New Approach to Multivariate Standard Addition Based on Multivariate Curve Resolution by Alternating Least-Squares: Application to Voltammetric Data.

A multivariate version of the classical univariate standard addition method is proposed for the analysis of samples generating overlapping signals in the presence of notorious matrix effects. Unlike previous versions based on multivariate calibration by partial least-squares (PLS), the proposed strategy takes advantage of a self-modeling methodology: multivariate curve resolution by alternating least-squares (MCR-ALS) enhanced with signal shape constraints based on parametric functions. In this way, there is no need for the full multivariate response of a blank solution, and in multianalyte determinations, the standard additions can be made with a solution containing all of the analytes, which constitutes a clear advance as compared to PLS approach. The proposed method has been successfully tested in the voltammetric determination of hydroquinone and catechol in solutions of increasing complexity and appears to be a promising tool in the field of electroanalysis.

Enhanced voltammetric performance of sensors based on oxidized 2D layered black phosphorus.

The exceptional properties of 2D layered black phosphorus (BP) make it a promising candidate for electrochemical sensing applications and, even though BP is considered unstable and tends to degrade by the presence of oxygen and moisture, its oxidation can be beneficial in some situations. In this work, we present an unequivocal demonstration that the exposition of BP-based working electrodes to normal ambient conditions can indeed be advantageous, leading to an enhancement of voltammetric sensing applications. This point was proved using a BP modified screen-printed carbon electrode (BP-SPCE) for the voltammetric determination of dopamine (DA) as a model target analyte. Oxidized BP-SPCE (up to 35% of PxOy at the surface) presented an enhanced analytical performance with a 5-fold and 2-fold increase in sensitivity, as compared to bare-SPCE and non-oxidized BP-SPCE stored in anhydrous atmosphere, respectively. Good detection limit, repeatability, reproducibility, stability, selectivity, and accuracy were also achieved. Overall, the results presented herein display the prominent possibilities of preparing and working with BP based-sensors in normal ambient settings and showcase their implementation under physiological conditions.

Differential cellular and molecular effects of bortezomib, a proteasome inhibitor, in human breast cancer cells.

The cellular and molecular effects of the proteasome inhibitor bortezomib on breast cancer cells are as yet poorly characterized. Here, in a panel of six breast cancer cell lines, bortezomib reduced viability in a concentration-dependent, time-dependent, and cell line-dependent manner. Proteasome activity was relatively high in two of the three more resistant cell lines. No relationship was observed between bortezomib effects on cell viability and expression/phosphorylation of HER-2, epidermal growth factor receptor (EGFR), AKT, or extracellular signal-regulated kinase 1/2 (ERK1/2). Molecular effects of bortezomib were further studied in SK-BR-3 and BT-474 cells because they share expression of EGFR and overexpression of HER-2 while, in contrast, SK-BR-3 cells were 200-fold more sensitive to this agent. Proteasome activity was inhibited to a similar extent in the two cell lines, and known proteasome substrates accumulated similarly. In SK-BR-3 cells, a marked inhibition of EGFR, HER-2, and AKT phosphorylation was observed at a clinically relevant concentration of bortezomib. In contrast, phosphorylation of Raf/mitogen-activated protein kinase kinase 1/2 (MEK 1/2)/ERK1/2 increased by bortezomib. In BT-474 cells, the effects were much less pronounced. Treatment of SK-BR-3 cells with bortezomib combined with pharmacologic inhibitors of EGFR, phosphatidylinositol 3'-kinase, or MEK resulted in modest or no enhancement of the effects on cell viability. Collectively, these results show that bortezomib has differential cellular and molecular effects in human breast cancer cells. The bortezomib-observed effects on signaling transduction molecules might be relevant to help to design mechanistic-based combination treatments.

Inhibition of the canonical IKK/NF kappa B pathway sensitizes human cancer cells to doxorubicin.

The NF kappa B family is composed by five subunits (p65/RelA, c-Rel, RelB, p105-p50/NF kappa B(1), p100-p52/NF kappa B(2)) and controls the expression of many genes that participate in cell cycle, apoptosis, and other key cellular processes. In a canonical pathway, NF kappa B activation depends on the IKK complex activity, which is formed by three subunits (IKKalpha and IKKbeta and IKKgamma/NEMO). There is an alternative NF kappa B activation pathway that does not require IKKbeta or IKKgamma/NEMO, in which RelB is a major player. We report in a panel of human breast cancer cells that the IKK/NF kappa B system is generally overexpressed in breast cancer cells and there is heterogeneity in expression levels of individual members between different cell lines. Doxorubicin, an anticancer agent used in patients with breast cancer, activated NF kappa B and appeared to be less effective in cells expressing predominantly members of the canonical IKK/NF kappa B. Two NF kappa B inhibitors, bortezomib and NEMO-Binding Domain Inhibitory Peptide, prevented doxorubicin-induced NF kappa B activation and increased doxorubicin antitumor effects in BT-474 cells. Transient down-regulation of members of the canonical pathway (p65, p52, c-Rel and IKKgamma/NEMO) by siRNA in HeLa cells increased doxorubicin cytotoxicity. In contrast, silencing of RelB, a key subunit of the alternative pathway, had no evident effects on doxorubicin cytotoxicity. To conclude, NF kappa B inhibition sensitized cells to doxorubicin, implying directly p65, p52, c-Rel and IKKgamma/NEMO subunits in chemoresistance, but not RelB. These findings suggest that selective inhibition of the canonical NF kappa B pathway is sufficient to improve doxorubicin antitumor effects.