Lipid-based systems loaded with PbS nanocrystals: near infrared emitting trackable nanovectors.

Hydrophobic PbS nanocrystals (NCs) emitting in the near infrared spectral region were encapsulated in the core of micelles and in the bilayer of liposomes, respectively, to form polyethylene glycol (PEG)-grafted phospholipids. The phospholipid-based functionalization process of PbS NCs required the replacement of the pristine capping ligand at the NC surface with thiol molecules. The procedures carried out for two systems, micelles and liposomes, using PEG-modified phospholipids were carefully monitored by optical, morphological and structural investigations. The hydrodynamic diameter and the colloidal stability of both micelles and liposomes loaded with PbS NCs were evaluated using Dynamic Light Scattering (DLS) and ζ-potential experiments, and both were satisfactorily stable in physiological media. The cytotoxicity of the resulting PbS NC-loaded nanovectors was assessed by the in vitro investigation on Saos-2 cells, indicating that the toxicity of the PbS NC loaded liposomes was lower than that of the micelles with the same NC cargo, which is reasonable due to the different overall composition of the two prepared nanocarriers. Finally, the cellular uptake in the Saos-2 cells of both the NC containing systems was evaluated by means of confocal microscopy studies by exploiting a visible fluorescent phospholipid and demonstrating the ability of both luminescent nanovectors to be internalized. The obtained results show the great potential of the prepared emitting nanoprobes for imaging applications in the second biological window.

Quantitative analysis of lymphocyte-Salmonella interaction and effect of lymphocyte irradiation by Helium-Neon laser.

A model system has been developed to quantitatively investigate bacteria-cell interaction using a rough mutant of Salmonella and human peripheral blood lymphocytes. The effect of lymphocyte irradiation by low-power continuous wave Helium-Neon laser has been investigated since laser therapy in wound and decoubitous ulcer healing could involve the lymphoid cell function. Helium-Neon laser irradiation is shown here to enhance the adherence of Salmonella to lymphocytes. In particular, changes in newly defined binding parameters show that laser irradiation increases the frequency of binding-lymphocytes, the affinity of Salmonella for lymphocytes and the number of lymphocyte receptor sites as well.

Kinetic studies of the uptake of aspartate aminotransferase and malate dehydrogenase into mitochondria in vitro.

Kinetic measurements of the uptake of native mitochondrial aspartate aminotransferase and malate dehydrogenase into mitochondria in vitro were carried out. The uptake of both the enzymes is essentially complete in 1 min and shows saturation characteristics. The rate of uptake of aspartate aminotransferase into mitochondria is decreased by malate dehydrogenase, and vice versa. The inhibition is exerted by isoenzyme remaining outside the mitochondria rather than by isoenzyme that has been imported. The thiol compound beta-mercaptoethanol decreases the rate of uptake of the tested enzymes; inhibition is a result of interaction of beta-mercaptoethanol with the mitochondria and not with the enzymes themselves. The rate of uptake of aspartate aminotransferase is inhibited non-competitively by malate dehydrogenase, but competitively by beta-mercaptoethanol. The rate of uptake of malate dehydrogenase is inhibited non-competitively by aspartate aminotransferase and by beta-mercaptoethanol. beta-Mercaptoethanol prevents the inhibition of the rate of uptake of malate dehydrogenase by aspartate aminotransferase. These results are interpreted in terms of a model system in which the two isoenzymes have separate but interacting binding sites within a receptor in the mitochondrial membrane system.