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Abnormal blood uric acid (UA) levels can lead to its crystallization in the joints, consequently resulting in gout. Accurate detection of UA in the blood is imperative for the early diagnosis of gout. However, electrochemical UA biosensors are vulnerable to antioxidants in the blood, limiting accurate UA detection. To address this issue, we focused on the function of uric acid transporter 1 (URAT1), which is selectively permeable to UA. URAT1 is abundant in the kidney cell membrane (KCM). To apply URAT1 to a sensor, we developed a KCM-coated UA biosensor (called the KCM sensor) that could selectively detect UA through URAT1. The KCM coating in the fabricated KCM sensor was verified via scanning electron microscopy, atomic force microscopy, and confocal microscopy. The KCM sensor enabled the detection of UA in the range of 0–1000 μM, with a limit of detection of 8.5 μM, suggesting that it allows the diagnosis of the early stages of gout. On the other hand, the UA permeability of the KCM sensor was significantly reduced in the presence of a URAT1 inhibitor, implying that URAT1 is a key factor for UA detection. The selectivity of the KCM sensor was demonstrated by measuring the amount for UA in the presence of various antioxidants. Finally, the KCM sensor was capable of measuring UA in human serum and was reproducible with 0.5–1.6% deviation. The UA permeability and selectivity of the KCM sensor were maintained even after 3 weeks of storage.

Hydroxyapatite nanoparticle-complexed collagen (HAP/Col) hydrogels have been widely used in biomedical applications as a scaffold for controlled drug release (DR). The time-variant mechanical properties (Young's modulus, E) of HAP/Col hydrogels are highly relevant to the precise and efficient control of DR. However, the correlation between the DR and the E of hydrogels remains unclear because of the lack of a nondestructive and continuous measuring system. To reveal the correlations, herein, we investigate the time-variant behavior of E for HAP/Col hydrogels during 28 days using the atomic force microscopy (AFM) nanoindentation technique. The initial E of hydrogels was controlled from 200 to 9000 Pa by the addition of HAPs. Subsequently, we analyzed the relationship between the DR of the hydrogels and the changes in their mechanical properties (ΔE) during hydrogel degradation. Interestingly, the higher the initial E value of HAP/Col hydrogels is, the higher is the rate of hydrogel degradation over time. However, the DR of hydrogels with higher initial E appeared to be significantly delayed by up to 40% at a maximum. The results indicate that adding an appropriate amount of HAPs into hydrogels plays a crucial role in determining the initial E and their degradation rate, which can contribute to the properties that prolong DR. Our findings may provide insights into designing hydrogels for biomedical applications such as bone regeneration and drug-delivery systems.

The generation of toxic amyloid β (Aβ) oligomers is a central feature of the onset and progression of Alzheimer’s disease (AD). Drug discoveries for Aβ oligomer degradation have been hampered by the difficulty of Aβ oligomer purification and a lack of screening tools. Here, we report a plasmonic nanoparticle amyloid corona (PNAC) for quantifying the efficacy of Aβ oligomeric aggregate-degrading drugs. Our strategy is to monitor the drug-induced degradation of oligomeric aggregates by analyzing the colorimetric responses of PNACs. To test our strategy, we use Aβ-degrading proteases (protease XIV and MMP-9) and subsequently various small-molecule substances that have shown benefits in the treatment of AD. We demonstrate that this strategy with PNAC can identify effective drugs for eliminating oligomeric aggregates. Thus, this approach presents an appealing opportunity to reduce attrition problems in drug discovery for AD treatment., Effective screening of drugs to treat amyloid oligomeric aggregates associated with Alzheimer’s is needed for drug development. Here the authors report on the creation of an amyloid corona around a plasmonic nanoparticle to monitor amyloid degradation when exposed to potential drugs and demonstrate application.

The clinical use of bioactive molecules in bone regeneration has been known to have side effects, which result from uncontrolled and supraphysiological doses. In this study, we demonstrated the synergistic effect of two bioactive molecules, bone morphogenic protein-2 (BMP-2) and alendronate (ALN), by releasing them in a sequential manner. Collagen-hydroxyapatite composite scaffolds functionalized using BMP-2 are loaded with biodegradable microspheres where ALN is encapsulated. The results indicate an initial release of BMP-2 for a few days, followed by the sequential release of ALN after two weeks. The composite scaffolds significantly increase osteogenic activity owing to the synergistic effect of BMP-2 and ALN. Enhanced bone regeneration was identified at eight weeks post-implantation in the rat 8-mm critical-sized defect. Our findings suggest that the sequential delivery of BMP-2 and ALN from the scaffolds results in a synergistic effect on bone regeneration, which is unprecedented. Therefore, such a system exhibits potential for the application of cell-free tissue engineering.

The future of sensing and diagnostic devices for developing countries should be, as described by the World Health Organization (WHO), ASSURED: Affordable, Sensitive, Specific, User-friendly, Rapid and robust, Equipment free, and Deliverable to end users [1]. Paper-based sensors using colorimetric approaches are significant because they feature all key factors for ideal diagnostic devices. Conventional sensors, such as enzyme-linked immunosorbent assay (ELISA), are bulky and complex, requiring different functional blocks including transducers, processing units, detection units, and so on, which can delay sensor response [2]. Current technology based on colorimetry is concerned with the miniaturization of size, decreasing cost, permitting in situ use, and achieving freedom from additional instruments. Moreover, colorimetric sensors can be used for the instantaneous detection of analytes (e.g., protein, DNA, small molecules, etc.), by showing a visually detectable color change [3]. The color change or intensity is proportional to the analyte concentration, which indicates that colorimetric assays have capacities beyond binary sensing.

The coronavirus disease (COVID-19) pandemic has spread to nearly every corner of the globe, significantly impacting economies and societies. Despite advances in detection technologies that target viral pathogens, all countries are facing an unprecedented need to perform biosensing in a rapid, sensitive, selective, and reliable way to deal with global and urgent problems. To date, the reverse transcription-polymerase chain reaction has been the gold-standard method for COVID-19 diagnosis. However, it requires complex facilities and elaborate training and is hampered by limited testing capacity and delayed results. Herein, we review state-of-the-art research into point-of-care biosensors for early severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) detection. We include a general description of the nanotechnological techniques used to develop biosensors, along with the latest research into various biosensors for SARS-CoV-2 detection and a summary of their limitations for practical use. Finally, we discuss future perspectives and directions. This critical review offers the biosensor community insight into how to progress the present research, which may streamline the removal of the problems facing rapid and large-scale SARS-CoV-2 screening.

For the diabetes diagnosis, noninvasive methods are preferred to invasive methods; urine glucose measurement is an example of a noninvasive method. However, conventional noninvasive methods for urine glucose measurement are not intuitive. Furthermore, such methods exhibit low selectivity because they can detect interfering molecules in addition to glucose. Herein, we fabricate a noninvasive, intuitive, and highly selective paper sensor consisting of polyaniline nanoparticles (PAni-NPs) and red blood cell membranes (RBCMs). The PAni-NPs (adsorbed on the paper) are highly sensitive to hydrogen ions and change color from emeraldine blue to emeraldine green within a few seconds. The RBCM (coated on the PAni-NP-adsorbed paper) having the glucose transporter-1 protein plays the role of a smart filter that transports glucose but rejects other interfering molecules. In particular, the selectivity of the RBCM-coated PAni-NP-based paper sensor was approximately improved ∼85%, compared to the uncoated paper sensors. The paper sensor could detect urine glucose over the range of 0–10 mg/mL (0–56 mM), with a limit of detection of 0.54 mM. The proposed paper sensor will facilitate the development of a highly selective and colorimetric urine glucose monitoring system.

Quantifying the physical properties of individual exosomes containing amyloid-β

Polyaniline nanoskein (PANS), which have polyaniline nanofibers, is developed. PANS is formulated via sequential extracting, heating, and swelling processes. The compositions of PANS have been analyzed using X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, and Brunauer-Emmett-Teller analysis, and the results of which indicate that PANS is composed of solely organic materials. Moreover, PANS have been shown convertible absorbance characteristics according to surrounding acidic environments, and using these characteristics, the possibility of PANS for sensing of surrounding redox states changes is presented.

Additional file 1. Addtional experiments of control group and characterization results.

Leukocytes are coated with a layer of heterogeneous carbohydrates (glycans) that modulate immune function, in part by governing specific interactions with glycan-binding proteins (lectins). Although nearly all membrane proteins bear glycans, the identity and function of most of these sugars on leukocytes remain unexplored. Here, we characterize the N-glycan repertoire (N-glycome) of human tonsillar B cells. We observe that naive and memory B cells express an N-glycan repertoire conferring strong binding to the immunoregulatory lectin galectin-9 (Gal-9). Germinal center B cells, by contrast, show sharply diminished binding to Gal-9 due to upregulation of I-branched N-glycans, catalyzed by the β1,6-N-acetylglucosaminyltransferase GCNT2. Functionally, we find that Gal-9 is autologously produced by naive B cells, binds CD45, suppresses calcium signaling via a Lyn-CD22-SHP-1 dependent mechanism, and blunts B cell activation. Thus, our findings suggest Gal-9 intrinsically regulates B cell activation and may differentially modulate BCR signaling at steady state and within germinal centers., Leukocytes are coated with glycans that modulate immune function through interactions with lectins. Here, the authors characterize the N-glycan repertoire of human tonsillar B cells. They report that Gal-9 is an intrinsic regulator of B cell activation that may differentially modulate BCR signaling at steady state and within germinal centers due to expression of I-branched glycans.

Nitrogen dioxide (NO2) is one of the toxic gas that causes debilitating disease in the respiratory system. Due to imprudent industrial development, the need for a facile and sensitive gas detection has been grown. Here, we develop a simple and disposable NO2 gas sensor employing carbon adhesive tape (CAT) as the gas detection element. The CAT developed in this study contained a large amount of carbon black material to adsorb NO2 gas molecules. Experiments revealed that the gas molecules were bound rapidly to the CAT sensor (

Circulating tumor cells (CTCs), which are thought to be the main candidate for metastasis, are gaining importance owing to their potential impact on human health and public welfare. For capturing CTCs, antigen-antibody interaction has been used in which specific antigens expressed on cell surface of CTCs can be bound to antibodies immobilized on substrates. Conventional detection methods for CTCs have often suffered not only from relatively low antigen-antibody coupling efficiency but also from cumbersome fabrication processes of micro/nano-structures for CTCs capture. Herein, we report a facile, robust antibody-based CTCs detection technique using centrifugal force, which can enhance the capturing efficacy of CTCs. We validate chemical functionalization process of antibodies on a silica substrate by using atomic force microscopy. Furthermore, it turned out that the centrifugal force from a benchtop centrifuge is enough to produce a ~2.3-fold increase in capture yield of CTCs through enhancement of binding avidity between CTCs and the antibodies. Our result points out the great potential of our method for practical application in CTCs diagnostics and opens a new avenue for biological and chemical sensing.

Amyloid-β (Aβ) peptides can be aggregated into β-sheet rich fibrils or plaques and deposited on the extracellular matrix of brain tissues, which is a hallmark of Alzheimer’s disease. Several drug candidates have been designed to retard the progression of the neurodegenerative disorder or to eliminate toxic Aβ aggregates. Recently, 4-(2-Hydroxyethyl)-1-piperazinepropanesulfonic acid (EPPS) has emerged as a promising drug candidates for elimination of toxic Aβ aggregates. However, the effect of EPPS on the degradation of Aβ aggregates such as fibrils has not yet been fully elucidated. In this article, we investigate the EPPS-driven degradative behavior of Aβ aggregates at the molecular level by using high-resolution atomic force microscopy. We synthesized Aβ fibrils and observed degradation of fibrils following treatment with various concentrations (1–50 mM) of EPPS for various time periods. We found that degradation of Aβ fibrils by EPPS increased as a function of concentration and treatment duration. Intriguingly, we also found regeneration of Aβ aggregates with larger sizes than original aggregates at high concentrations (10 and 50 mM) of EPPS. This might be attributed to a shorter lag phase that facilitates reformation of Aβ aggregates in the absence of clearance system.

Nitrogen dioxide (NO2) detection is critical because NO2 is a typical toxic gas that is harmful to humans as well as the environment. Over the last few decades, various nanomaterials such as nanowires, nanoparticles, carbon nanotubes, and graphene have been widely utilized to construct the platform (i.e., supporting material) of NO2 gas sensors. Among these materials, carbon nanomaterials (e.g., graphene and carbon nanotubes) have received increasing attention owing to their outstanding physical and electrical properties required for NO2 detection. Recently, many attempts have been made to blend the carbon nanomaterials with other materials, resulting in the creation of composite materials with enhanced electrical conductivity and physical properties for highly sensitive and selective detection of NO2 gas. As such, blended or stacked carbon composite materials offer higher efficiency (i.e., improved sensitivity and response/recovery time) for detecting NO2 gas in comparison with pristine carbon nanomaterials. In this review, we consider state-of-the-art amperometric NO2 gas sensors based on carbon nanomaterials with respect to their dimensionalities, and we discuss the enhanced gas-sensing performance achieved by using composite materials.

Aluminum can be ionized in water by reacting with chlorides. Aluminum ions (Al3+) are believed to be very harmful to human health and are associated with Alzheimer’s disease. The detection of Al3+ is extremely important, but conventional methods suffer from low sensitivity and cumbersome processes. Herein, we report ultra-sensitive and label-free detection of Al3+ using gold nanoparticles (AuNPs) and Kelvin probe force microscopy (KPFM). Al3+ was exposed on citrated AuNPs with different concentrations; Al3+/AuNP complexes were constructed via binding interactions between Al3+ and the citrates. By probing the Al3+/AuNP complexes, we quantified the degree of interactions between Al3+ and the citrated AuNPs using KPFM. As the Al3+ concentration decreased, KPFM succeeded in exhibiting ultra-sensitive detection as low as 2 amol (limit of detection 1 pM, single droplet 2 μL). We tested real samples from a sheet of aluminum foil, and detected ∼748 amol (∼374 pM, single droplet 2 μL) Al3+. The results indicate that the combination of AuNPs and KPFM offers a robust, facile, and an ultra-sensitive platform technology for detecting Al3+.

Here, we report a new concept of both the adhesive manner and material, named “adhesive leaf (AL),” based on the leaf of the plant Heteropanax fragrans. The treatment of the corona discharge on the leaf surface can cause the nano-/microdestruction of the leaf epidermis, resulting in an outward release of sap. The glucose-containing sap provided the AL with a unique ability to stick to various substrates such as steel, polypropylene, and glass. Moreover, we reveal that the AL adhesion strength depends on the AL size, as well as the corona-discharge intensity. Conventional adhesives, such as glue and bond, lose their adhesive property and leave dirty residues upon the removal of the attached material. Unlike the conventional methods, the AL is advantageous as it can be repeatedly attached and detached thoroughly until the sap liquid is exhausted; its adhesive ability is maintained for at least three weeks at room temperature. Our findings shed light on a new concept of a biodegradable adhesive material that is created by a simple surface treatment.

Alzheimer's disease (AD) is the most common cause of neurodegenerative disorder in elderly people, and has become a social problem in aging societies globally. Amyloid-β (Aβ) aggregates (i.e., Aβ fibrils and plaques) present in the brains of AD patients are hallmarks of AD. Although various promising anti-Aβ drugs have been tested in pre-clinical and randomized controlled trials, the trial results have not yet been translated into clinical practice due to increasing time and cost of drug development. Recent investigations have addressed how the formation of Aβ aggregates is influenced by the surface of gold nanoparticles (AuNPs) to obtain a detailed understanding of the in vivo process of amyloid formation. Particularly, AuNPs catalytically provide nucleation sites to accelerate the formation of Aβ aggregates. Moreover, AuNPs have great potential as a sensing tool due to their optical property. Employing this dual function (i.e., catalytic and optical property), AuNP-based colorimetry is highlighted as a simple and innovative method for monitoring the efficacy of anti-Aβ reagents. In this review, we briefly survey important developments and designs of anti-Aβ drugs. The significance and perspectives of AuNP-based drug-screening in pharmacologic research are also discussed.

Here, we demonstrate a powerful method to discriminate DNA mismatches at single-nucleotide resolution from 0 to 5 mismatches (χ0 to χ5) using Kelvin probe force microscopy (KPFM). Using our previously developed method, we quantified the surface potentials (SPs) of individual DNA-capped nanoparticles (DCNPs, ∼100 nm). On each DCNP, DNA hybridization occurs between ∼2200 immobilized probe DNA (pDNA) and target DNA with mismatches (tDNA, ∼80 nM). Thus, each DCNP used in the bioassay (each pDNA-tDNA interaction) corresponds to a single ensemble in which a large number of pDNA-tDNA interactions take place. Moreover, one KPFM image can scan at least dozens of ensembles, which allows statistical analysis (i.e., an ensemble average) of many bioassay cases (ensembles) under the same conditions. We found that as the χn increased from χ0 to χ5 in the tDNA, the average SP of dozens of ensembles (DCNPs) was attenuated owing to fewer hybridization events between the pDNA and the tDNA. Remarkably, the SP attenuation vs. the χn showed an inverse-linear correlation, albeit the equilibrium constant for DNA hybridization exponentially decreased asymptotically as the χn increased. In addition, we observed a cascade reaction at a 100-fold lower concentration of tDNA (∼0.8 nM); the average SP of DCNPs exhibited no significant decrease but rather split into two separate states (no-hybridization vs. full-hybridization). Compared to complementary tDNA (i.e., χ0), the ratio of no-hybridization/full-hybridization within a given set of DCNPs became ∼1.6 times higher in the presence of tDNA with single mismatches (i.e., χ1). The results imply that our method opens new avenues not only in the research on the DNA hybridization mechanism in the presence of DNA mismatches but also in the development of a robust technology for DNA mismatch detection.

Graphene-based electronic textiles (e-textiles) have generally fabricated with one-dimensional (1D) textile (e.g., yarn) to serve as wearable devices or smart textiles for detecting hazardous gases. For an improved sensing performance, flexible 1D e-textile yarns can be woven and patterned to form two-dimensional (2D) sheets; however, these sheets suffer from batch-to-batch variations while manufacturing by hand. To address these issues, we fabricated a graphene-based electronic sheet (GES) on a polyester sheet with a uniform grid fishnet pattern. The 2D GES exhibited high conductance (∼7 μS) and sensitivity toward NO2 (0.34 μA/ppm) and NH3 (0.16 μA/ppm), which are indicative of a significantly improved performance as compared to that of the 1D e-textile yarn. Furthermore, the 2D GES not only exhibited an improved NO2 sensing response that was approximately three times higher than that of the 1D e-textile yarn but also showed other advantages, such as being 19 times lighter and 5 times thinner per unit area. Moreover, we confirmed that the GES enabled the detection of not only NO2, which is emitted from vehicle exhausts but also the NH3 present in the atmosphere and artificial breath. We also found that the GES possessed high mechanical flexibility to endure a 1,000-cycle bending test. These results suggest that the GES could be a next-generation 2D wearable gas sensor for detecting toxic environmental gases and monitoring health by exhalation.

Without appropriate treatment, Staphylococcus aureus (S. aureus) infection can cause life-threatening diseases (e.g., meningitis, pneumonia, bacteremia, and sepsis). However, a rapid and accurate point-of-care test for the infection remains challenging. The bacterium secretes α-hemolysin (Hla), which spontaneously binds to the cell membrane of erythrocyte, and eventually lyses the cell via pore formation. Taking advantage of this phenomenon, we apply the erythrocyte membrane (EM) extracted from human whole blood as a novel bioreceptor for detecting Hla, fabricating erythrocyte-camouflaged biosensors (ECB) by coating EM onto electrochemical impedance electrodes. We verify the existence of EM on the ECB by using confocal microscopy and atomic force microscopy. We demonstrate that ECBs sensitively detect Hla spiked in phosphate buffer saline and human serum. Also, the sensor shows higher sensitivity to Hla than major blood proteins, such as human serum albumin, fibrinogen, and gamma globulin. Specifically, the signal intensities for Hla are 8.8–12.7 times higher than those in the same concentration of those blood proteins. The detection limit of the ECB for Hla is 1.9 ng/ml while the dynamic range is 0.0001–1 mg/ml. Finally, we validate the constant sensing performance of ECB with 99.0 ± 5.6% accuracy for 35 days of storage.

© 2017, © 2017 Taylor & Francis. At the edge of a confluent cell layer, cell-free empty space is a cue that can drive directed collective cellular migration. Similarly, contact guidance is also a robust mechanical cue that can drive cell migration. However, it is unclear which of the two effects is stronger, and how each mechanism affects collective migration. To address this question, here we explore the trajectories of cells migrating collectively on a substrate containing micropatterned grooves (10–20 μm in periodicity, 2 μm in height) compared with unpatterned control substrates. Compared with unpatterned controls, the micropatterned substrates attenuated path variance by close to 70% and augmented migration coordination by more than 30%. Together, these results show that contact guidance can play an appreciable role in collective cellular migration. Also, our result can provide insights into tissue repair and regeneration with the remodeling of the connective tissue matrix.

Biological processes related to amyloid-β (Aβ ) aggregation and deposition are associated with the onset of Alzheimer’s disease. Although these processes are attributed to electrostatic interactions between the Aβ42 sequences, the electrical properties of Aβ aggregates (i.e., oligomers and fibrils) have not yet been fully explored despite their importance. Here, we investigated the nanoelectrical properties (i.e., surface potential) of Aβ42 aggregates using Kelvin probe force microscopy (KPFM) and found that the surface potential of the Aβ42 aggregates was changed from positive to negative with pH, passing across zero surface potential at pH=5.2-5.4. The measured surface potentials were ranged from 48 to -35 mV/nm for both the oligomers and the fibrils. From our observations, we determined the isoelectric points (pIs) of both cases. Using the commercial software PyMOL, we also converted the surface potential of a single monomorphic Aβ42 fibril; in the simulation, we calculated the net charges of the monomorphic fibrils depending on pH, predicted its pI by Boltzmann curve fitting, and compared these results with our experimental KPFM data.

With the rapid development of nanotechnology and its associated waste stream, public concern is growing over the potential toxicity exposure to heavy metal ions poses to the human body and the environment. Herein, we report an extremely sensitive Kelvin probe force microscopy (KPFM)-based platform for detecting nanotoxic materials (e.g. Ag+) accomplished by probing the integrated surface potential differences of a single gold nanoparticle on which an interaction between probe DNA and target DNA occurs. This interaction can amplify the surface potential of the nanoparticle owing to the coordination bond mediated by Ag+ (cytosine-Ag+-cytosine base pairs). Interestingly, compared with conventional methods, this platform is capable of extremely sensitive Ag+ detection (∼1 fM) in a remarkably wide-range (1 fM to 1 μM). Furthermore, this platform enables Ag+ detection in a practical sample (general drinking water), and this KPFM-based technique may have the potential to detect other toxic heavy metal ions and single nucleotide polymorphisms by designing specific DNA sequences.

Cancer biomarkers, an indication of cancer cells in the body, can play an important role in diagnosis, prognosis, and the prediction of treatment efficacy as well as recurrence. Here, we developed a simple Raman spectroscopic method that utilized a silver nanoforest (SNF) substrate and a hand-held Raman spectrometer for identifying cancer protein biomarkers with very high sensitivity. First, various concentrations of ethanol solutions were analyzed using the hand-held Raman spectrometer to confirm its performance. Next, the functionality of the SNF substrate, in other words, the effect of the surface enhanced Raman scattering was characterized by measuring varying, known concentrations of rhodamine 6G. The novel structure of the SNF substrate can provide the enhancement factor of 1.13 × 107. Following the characterization, the Raman spectra of cancer biomarkers, epithelial cell adhesion molecule (EpCAM) and carcinoembryonic antigen (CEA), were examined using the hand-held Raman spectrometer with the SNF substrate. As low as 0.2 picomoles of the protein were successfully detected with very tiny amount of sample solutions (~2 µl) containing cancer biomarkers. The developed technique allows for the simple, convenient measurement of cancer protein biomarkers using the SNF substrate and hand-held Raman spectrometer. We believe these findings will motivate the creation of Raman libraries for cancer biomarkers.

Aluminum ions are very toxic to human health, especially in relation to neurodegenerative diseases. However, conventional methods of detecting such toxic ions suffer from the use of poisonous chemical probes and complex processes. Herein, we report an eco-friendly and enhanced colorimetric method of aluminum ion detection using green-synthesized gold nanoparticles (AuNPs) from apple (Malus domestica) extract. The apple extract-based AuNPs (AX-AuNPs) contain abundant pectin different from citrate-based AuNPs. The pectin-rich AX-AuNPs improved the sensitivity of the colorimetric detection of aluminum ions. The detection limit was about 20 μM both in artificial and drinking water-based real samples. Interestingly, it is turned out that the AX-AuNPs were aggregated naturally after the chemical assay because of solution getting decayed. For the environmental perspective, it was great that the lump of AX-AuNP aggregates could easily be removed from the solutions before solution discard. Overall, our results indicate that AX-AuNPs offer a high-selectivity, enhanced colorimetric detection of aluminum ions in a short time (less than 1 min), based on an eco-friend synthesis and disposal manner of AuNPs.

Ascorbic acid, which is widely used as a therapeutic agent for various disorders (e.g. chronic diseases and cancers), has potential therapeutic roles for neurodegenerative disease such as Huntington’s, Parkinson’s and Alzheimer’s diseases. The ability to impede amyloid fibril formation has a great demand on developing clinical medicine with respect to successfully preventing neurodegenerative diseases. Here, we report that L-ascorbic acid inhibits β-lactoglobulin amyloid formation in vitro. For quantitative characterization of the inhibitory effect of L-ascorbic acid on fibrillation, we performed high-resolution atomic force microscopy and thioflavin T fluorescence assay. Fourier transform infrared spectra indicated secondary structure differences of fibrils formed with and without ascorbic acid. These results suggest great potential of ascorbic acid for use in the prevention or treatment of amyloidogenic diseases. Open image in new window

Understanding of the interactions of silver ions (Ag+) with polynucleotides is important not only to detect Ag+ over a wide range of concentrations in a simple, robust, and high-throughput manner but also to investigate the intermolecular interactions of hydrogen and coordinate interactions that are generated due to the interplay of Ag+, hydrogen ions (H+), and polynucleotides since it is critical to prevent adverse environmental effects that may cause DNA damage and develop strategies to treat this damage. Here, we demonstrate a novel approach to simultaneously detect Ag+ satisfying the above requirements and examine the combined intermolecular interactions of Ag+–polycytosine and H+–polycytosine DNA complexes using dielectrophoretic tweezers-based force spectroscopy. For this investigation, we detected Ag+ over a range of concentrations (1 nM to 100 μM) by quantifying the rupture force of the combined interactions and examined the interplay between the three factors (Ag+, H+, and polycytosine) using the...

Quantifying the physical properties of individual exosomes containing amyloid-β42 (Aβ42) is crucial for a better understanding of an underpinning mechanism of Alzheimer’s disease expression which is associated with the Aβ42 transfer. Because of the lack of proper tools, however, there have been very few studies on how the amount of Aβ42 affects the physical properties of exosomes. To answer the question, we investigated the physical properties of exosomes secreted by neuroblastoma by probing individual exosomes using electrostatic force microscopy. Interestingly, we observed that when the higher concentration of Aβ42 oligomers was fed to cells, the higher surface charge of the exosomes appeared. This result indicates that the exosomes contain more Aβ42 with the increase in Aβ42 concentration in cell media, implying that they serve as transport vesicles for Aβ42. Our approach could help to better understand how the neuronal exosomes are related to the propagation of neurodegenerative diseases and to seek how to make an early diagnosis of those diseases.

The surface potential of nanoparticles plays a key role in numerous applications, such as drug delivery and cellular uptake. The estimation of the surface potential of nanoparticles as drug carriers or contrast agents is important for the design of nanoparticle-based biomedical platforms. Herein, we report the direct measurement of the surface potential of individual gold nanorods (GNRs) via Kelvin probe force microscopy (KPFM) at the nanoscale. GNRs were capped by a surfactant, cetyltrimethylammonium bromide (CTAB), which was removed by centrifugation. CTAB removal is essential for GNR-based biomedical applications because of the cytotoxicity of CTAB. Applying KPFM analysis, we found that the mean surface potential of the GNRs became more negative as the CTAB was removed from the GNR. The results indicate that the negative charge of GNRs is covered by the electrostatic charge of the CTAB molecules. Similar trends were observed in experiments with gold nanospheres (GNS) capped by citrates. Overall, KPFM-based techniques characterize the surfactant of individual nanoparticles (i.e. GNR or GNS) with high resolution by mapping the surface potential of a single nanoparticle, which aids in designing engineered nanoparticles for biomedical applications.

Cortisol, which is a stress biomarker that causes various mental disorders, is found in sweat, saliva, blood, and urine. Because mental disorders resulting from stress are a silent contributor to various diseases, the detection of cortisol level is an important step in their prevention. Here, we developed a highly sensitive, localized surface plasmon resonance (LSPR) aptasensor for the direct detection of cortisol in saliva. The LSPR aptasensor was constructed using gold nanoparticles of different sizes. Subsequently, the surface of the LSPR substrate was immobilized using an aptamer for capturing cortisol. The detection capability of the LSPR aptasensor was compared with that of the antibody- immobilized sensor. The LSPR aptasensor displayed excellent detection capability for a wide range of cortisol concentrations extending from 0.1–1000 nM with a detection limit of 0.1 nM. In addition, the LSPR aptasensor was able to selectively detect cortisol among other substances with similar chemical structures (e.g., cortisone, corticosterone, progesterone, and triamcinolone). These results indicate that the LSPR aptasensor may be used for the highly sensitive and selective detection of cortisol in salivary samples.

Amyloid aggregates have emerged as a significant hallmark of neurodegenerative diseases such as Alzheimer's and Parkinson's diseases. Although it has been recently reported that microwave heating induces amyloid aggregation compared with conventional heating methods, the mechanism of amyloid aggregate induction has remained unclear. In this study, we investigated the formation of oligomeric amyloid aggregates (OAAs) by microwave irradiation at microscale volumes of solution. Microwave irradiation of protein monomer solution triggered rapid formation of OAAs within 7 min. We characterized the formation of OAAs using atomic force microscopy, thioflavin T fluorescent assay and circular dichroism. In the microwave system, we also investigated the inhibitory effect on the formation of amyloid aggregates by L-ascorbic acid as well as enhanced amyloid aggregation by silver nanomaterials such as nanoparticles and nanowires. We believe that microwave technology has the potential to facilitate the study of amyloid aggregation in the presence of chemical agents or nanomaterials.

We have characterized micro-droplet generation using water immiscible hexafluorophosphate ([PF6])- and bis(trifluoromethylsulfonyl)imide ([Tf2N])-based room temperature ionic liquids (RTILs). The interfacial tension between total 7 RTILs and phosphate buffered saline (PBS) was measured using a tensiometer for the first time. PBS is one of the most commonly used buffer solutions in cell-related researches. The measured interfacial tension ranges from 8.51 to 11.62 and from 9.56 to 13.19 for [Tf2N]- and [PF6]-based RTILs, respectively. The RTILs micro-droplets were generated in a microfluidic device. The micro-droplet size and generation frequency were determined based on continuous monitoring of light transmittance at the interface in microchannel. The size of RTIL micro-droplets was inversely proportional to the increase of PBS solution flow rate and RTILs hydrophobicity, while droplet generation frequency was proportional to those changes. The measured size of RTILs droplets ranged from 0.6 to 10.5 nl, and from 1.0 to 17.1 nl for [Tf2N]- and [PF6]-based RTILs, respectively. The measured frequency of generated RTILs droplets ranged from 2.3 to 37.2 droplet/min, and from 2.7 to 17.1 droplet/min for [Tf2N]- and [PF6]-based RTILs, respectively. The capillary numbers were calculated depending on the RTILs, and ranged from 0.51×10-3 to 1.06×10-3 and from 5.00×10-3 to 8.65×10-3, for [Tf2N]- and [PF6]-based RTILs, respectively. The interfacial tension between RTILs and PBS will contribute to developing bioprocesses using immiscible RTILs. Also, the RTILs micro-droplets will enable the high-throughput monitoring of various biological and chemical reactions using RTILs as new reaction media.

We developed an electrochemical enzymatic biosensor coated with red blood cell membrane (RBCM) for highly selective glucose measurement. The RBCM containing its membrane proteins (glucose transporter-1) was extracted from a human red blood cell (RBC), and then placed on an established enzymatic glucose sensor by the vesicle fusion method. In the newly fabricated glucose sensor, the RBCM plays the role in the diffusion barrier of preventing the penetration of interfering molecules, while in contrast making glucose molecules permeable. We employed scanning electron microscopy and atomic force microscopy to analyze the RBCM diffusion barriers. The performance of our glucose sensors with diffusion barriers was tested regarding selectivity to glucose against other interfering molecules, such as ascorbic acid, uric acid, and galactose. Remarkably, employing the RBCM significantly improved the selectivity and accuracy of the glucose measurement, even under human serum, compared to the uncoated sensors. This result implies that the RBCM serves well as a highly permselective layer to glucose molecules, and a diffusion barrier to other molecules.

Matrix metalloproteinase (MMP) is a key marker and target molecule for cancer diagnosis, as MMP is able to cleave peptide chains resulting in degradation of extracellular matrix (ECM), a necessary step for cancer development. In particular, MMP2 has recently been recognized as an important biomarker for lung cancer. Despite the important role of detecting MMP molecules in cancer diagnosis, it is a daunting task to quantitatively understand a correlation between the status of cancer development and the secretion level of MMP in a blood droplet. Here, we demonstrate a nanoscale cancer diagnosis by nanomechanical quantitation of MMP2 molecules under cancer progression with using a blood droplet of lung cancer patients. Specifically, we measured the frequency dynamics of nanomechanical biosensor functionalized with peptide chains mimicking ECM in response to MMP2 secreted from tumors in lung with different metastasis level. It is shown that the frequency shift of the biosensor, which exhibits the detection sensitivity below 1 nM, enables the quantitation of the secretion level of MMP2 molecules during the progression of cancer cells or tumor growth. More importantly, using a blood droplet of lung cancer patients, nanomechanical biosensor is shown to be capable of depicting the correlation between the secretion level of MMP2 molecules and the level of cancer metastasis, which highlights the cantilever-based MMP2 detection for diagnosis of lung cancer. Our finding will broaden the understanding of cancer development activated by MMP and allow for a fast and point-of-care cancer diagnostics.

Ultrasonic treatment (UST) has been used not only to accelerate protein fibril growth and amplify infectious prion proteins from biological fluids, but also to break amyloid-like fibrils for treatment. Despite the applicability of UST to clinical treatment, both the decomposition characteristics of fibrils and the regrowth mechanisms of the decomposed fibrils remain unclear. Here, we report UST-driven decomposition of amyloid-like fibrils into shorter fibrils and the principles of fibril regrowth via conventional heating. Short fibrils decomposed by UST can be reconstructed into mature fibrils with the addition of monomeric protein, but the regrowth of short fibrils rarely occurs in the absence of monomeric protein. Interestingly, the reconstructed fibrils possess electric properties similar to those of the original fibrils. We propose a model that describes the regrowth process of amyloid-like fibrils decomposed by UST, which sheds light on future biomedical applications of UST for the treatment of amyloidogenic diseases.

It has been of high significance to devise a biochemical analytical tool kit enabling the detection of few circulating tumor cells (CTCs) for early diagnosis of cancer. Despite recent effort made to detect few CTCs, it is still challenging to sense such cells with their low concentration and/or the minute amount of marker proteins expressed on few CTCs. In this work, we report the label-free recognition of carcinoembryonic antigens (CEAs) expressed on few CTCs by using a carbon nanotube (CNT) sensor coupled with scanning probe microscopy imaging for cancer diagnosis. It is shown that a CNT-patterned surface is able to specifically capture the CEA molecules in the whole cell lysate of CTCs with their concentration even up to 10(-3) cells/mL. Our work sheds light on our bioassay based on a CNT-patterned surface for highly sensitive, label-free detection of marker proteins expressed on few tumor cells, which may open a new avenue in early diagnosis of cancer by providing a novel biochemical analysis tool kit.

Nanomaterials have recently received significant attention as photothermal agents and fluorescence contrast agents for molecular therapeutics due to their unique optical properties (e.g. light absorption). In particular, single-walled carbon nanotubes (SWNTs) have been recently utilized as photothermal agents (for photothermal therapy) because of the solubility of SWNTs as well as their light absorbing capability at the near-infrared region. In this work, we have developed the SWNT-based photothermal agents using pyrene-based PEGylation of SWNTs. FT-IR and/or H-NMR spectroscopies have validated the PEGylation of SWNTs, and it is shown that water-soluble SWNTs are able to generate heat under near-infrared (NIR) irradiation of 5W/cm2. Moreover, it is found that our pyrene-based PEGylated SWNTs exhibit the fluorescence characteristic under the excitation wavelength of 340 nm. Our study sheds light on the pyrenyl PEGylated SWNTs as photothermal agents and/or fluorescence contrast agents for the future applications in molecular therapeutics.

Kelvin probe force microscopy (KPFM) is a robust toolkit for profiling the surface potential (SP) of biomolecular interactions between DNAs and/or proteins at the single molecule level. However, it has often suffered from background noise and low throughput due to instrumental or environmental constraints, which is regarded as limiting KPFM applications for detection of minute changes in the molecular structures such as single-nucleotide polymorphism (SNP). Here, we show KPFM imaging of DNA-capped nanoparticles (DCNP) that enables SNP detection of the BRCA1 gene owing to sterically well-adjusted DNA–DNA interactions that take place within the confined spaces of DCNP. The average SP values of DCNP interacting with BRCA1 SNP were found to be lower than the DCNP reacting with normal (non-mutant) BRCA1 gene. We also demonstrate that SP characteristics of DCNP with different substrates (e.g., Au, Si, SiO2, and Fe) provide us with a chance to attenuate or augment the SP signal of DCNP without additional enhancement of instrumentation capabilities.

The direct quantification of weak intermolecular binding interactions is very important for many applications in biology and medicine. Techniques that can be used to investigate such interactions under a controlled environment, while varying different parameters such as loading rate, pulling direction, rupture event measurements, and the use of different functionalized probes, are still lacking. Herein, we demonstrate a biaxial dielectrophoresis force spectroscopy (BDFS) method that can be used to investigate weak unbinding events in a high-throughput manner under controlled environments and by varying the pulling direction (i.e., transverse and/or vertical axes) as well as the loading rate. With the BDFS system, we can quantitatively analyze binding interactions related to hydrogen bonding or ionic attractions between functionalized microbeads and a surface within a microfluidic device. Our BDFS system allowed for the characterization of the number of bonds involved in an interaction, bond affinity, kinetic rates, and energy barrier heights and widths from different regimes of the energy landscape.

…(MMPs;greenmissilesinthepicture)expressedonacancercellsurfacecanbesensedby a resonant cantilever device (satellite arm in the picture), as J. Yang, D. S. Yoon, T.Kwon et al. report in their Communication on page 5837 ff. Active MMPs attack thepeptide sequence that is immobilized on the cantilever surface. The peptide cleavageleads to an increase in the resonant frequency of the cantilever, owing to a decrease inthe mass of immobilized peptide.

We report the scanning probe microscope (SPM)-based single-molecule recognition of biomolecular interactions between protein kinase and small ligands (i.e., ATP and Imatinib). In general, it is difficult to sense and detect the small ligands bound to protein kinase (at single-molecule resolution) using a conventional atomic force microscope (AFM) due to the limited resolution of conventional AFM for detecting the miniscule changes in molecular size driven by ligand binding. In this study, we have demonstrated that Kelvin probe force microscopy (KPFM) is able to articulate the surface potential of biomolecules interacting with ligands (i.e., the protein kinase-ATP interactions and inhibition phenomena induced by antagonistic molecules) in a label-free manner. Furthermore, measured surface potentials for biomolecular interactions enable quantitative descriptions on the ability of protein kinase to interact with small ligands such as ATP or antagonistic molecules. Our study sheds light on KPFM that allows the precise recognition of single-molecule interactions, which opens a new avenue for the design and development of novel molecular therapeutics.

Amyloid fibrils have recently been highlighted due to their excellent mechanical properties, which not only play a role in their biological functions but also imply their applications in biomimetic material design. Despite recent efforts to unveil how the excellent mechanical properties of amyloid fibrils originate, it has remained elusive how the anisotropic nanomechanical properties of hierarchically structured amyloid fibrils are determined. Here, we characterize the anisotropic nanomechanical properties of hierarchically structured amyloid fibrils using atomic force microscopy experiments and atomistic simulations. It is shown that the hierarchical structure of amyloid fibrils plays a crucial role in determining their radial elastic property but does not make any effect on their bending elastic property. This is attributed to the role of intermolecular force acting between the filaments (constituting the fibril) on the radial elastic modulus of amyloid fibrils. Our finding illustrates how the hierarchical structure of amyloid fibrils encodes their anisotropic nanomechanical properties. Our study provides key design principles of amyloid fibrils, which endow valuable insight into the underlying mechanisms of amyloid mechanics.

Supercoiling DNA (folding DNA into a more compact molecule) from open circular forms requires significant bending energy. The double helix is coiled into a higher order helix form; thus it occupies a smaller footprint. Compact packing of DNA is essential to improve the efficiency of gene delivery, which has broad implications in biology and pharmaceutical research. Here we show that low-intensity pulsed ultrasound can pack open circular DNA into supercoil form. Plasmid DNA subjected to 5.4 mW/cm2 intensity ultrasound showed significant (p-values

Amyloid fibrils are a hallmark of neurodegenerative diseases and exhibit a conformational diversity that governs their pathological functions. Despite recent findings concerning the pathological role of their conformational diversity, the way in which the heterogeneous conformations of amyloid fibrils can be formed has remained elusive. Here, we show that microwave-assisted chemistry affects the self-assembly process of amyloid fibril formation, which results in their conformational heterogeneity. In particular, microwave-assisted chemistry allows for delicate control of the thermodynamics of the self-assembly process, which enabled us to tune the molecular structure of β-lactoglobulin amyloid fibrils. The heterogeneous conformations of amyloid fibrils, which can be tuned with microwave-assisted chemistry, are attributed to the microwave-driven thermal energy affecting the electrostatic interaction during the self-assembly process. Our study demonstrates how microwave-assisted chemistry can be used to gain insight into the origin of conformational heterogeneity of amyloid fibrils as well as the design principles showing how the molecular structures of amyloid fibrils can be controlled.

Quantitative detection of the biological properties of living cells is essential for a wide range of purposes, from the understanding of cellular characteristics to the development of novel drugs in nanomedicine. Here, we demonstrate that analysis of cell biological properties within a microfluidic dielectrophoresis device enables quantitative detection of cellular biological properties and simultaneously allows large-scale measurement in a noise-robust and probeless manner. Applying this technique, the static and dynamic biological responses of live B16F10 melanoma cells to the small-molecule drugs such as N-ethylmaleimide (NEM) and [(dihydronindenyl)oxy]alkanoic acid (DIOA) were quantitatively and statistically examined by investigating changes in movement of the cells. Measurement was achieved using subtle variations in dielectrophoresis (DEP) properties of the cells, which were attributed to activation or deactivation of K(+)/Cl(-) cotransporter channels on the cell membrane by the small-molecule drugs, in a microfluidic device. On the basis of quantitative analysis data, we also provide the first report of the shift of the complex permittivity of a cell induced by the small-molecule drugs. In addition, we demonstrate interesting quantifiable parameters including the drug effectiveness coefficient, antagonistic interaction coefficient, kinetic rate, and full width at half-maximum, which corresponded to changes in biological properties of B16F10 cells over time when NEM and DIOA were introduced alone or in combination. Those demonstrated parameters represent very useful tools for evaluating the effect of small-molecule drugs on the biological properties of cells.