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Reducing energy consumption is one of the most effective ways to solve the problem of energy shortage. In this work, nature-inspired paint microgroove arrays with different periods were fabricated using a one-step laser ablation method. A wind tunnel experiment was performed at two wind speeds, 27.7 and 33.3 m/s, to collect drag force data on smooth and structured paint coatings. The results showed that microgroove arrays oriented perpendicular to the flow direction were beneficial to drag reduction, and a drag reduction rate of up to 7.2% was obtained. Meanwhile, the microgroove arrays induced by laser ablation changed the wettability of the paint surface to hydrophobicity. The contact angle shows a slightly decreasing trend with an increase in the periodic scale. Furthermore, the anticorrosion properties of these microgrooves make them advantageous in harsh environments. The fabricated drag-reducing paint microstructures, with the features of self-cleaning and durability, have the potential to be applied on vehicles to realize speed improvement and energy saving.

Currently, silver nanoparticles (AgNPs) are the most produced nanoparticles in global market and have been widely utilized in the biomedical field. Here, we investigated the morphological and mechanical effects of AgNPs on cancerous cells of A549 cells and SMMC-7721 cells with atomic force microscope (AFM). The influences of AgNPs on the morphological properties and mechanical properties of cancerous cells were characterized utilizing the force-volume (FV) mode and force spectroscopy (FS) mode of AFM measurement. We mainly focus on the comparison of the effects of AgNPs on the two types of cancerous cells based on the fitting results of calculating the Young's moduli based on Sneddon model. The results showed that the morphology changed little but the mechanical properties of height, roughness, adhesion force and Young's moduli of two cancerous cells varied significantly with the stimulation of different concentrations of AgNPs. This research has provide insights into the classification and characterization of the effects of the various concentrations of AgNPs on the cancerous cells in vitro by utilizing AFM methodologies for disease therapy. This article is protected by copyright. All rights reserved.

Osteosarcoma (OS) is a primary malignant bone tumor that occurs mainly in adolescents. Researchers are devoting to develop combination therapy methods in a multifunctional nanoplatform for the treatment of osteosarcoma. The results of previous research have shown that up-regulation of miR- 520a-3p could induce anticancer effects in osteosarcoma. In order to improve the effect of gene therapy (GT), we attempted to carry miR-520a-3p in a multifunctional vector for comprehensive therapy. Fe 2 O 3 is a type of magnetic resonance imaging contrast that is widely used as a drug delivery agent. When coated with polydopamine (PDA), it can also be used as a photothermal therapy (PTT) agent (Fe 2 O 3 @ PDA). To deliver nanoagents targeted to a tumor site, folic acid (FA) conjugated with Fe 2 O 3 @PDA was manufactured as FA-Fe 2 O 3 @PDA. FA was chosen as the target molecule to enhance utilization and reduce toxicity of nanoparticles. However, the therapeutic efficacy of FA-Fe 2 O 3 -PDA combined with miR-520a-3p has not yet been studied. In this study, we synthesized FA-Fe 2 O 3 @PDA-miRNA and investigated the potential of combining PDA regulated PTT and miR-520a-3p regulated GT to kill osteosarcoma cells. The results indicated that down-regulation of interleukin 6 receptor (IL6R) by miR- 520a-3p and the photothermal ability of PDA could induce satisfactory anticancer effects in osteosarcoma, and the curative ratio was better than that used alone PTT or GT. Moreover, as a kind of T 2 magnetic contrast, miRNA-Fe 2 O 3 @PDA-FA can be used for magnetic resonance imaging (MRI). These findings indicated that miRNA-Fe 2 O 3 @PDA-FA is an effective anti-tumor nanovector for PTT combined with GT.

Surface-enhanced Raman scattering (SERS) has attracted attention because of its enormous potential to detect molecules with low concentrations. The method of fabricating SERS substrates is of great importance for improving the detection resolution. However, SERS substrates with different triangular pyramid tips fabricated by using the tip-based nanoindentation method has not been reported. Here, we prepared arrayed micro/nanocavities on copper-based graphene using the continuous indentation method with a Berkovich tip and a cube-corner tip, which have different face angles. Gold nanoparticles were then sputtered onto the graphene-copper micro/nanocavities to form the Au@GR@Cu micro/nanocavities SERS substrates. The substrates formed using the Berkovich tip and cube-corner tip were labeled B2-B9 and C2-C9, respectively, in which the numbers indicate the machining feed. Rhodamine 6G (R6G) was employed, and the Raman intensities of R6G on the differently arrayed Au@GR@Cu micro/nanocavities were measured. The Raman intensities of R6G were stronger on the pile-ups than on the inverted triangular pyramid cavities. The Raman intensities of R6G were highest on the C2 and B2 structures and lowest on the C9 and B9 structures. The Raman intensities of R6G on the arrayed Au@GR@Cu micro/nanocavities fabricated by the cube-corner tip were stronger than those on the arrayed Au@GR@Cu micro/nanocavities fabricated using the Berkovich tip with the same machining feed. In addition, the electric field intensity and distribution of the B9 and C9 arrayed Au@GR@Cu were simulated using Comsol software. Au@GR@Cu structures fabricated by the cube-corner tip were generated with higher electric field intensities. Furthermore, the relative standard deviations at 1362 cm -1of R6G were 6.19 and 6.62% on the C2 and C4 surfaces, respectively, showing good homogeneity. The SERS spectra of 10 -9mol/L malachite green solution and 10 -6mol/L carbaryl solution were recognized on the C1, C2, and C4 surfaces on day 1 and after 3 months, respectively. After storage at room temperature for 3 months, the reductions in the Raman intensities were less than 10%, indicating excellent stability. The results showed that the arrayed Au@GR@Cu micro/nanocavities fabricated using the cube-corner tip performed better than those fabricated using the Berkovich tip and exhibited excellent uniformity, availability, and stability, providing great potential for detecting pesticides at low concentrations.

Chemically and biologically modified substrates for single-cell patterning have been studied extensively, but physically modified structures for single-cell patterning still need further study. In this paper, physically modified silicon nanostructures were introduced to study their effect on SHSY5Y cells. Double-beam double exposure laser interference lithography combined with metal-assisted etching (MACE) was used to fabricate the physically modified silicon nanostructures. It was found that the cells on the gratings stretched and grew orderly along the grating with a small cell area and almost the same cell length compared with those on the Si wafer (control group). While on the grids, the cells were round with limited spreading, grew independently and had the smallest cell area and cell length. Moreover, the localization ratio of cells adhered onto the areas of nanopillars in the grid structures with different periods has been investigated. The results suggest that the physically modified grid silicon nanostructures can regulate the single-cell localization growth and the rational design of substrate structures can maximize the single-cell localization ratio. The findings provide guidance for the design of physically modified nanostructures and regulating single cell patterning, and a better understanding of single-cell localized growth.

Hydrogen peroxide (H2O2), as a biomarker in a series of physiological processes, plays a crucial role in investigating the pathogenesis of some diseases. The highly sensitive and selective detection of H2O2 release from living cells has aroused tremendous research interests. Herein, a non-enzymatic electrochemical H2O2 biosensor was constructed based on AgPt bimetallic nanoparticle-structured MoS2 nanohybrid (AgPt/MoS2) as an electrocatalyst. The AgPt/MoS2 nanohybrid was successfully synthesized by a facile wet-chemical method. Compared with AgPt nanoparticles, the AgPt/MoS2 nanohybrid exhibited significant enhancement in catalytic performance towards H2O2. The main factor is that MoS2 nanosheets as a supporting material promote AgPt nanoparticles to expose more active sites. The electrochemical response of the AgPt/MoS2 hybrid-based biosensor to H2O2 was linear in the range of 20 μM-4 mM, and the detection limit was calculated as 1.0 μM. To prove practicality, the biosensor was further applied to detect H2O2 release from living SMMC-7721 cells. These results indicate the potential applications of the developed biosensor in monitoring physiological processes.

Cell viability detection plays a crucial role in apoptosis and anticancer drug research. Compared with conventional colorimetric assays and organic fluorescent probe-based imaging, it is greatly desired to develop a simple and facile fluorescent probe for in situ real-time detection of cell viability. Herein, MoS2 nanoflakes are employed as fluorescent probes for detecting cancer cell viability by using their inherent tunable photoluminescence (PL) properties by ion intercalation. The appropriate amount of MoS2 nanoflakes for A549 lung cancer cells was firstly determined by MTT assay. After MoS2 nanoflakes successfully covered cells, the effects of the nanoflakes on cell morphology and mechanical properties were studied by atomic force microscopy (AFM). Then, the modulation of PL by potassium ions (K+) from cells was investigated at different cell viabilities. The results showed that PL intensity increased as cell viability decreased. Finally, the nanoflakes were further used as fluorescent probes to assess the cell viability change induced by anticancer drugs. The results showed that with the increase of drug concentration, the fluorescence intensity increased, indicating a decrease in cell viability. The ion-modulated PL of MoS2 nanoflakes makes MoS2 a promising candidate for applications in anticancer drug screening.

Cellular mechanical properties (CMPs) have been frequently reported as biomarkers for cell cancerization to assist objective cytology, compared to the current subjective method dependent on cytomorphology. However, single or dual CMPs cannot always successfully distinguish every kind of malignant cell from its benign counterpart. In this work, we extract 4 CMPs of four different graded bladder cancer (BC) cell lines by AFM (atomic force microscopy)-based nanoindentation to generate a CMP database, which is used to train a cancerization-grade classifier by machine learning. The classifier is tested on 4 categories of BC cells at different cancer grades. The classification shows split-independent robustness and an accuracy of 91.25% with an AUC-ROC (ROC stands for receiver operating characteristic, and ROC curve is a graphical plot which illustrates the performance of a binary classifier system as its discrimination threshold is varied) value of 97.98%. Finally, we also compare our proposed method with traditional invasive diagnosis and noninvasive cancer diagnosis relying on cytomorphology, in terms of accuracy, sensitivity and specificity. Unlike former studies focusing on the discrimination between normal and cancerous cells, our study fulfills the classification of 4 graded cell lines at different cancerization stages, and thus provides a potential method for early detection of cancerization. STATEMENT OF SIGNIFICANCE: We measured four cellular mechanical properties (CMPs) of 4 graded bladder cancer (BC) cell lines using AFM (atomic force microscopy). We found that single or dual CMPs cannot fulfill the task of BC cell classification. Instead, we employ MLA (Machine Learning Algorithm)-based analysis whose inputs are BC CMPs. Compared with traditional cytomorphology-based prognoses, the non-invasive method proposed in this study has higher accuracy but with many fewer cellular properties as inputs. The proposed non-invasive prognosis is characterized with high sensitivity and specificity, and thus provides a potential tumor-grading means to identify cancer cells with different metastatic potential. Moreover, our study proposes an objective grading method based on quantitative characteristics desirable for avoiding misdiagnosis induced by ambiguous subjectivity.

Macro-mechanical simulation software cannot easily simulate the atomic resolution of the tapping mode atomic force microscope (TM-AFM), so the accuracy of the corresponding mechanical model is questioned. In this paper, a TM-AFM simulation model is established using classical molecular dynamics (MD). The model simulated the tapping of gold (Au) and aluminum (Al) by probes with various amplitudes. The simulation yielded the z-direction force curves, trajectory curves and indentation curves of the probe. The amplitude change and the phase shift of the probe at various amplitudes were calculated from the direct measurement results. A contact jump and detachment jump become evident and are significant to energy and force results. The recovery ability of Al after indenting is smaller than that of Au. The energy calculations can be fitted to a high goodness of fit, reaching 0.99 and better; hence, the amplitude and phase shift variations of the probe can be used to fit the stored and dissipated energies, the sample energies when the sample is tapped. In this way, the TM-AFM is able to calculate the mechanical properties of the sample, and thus characterize the sample.

This study aims to study the effect of light size and intensity on photoconductive effect-based optically-induced dielectrophoresis (ODEP) for three-dimensional manipulation of cells. HL-7702 cells and SMMC-7721 cells in sucrose solution were manipulated three-dimensionally by ODEP. We found that the ODEP force generated by the three-dimensional non-uniform electric field will form a three-dimensional space, and the positive ODEP force will attract the cells near the space into it. When the number of cells is large, the three-dimensional stacking phenomenon will occur, that is, the three-dimensional assembly of cells. When the size of the light spot is similar to that of the cell, the projector with weak light intensity can only manipulate a single cell, while the laser with higher light intensity can carry out cell three-dimensional assembly. When the light intensity is similar, the larger size of light can produce larger a three-dimensional assembly space. So the cell three-dimensional manipulation by ODEP is achieved only when the photoconductive effect induced by the light pattern reaches the required intensity. The three-dimensional manipulation of cells by ODEP is from plane to stereo, and its realization is related to the light size and the photoconductive layer resistance determined by light intensity. And the three-dimensional space of assembling cells is related to the light size and intensity, and the larger and stronger the light, the larger the space.

A cardiomyocyte is the basic structural and functional unit of the heart, which is the actual executor of the systolic function. The study of the contraction and relaxation characteristics of cardiomyocyte is of great significance to the physiological behavior and pathology of the heart. How to dynamically express its contraction and relaxation behaviors in 3D has become a challenging issue. Although the video analysis method under the optical microscope can observe the changes in the horizontal direction, it is difficult to describe the changes in the vertical direction. The atomic force microscope (AFM) can accurately express the mechanical and morphological characteristics of the changes in the vertical direction, but it cannot be fully expressed in real time because it is acquired by scanning with a single probe. In order to express the contraction and relaxation characteristics of cardiomyocyte accurately and three dimensionally, a dynamic imaging method in this study is proposed using the periodicity of AFM acquisition and the periodicity of cardiomyocyte contraction. Compared with the optical experiment, it is proven that this method can dynamically represent the contraction and relaxation processes of cardiomyocyte and solve the problem of how to express it in 3D. It brings a new way for the study of physiological characteristics of cardiomyocytes and dynamic imaging by AFM.

Various cell culture substrates have been developed for cell patterning to control cell distributions and orientations in tissue engineering, drug screening and regenerative medicine. In this study, a preparation method of modified fiber membranes was applied in the field of cell patterning, and the obtained fiber membranes guided the cell distributions and orientations flexibly. The aligned electrospinning fiber membranes were dip-coated with polydimethylsiloxane (PDMS) to improve the stability of wettability, and then it was treated with oxygen plasma with a photomask to obtain a hydrophilic-hydrophobic surface micropattern. The morphologies, wettabilities and chemical structures of the membranes were analyzed by using a scanning electron microscope (SEM), drop shape analysis instrument, energy dispersive spectrometer (EDS) and Fourier transform infrared (FTIR) spectrometer. The L929 cells were cultured on the obtained membranes to observe the controlled cell distributions and orientations by using a SEM and fluorescence microscope. The results indicate that the treated membranes have the ability to control both cell distributions and orientations simultaneously. This method offers a novel approach to develop cell culture substrates for cell patterning in tissue engineering.

Diabetes has become a major public health problem in the world for many years, and it is driving us to probe into its complex mechanism of insulin secretion in pancreatic β cells. The nanoscale resolution characterization of pancreatic β cells in response to glucose led to insights into diverse mechanical and functional processes at the single cell level. Recent advances allowed the direct observations of cytoskeleton dynamics which were quantitatively determined. Here, we firstly performed the glucose stimulation with multiple physiologically relevant glucose patterns. Atomic force microscopy (AFM) produced high spatial resolution mechanical images together with the insulin secretions linking the physical interactions to the biochemical process of INS-1 cells. Altered material properties of the INS-1 cells revealed the regulation of multiple glucose stimulation patterns. Rapidly responded to high glucose (HG), INS-1 cells presented the unique meshing networks of elasticities. The decreases of Young's modulus (YM) and insulin secretion suggested that mechanical changes affected the insulin release. Furthermore, the frequency and gradient of glucose patterns induced nanomechanical and secreting changes of the INS-1 cells and gained the knowledge on the potential controllability of glucose. The relationships between the cellular mechanics and insulin secretion of INS-1 cells could contribute to establish a mechanical cell model for the study of β cells in diabetes. The results also indicated the cell mechanics as promising mechanical biomarkers for β cells, and promoted the understanding of specific mechanical mechanism of glucose regulation, which lighted on the further application of functional glucose regulation in therapy.

Hypoxia is a key factor in tumor microenvironments. Tumor-derived exosomes under hypoxia have their functions of communication between local and remote cells, and play an important role in tumor growth and metastasis. However, the effect of tumor-derived exosomes on cell structures and functions under hypoxia is unknown. In this work, the effects of exosomes derived from hepatocellular carcinoma cells (HCC-LM3) under normoxia (N-exos) and hypoxia (H-exos) environments on the biological and physical properties of target cells were stduied. The N-exos promoted the proliferation of hepatocytes (HL-7702) at 1.5 mg/mL, while the H-exos promoted the proliferation of hepatocytes at a lower concentration (1.0 mg/mL). After the cells cultured with the same concentrations of N-exos and H-exos for different time periods, the cell migration was enhanced. The stress fibers of the cells became loose and the cytoskeleton was rearranged, which were time dependent. The changes in morphological and mechanical parameters of the HL-7702 cells were detected by atomic force microscopy (AFM). The results showed that the cell edges became irregular and the filopodia were increased versus the exosomes treatment time. The heights and elastic moduli of cells were reduced. Compared with N-exos, H-exos had a more significant effect on the biological and physical properties of target cells. The results provide a method for studying how tumor-derived exosomes affect the interaction between tumor cells and their hypoxic microenvironment.

Mechanobiology analysis has been considered one of the important parameters to explore the physiological behavior inside cells. However, the morphology and mechanical characterization of live cells by employing atomic force acoustic microscopy (AFAM) has rarely been investigated to date. In this paper, the morphological and mechanical properties of five various live cells in vitro based on AFAM is detected for the first time. Combining AFAM with inverted optical microscopy and scanning electron microscopy (SEM), it has enabled the imaging of various live cells. According to the AFAM experimental results, the mechanical properties of live cells were obtained by fitting the force–depth curves with Hertz–Sneddon model. The conducted experiments and obtained results verified that it is viable to furnish insights into the multifunctional applicability of the AFAM-based characterization in mechanobiology, which has the advantages of making a contribution to diagnosing diseased cells.

Ultrathin broadband absorber maintaining a near-uniform low reflectivity over a broadband wavelength is essential for many optical applications, such as light harvesting and nanoscale imaging. Recently, there has been considerable interest in employing arrays of high-index dielectric Mie resonators on surfaces to trap light and reduce the reflectivity. For such Mie-resonant metasurfaces, however, antireflection properties featuring both a flat low reflectance curve and a wide bandwidth are hard to be satisfied simultaneously, and an efficient large-scale nanofabrication technique rarely exists. Here, we present a high-throughput laser interference induced quasi-random patterning (LIIQP) technique to fabricate quasi-random Mie resonators in large scale. Mie resonators with feature sizes down to sub-100 nm have been fabricated using a 1064 nm laser source. Each Mie resonator concentrates light at its shape-dependent resonant frequency, and all such resonators are arranged quasi-randomly to provide both rich (with broadband Fourier components) and strong (with large intensities) Fourier spectra. Specifically, a near-uniform broadband reflectivity over 400-1100 nm spectrum region has been confined below 3% by fabricating a large-scale ultrathin (around 400 nm) absorber. Our concept and high-throughput fabrication technique allows the rapid production of quasi-random dielectric Mie-resonant metasurfaces in a controllable way, which can be used in various promising applications including thin-film solar cells, display, and imaging.

Magnetic nanoparticles (MNPs) are often used as drug-carrying particles for targeted therapy of tumors. Studying their effects on cell activity and mechanical properties is of great significance for the targeted treatment of tumors. In this paper, we used a combination of atomic force microscopy (AFM) and fluorescent labeling to study the mechanical properties of cells after the endocytosis of MNPs. Colon cancer cells SW480 were selected to co-culture with MNPs with a particle size of 50 nm, and the cell viability was measured and systematically analyzed under different conditions. The results showed that the safe dose of MNPs to colon cancer cells SW480 was 50 µg/mL, and when the amount exceeded 50 µg/mL, the cell viability decreased significantly. Increase the concentration of MNPs step by step within the safe dose of 0-50 µg/mL. Through the analysis of a large number of data measured by AFM, the results show that the mechanical properties of cells change significantly with the increase of MNPs concentration. In this paper, the experimental results are analyzed by comparing concentration gradients. The concentrations are set to 0, 30, and 50 µg/mL , respectively, to verify the influence of MNPs on the mechanical properties of cells.