Chitosan nanocomposites with CdSe/ZnS quantum dots and porphyrin.

Water-soluble nanocomposites based on CdSe/ZnS quantum dots (QDs) and hydrophobic tetraphenylporphyrin (TPP) molecules passivated by chitosan (CS) have been formed. Magnetic circular dichroism (MCD) spectra evidence TPP presence in both monomeric and agglomerated forms in the nanocomposites. The nanocomposites demonstrate more pronounced singlet oxygen generation compared to free TPP in CS at the same concentration due to the intracomplex Förster resonance energy transfer (FRET) with a 45% average efficiency.

Enantioselective cytotoxicity of ZnS:Mn quantum dots in A549 cells.

Chirality strongly influences many biological properties of materials, such as cell accumulation, enzymatic activity, and toxicity. In the past decade, it has been shown that quantum dots (QDs), fluorescent semiconductor nanoparticles with unique optical properties, can demonstrate optical activity due to chiral ligands bound on their surface. Optically active QDs could find potential applications in biomedical research, therapy, and diagnostics. Consequently, it is very important to investigate the interaction of QDs capped with chiral ligands with living cells. The aim of our study was to investigate the influence of the induced chirality of Mn-doped ZnS QDs on the viability of A549 cells. These QDs were stabilized with D- and L-cysteine using a ligand exchange technique. The optical properties of QDs were studied using UV-Vis, photoluminescence (PL), and circular dichroism (CD) spectroscopy. The cytotoxicity of QDs was investigated by high content screening analysis. It was found that QDs stabilized by opposite ligand enantiomers, had identical PL and UV-Vis spectra and mirror-imaged CD spectra, but displayed different cytotoxicity: QDs capped with D-cysteine had greater cytotoxicity than L-cysteine capped QDs.

Enantioselective cellular uptake of chiral semiconductor nanocrystals.

The influence of the chirality of semiconductor nanocrystals, CdSe/ZnS quantum dots (QDs) capped with L- and D-cysteine, on the efficiency of their uptake by living Ehrlich Ascite carcinoma cells is studied by spectral- and time-resolved fluorescence microspectroscopy. We report an evident enantioselective process where cellular uptake of the L-Cys QDs is almost twice as effective as that of the D-Cys QDs. This finding paves the way for the creation of novel approaches to control the biological properties and behavior of nanomaterials in living cells.

[Short peptides stimulate skin cell regeneration during ageing].

The actual goal of gerontocosmetology is deal with the research of new effective and harmless low- molecular substances. The influence of LK and AEDG peptides in concentrations 0.05-2.00 ng/ml on organotypic skin cell cultures proliferation in young and old animals were investigated. Peptides stimulated skin fibroblasts proliferation on 29-45% in skin cell cultures of young and old rats. This effect was observed in smaller concentration diapason and level during skin ageing in old cell cultures as compared to young cell cultures. These data open new approach for creation cosmetology substances in the base of LKand AEDG peptides.

Reversible photoluminescence quenching of CdSe/ZnS quantum dots embedded in porous glass by ammonia vapor.

The photoluminescence response of semiconductor CdSe/ZnS quantum dots embedded in a borosilicate porous glass matrix to exposure to ammonia vapor is investigated. The formation of surface complexes on the quantum dots results in quenching of the photoluminescence and a shortening of the luminescence decay time. The process is reversible, desorption of ammonia molecules from the quantum dot surface causes the photoluminescence to recover. The sensitivity of the quantum dot luminescence intensity and decay time to the interaction time and the reversibility of the photoluminescence changes make the CdSe/ZnS quantum dots in porous glass system a candidate for use as an optical sensor of ammonia.

Electrically controlled polarized photoluminescence of CdSe/ZnS nanorods embedded in a liquid crystal template.

A novel homogeneous composite material, consisting of luminescent CdSe/ZnS quantum nanorods, embedded in the nematic liquid crystal 5CB, has been prepared. Liquid crystal cells and free-standing stretched polymer films incorporating this composite material were characterized using polarized micro-photoluminescence and electro-optical measurements under an applied electric field. A liquid crystal induced, macroscopic orientation of the nanorods in a thin layer of the material has been demonstrated. A conventional liquid crystal cell, filled with this composite, exhibits 40% modulation of the nanorod's photoluminescence intensity when subjected to an external electric field. These results indicate that quantum nanorods may have practical applications in photonic devices.

Track membranes with embedded semiconductor nanocrystals: structural and optical examinations.

We studied the optical properties of poly(ethylene terephthalate) ion track membranes of 1.5, 0.5 and 0.05 µm pores impregnated with luminescent semiconductor CdSe/ZnS nanocrystals of different diameters (2.5 and 5 nm). The nanocrystals were embedded from their colloidal solutions in toluene by the immersion of a membrane in a colloidal solution. Localization of quasi-isolated weakly interacting CdSe/ZnS nanocrystals in a loosened layer on the track pore wall surface along with the existence of empty pores was demonstrated. We observed also the spatial separation of nanocrystals of 2.5 and 5 nm in size along the 50 nm pores.

Local GABAergic modulation of the activity of serotoninergic neurons in the nucleus raphe magnus.

Experiments on rat brainstem sections in membrane potential clamping conditions addressed the effects of serotonin and GABA on serotoninergic neurons in the nucleus raphe magnus. Local application of serotonin stimulated inhibitory postsynaptic currents (IPSC) in 45% of the serotoninergic neurons studied. This response was not seen in the presence of the fast sodium channel blocker tetrodotoxin. The GABAA receptor antagonist gabazine blocked IPSC in both serotonin-sensitive and serotonin-insensitive neurons. Application of GABA evoked generation of a membrane current (IGABA), which was completely blocked by gabazine. These results indicate self-regulation of the activity of serotoninergic neurons in the nucleus raphe magnus via a negative feedback circuit involving local GABAergic interneurons.

[Local GABA-ergic modulation of serotonergic neuron activity in the nucleus raphe magnus].

In voltage-clamp experimental on slices of the rat brainstem the effects of 5-HT and GABA on serotonergic neurons of nucleus raphe magnus were investigated. Local applications of 5-HT induced an increase in IPCSs frequency and amplitude in 45% of serotonergic cells. The effect suppressed by the blocker of fast sodium channels tetradotoxin. Antagonist of GABA receptor gabazine blocked IPSCs in neurons both sensitive and non-sensitive to 5-HT action. Applications of GABA induced a membrane current (I(GABA)), which was completely blocked by gabazine. The data suggest self-control of the activity of serotonergic neurons in nucleus raphe magnus by negative feedback loop via local GABAergic interneurons.

Comparison of two floor mat lead dust collection methods and their application in pre-1950 and new urban houses.

This study investigated commercial floor mats as an alternative method to assess lead in residential dust in inner-city houses. Mats were placed for 3 weeks in interior entry-ways of 34 row houses built before 1950 and 17 new row houses in Baltimore City. A high volume sampler (an HVS3 floor model cyclone-based vacuum) and a hand-held portable cyclone sampler were used in the laboratory to collect side-by-side samples of mat dust. Both devices yielded comparable estimates of lead dust deposition, dust lead concentration, and dust deposition on field mat samples and had similar sampling efficiencies on mats spiked with various types of standard reference materials. The older houses had significantly higher daily lead dust deposition (mean = 130 micrograms/ft2/day by HVS3) than the newer houses (mean = 9 micrograms/ft2/day by HVS3), due to higher dust lead concentrations (mean = 1149 ppm vs mean = 107 ppm by HVS3) and not to differences in daily dust deposition (mean = 118 mg/ft2/day vs mean = 87 mg/ft2/day by HVS3) [corrected]. Mats were found to be a feasible method for the collection of dust that has accumulated for a known amount of time. Current wipe and vacuum methods do not allow for the estimation of dust deposition rates. Further research is needed to understand the role of floor mats as a risk assessment tool.

Soviet and post-Soviet environmental management: lessons from a case study on lead pollution.

Through a case study on lead pollution in the former Soviet Union, the linkage of policy, environmental science, and environmental management is explored, and compared with the US experience. Soviet bans on leaded gasoline and lead-based paint appear to have been effective. Regional governments, in cooperation with the petroleum industry, are taking the initiative in phasing out leaded gasoline, to some extent in defiance of federal policy. Problems with management of lead-acid batteries have been worsened by the collapse of the political system. Lack of reliable environmental data impedes reliable environmental assessment. The types of environmental measurements reflect an emphasis on multipollutant environmental contamination, rather than on human exposure to single pollutants.

Pilot study of sources of lead exposure in Moscow, Russia.

This preliminary investigation of sources of lead exposure in Moscow, Russia, by Russian and US collaborators measured lead in paint, interior dust, and drinking water in seven day-care centres, and in petrol, soil and canned food. Some paint samples exceeded US regulatory standards for lead in paint on surfaces (0.5%). Dust lead loadings were < 1.7 µg cm(-2) and below the guidance levels of the US EPA. Drinking water lead concentrations were at or below the US drinking water standard of 15 µg L(-1). Lead concentrations in petrol from Moscow vehicles and petrol stations were consistent with a regulation banning the sale of leaded petrol within the Moscow City limits. Except for baby food, lead levels were higher in the Russian canned foods (range 6 to 1240 µg kg(-1), dry weight) compared to corresponding US canned foods, with ratios of Russian to US levels of up to 120:1 for evaporated milk. Lead concentrations in soil generally ranged from 500 to 2000 µg g(-1), levels that would trigger hazard reduction measures according to US EPA guidance. These findings, together with the use of lead in petrol outside Moscow, indicate multiple sources of lead exposure in Russia. Priorities for future research are discussed including the establishment of interlaboratory quality control programmes.