Abstract. Continuous in situ measurements of aerosol optical properties were conducted from 29 June to 29 July 2012 in Granada (Spain) with a seven-wavelength Aethalometer, a Multi-Angle Absorption Photometer, and a three-wavelength integrating nephelometer. The aim of this work is to describe a methodology to obtain the absorption coefficients (babs) for the different Aethalometer wavelengths. In this way, data have been compensated using algorithms which best estimate the compensation factors needed. Two empirical factors are used to infer the absorption coefficients from the Aethalometer measurements: C – the parameter describing the enhancement of absorption by particles in the filter matrix due to multiple scattering of light in the filter matrix – and f, the parameter compensating for non-linear loading effects in the filter matrix. Spectral dependence of f found in this study is not very strong. Values for the campaign lie in the range from 1.15 at 370 nm to 1.11 at 950 nm. Wavelength dependence in C proves to be more important, and also more difficult to calculate. The values obtained span from 3.42 at 370 nm to 4.59 at 950 nm. Furthermore, the temporal evolution of the Ångström exponent of absorption (αabs) and the single-scattering albedo (ω0) is presented. On average αabs is around 1.1 ± 0.3, and ω0 is 0.78 ± 0.08 and 0.74 ± 0.09 at 370 and 950 nm, respectively. These are typical values for sites with a predominance of absorbing particles, and the urban measurement site in this study is such. The babs average values are of 16 ± 10 Mm−1 (at 370 nm) and 5 ± 3 Mm−1 (at 950 nm), respectively. Finally, differences between workdays and Sundays have been further analysed, obtaining higher babs and lower ω0 during the workdays than on Sundays as a consequence of the diesel traffic influence.

The aim of this study was to evaluate the activity of gamma interferon (IFN-␥) when it was either adsorbed onto or loaded into albumin nanoparticles. Brucella abortus-infected macrophages and infected BALB/c mice were selected as the models for testing of the therapeutic potentials of these cytokine delivery systems, in view of the well-established role of IFN-␥-activated macrophages for the control of Brucella sp. infections. Whereas the encapsulation of IFN-␥ inside the matrix of nanoparticles completely abrogated its activity, adsorbed IFN-␥ increased by 0.75 log unit the bactericidal effect induced by RAW macrophages activated with free IFN-␥, along with a higher level of production of nitric oxide. In infected BALB/c-mice, IFN-␥ adsorbed onto nanoparticles was also more active than free cytokine in reducing the number of bacteria in the spleens, and the effect was mediated by an increased ratio of IFN-␥-secreting (Th1) to interleukin-4-secreting (Th2) cells. Overall, albumin nanoparticles would be suitable as carriers that target IFN-␥ to macrophages and, thus, potentiate their therapeutic activity.

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Although interferon gamma (IFN-gamma has been extensively studied as a potent activator for macrophages and as a promising adjuvant in vaccines, its rapid biodegradation and clearance have severely limited its clinical efficacy. Our major objective in this work was to develop formulation conditions to get high association of the cytokine to albumin nanoparticles, without leading any conformational changes and subsequent loss of activity. To achieve this objective, two different formulations were prepared by either 1) incubation between the cytokine and the newly prepared nanoparticles (IFN-NPA) or 2) between the protein and IFN-gamma prior coacervation (IFN-NPB). Steady-state fluorescence emission spectra revealed that the environment of the tryptophan (Trp) residue was not affected by conditions of mechanical stress required for preparing nanoparticles. A bioassay for antiproliferative activity with Hela cells indicated that the cytokine, after their desorption from the surface of nanoparticles (IFN-NPA), fully retained its activity. It also indicated that the cytokine was principally associated with nanoparticles via electrostatic interactions and confirmed by desorption experiments carried out in media with different pH and ionic strength, with burst effect ranked in the order pH 5 > pH 7.4 > pH 8.5. Also, the adsorption of IFN-gamma onto these carriers was able to improve the priming effects of IFN-gamma on the nitric oxide production (NO) by RAW macrophages. On the contrary, when we incubated the cytokine with the albumin solution prior to the desolvation process for preparing nanoparticles (IFN-NPB), we obtained better encapsulation efficiencies (around 100%), but the cytokine was inactive: it was not detected by ELISA or bioassay in Hela cells and unable to stimulate NO production by macrophages.

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