Mechanism of silica deposition in sorghum silica cells.

Grasses take up silicic acid from soil and deposit it in their leaves as solid silica. This mineral, comprising 1-10% of the grass dry weight, improves plants' tolerance to various stresses. The mechanisms promoting stress tolerance are mostly unknown, and even the mineralization process is poorly understood. To study leaf mineralization in sorghum (Sorghum bicolor), we followed silica deposition in epidermal silica cells by in situ charring and air-scanning electron microscopy. Our findings were correlated to the viability of silica cells tested by fluorescein diacetate staining. We compared our results to a sorghum mutant defective in root uptake of silicic acid. We showed that the leaf silicification in these plants is intact by detecting normal mineralization in leaves exposed to silicic acid. Silica cells were viable while condensing silicic acid into silica. The controlled mineral deposition was independent of water evapotranspiration. Fluorescence recovery after photobleaching suggested that the forming mineral conformed to the cellulosic cell wall, leaving the cytoplasm well connected to neighboring cells. As the silicified wall thickened, the functional cytoplasm shrunk into a very small space. These results imply that leaf silica deposition is an active, physiologically regulated process as opposed to a simple precipitation.

Gold Nanorods Based Air Scanning Electron Microscopy and Diffusion Reflection Imaging for Mapping Tumor Margins in Squamous Cell Carcinoma.

A critical challenge arising during a surgical procedure for tumor removal is the determination of tumor margins. Gold nanorods (GNRs) conjugated to epidermal growth factor receptors (EGFR) (GNRs-EGFR) have long been used in the detection of cancerous cells as the expression of EGFR dramatically increases once the tissue becomes cancerous. Optical techniques for the identification of these GNRs-EGFR in tumor are intensively developed based on the unique scattering and absorption properties of the GNRs. In this study, we investigate the distribution of the GNRs in tissue sections presenting squamous cell carcinoma (SCC) to evaluate the SCC margins. Air scanning electron microscopy (airSEM), a novel, high resolution microscopy is used, enabling to localize and actually visualize nanoparticles on the tissue. The airSEM pictures presented a gradient of GNRs from the tumor to normal epithelium, spread in an area of 1 mm, suggesting tumor margins of 1 mm. Diffusion reflection (DR) measurements, performed in a resolution of 1 mm, of human oral SCC have shown a clear difference between the DR profiles of the healthy epithelium and the tumor itself.

Study of Osteoclast Adhesion to Cortical Bone Surfaces: A Correlative Microscopy Approach for Concomitant Imaging of Cellular Dynamics and Surface Modifications.

Bone remodeling relies on the coordinated functioning of osteoblasts, bone-forming cells, and osteoclasts, bone-resorbing cells. The effects of specific chemical and physical bone features on the osteoclast adhesive apparatus, the sealing zone ring, and their relation to resorption functionality are still not well-understood. We designed and implemented a correlative imaging method that enables monitoring of the same area of bone surface by time-lapse light microscopy, electron microscopy, and atomic force microscopy before, during, and after exposure to osteoclasts. We show that sealing zone rings preferentially develop around surface protrusions, with lateral dimensions of several micrometers, and ∼1 µm height. Direct overlay of sealing zone rings onto resorption pits on the bone surface shows that the rings adapt to pit morphology. The correlative procedure presented here is noninvasive and performed under ambient conditions, without the need for sample labeling. It can potentially be applied to study various aspects of cell-matrix interactions.

Introduction of correlative light and airSEM™ microscopy imaging for tissue research under ambient conditions.

A complete fingerprint of a tissue sample requires a detailed description of its cellular and extracellular components while minimizing artifacts. We introduce the application of a novel scanning electron microscope (airSEM™) in conjunction with light microscopy for functional analysis of tissue preparations at nanometric resolution (<10 nm) and under ambient conditions. Our metal-staining protocols enable easy and detailed visualization of tissues and their extracellular scaffolds. A multimodality imaging setup, featuring airSEM™ and a light microscope on the same platform, provides a convenient and easy-to-use system for obtaining structural and functional correlative data. The airSEM™ imaging station complements other existing imaging solutions and shows great potential for studies of complex biological systems.

Photothermal bundle measurement of phantoms and blood as a proof of concept for oxygenation saturation measurement.

This study's objective is to validate a method for the measurement of two compound phantoms as a proof of concept for oxygen saturation level measurement via a thermal imaging bundle. The method consists of a thermal imaging system and an algorithm which estimates the compound concentration according to temperature rise. A temperature rise is obtained by illuminating the tissue with a laser with different wavelengths in the NIR range and measured using a thermal camera. A coherent thermal imaging bundle was used for image transmittance for minimal invasive transendoscopic use. The algorithm's estimation ability was evaluated using agar phantoms of varying Methylene Blue and ICG ratios as well as blood samples The Methylene Blue ratio in each phantom was estimated and the calculated average RMS of the error was 9.38%, a satisfying value for this stage, verifying the algorithm's and bundle's suitability for the use in a minimal invasive system.

Thermal imaging method for estimating oxygen saturation.

The objective of this study is to develop a minimal invasive thermal imaging method to determine the oxygenation level of an internal tissue. In this method, the tissue is illuminated using an optical fiber by several wavelengths in the visible and near-IR range. Each wavelength is absorbed by the tissue and thus causes increase in its temperature. The temperature increase is observed by a coherent waveguide bundle in the mid-IR range. The thermal imaging of the tissue is done using a thermal camera through the coherent bundle. Analyzing the temperature rise allows estimating the tissue composition in general, and specifically the oxygenation level. Such a system enables imaging of the temperature within body cavities through a commercial endoscope. As an intermediate stage, the method is applied and tested on exposed skin tissue. A curve-fitting algorithm is used to find the most suitable saturation value affecting the temperature function. The algorithm is tested on a theoretical tissue model with various parameters, implemented for this study, and on agar phantom models. The calculated saturation values are in agreement with the real saturation values.