Exosomal miRNA expression derived from tumor cells provides a valuable and promising noninvasive modality for the early diagnosis and assessment of the efficacy of cancer treatment. However, accurate detection and identification of miRNA within exosomes have been challenging due to its low abundance and the complexity and tedious extraction with large sample volumes in the separation process. Here, we developed an electrically activated nanoplatform for rapid and sensitive detection and identification of exosome miRNA, through triggering miRNA release by opening exosomes that were captured on the electrode surface using a slightly applied electric field (50 mV), and simultaneously detected them with surface-enhanced Raman spectroscopy (SERS) in situ. The method possessed superior specificity and sensitivity for exosomal miRNA detection, with a low detection concentration of 0.5 nM. The SERS sensor chips also showed a superior sensing performance of exosomal miRNA in complex body fluids such as urine and blood. We found that exosomal miRNA contents derived from tumor cells were significantly higher than those in normal cells, and importantly, the concentrations of exosomes secreted from three different cell lines were distinctly augmented after mild electrical stimulation (ES) treatment. Furthermore, the miRNA expression within exosomes was upregulated after the ES treatment of cells. The developed approach and SERS detection platform for exosomal miRNA are promising for noninvasive and precise screening, classification, and monitoring of cancer.
Alkaline phosphatase (ALP) is a widely used indicator in the diagnosis of various diseases. Thus, it is also urgent to develop simple and efficient methods, which can meet the accurate determination of ALP activity in physiological environments. In this study, enzyme-triggered click chemistry combined with the surface-enhanced Raman spectroscopy (SERS) technique was developed for the highly sensitive detection of the ALP activity in complex biological samples. ALP was able to catalyze the ascorbic acid-phosphate (AAP) to generate ascorbic acid (AA). Then, AA could reduce Cu(II) to produce Cu(I), which plays the role of a catalyst to promote the click reaction of azide terephthalic acid (ATA) and 4-acetylene biphenyl (4-AB), resulting in the SERS signal intensity of free 4-AB in the solution was clearly reduced along with the click reaction carried on, and showed a quantitative relationship with the concentration of ALP. The proposed method has the advantages of high sensitivity, selectivity and excellent repeatability. As a proof of concept, the new developed SERS-click strategy was applied to the specific determination of the ALP activity in clinical serum samples, cellular lysate samples and the ALP inhibitor assessment successfully, indicating that the proposed ALP-triggered click chemistry assay has a significant potential application in medical diagnosis.
A simplified analysis model of the overall steel frame with external wall panels is established by finite element numerical method, and the influence of external wall panels on the internal force and seismic performance of the steel frame is studied. Pushover analysis and cyclic loading analysis are carried out on the simplified model. The results show that the external wall panel can improve the initial stiffness and ultimate bearing capacity of the steel frame, and after considering the external wall panel, the shear demand of the column increases accordingly. Moreover, compared with the pure steel frame, the ability of the steel frame structure with the external wall panel to maintain the strength and rigidity and the energy consumption capacity are significantly improved, and the cumulative energy consumption can increase by about 16.6%. The contribution of the external wall panels to the horizontal force of the steel frame structure can reach up to about 22% when the node sliding reaches the limit, and then gradually decreases to 3.5-5.4% with the increase of the loading displacement, which still has a non-negligible impact on improving the lateral resistance of the structure.
The practicability of existing self-centering braces is largely limited by their small deformability and insufficient energy dissipation. This paper presents a new type of velocity-dependent self-centering brace called viscoelastic self-centering brace (VSCB), which employs viscoelastic dampers (VED) and SMA cables as the kernel elements. The SMA cables can offer large recoverable deformation, and the viscoelastic dampers, which are velocity-dependent, provide considerable energy dissipation under high-frequency loading excitations but tend to have less detrimental influence on the self-centering capability during the shakedown of the system. A comprehensive system-level analysis on three carefully designed prototype buildings was conducted, including a buckling restrained braced frame (BRBF), a pure self-centering braced frame (SCBF) and a viscoelastic self-centering braced frame (VSCBF). The results show that compared with the SCBF, the VSCBF maintains the benefit of small residual inter-story drift (RID) and in addition, exhibits obviously reduced peak inter-story drift (PID) and peak floor acceleration (PFA).
Telomerase is a significant biomarker for its potential in cancer early diagnosis and therapy. Exploring telomerase activity in single cells presents great challenges due to the complexity and small amount of total protein in telomerase as well as the lack of an effective amplification method for its analysis. Herein, we developed a surface-enhanced Raman spectroscopy (SERS) and fluorescence dual-channel microfluidic droplet platform for the in situ and highly sensitive determination of low-abundance telomerase activity in single cells. In this work, the nanoprobe is composed of gold nanoparticles (AuNPs) functionalized by the telomerase primer and the signal sequence (Cy5-labeled DNA strand). The dual-signal switching of the SERS turn-off and fluorescence turn-on mechanisms for Cy5 response to telomerase allows for the highly sensitive and reliable determination of telomerase at single-cell level. As a result, The SERS–fluorescence microdroplet platform exhibits excellent performance for the efficient investigate thoroughly of cell heterogeneity upon telomerase expression and the dynamic monitoring of variation in intracellular telomerase activity during treatment with a telomerase inhibitor. The proposed platform will help to decipher the heterogeneity of cell populations and is potentially applicable in the clinical diagnosis of diseases related to telomerase activity.
Abstract Studies have found that matrix metalloproteinase-9 (MMP-9) plays a significant role in cancer cell invasion, metastasis, and tumor growth. But it is a challenge to go for highly sensitive and selective detection and targeting of MMP-9 due to the similar structure and function of the MMP proteins family. Herein, a novel surface-enhanced Raman scattering (SERS) sensing strategy was developed based on the aptamer-induced SERS “hot spot” formation for the extremely sensitive and selective determination of MMP-9. To develop the nanosensor, one group of gold nanospheres was modified with MMP-9 aptamer and its complementary strand DNA1, while DNA2 (complementary to DNA1) and the probe molecule 5,5′-dithiobis-(2-nitrobenzoic acid) (DTNB) were grafted on the surface of the other group of gold nanospheres. In the absence of MMP-9, DTNB located on the 13-nm gold nanospheres has only generated a very weak SERS signal. However, when MMP-9 is present, the aptamer preferentially binds to the MMP-9 to construct MMP-9–aptamer complex. The bare DNA1 can recognize and bind to DNA2, which causes them to move in close proximity and create a SERS hot spot effect. Due to this action, the SERS signal of DTNB located at the nanoparticle gap is greatly enhanced, achieving highly sensitive detection of MMP-9. Since the hot spot effect is caused by the aptamer that specifically recognizes MMP-9, the approach exhibits excellent selectivity for MMP-9 detection. Based on the benefits of both high sensitivity and excellent selectivity, this method was used to distinguish the difference in MMP-9 levels between normal and cancer cells as well as the expression of MMP-9 from cancer cells with different degrees of metastasis. In addition, this strategy can accurately reflect the dynamic changes in intracellular MMP-9 levels, stimulated by the MMP-9 activator and inhibitor. This strategy is expected to be transformed into a new technique for diagnosis of specific cancers related to MMP-9 and assessing the extent of cancer occurrence, development and metastasis. Graphical Abstract
Programmed cell death ligand 1 (PD-L1) is considered a major immune checkpoint protein that mediates antitumor immune suppression and response. Effectively regulating PD-L1 expression and dynamic monitoring has become a significant challenge in immunotherapy. Herein, we adopted smart surface-enhanced Raman scattering (SERS) nanoprobes to discriminate and monitor the dynamic expression of PD-L1 under external electrostimulation (ES). The PD-L1 expression levels in three cell lines (MCF-7 cells, HeLa cells, and H8 cells) were assessed before and after ES. The results reveal that ES could effectively and rapidly mediate a transformation in the PD-L1 content (or activity) on the cell membrane. Moreover, the molecular profiles of the cell membrane before and after ES were revealed by using the label-free SERS method with the help of immune plasmonic nanoparticles. The cell membrane protein information presented identifiable conformation changes after ES, showing a significant inhibitory effect on the bridge of PD-L1 and its antibody. This study indicates that ES is superior to chemical drugs due to lesser side effects because ES-based regulation does not depend on intracellular signalling pathways. This strategy is versatile and robust for discriminating and monitoring PD-L1 on cell membranes, thus providing potential clinical application value to PD-L1-mediated systems. This study also offers a practical way to assess the molecular profiles of cell membrane proteins in the presence of an external stimulus, which may be applicable to many membrane protein-related studies.
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