Aquatic Functional Materials: Creation of New Materials Science for Environment-Friendly and Active Functions

金沢大学ナノ生命科学研究所本研究ではFM-AFM・3D-SFMのための高速・広域走査機構の開発に取り組み、本技術を幅広い材料／水界面のサブナノスケール解析へ用いるための技術基盤を確立することを目的としている。これまでに、3D-SFMコントローラのデータ収録システムの改善に取り組み、固液界面の３次元サブナノスケール構造を高速に捉えることに成功している。また、広域走査が可能な走査機構（スキャナ）の開発にも取り組み、上記と組み合わせることで高速広域走査を実現した。今年度は、開発した装置の実用性を実証するため、幅広い結晶や材料と水の界面のAFM計測に取り組んだ。まずはカルサイト（CaCO3）結晶表面に形成されたエッチピットの純水中での構造変化をサブナノスケールでその場観察した。（J. Phys. Chem. Lett., 2021）。また、飽和溶液中で成長するカルサイトのステップ端の動的な構造変化を原子分解能で捉え、溶解過程で見られた遷移領域が成長過程のステップ端においても存在することを明らかにした（Faraday Discuss., 2022）。また、材料として、螺旋ポリマーの凹凸を液中においてサブナノスケールで可視化した（Chem. Commum., 2021）他、新学術領域内共同研究を通して様々な材料の表面・固液界面構造を計測した。このように、本研究で開発したシステムが幅広い材料／水界面の構造解析へ応用できることを実証した。研究課題/領域番号:20H05212, 研究期間(年度):2020-04-01 – 2022-03-31出典：研究課題「高速広域３次元走査型力顕微鏡による固液界面構造・現象の原子・分子スケール計測」課題番号20H05212（KAKEN：科学研究費助成事業データベース（国立情報学研究所）） （https://kaken.nii.ac.jp/ja/grant/KAKENHI-PUBLICLY-20H05212/）を加工して作

Real-time atomic-resolution imaging of crystal growth process in water by phase modulation atomic force microscopy at one frame per second

Recent advancement in dynamic-mode atomic force microscopy (AFM) has enabled its operation in liquid with atomic-scale resolution. However, its imaging speed has often been too slow to visualize atomic-scale dynamic processes. Here, we propose a method for making a significant improvement in the operation speed of dynamic-mode AFM. In this method, we use a wideband and low-latency phase detector with an improved algorithm for the signal complexification. We demonstrate atomic-scale imaging of a calcite crystal growth process in water at one frame per second. The significant improvement in the imaging speed should enable various studies on unexplored atomic-scale interfacial processes. © 2013 AIP Publishing LLC

高速液中周波数変調原子間力顕微鏡の開発とそれを用いたカルサイト結晶溶解過程の原子レベル解析

13301甲第4409号博士(工学)金沢大学博士論文本文Full 以下に掲載：Review of Scientific Instruments 84(4) pp.043705-1-043705-8 2013. AIP Publishing. 共著者：K. Miyata, S. Usho, S. Yamada, S. Furuya, K. Yoshida, H. Asakawa, T. Fukum

Ion-specific nanoscale compaction of cysteine-modified poly(acrylic acid) brushes revealed by 3D scanning force microscopy with frequency modulation detection

Stimuli-responsive polyelectrolyte brushes adapt their physico-chemical properties according to pH and ion concentrations of the solution in contact. We synthesized a poly(acrylic acid) bearing cysteine residues at side chains and a lipid head group at the terminal, and incorporated them into a phospholipid monolayer deposited on a hydrophobic silane monolayer. The ion-specific, nanoscale response of polyelectrolyte brushes was detected by using three-dimensional scanning force microscopy (3D-SFM) combined with frequency modulation detection. The obtained topographic and mechanical landscapes indicated that the brushes were uniformly stretched, undergoing a gradual transition from the brush to the bulk electrolyte in the absence of divalent cations. When 1 mM calcium ions were added, the brushes were uniformly compacted, exhibiting a sharper brush-to-bulk transition. Remarkably, the addition of 1 mM cadmium ions made the brush surface significantly rough and the mechanical landscape highly heterogeneous. Currently, cadmium-specific nanoscale compaction of the brushes is attributed to the coordination of thiol and carboxyl side chains with cadmium ions, as suggested for naturally occurring, heavy metal binding proteins

Improvements in fundamental performance of liquid-environment atomic force microscopy with true atomic resolution

Recently, there have been significant advancements in liquid-environment atomic force microscopy (AFM) with true atomic resolution. The technical advancements are followed by a rapid expansion of its application area. Examples include subnanometer-scale imaging of biological systems and three-dimensional measurements of water distributions (i.e., hydration structures) and fluctuating surface structures. However, to continue this progress, we should improve the fundamental performance of liquid-environment dynamic-mode AFM. The present AFM technique does not allow real-time imaging of atomic-scale dynamic phenomena at a solid-liquid interface. This has hindered atomic-level understanding of crystal growth and dissolution, catalytic reactions and metal corrosion processes. Improvement in force sensitivity is required not only for such a high-speed imaging but also for various surface property measurements using a high-resolution AFM technique. In this review, we summarize recent works on the improvements in the force sensitivity and operation speed of atomic-resolution dynamic-mode AFM for liquid-environment applications. © 2015 The Japan Society of Applied Physics.Embargo Period 12 month

Note: High-speed Z tip scanner with screw cantilever holding mechanism for atomic-resolution atomic force microscopy in liquid

High-speed atomic force microscopy has attracted much attention due to its unique capability of visualizing nanoscale dynamic processes at a solid/liquid interface. However, its usability and resolution have yet to be improved. As one of the solutions for this issue, here we present a design of a high-speed Z-tip scanner with screw holding mechanism. We perform detailed comparison between designs with different actuator size and screw arrangement by finite element analysis. Based on the design giving the best performance, we have developed a Z tip scanner and measured its performance. The measured frequency response of the scanner shows a flat response up to ∼10 kHz. This high frequency response allows us to achieve wideband tip-sample distance regulation. We demonstrate the applicability of the scanner to high-speed atomic-resolution imaging by visualizing atomic-scale calcite crystal dissolution process in water at 2 s/frame

Depletion of perivascular macrophages delays ALS disease progression by ameliorating blood-spinal cord barrier impairment in SOD1G93A mice

Amyotrophic lateral sclerosis (ALS) is a fatal motor neuron disease in which non-cell-autonomous processes have been proposed as its cause. Non-neuronal cells that constitute the environment around motor neurons are known to mediate the pathogenesis of ALS. Perivascular macrophages (PVM) are immune cells that reside between the blood vessels of the central nervous system and the brain parenchyma; PVM are components of the neurovascular unit and regulate the integrity of the blood-spinal cord barrier (BSCB). However, it is not known whether regulation of BSCB function by PVM is involved in the pathogenesis of ALS. Here, we used SOD1G93A mice to investigate whether PVM is involved in the pathogenesis of ALS. Immunostaining revealed that the number of PVM was increased during the disease progression of ALS in the spinal cord. We also found that both anti-inflammatory Lyve1+ PVM and pro-inflammatory MHCII+ PVM subtypes were increased in SOD1G93A mice, and that subtype heterogeneity was shifted toward MHCII+ PVM compared to wild-type (WT) mice. Then we depleted PVM selectively and continuously in SOD1G93A mice by repeated injection of clodronate liposomes into the cerebrospinal fluid and assessed motor neuron number, neurological score, and survival. Results showed that PVM depletion prevented the loss of motoneurons, slowed disease progression, and prolonged survival. Further histological analysis showed that PVM depletion prevents BSCB collapse by ameliorating the reduction of extracellular matrix proteins necessary for the maintenance of barrier function. These results indicate that PVM are involved in the pathogenesis of ALS, as PVM degrades the extracellular matrix and reduces BSCB function, which may affect motor neuron loss and disease progression. Targeting PVM interventions may represent a novel ALS therapeutic strategy

Separate-type scanner and wideband high-voltage amplifier for atomic-resolution and high-speed atomic force microscopy

We have developed a liquid-environment atomic force microscope with a wideband and low-noise scanning system for atomic-scale imaging of dynamic processes at solid/liquid interfaces. The developed scanning system consists of a separate-type scanner and a wideband high-voltage amplifier (HVA). By separating an XY-sample scanner from a Z-tip scanner, we have enabled to use a relatively large sample without compromising the high resonance frequency. We compared various cantilever- and sample-holding mechanisms by experiments and finite element analyses for optimizing the balance between the usability and frequency response characteristics. We specifically designed the HVA to drive the developed scanners, which enabled to achieve the positioning accuracy of 5.7 and 0.53 pm in the XY and Z axes, respectively. Such an excellent noise performance allowed us to perform atomic-resolution imaging of mica and calcite in liquid. Furthermore, we demonstrate in situ and atomic-resolution imaging of the calcite crystal growth process in water. © 2013 AIP Publishing LLC