Scanning probe microscopy (SPM) techniques represent one of the most promising approaches to probe the physical and chemical properties of nanoscale materials. The growing convergence of physics and biology has demanded nanotechnology tools to understand the fundamental physics of biological systems. Despite the advantages of SPM techniques, there have been challenges with its application to characterization of biological specimens. In recent times, the development of one class of SPM technique, scanning ion conductance microscopy (SICM), has overcome these limitations and enabled noninvasive, nanoscale investigation of live cells. In this review article, we present the theory behind the SICM operating principles and data modeling. Based on this framework, we discuss recent research advances where the SICM technique has proven technically superior. SICM applications discussed herein include imaging of cell topography, monitoring of live cell dynamics, mechanical stimulation of live cells, and surface patterning. Additional findings on the combination of SICM with other SPM techniques as well as patch clamp electrophysiology are presented in the context of building integrated knowledge on the structure and function of live cells. In summary, SICM bridges physics and biology to enable a range of important biomedical applications.

Circulating tumor cells (CTCs), though exceedingly rare in the blood, are nonetheless becoming increasingly important in cancer diagnostics. Despite this keen interest and the growing number of potential clinical applications, there has been limited success in developing a CTC isolation platform that simultaneously optimizes recovery rates, purity, and cell compatibility. Herein, a novel tracheal carina-inspired bifurcated (TRAB) microfilter system is reported, which uses an optimal filter gap size satisfying both 100% theoretical recovery rate and purity, as determined by biomechanical analysis and fluid-structure interaction (FSI) simulations. Biomechanical properties are also used to clearly discriminate between cancer cells and leukocytes, whereby cancer cells are selectively bound to melamine microbeads, which increase the size and stiffness of these cells. Nanoindentation experiments are conducted to measure the stiffness of leukocytes as compared to the microbead-conjugated cancer cells, with these parameters then being used in FSI analyses to optimize the filter gap size. The simulation results show that given a flow rate of 100 μL min(-1), an 8 μm filter gap optimizes the recovery rate and purity. MCF-7 breast cancer cells with solid microbeads are spiked into 3 mL of whole blood and, by using this flow rate along with the optimized microfilter dimensions, the cell mixture passes through the TRAB filter, which achieves a recovery rate of 93% and purity of 59%. Regarding cell compatibility, it is verified that the isolation procedure does not adversely affect cell viability, thus also confirming that the re-collected cancer cells can be cultured for up to 8 days. This work demonstrates a CTC isolation technology platform that optimizes high recovery rates and cell purity while also providing a framework for functional cell studies, potentially enabling even more sensitive and specific cancer diagnostics.

In isolating circulating tumor cells (CTCs), which exist in extremely low concentrations in the blood, current methods have been limited by a trade‐off between recovery rate and purity. To overcome this challenge, M. S. Kim, S. S. Lee, J.‐G. Lee, and co‐workers present a sized‐based filtration method that combines two strategies: (1) using specific binding of solid microbeads conjugated with anti‐EpCAM antibodies to enhance the discrimination of CTCs from other blood constituents (mainly white blood cells) along with (2) a novel bio‐inspired bifurcated microfilter that minimizes fluidic stresses on these cells, once captured. The method approaches maximal recovery rate and purity, while allowing viable CTCs to be isolated, enabling not only their enumeration but also further molecular and cellular evaluation.

The range of scanning probe microscopy (SPM) applications for atomic force microscopy (AFM) is expanding in the biological sciences field, reflecting an increasing demand for tools that can improve our fundamental understanding of the physics behind biological systems. However, the complexity associated with applying SPM techniques in biomedical research hampers the full exploitation of its capabilities. Recently, the development of scanning ion conductance microscopy (SICM) has overcome these limitations and enabled contact-free, high resolution imaging of live biological specimens. In this work, we demonstrate the limitation of AFM for imaging biological samples in liquid due to artifacts arising from AFM tip–sample interaction, and how SICM imaging is able to overcome those limitations with contact-free scanning. We also demonstrate that SICM measurements, when compared to AFM, show better fit to the actual dimensions of the biological samples. Our results highlight the superiority of SICM imaging, enabling it to be widely adopted as a general and versatile research tool for biological studies in the nanoscale.

Acupuncture points have a notable characteristic in that they have a higher density of mast cells (MCs) compared with nonacupoints in the skin, which is consistent with the augmentation of the immune function by acupuncture treatment. The primo vascular system, which was proposed as the anatomical structure of the acupuncture points and meridians, also has a high density of MCs. We isolated the primo nodes from the surfaces of internal abdominal organs, and the harvested primo nodes were stained with toluidine blue. The MCs were easily recognized by their stained color and their characteristic granules. The MCs were classified into four stages according to the degranulation of histamine granules in the MCs. Using conventional optical microscopes details of the degranulation state of MCs in each stage were not observable. However, we were able to investigate the distribution of the granules on the surfaces of the MCs in each stage, and to demonstrate the height profiles and three-dimensional structures of the MCs without disturbance of the cell membrane by using the scanning ion conductance microscopy.