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.

Application of semiconductor quantum dots in bioimaging and biosensing.

In this review we present new concepts and recent progress in the application of semiconductor quantum dots (QD) as labels in two important areas of biology, bioimaging and biosensing. We analyze the biologically relevant properties of QDs focusing on the following topics: QD surface treatment and stability, labeling of cellular structures and receptors with QDs, incorporation of QDs in living cells, cytotoxicity of QDs and influence of the biological environment on the biological and optical properties of QDs. Initially, we consider utilization of QDs as agents in high-resolution bioimaging techniques that can provide information at the molecular levels. The diverse range of modern live-cell QD-based imaging techniques with resolution far beyond the diffraction limit of light is examined. In each technique, we discuss the pros and cons of QD use and deliberate how QDs can be further engineered to facilitate their application in the respective imaging techniques and to produce significant improvements in resolution. Then we review QD-based point-of-care bioassays, bioprobes, and biosensors designed in different formats ranging from analytic biochemistry assays and ELISA, to novel point-of-care smartphone integrated QD-based biotests. Here, a wide range of QD-based fluorescence bioassays with optical transduction, elecrochemiluminescence and photoelectrochemical assays are discussed. Finally, this review provides an analysis of the prospects of application of QDs in selected important areas of biology.

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.

Chlorin e6-ZnSe/ZnS quantum dots based system as reagent for photodynamic therapy.

Stable water-soluble complexes of Cd-free ZnSe/ZnS quantum dots (QDs) and chlorin e6 complexes have been prepared. These complexes have shown approximately 50% intracomplex fluorescence resonance energy transfer from QDs to chlorin e6. The photodynamic therapy (PDT) test of the complexes against the Erlich acsite carcinoma cell culture demonstrated a two-fold enhancement of the cancer cell photodynamic destruction as compared to that of free chlorin e6 molecules. It was shown that the PDT effect was significantly increased due to two factors: the efficient QD-chlorin e6 photoexcitation energy transfer and the improvement of cellular uptake of the photosensitizer in the presence of ZnSe/ZnS QDs.

[The effect of the initial level of immunity on the efficacy of antidiphtheria inoculations in children and adults]. / Vliianie iskhodnogo urovnia immuniteta na éffektivnost' protivodifteriinykh privivok u detei i vzroslykh.

Based on results of examination in the passive hemagglutination test of 1440 subjects at different ages, several distinguishing features were revealed of formation of artificial active antidiphtheria immunity depending on the basic level of immunity. Single revaccination of those subjects presenting with the basic immunity of less than 0.03 IU/ml provides defence against diphtheria in only 33.3 percent of adults and 50 percent of children, in those subjects presenting with immunity between 0.03 to 0.99 IU/ml it is highly effective, in the immunity 1 IU/ml and beyond the effect of further immunization is very low since 25 to 33.3 percent of subjects demonstrate enhancement of immunity, whereas 16.7 to 25 percent show lowering of it. The analysis of the immunological structure of the population shows that 45 to 60 percent of adults in different age groups need to be exposed to single revaccination, 14 to 37 present will find it insufficient, 3 to 36 percent redundant. We suggest that revaccination against diphtheria be conducted under control of the level of antitoxic immunity.