Single-shot Interferometric Polarization Microscopy

We developed a novel interferometric microscopy technique, named Single-shot interferometric polarization microscopy (SIPM), to measure the birefringence distribution of an anisotropic sample. We use right-handed circular polarized He-Ne laser to illuminate the sample. Meanwhile, we built a near common-path interferometer with a Wollaston prism and a linear polarizer. A new digital holography algorithm is developed to simultaneously retrieve the retardance and orientation distributions with a single shot. Samples of quarter wave plate and liquid crystal are used to validate the efficiency of our method. We can recover the retardance of anisotropic sample with 4% error by an imaging speed of 150fps. We believe that our method has a great potential to be applied in biomedical observation and material inspection. The experiment setup for Single-shot Interferometric Polarization Microscopy (SIPM) is shown in Fig.1(a). The wavelength of the laser is 633nm. The NA of the objective is 0.16 and the magnification is 4X. One of the axes of Wollaston Prism is set to be horizontal (zero degree), while the LP is 45 degree to the Wollaston prism. The design of near common-path interferometry provides with us the possibility of recovering the complex field, so that a single-shot image will elucidate the results of multiple measurements. Combining digital holography and Jones calculus, we designed an algorithm which can recover both the retardance and orientation angle distribution with a single interferometric image. Therefore, SIPM is much faster than the other intensity measurement based polarization microscopy techniques. Please click Additional Files below to see the full abstract

Dual-Channel Two-Photon Microscopy Study of Transdermal Transport in Skin Treated with Low-Frequency Ultrasound and a Chemical Enhancer

Visualization of transdermal permeant pathways is necessary to substantiate model-based conclusions drawn using permeability data. The aim of this investigation was to visualize the transdermal delivery of sulforhodamine B (SRB), a fluorescent hydrophilic permeant, and of rhodamine B hexyl ester (RBHE), a fluorescent hydrophobic permeant, using dual-channel two-photon microscopy (TPM) to better understand the transport pathways and the mechanisms of enhancement in skin treated with low-frequency ultrasound (US) and/or a chemical enhancer (sodium lauryl sulfate – SLS) relative to untreated skin (the control). The results demonstrate that (1) both SRB and RBHE penetrate beyond the stratum corneum and into the viable epidermis only in discrete regions (localized transport regions – LTRs) of US treated and of US/SLS-treated skin, (2) a chemical enhancer is required in the coupling medium during US treatment to obtain two significant levels of increased penetration of SRB and RBHE in US-treated skin relative to untreated skin, and (3) transcellular pathways are present in the LTRs of US treated and of US/SLS-treated skin for SRB and RBHE, and in SLS-treated skin for SRB. In summary, the skin is greatly perturbed in the LTRs of US treated and US/SLS-treated skin with chemical enhancers playing a significant role in US-mediated transdermal drug delivery

Improving liver fibrosis diagnosis based on forward and backward second harmonic generation signals

10.1063/1.4913907Applied Physics Letters106

Conventional and High-Speed Intravital Multiphoton Laser Scanning Microscopy of Microvasculature, Lymphatics, and Leukocyte-Endothelial Interactions

The ability to determine various functions of genes in an intact host will be an important advance in the postgenomic era. Intravital imaging of gene regulation and the physiological effect of the gene products can play a powerful role in this pursuit. Intravital epifluorescence microscopy has provided powerful insight into gene expression, tissue pH, tissue pO 2 , angiogenesis, blood vessel permeability, leukocyte-endothelial (L-E) interaction, molecular diffusion, convection and binding, and barriers to the delivery of molecular and cellular medicine. Multiphoton laser scanning microscopy (MPLSM) has recently been applied in vivo to overcome three drawbacks associated with traditional epifluorescence microscopy: (i) limited depth of imaging due to scattering of excitation and emission light; (ii) projection of three-dimensional structures onto a two-dimensional plane; and (iii) phototoxicity. Here, we use MPLSM for the first time to obtain high-resolution images of deep tissue lymphatic vessels and show an increased accuracy in quantifying lymphatic size. We also demonstrate the use of MPLSM to perform accurate calculations of the volume density of angiogenic vessels and discuss how this technique may be used to assess the potential of antiangiogenic treatments. Finally, high-speed MPLSM, applied for the first time in vivo, is used to compare L-E interactions in normal tissue and a rhabdomyosarcoma tumor. Our work demonstrates the potential of MPLSM to noninvasively monitor physiology and pathophysiology both at the tissue and cellular level. Future applications will include the use of MPLSM in combination with fluorescent reporters to give novel insight into the regulation and function of genes

Single-shot dual-wavelength interferometric microscopy

Interferometric microscopy (IM) can provide complex field information of the biological samples with high spatial and temporal resolution with virtually no photodamage. Measuring wavelength-dependent information in particular has a wide range of applications from cell and tissue refractometry to the cellular biophysical measurements. IM measurements at multiple wavelengths are typically associated with a loss in temporal resolution, field of view, stability, sensitivity, and may involve using expensive equipment such as tunable filters or spatial light modulators. Here, we present a novel and simple design for an interferometric microscope that provides single-shot off-axis interferometric measurements at two wavelengths by encoding the two spectral images at two orthogonal spatial frequencies that allows clean separation of information in the Fourier space with no resolution loss. We demonstrated accurate simultaneous quantification of polystyrene bead refractive indices at two wavelengths.National Institutes of Health (U.S.) (9P41EB015871-26A1)National Institutes of Health (U.S.) (5R01NS051320)National Institutes of Health (U.S.) (4R44EB012415)National Institutes of Health (U.S.) (1R01HL121386-01A1)National Science Foundation (U.S.) (CBET0939511