Quantitative imaging of single mRNA splice variants in living cells

Alternative messenger RNA (mRNA) splicing is a fundamental process of gene regulation, and errors in RNA splicing are known to be associated with a variety of different diseases. However, there is currently a lack of quantitative technologies for monitoring mRNA splice variants in cells. Here, we show that a combination of plasmonic dimer probes and hyperspectral imaging can be used to detect and quantify mRNA splice variants in living cells. The probes are made from gold nanoparticles functionalized with oligonucleotides and can hybridize to specific mRNA sequences, forming nanoparticle dimers that exhibit distinct spectral shifts due to plasmonic coupling. With this approach, we show that the spatial and temporal distribution of three selected splice variants of the breast cancer susceptibility gene, BRCA1, can be monitored at single-copy resolution by measuring the hybridization dynamics of the nanoplasmonic dimers. Our study provides insights into RNA and its transport in living cells, which could improve our understanding of cellular protein complexes, pharmacogenomics, genetic diagnosis and gene therapies.

Bandwidth-variable tunable optical filter unit for illumination and spectral imaging systems using thin-film optical band-pass filters

An optical filter unit is demonstrated, which uses two successively arranged tunable thin-film optical band-pass filters and allows for simultaneous adjustment of the central wavelength in the spectral range 522-555 nm and of the spectral bandwidth in the range 3-16 nm with a wavelength switching time of 8 ms∕nm. Different spectral filter combinations can cover the complete visible spectral range. The transmitted intensity was found to decrease only linearly with the spectral bandwidth for bandwidths >6 nm, allowing a high maximum transmission efficiency of >75%. The image of a fiber bundle was spectrally filtered and analyzed in terms of position-dependency of the transmitted bandwidth and central wavelength.

Monte Carlo modeling of light-tissue interactions in narrow band imaging

Light-tissue interactions that influence vascular contrast enhancement in narrow band imaging (NBI) have not been the subject of extensive theoretical study. In order to elucidate relevant mechanisms in a systematic and quantitative manner we have developed and validated a Monte Carlo model of NBI and used it to study the effect of device and tissue parameters, specifically, imaging wavelength (415 versus 540 nm) and vessel diameter and depth. Simulations provided quantitative predictions of contrast-including up to 125% improvement in small, superficial vessel contrast for 415 over 540 nm. Our findings indicated that absorption rather than scattering-the mechanism often cited in prior studies-was the dominant factor behind spectral variations in vessel depth-selectivity. Narrow-band images of a tissue-simulating phantom showed good agreement in terms of trends and quantitative values. Numerical modeling represents a powerful tool for elucidating the factors that affect the performance of spectral imaging approaches such as NBI.