Nanocytotoxicity: violacein and violacein-loaded poly (D, L-lactide-co-glycolide) nanoparticles acting on human leukemic cells.

Violacein is a compound obtained from Chromobacterium violaceum, a bacterium found in the Amazonian region. Violacein-loaded poly (D, L-lactide-co-glycolide) nanoparticles has a similar inhibitory effect evaluated by trypan blue assay on leukemic HL60 cells than the free form. However, the cytotoxic effects evaluated by phosphatase activity and MTT reduction assays were lower for the encapsulated form than for free violacein. Based on morphological changes, violacein and violacein entrapped in nanoparticles were found to induce terminal differentiation (assessed by nitro blue tetrazolium reduction) in HL60 cells. Thus, both formulations inhibit HL60 cell growth in vitro, partly by inducing cytotoxic effects and cell differentiation. Flow cytometric analysis of HL60 cells after treatment for 12 h showed that violacein-loaded PLGA induced apoptosis, with maximum cell death at a concentration of 2 microM. Violacein and violacein/PLGA induced opposite effects on the mitochondrial swelling which indicates altered mitochondrial function. The mitochondrial activity was also checked by flow cytometry studies. Labelled cells with the probe JC1 displayed a basal hypopolarized status of the mitochondria in treated cells. Based on morphological changes, alterations in phospholipid asymmetry and changes in mitochondrial polarization, violacein and nanoparticles containing violacein were found to trigger cell death by apoptosis. These methodologies are promising as diagnostic and mechanistic effects of nanoparticles in cell cultures.

Coexistence of liquid phases in the sodium polyphosphate-chromium nitrate-water system.

The formation of coexisting liquid phases out of aqueous aluminum polyphosphate solutions was previously suggested as an essential step in aluminum polyphosphate nanoparticle formation. This hypothesis could not be directly verified because the separation of the two phases is very difficult, but a different situation was found in the case of chromium (III) polyphosphate. The phase diagram of the sodium polyphosphate-chromium nitrate-water system at 25 degrees C presents an extensive region with two coexisting liquid phases (L-L), together with a single liquid phase (L) and a solid-liquid (S-L) domain. Within the L-L region, admixture of the reagents produces initially a turbid liquid, out of which two transparent liquid phases separate in a short time, under gravity: one is dense, dark, and viscous while the other has a light color and a lower density. The amounts of the separated phases were determined, as well as their viscosities, densities, pH, UV-vis spectra, and relevant molalities: P (from polyphosphate), Cr(3+), NO(-)(3+), and Na(+). The two liquid phases undergo significant color, pH, and viscosity changes with time. The calculated phase diagrams display the major features of the experimental phase diagram.