Femtomolar DNA detection by parallel colorimetric darkfield microscopy of functionalized gold nanoparticles.

We introduce a sensing platform for specific detection of DNA based on the formation of gold nanoparticles dimers on a surface. The specific coupling of a second gold nanoparticle to a surface bound nanoparticle by DNA hybridization results in a red shift of the nanoparticle plasmon peak. This shift can be detected as a color change in the darkfield image of the gold nanoparticles.

Acousto-optic-assisted diffuse optical tomography.

We introduce and experimentally demonstrate acousto-optic-assisted diffuse optical tomography (DOT) using a holography-based acousto-optic setup. The method is based on probing a scattering medium with a localized acoustical modulation of the phase of the scattered light. The optical properties of the scattering medium are recovered with ultrasound-limited resolution by applying DOT reconstruction methods on a set of the measured intensities of light, modulated at different locations throughout the medium.

Light interactions with gold nanorods and cells: implications for photothermal nanotherapeutics.

Gold nanorods (AuNR) can be tailored to possess an intense and narrow longitudinal plasmon (LP) absorption peak in the far-red to near-infrared wavelength region, where tissue is relatively transparent to light. This makes AuNRs excellent candidates as contrast agents for photoacoustic imaging, and as photothermal therapeutic agents. The favorable optical properties of AuNR which depend on the physical parameters of shape, size and plasmonic coupling effects, are required to be stable during use.

Millimeter-resolution acousto-optic quantitative imaging in a tissue model system.

We have investigated the application of ultrasound modulated coherent light for quantitative determination of the ratio of dye concentrations and total concentration of absorbers in a blood vessel-mimicking sample. A 3-mm-diam tube containing the mixture of dyes inside an Intralipid-based gel with optical properties similar to tissue was interrogated by two different laser wavelengths in combination with intense microsecond ultrasound bursts. The use of calibration curves allowed us to extract quantitative information on the ratio of dye concentrations with the accuracy of better than 15%, as well as on the total concentration.

Signal amplification on planar and gel-type sensor surfaces in surface plasmon resonance-based detection of prostate-specific antigen.

This article describes surface plasmon resonance (SPR)-based detection of prostate-specific antigen (PSA), comparing amplification with colloidal gold (10nm diameter) and latex microspheres (120 nm diameter) on planar- and gel-type sensor surfaces. As matrix, 3% BSA in PBS was used. Experimental data were compared with model calculations that predict the SPR signal that results from covering of the different sensor surfaces with each of the particles used.