Quenching of fluorescence of 1-hydroxypyrene-3,6,8-trisulfonate (HPTS) by Cu2+, Co2+, Ni2+, I-, and cetylpyridinium (CP+) ions in water/AOT/heptane microemulsion

Redox switching of an artificial transmembrane signal transduction system

Transmission of chemical signals across lipid bilayer membranes can be achieved using membrane-anchored molecules, where molecular motion across the bilayer is controlled by switching the polarity of two different head groups. An external redox signal delivered by ascorbic acid was used to trigger membrane translocation in a synthetic transduction system.

N,N,N-Trimethyl chitosan nanoparticles for the delivery of monoclonal antibodies against hepatocellular carcinoma cells

N,N,N-Trimethyl chitosan chloride is capable of forming nanocomplexes with protein through ionotropic gelation. A monoclonal antibody, raised against human liver heparan sulfate proteoglycan and specifically inhibiting hepatocellular carcinoma in vitro, was prepared in nanocomplexes of this modified chitosan. The smallest nanocomplexes (59 ± 17 nm, zeta-potential 16.5 ± 0.5 mV) were obtained at polysaccharide:antibody ratios of 5:0.3. Spherical particles with a smooth surface and compact structure having a mean diameter of ~11.2 ± 0.09 nm were investigated by Atomic Force Microscopy. Cellular uptake of fluorescently labeled nanocomplexes was studied in mouse monocyte models of cancer and normal cells. External and internal fluorescence was analyzed by flow cytometry. The results demonstrate that the nanocomplexes could enter cells and were retained for a longer period of time in cancer cells where they exhibited greater toxicity. These nanocomplexes appear safe and could potentially enhance the half-life of added antibodies.

Selective enhancement of carbon nanotube photoluminescence by resonant energy transfer

Highly selective: Enhancement of the photoluminescence (PL) emission efficiency of selected chiral forms of semiconducting single-walled carbon nanotubes (SWCNTs) is presented (see figure). Excitation of Nile blue A in the presence of SWCNTs results in the quenching of its fluorescence. The energy is resonantly transferred to the (7,5) SWCNT whereas the (8,7) tube is not in resonance; hence, its PL remains unaffected.We report on a simple method for enhancing the efficiency of photoluminescence (PL) emission from selected chiral forms of semiconducting single-wall carbon nanotubes (SWCNTs). The method is based on the use of a fluorescent dye (Nile blue A) that shows the capability of resonant energy transfer on to nanotubes. The excitation of Nile blue A in the presence of SWCNTs results in the quenching of its fluorescence and the energy is resonantly transferred to certain chiral forms. The PL emission from these chiral forms shows a marked increase in efficiency signifying the occurrence of Förster type resonant energy transfer (FRET). Due to its simplicity, this procedure has widespread implications for the detection of carbon nanotubes as well as for their use as fluorophores in FRET-based in vivo and in vitro biological applications.