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Fluorescent silver nanoclusters (Ag NCs) displaying dual-excitation and dual-emission properties have been developed for the specific detection of NAD(+) (nicotinamide adenine dinucleotide, oxidized form). With the increase of NAD(+) concentrations, the longer wavelength emission (with the peak at 550 nm) was gradually quenched due to the strong interactions between the NAD(+) and Ag NCs, whereas the shorter wavelength emission (peaking at 395 nm) was linearly enhanced. More important, the dual-emission intensity ratio (I395/I550), fitting by a single-exponential decay function, can efficiently detect various NAD(+) levels from 100 to 4000 μM, as well as label NAD(+)/NADH (reduced form of NAD) ratios in the range of 1-50.

We report selective detection of homocysteine (Hcy) through luminescent poly methyl vinyl ether-alt-maleic acid (PMVEM) silver nanoclusters (Ag NCs), which were synthesized using PMVEM as scaffold. The as-developed PMVEM-Ag NCs have two emission peaks at 460 and 540 nm. After Hcy was added, the thiol moiety of Hcy can efficiently coordinate on Ag NCs, resulting in luminescence quenching of the 460 and 540 nm peaks. However, the ratio of these two emission peak was linearly correlated with the Hcy concentration from 5 to 100 μmol/L. The detection limits was 1 μmol/L. The detection of Hcy used the ratio of the two emission peaks, which permit selective detection of Hcy and quantitive determination of Hcy levels.

treated cells. Imaging results indicated the reconstruction of cancer induced changes in response to NaB treatment by modulating the saturated, unsaturated, triglyceride, protein and nucleic acid content in the treated cells. The findings of this study supported that FTIR spectroscopic and imaging techniques are valuable, label-free and sensitive bio-analytical tools for cancer diagnostics and investigating the global roles of drugs on cancer treatment.

The pyridine nucleotides (NADþ, NADPþ) are the major coenzymes participate in multiple redox processes in living cells. Both NADþ and NADPþ are not fluorescent and almost structurally identical, so it is difficult to directly distinguish NADþ or NADPþ via optical methods (such as fluorescence and Raman spectroscopy). We report here a sensitive probe of NADþ/NADPþ based on fluorescent silver nanoclusters with dual emission band. The silver nanoclusters with an initial fluorescent emission peak at 410 nm were synthesized by etching large size silver nanoparticles. With the addition of NADþ/ NADPþ solution, due to the strong coupling (charge-transfer) between silver nanoclusters and ligands (NADþ/NADPþ), a new fluorescence emission peak of the silver nanoclusters was found and raised at 550 nm and the fluorescence intensity was dependent on the ratio between NADþ and NADPþ. The time-resolved fluorescence decay (at 550 nm) of silver nanoclusters showed a single-exponential decay lifetime of 3.9 ns caused by the strong coupling between silver nanoclusters and ligands (NADþ/NADPþ). Meanwhile, the 410 nm emission was also selectively enhanced by the different ratio of NADþ /NADPþ molecules. The intensity ratio of fluorescence emission at 410nm and 550nm may be useful to monitor the levels of NADþ /NADPþ in aqueous solutions, cellular extracts and living cells. Candidate mechanisms and the analysis of time resolved emission spectra will be discussed. Drug resistance is one of the major challenges in treatment of cancer. The study of the intake of drugs by cancer cells therefore is vital for elucidating the mechanism of drug resistance. Currently to quantify the intake of drugs involve destructive methods such as lysing the cell at each time point of analysis followed by UV-Vis or fluorescence measurements. With this approach, different batches of cell are used for each time point, increasing the biological variability, and it is not possible to perform further analysis on the same cell sample. Attenuated total reflection Fourier transform infrared (ATR FT-IR) is a promising non-destructive label-free while chemically specific technique for analysis of biomedical samples. In this work we demonstrated the quantification of drugs (e.g. doxorubicin), in situ, using the ATR FT-IR method to obtain the drug diffusion profile in the live cell. HeLa cells grown on a multi-bounce ATR crystal were treated with 20 micromolar of doxorubicin, a concentration level that is relevant to cancer studies, and FT-IR spectra were collected in a time course using a MCT detector. Quantification of doxorubicin in the cell was made using the signature peak at 1284 cm-1 showing the accumulation of the drug in cells as a function of time. The results from the ATR FT-IR measurements have shown that the doxorubicin concentration in the living cell increases from 0 to >50 micromolar after 2 hours of treatment demonstrating the partitioning effect of the drug in the cell. Furthermore, the cells also present a signature spectrum, which allows to follow...