Time-resolved in situ measurement of mitochondrial malfunction by energy transfer spectroscopy

Convenient and Efficient Synthesis of a Lanthanide-Coordinated, Diethylene Triamine Pentaacetic Acid Labeled Biopolymer as an Assay for the Cholecystokinin B Receptor

To develop an assay for the cholecystokinin B receptor with an Eu(3+)-labeled cholecystokinin peptide via a diethylene triamine pentaacetic acid chelating linker, a commercial dianhydride diethylene triamine pentaacetic acid precursor was directly attached to the N-terminus of cholecystokinin peptides by a solid-phase synthesis method with a satisfactory yield and purity after reverse-phase high-performance liquid chromatography separation. Lanthanide was then coordinated to the peptide via a diethylene triamine pentaacetic acid bifunctional agent. This method is a useful approach to the large-scale synthesis of lanthanide(3+)-coordinated, diethylene triamine pentaacetic acid labeled biopolymers. This research provides not only a simple and convenient method for the preparation of lanthanide-based peptide ligand libraries but also possible lanthanide-based high-throughput screening of peptide receptors with a timeresolved fluorescence assay system. Five biopolymers were synthesized and characterized with high-resolution electrospray ionization in this study.

Nanocluster model of photothermal assay: application for high-sensitive monitoring of nicotine-induced changes in metabolism, apoptosis, and necrosis at a cellular level

This study evaluates the capability of a photothermal (PT) assay to monitor the impact of nicotine on pancreatic cancer cells (AR42J). The specific PT response is closely proportional to nicotine concentrations at concentration range 1 nM to 100 microM, while at high concentrations of nicotine ranging from 1 mM to 50 mM, PT response shows dramatic decrease. According to the theoretical model, the mechanism of the PT assay is associated with metabolic and apoptotic-related shrinking of local cellular absorbing nanoscale zones caused by increased local absorption at low nicotine doses, while high doses of nicotine lead to apoptotic release of absorbing component (cytochrome c) into the intracellular space, and necrotic swelling of organelles, thereby causing a decrease in local absorption. This model is verified with conventional imaging and with Annexin-V Propidium iodide kits. The PT assay, in addition to its high sensitivity (3 orders of magnitude better than conventional assay), shows the potential to distinguish between various functional states of cells that are associated with changes in metabolism, early and late stages of apoptosis, and necrosis. Comparison of PT responses of pancreatic tumor cells AR42J with isolated primary pancreatic acinar cells and HepG2 cells shows a universal nature of PT assay.

Photothermal images of live cells in presence of drug

A new method for the study of drug-cell interaction is suggested. It is based on optical monitoring of cell response to drug impact. To detect this response, a high sensitive photothermal imaging technique has been developed. This technique is based on irradiation of the cells with a focused short pulse double-frequency pump laser (532 nm, 8 ns) and monitoring the laser-induced local thermal effects. This is realized with a second collinear dye laser pulse (630 nm, 6 ns) that probes the heated cell absorbing zones. The temperature-dependent variations of the refractive index in the absorbing zones in cross section of probe beam are recorded with phase-contrast technique. The photothermal (PT) image represents a two-dimensional depth-integrated temperature distribution in the irradiated volume and correlates with the conventional optical absorption images. It was experimentally shown that the introduction of NaN(3) or anti-tumor drug in the cell suspension led to a change in the structure of PT images of human lymphocytes and human lympholeukemia cells, respectively. It was hypothesized that the observed effects could be associated with the change of redox state of respiratory chain component.