Search

Reports on the toxicity of inorganic nanoparticles used in sunscreen, in particular of zinc oxide and titanium dioxide, have raised concerns about a possible particle penetration through the skin barrier. We used two-photon imaging to visualize the distribution of zinc-oxide nanoparticles after topical application of a commercially available sunscreen on human skin in vivo and to investigate a possible penetration of nanoparticles beyond the stratum corneum. Two-photon imaging is in particular suitable for these investigations since the excitation and the nonlinear signal light from zinc-oxide nanoparticles as well as the endogenous skin autofluorescence are all spectrally well-separated which allows a clear identification of the signal origin by detection in two-spectral channels. Furthermore, microscopic modifications in the cutaneous structure like skin wrinkles which exhibit different thicknesses of the dermal layers and at the same time are regions where nanoparticle accumulation can be specifically investigated. The results indicate no penetration of nanoparticle through the barrier of the stratum corneum of healthy skin even in microscopic wrinkles. [ABSTRACT FROM AUTHOR]

A preliminary clinical trial using state-of-the-art multiphoton tomography (MPT) and optical coherence tomography (OCT) for three-dimensional (3D) multimodal in vivo imaging of normal skin, nevi, scars and pathologic skin lesions has been conducted. MPT enabled visualization of sub-cellular details with axial and transverse resolutions of <2 μm and <0.5 μm, respectively, from a volume of 0.35 × 0.35 × 0.2 mm3 at a frame rate of 0.14 Hz (512 × 512 pixels). State-of-the-art OCT, operating at a center wavelength of 1300 nm, was capable of acquiring 3D images depicting the layered architecture of skin with axial and transverse resolutions ∼8 μm and ∼20 μm, respectively, from a volume of 7 × 3.5 × 1.5 mm3 at a frame rate of 46 Hz (1024 × 1024 pixels). This study demonstrates the clinical diagnostic potential of MPT/OCT for pre-screening relatively large areas of skin using 3D OCT to identify suspicious regions at microscopic level and subsequently using high resolution MPT to obtain zoomed in, sub-cellular level information of the respective regions (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

We present combined epi-coherent anti-Stokes Raman scattering (CARS) and multiphoton imaging with both chemical discrimination and subcellular resolution on human skin invivo. The combination of both image modalities enables label-free imaging of the autofluorescence of endogenous fluorophores by two-photon excited fluorescence, as well as imaging of the distribution of intercellular lipids, topically applied substances and water by CARS. As an example for medical imaging, we investigated healthy and psoriasis-affected human skin with both image modalities in vivo and found indications for different lipid distributions on the cellular level. Microsc. Res. Tech., 2011. © 2011 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Our laboratory has previously developed a bacterial cancer therapy strategy by targeting tumors using engineered Salmonella typhimurium auxotrophs (S. typhimurium A1-R) that were generated to grow in viable as well as necrotic areas of tumors but not in normal tissue. The mechanism by which A1-R kills cancer cells is unknown. In the present report, high-resolution multiphoton tomography was used to investigate the cellular basis of bacteria killing of cancer cells in live mice. Lewis lung cancer cells (LLC) were genetically labeled with red fluorescent protein (RFP) and injected subcutaneously in nude mice. After tumor growth was observed, the mice were treated with A1-R bacteria expressing GFP, via tail-vein injection. Mice without A1-R treatment served as untreated controls. The imaging system was 3D scan head mounted on a flexible mechano-optical articulated arm. A tunable 80 MHz titanium:sapphire femtosecond laser (710-920 nm) was used for the multiphoton tomography. We applied this high-resolution imaging tool to visualize A1-R bacteria targeting the Lewis lung cancer cells growing subcutaneously in nude mice. The tomographic images revealed that bacterially-infected cancer cells greatly expanded and burst and thereby lost viability. Similar results were seen in vitro using confocal microscopy. The bacteria targeted the tumor within minutes of tail-vein injection. Using mice in which the nestin-promoter drives GFP and in which blood vessels are labeled with GFP, the bacteria could be imaged in and out of the blood vessels. Collagen scaffolds within the tumor were imaged by second harmonic generation (SHG). The multiphoton tomographic system described here allows imaging of cancer cell killing by bacteria and can therefore be used to further understand its mechanism and optimization for clinical application.