Coencapsulation of disulfiram and doxorubicin in liposomes strongly reverses multidrug resistance in breast cancer cells.

Disulfiram (DSF) is an inhibitor of P-glycoprotein (Pgp), the main obstacle limiting the success of doxorubicin (DOX), but it has poor solubility and stability. With the aim to overcome these limitations we prepared liposomes coencapsulating DSF and DOX (LipoDSF-DOX). Liposome stability, drugs release profile, effects on DOX cytotoxicity, Pgp activity and expression in breast cancer cells were evaluated. We observed that LipoDSF-DOX with a 1:3 weight ratio, with DSF in lipid bilayer and DOX in aqueous core, released DSF faster than DOX. LipoDSF-DOX increased DOX intracellular accumulation and cytotoxicity in Pgp-expressing breast cancer cells, with an efficacy superior to the mixture of free DSF and DOX, thanks to a differential kinetics of release of DSF and DOX when carried by liposomes. The mechanism of the increased DOX retention relied on the DSF-induced sulfhydraton of Pgp and followed by its ubiquitination. These events reduced Pgp expression and catalytic activity in LipoDSF-DOX-treated cells. Our results show that LipoDSF-DOX effectively reversed DOX resistance in Pgp-expressing breast cancer cells, exploiting the temporally different kinetics of release of DSF and DOX, optimized to decrease expression and activity of Pgp.

Uncertainty evaluation for the quantification of low masses of benzo[a]pyrene: Comparison between the Law of Propagation of Uncertainty and the Monte Carlo method.

A proper evaluation of the uncertainty associated to the quantification of micropollutants in the environment, like Polycyclic Aromatic Hydrocarbons (PAHs), is crucial for the reliability of the measurement results. The present work describes a comparison between the uncertainty evaluation carried out according to the GUM uncertainty framework and the Monte Carlo (MC) method. This comparison was carried out starting from real data sets obtained from the quantification of benzo[a]pyrene (BaP), spiked on filters commonly used for airborne particulate matter sampling. BaP was chosen as target analyte as it is listed in the current European legislation as marker of the carcinogenic risk for the whole class of PAHs. MC method, being useful for nonlinear models and when the resulting output distribution for the measurand is non-symmetric, can particularly fit the cases in which the results of intrinsically positive quantities are very small and the lower limit of a desired coverage interval, obtained according to the GUM uncertainty framework, can be dramatically close to zero, if not even negative. In the case under study, it was observed that the two approaches for the uncertainty evaluation provide different results for BaP masses in samples containing different masses of the analyte, MC method giving larger coverage intervals. In addition, in cases of analyte masses close to zero, the GUM uncertainty framework would give even negative lower limit of uncertainty coverage interval for the measurand, an unphysical result which is avoided when using MC method. MC simulations, indeed, can be configured in a way that only positive values are generated thus obtaining a coverage interval for the measurand that is always positive.

Rapid and sensitive detection of melamine in milk with gold nanoparticles by Surface Enhanced Raman Scattering.

A rapid and sensitive method to detect melamine in liquid milk based on Surface Enhanced Raman Scattering (SERS) spectroscopy is presented, exploiting the selective binding of gold nanoparticles (AuNPs) with this analyte. This interaction promotes the aggregation of the AuNPs inducing a huge enhancement of the melamine signals in the Raman spectrum due to the formation of SERS "hot spots". An external standard calibration method was employed for quantitative analysis and the method was validated for linearity, sensitivity, repeatability and recovery. A good linearity (R(2)=0.99) was found in the concentration range of 0.31-5.0 mg l(-1) in milk with a limit of detection of 0.17 mg l(-1). This method does not require a long extraction procedure (total analysis time can be lower than 30 min) and can be reliably used for melamine detection in milk matrix in accordance with the European law limits.