STEM-in-SEM high resolution imaging of gold nanoparticles and bivalve tissues in bioaccumulation experiments

Abstract

The methodology termed scanning transmission electron microscopy in scanning electron microscopy (STEM-in-SEM) has been used in this work to study the uptake of citrate stabilized gold nanoparticles (AuNPs) (average particle sizes of 23.5 ± 4.0 nm) into tissue samples upon in vitro exposure of the dissected gills of the Ruditapes philippinarum marine bivalve to the nanoparticle suspensions. The STEM-in-SEM methodology has been optimized for achieving optimum resolution under SEM low voltage operating conditions (20-30 kV). Based on scanning microscope assessments and resolution testing (SMART), resolutions well below 10 nm were appropriately achieved by working at magnifications over 100k×, with experimental sample thickness between 300 and 200 nm. These relatively thick slices appear to be stable under the beam and help avoid NP displacement during cutting. We herein show that both localizing of the internalized nanoparticles and imaging of ultrastructural disturbances in gill tissues are strongly accessible due to the improved resolution, even at sample thicknesses higher than those normally employed in standard TEM techniques at higher voltages. Ultrastructural imaging of bio-nano features in bioaccumulation experiments have been demonstrated in this study.

Advantages and Limitations of Current Techniques for Analyzing the Biodistribution of Nanoparticles

“…There are a number of different types of electron microscopes, with transmission electron microscopy (TEM), scanning electron microscopy (SEM) and variations of the two techniques having been utilized for this application. In comparison to TEM, in which the electron beam crosses the sample where it is then focused by the objective lens to form an image, SEM utilizes an electron beam that is scanned across or over a sample (rather than through a sample) and imaging is performed by mapping signal intensity synchronously with the scan to produce a magnified image of an object (Garcia-Negrete et al, 2015 ; Robson et al, 2018 ). Typically, tissue samples are fixed with chemicals (commonly formalin) and then undergo dehydration with serial alcohol and propylene oxide, prior to embedment in embedding resin (e.g., glycidether 100, EPON 812, Embed 812).…”

Performance improvement in carbon fiber reinforced polymer-based composites

“…的理论与方法 提出了多维度/多尺度协同增强/增韧/阻隔的新 方法和原理, 通过纳米杂化材料在微米纤维间、纤维 /树脂间的"搭桥效应"及其化学反应性, 构建以纳米 杂化材料为桥接点的三维立体交联结构的三相材料 体系(图6(d)) [33] , 同时以RVE模型为基础建立非规则 几何形态杂化纳米材料增强机制的有限元分析方法 (图6(a)~(c)) [46] , 预测和分析纳米杂化材料的多尺度 增强机制, 并基于Fick定律、Nielsen理论等提出了纳 米杂化材料的多尺度阻隔机理 [29] , 最终为实现复合 材料的高性能化提供理论基础 [21,45,52] . [53,54] , 建立了纳米纤维原位相分离 非均相增韧的模型 [55] , 阐明了增韧、增强与耐热协同 效应的实现机制 [56,57] , 解决了层间增韧与树脂基体 的流动性、渗透性和浸润性之间的矛盾 [19] , 发展了一 种 新 的 层 间 同 步 增 韧 增 强 CFRP 的 制 备 方 法 .…”

Analytical microscopy of iron-based superconducting materials

“…Using a high angle annular detector, we can obtain z-contrast images with spatial resolution well below 10 nm [49]. STEM-in-SEM has advantages over TEM of lower accelerating voltages for beam sensitive samples, larger field-of-view, contrast enhancement and no projection lens producing chromatic aberration.…”