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The assembly of α-synuclein (αS) oligomers is recognized as the main pathological driver of synucleinopathies. While the elimination of toxic αS oligomers shows promise for the treatment of Parkinson's disease (PD), the discovery of αS oligomer degradation drugs has been hindered by the lack of proper drug screening tools. Here, we report a drug screening platform for monitoring the efficacy of αS-oligomer-degrading drugs using amyloid-shelled gold nanocomplexes (ASGNs). We fabricate ASGNs in the presence of dopamine, mimicking the in vivo generation process of pathological αS oligomers. To test our platform, the first of its kind for PD drugs, we use αS-degrading proteases and various small molecular substances that have shown efficacy in PD treatment. We demonstrate that the ASGN-based in vitro platform has strong potential to discover effective αS-oligomer-targeting drugs, and thus it may reduce the attrition problem in drug discovery for PD treatment.

Proteolysis of amyloids is related to prevention and treatment of amyloidosis. What if the conditions for proteolysis were the same to those for amyloid formation? For example, pepsin, a gastric protease is activated in an acidic environment, which, interestingly, is also a condition that induces the amyloid formation. Here, we investigate the competition reactions between proteolysis and synthesis of amyloid under pepsin-activated conditions. The changes in the quantities and nanomechanical properties of amyloids after pepsin treatment were examined by fluorescence assay, circular dichroism and atomic force microscopy. We found that, in the case of pepsin-resistant amyloid, a secondary reaction can be accelerated, thereby proliferating amyloids. Moreover, after this reaction, the amyloid became 32.4 % thicker and 24.2 % stiffer than the original one. Our results suggest a new insight into the proteolysis-driven proliferation and rigidification of pepsin-resistant amyloids.

Colorimetric glucose sensors using enzyme-coronated gold nanoparticles have been developed for high-throughput assays to monitor the blood glucose levels of diabetic patients. Although those sensors have shown sensitivity and wide linear detection ranges, they suffer from poor selectivity and stability in detecting blood glucose, which has limited their practical use. To address this limitation, herein, we functionalized glucose-oxidase-coronated gold nanoparticles with an erythrocyte membrane (EM-GOx-GNPs). Because the erythrocyte membrane (EM) selectively facilitates the permeation of glucose via glucose transporter-1 (GLUT1), the functionalization of GOx-GNPs with EM improved the stability, selectivity (3.3- to 15.8-fold higher), and limit of detection (LOD). Both membrane proteins, GLUT1 and aquaporin-1 (AQP1), on EM were shown to be key components for selective glucose detection by treatment with their inhibitors. Moreover, we demonstrated the stability of EM-GOx-GNPs in high-antioxidant-concentration conditions, under long-term storage (∼4 weeks) and a freeze-thaw cycle. Selectivity of the EM-GOx-GNPs against other saccharides was increased, which improved the LOD in phosphate-buffered saline and human serum. Our results indicated that the functionalization of colorimetric glucose sensors with EM is beneficial for improving selectivity and stability, which may make them candidates for use in a practical glucose sensor.

Graphene-based electronic textile (e-textile) gas sensors have been developed for detecting hazardous NO2 gas. For the e-textile gas sensor, electrical conductivity is a critical factor because it directly affects its sensitivity. To obtain a highly conductive e-textile, biomolecules have been used for gluing the graphene to the textile surface, though there remain areas to improve, such as poor conductivity and flexibility. Herein, we have developed a dopamine-graphene hybrid electronic textile yarn (DGY) where the dopamine is used as a bio-inspired adhesive to attach graphene to the surface of yarns. The DGY shows improved electrical conductivity (∼40 times) compared to conventional graphene-based e-textile yarns with no glue. Moreover, it exhibited improved sensing performance in terms of short response time (∼2 min), high sensitivity (0.02 μA/ppm), and selectivity toward NO2. The mechanical flexibility and durability of the DGY were examined through a 1000-cycle bending test. For a practical application, the DGY was attempted to detect the NOx emitted from vehicles, including gasoline, diesel, and fuel cell electric vehicles. Our results demonstrated that the DGYs-as a graphene-based e-textile gas sensor for detecting NO2-are simple to fabricate, cheap, disposable, and mechanically stable.

Graphene electronic textiles (e-textiles) have attracted significant attention in various sensing applications owing to their strong advantages. During the fabrication of these textiles, there are factors to consider, such as electrical conductivity, mechanical flexibility, weight, and applicability in other practical applications. Bioinspired lotus fiber has appropriate advantages to be used as graphene e-textiles, including lightweight (2 gas molecules within a short exposure time (~3 min), including a low detection limit (~1 ppm), selectivity, and resistance to relative humidity. Moreover, we verified the mechanical flexibility of RGOLF through a 1,000-cycle bending test. These results suggest that the bioinspired RGOLF could be used as a gas sensor in environmental air with a strong potential for use in various wearable applications.

Melanoma is visible unlike other types of cancer, but it is still challenging to diagnose correctly because of the difficulty in distinguishing between benign nevus and melanoma. We conducted a robust investigation of melanoma, identifying considerable differences in local elastic properties between nevus and melanoma tissues by using atomic force microscopy (AFM) indentation of histological specimens. Specifically, the histograms of the elasticity of melanoma displayed multimodal Gaussian distributions, exhibiting the heterogeneous mechanical properties, in contrast with the unimodal distributions of elasticity in the benign nevus. We identified this notable signature was consistent regardless of blotch incidence by sex, age, anatomical site (e.g., thigh, calf, arm, eyelid, and cheek), or cancer stage (I, IV, and V). In addition, we found that the non-linearity of the force-distance curves for melanoma is increased compared to benign nevus. We believe that AFM indentation of histological specimens may technically complement conventional histopathological analysis for earlier and more precise melanoma detection.

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 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 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.

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.