,4-triazole enhanced their PTL-mediated ROS generation and cell death. The siRNA-mediated knockdown of catalase in KMS-5 cells decreased its activity and sensitized them to PTL. Our findings indicate that PTL induced apoptosis in MM cells depends on increased ROS and intracellular catalase activity is a crucial determinant of their sensitivity to PTL.

Bmf contributes to histone deacetylase inhibitor-mediated enhancing effects on apoptosis after ionizing radiation.

Histone deacetylase (HDAC) inhibitors augment ionizing radiation (IR)-induced apoptosis in several cancer cells by undefined mechanism(s). We recently found that the HDAC inhibitors induce a BH3-only protein Bmf in human squamous carcinoma SAS cells. We extended this study and found that 2.5 nM FK228 pretreatment could not induce apoptosis but augmented IR-induced death. The FK228 pretreatment increased Bmf expression level, and siRNA-mediated knockdown of Bmf transcripts strongly inhibited its augmentation of IR-induced cell death, disruption of mitochondrial membrane potential and DNA fragmentation. Another HDAC inhibitor CBHA pretreatment similarly augmented IR-induced apoptosis, and this effect was also inhibited by Bmf knockdown. Bmf overexpression augmented IR-induced death, and the augmented effects of FK228 were similarly observed in another squamous carcinoma HSC2 cells. Overexpression of histone acetyltransferase p300 mimicked the effects of the HDAC inhibitors, i.e., it enhanced IR-induced death, which was mostly abolished by Bmf knockdown. Taken together, histone hyperacetylation may enhance IR-induced death via activation of Bmf transcription, thereby implying Bmf as a key molecule for HDAC inhibitors (FK228 and CBHA)-mediated enhancing effect on IR-induced cell death.

Histone deacetylase inhibitors FK228, N-(2-aminophenyl)-4-[N-(pyridin-3-yl-methoxycarbonyl)amino- methyl]benzamide and m-carboxycinnamic acid bis-hydroxamide augment radiation-induced cell death in gastrointestinal adenocarcinoma cells.

HDAC inhibitors induce histone hyperacetylation by a relative increase of histone acetyltransferase activity. Histone hyperacetylation may affect chromatin structure and susceptibility to DNA-damaging stress, such as IR. We here investigate whether these inhibitors can radiosensitize human gastric MKN45 and colorectal DLD1 adenocarcinoma cells. In both cells, FK228 pretreatment at minimally toxic concentrations clearly augmented IR-induced cell death, DNA fragmentation and caspase-3/-8 activation. In contrast, 5-FU did not clearly augment IR-induced cell death and caspase-3 activation. FK228 increased expression of proapoptotic BH3-only Bim proteins, and gene transfer-mediated overexpression of Bimalpha radiosensitized DLD1 cells. These data suggest that the FK228-mediated increase of Bim expression may at least partially contribute to its augmentation of radiation-induced apoptosis. However, FK228 did not distinctly affect IR-induced phosphorylation of H2AX, which is an initial event followed by DNA damage. FK228 strongly augmented IR-induced growth suppression of MKN45 tumor xenografts. In addition, other HDAC inhibitors, MS275 and CBHA, similarly augmented IR-induced cell death in both cell types. Our results suggest that these HDAC inhibitors may enhance the efficacy of radiation therapy in gastrointestinal cancer cells.