Confined detection volume of fluorescence correlation spectroscopy by bare fiber probes.

A fiber-tip-based near-field fluorescence correlation spectroscopy (FCS) has been developed for confining the detection volume to sub-diffraction-limited dimensions. This near-field FCS is based on near-field illumination by coupling a scanning near-field optical microscope (SNOM) to a conventional confocal FCS. Single-molecule FCS analysis at 100 nM Rhodamine 6G has been achieved by using bare chemically etched, tapered fiber tips. The detection volume under control of the SNOM system has been reduced over one order of magnitude compared to that of the conventional confocal FCS. Related factors influencing the near-field FCS performance are investigated and discussed in detail. In this proof-of-principle study, the preliminary experimental results suggest that the fiber-tip-based near-field FCS might be a good alternative to realize localized analysis at the single-molecule level.

Intracellular applications of analytical SERS spectroscopy and multispectral imaging.

The aim of this tutorial review is to give an overview of the state of the art of intracellular applications of analytical SERS spectroscopy. We pay particular attention to nanoparticle-based SERS spectroscopy since this currently dominates the published literature on non-disturbing analysis of live cells. We describe recent advances in this domain due to the development of multispectral imaging and to the combined use of SERRS (surface-enhanced resonance Raman scattering) and fluorescence spectroscopy. Finally, a perspective view is given on the tip-based approaches like tip-enhanced Raman spectroscopy (TERS) which allow micrometric and nanometric resolution.

Imaging of P-glycoprotein of H69/VP small-cell lung cancer lines by scanning near-field optical microscopy and confocal laser microspectrofluorometer.

Chemoresistance remains the major obstacle to successful therapy of the lung cancer. The multi-drug resistance (MDR) is generally associated with altered expression of drug transporter proteins, such as P-glycoprotein (P-gp). So the distribution of P-gp on the membrane is of great importance to further study the interaction between drug and P-gp. In the present work, the P-gp of the H69/VP small-lung cancer cells was detected using monoclonal antibody UIC2. A secondary goat-anti mouse antibody coupled with biotin was used. The fluorescence emission was detected from a streptavidin-Texas Red. Results were investigated by a homemade scanning near-field optical microscope (SNOM) coupled to a confocal laser microspectrofluorometer (CLMF). Topographical images and localized spectra were obtained at the level of one cell membrane. It was found that the distribution of P-gp is not homogeneous and this observation is basically in accord with the fluorescent images obtained by classical microscopy. The distribution of P-gp would be localized in a higher region on a cell surface. This methodology would also enhance our understanding of MDR under physiological conditions.