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Circulating tumour DNA (ctDNA) has emerged as an ideal biomarker for the early diagnosis and prognosis of gastric cancer (GC). In this work, a pump-free, high-throughput microfluidic chip coupled with catalytic hairpin assembly (CHA) and hybridization chain reaction (HCR) as the signal cascade amplification strategy (CHA-HCR) was developed for surface-enhanced Raman scattering (SERS) assays of PIK3CA E542K and TP53 (two GC-related ctDNAs). The chip consisted of six parallel functional units, enabling the simultaneous analysis of multiple samples. The pump-free design and hydrophilic treatment with polyethylene glycol (PEG) realized the automatic flow of reaction solutions in microchannels, eliminating the dependence on external heavy-duty pumps and significantly improving portability. In the reaction region of the chip, products generated by target-triggered CHA initiated the HCR, forming long nicked double-stranded DNA (dsDNA) on the Au nanobowl (AuNB) array surface, to which numerous SERS probes (Raman reporters and hairpin DNA-modified Cu 2 O octahedra) were attached. This CHA-HCR strategy generated numerous active "hot spots" around the Cu 2 O octahedra and AuNB surface, significantly enhancing the SERS signal intensity. Using this chip, an ultralow limit of detection (LOD) for PIK3CA E542K (1.26 aM) and TP53 (2.04 aM) was achieved, and the whole process was completed within 13 min. Finally, a tumour-bearing mouse model was established, and ctDNA levels in mouse serum at different stages were determined. To verify the experimental accuracy, the gold-standard qRT-PCR assay was utilized, and the results showed a high degree of consistency. Thus, this rapid, sensitive and cost-effective SERS microfluidic chip has potential as an ideal detection platform for ctDNA monitoring., (© 2022. The Author(s).)

Circulating tumour DNAs (ctDNAs) have been reported to be associated with real-time information of progression; however, an accurate and sensitive method has not been established. Herein, a novel dual-signal amplification strategy based on a pump-free surface-enhanced Raman scattering (SERS) microfluidic chip and a catalytic hairpin assembly (CHA) technique was developed for the dynamic monitoring of BRAF V600E and KRAS G12V, which are two non-small cell lung cancer (NSCLC)-related ctDNAs. In the presence of targets, CHA reactions can be triggered between two hairpin DNAs, fixing Pd-Au core-shell nanorods (Pd-AuNRs) onto the magnetic beads (MBs) surface. Thereafter, the composite structures can assemble under the action of magnet, enabling dual-amplification of SERS signal. Using this strategy, the limit of detection (LOD) was low (i.e. at the aM level) in serum. Furthermore, the entire chip-based analysis process could be completed within 5 min, eliminating manual incubation and heavy-duty injection pumps. The selectivity, reproducibility and uniformity of the proposed pump-free SERS microfluidic chip were satisfactory. This superior analysis strategy was finally applied to quantify BRAF V600E and KRAS G12V in tumour-bearing nude mice serum, the results of which corresponded with those of real-time polymerase chain reaction. Overall, this study provides a promising alternative tool for the dynamic monitoring of ctDNA expression level which can benefit the clinical diagnosis of NSCLC., (Copyright © 2022 Elsevier B.V. All rights reserved.)

The evaluation of tumor biomarkers in blood specimens is vital for patients with cervical lesions. Herein, an ultrasensitive surface enhanced Raman scattering (SERS) platform was proposed for simultaneous detection of cervical-lesion-related serum biomarkers. Raman reporter labeled Au-Ag nanoshells (Au-AgNSs) acted as SERS tags and an Au-Ag nanobox (Au-AgNB) array substrate prepared by the oil-water interface self-assembly method was used as a capture substrate. This single-layer Au-AgNB array substrate was proved to have exceptional uniformity by atomic force microscopy and SERS mapping. Numerous "hot spots" and specific adsorption surfaces offered by the Au-AgNB array substrate were confirmed by the finite difference time domain method, which could generate a SERS signal in electromagnetic enhancement. Binding of antigens between antibodies on Au-AgNSs and the Au-AgNB array substrate led to the formation of a sandwich-structure by the two metal nanostructures. Consequently, an ultralow detection limit of 6 pg mL -1 for squamous cell carcinoma antigen (SCCA) and 5 pg mL -1 for survivin in a wide linear logarithmic range of 10 pg mL -1 to 10 μg mL -1 was acquired. High selectivity and reproducibility with relative standard deviations of 7.701% and 6.943% were detected. Furthermore, the simultaneous detection of the two biomarkers in practical specimens was conducted, and the results were consistent with those of the enzyme-linked immunosorbent assay. This platform exhibited good robustness in the rapid and sensitive detection of SCCA and survivin, which could be a promising tool in early clinical diagnosis for different grades of cervical lesions., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Herein, we proposed a novel biosensor based on a high-density "hot spot" Au@SiO 2 array substrate and rolling circle amplification (RCA) strategy for the ultrasensitive detection of CpG methyltransferase (M.SssI) activity. In the presence of M.SssI, the RCA process can be triggered, causing the augmentation of the single-stranded DNA (ssDNA) at the tail of the double-stranded DNA (dsDNA), and the ssDNA can be hybridized with numerous DNA probes labeled with Raman reporters in the next steps. Afterwards, the resultant ssDNA can be modified to the Au@SiO 2 array substrate with the SERS enhancement factor of 7.49 × 10 6 . The substrate was synthesized by using a monolayer SiO 2 array to pick up the Au nanoparticle (AuNP) array and finite-difference time-domain (FDTD) simulation showed its excellent SERS effect. Particularly, the developed biosensor displayed a significant sensitivity with a broad detection range covering from 0.005 to 50 U mL -1 , and the limits of detection (LODs) in PBS buffer and human serum were 2.37 × 10 -4 U mL -1 and 2.51 × 10 -4 U mL -1 , respectively. Finally, in order to verify the feasibility of its clinical application, the serum samples of healthy subjects and breast cancer, prostate cancer, gastric cancer and cervical cancer patients were analyzed, and the reliability of the results was also confirmed by western blot (WB) experiments. Taking advantage of these merits, the proposed biosensor can be a very promising alternative tool for the detection of M.SssI activity, which is of vital importance in the early detection and prevention of tumors.

An innovative surface-enhanced Raman spectroscopy and lateral flow assay (SERS-LFA) biosensor combined with aptamer recognition had been developed for the convenient, rapid, sensitive and accurate detection of thrombin and platelet-derived growth factor-BB (PDGF-BB) associated with prostate cancer simultaneously. During the biosensor operation, thrombin and PDGF-BB in the sample were recognized and combined by thiol-modified aptamers immobilized on Au-Ag hollow nanoparticles (Au-Ag HNPs) surface and biotinylated aptamers immobilized on the test lines of the biosensor. Thus, thrombin and PDGF-BB were simultaneously captured between detection aptamers and capture aptamers in a sandwich structure. Finite difference time domain simulation confirmed that 'hot spots' appeared at the gaps of Au-Ag HNPs dimer in the enhanced electromagnetic field compared to that of a single Au-Ag HNP, indicating that the aggregated Au-Ag HNPs owned a good SERS signal amplification effect. The detection limits of thrombin and PDGF-BB in human plasma were as low as 4.837 pg ml -1 and 3.802 pg ml -1 , respectively. Moreover, the accuracy of the biosensor which was applied to detect thrombin and PDGF-BB in prostate cancer plasma had been verified. This designed biosensor had broad application prospects in the clinical diagnosis of prostate cancer., (© 2021 IOP Publishing Ltd.)

The highly sensitive and reliable detection, imaging, and monitoring of changes of intracellular caspase-3 are critical for understanding the cell apoptosis and studying the progression of caspase-3-related cervical cancer. Herein, we present a novel surface-enhanced Raman scattering (SERS) probe for the detection of caspase-3 during cervical cancer cell apoptosis, composed of Au nanoboxes modified with Nile blue A as a Raman reporter and a caspase-3-specified peptide as a molecular cross-linker. In the presence of caspase-3, the substrate peptides can be cleaved and the changed surface charge of the Au nanoboxes results in the Au nanoboxes-NBA-peptide assembling to form aggregates and a great enhancement of SERS signal. The finite-difference time-domain simulation showed that hot spots mainly located in the nanogaps of the aggregated Au nanoboxes, which in theory proved the rationality of this signal amplification method. The SERS probes exhibited excellent reproducibility and selectivity toward caspase-3. A detection limit of 0.127 fM was obtained for caspase-3, with a dynamic range from 1 fM to 1 nM. MTT assay demonstrated that the probes had no obvious cytotoxicity within a certain concentration range. HeLa cells were treated with doxorubicin to induce long-term apoptosis. Upon cellular uptake of these probes, the spatiotemporal dynamics of caspase-3 in apoptotic cells could be real-time monitored using SERS. The activity of caspase-3 increased with the prolongation of apoptosis time. The SERS results were in accordance with that of western blotting assay. This kind of probe can offer great potential for the determination of enzymatic activities in the physiological processes of cells.

A CoNi-based metal-organic framework (CoNi-MOF) nanosheet array is synthesized by the treatment of a CoNi layered double hydroxide nanosheet array on Ni foam with 3,5-diaminobenzoic acid. The CoNi-MOF nanosheet array with amino and carboxyl groups can be used to capture the human chorionic gonadotropin (HCG) primary antibody (HCG Ab1). Nile Blue decorated ZnNi-MOF (NB@ZnNi-MOF) spheres immobilized with HCG secondary antibodies (HCG Ab2) are used for signal amplification. When HCG exists in an analytical sample, a sandwich structure is formed and an electrochemical signal is produced. The analytical signal generated during the detection is caused by the conversion of Co(ii) and Co(iii) in the CoNi-MOF nanosheet array. The Nile Blue of the NB@ZnNi-MOF sphere, as a kind of redox-active species, is responsible for the electrochemical signal amplification in the immunosensor. On the basis of the above advantages, the HCG immunosensor exhibits a lower limit of detection (1.85 × 10-3 mIU mL-1) and a wide linear range from 0.005 mIU mL-1 to 250 mIU mL-1. Additionally, this immunosensor is used to quantitatively detect HCG in human blood serum and shows good correlations with the standard enzyme-linked immunosorbent assay (ELISA), providing a high value on clinical diagnosis.

Cytochrome c (Cyt c) is a biomarker of early apoptosis that plays a critical role in the diagnosis and therapy of non-small cell lung cancer (NSCLC). In this work, we proposed a novel surface-enhanced Raman scattering (SERS)-based biosensor to implement the ultrasensitive detection of Cyt c in the serum of NSCLC patients. The SERS-supporting substrates based on hydrophobic filter paper were composed of gold nanourchins (GNUs) surface-functionalized with the Cyt c aptamer and the cyanine 5-labeled complementary DNA. In the existence of Cyt c, it could specifically bind to its aptamer, which leads to the detachment of complementary strands modified with Cy5 and the great weakness of SERS signal. The finite-difference time domain (FDTD) simulation showed that the excellent SERS performance of GNUs aggregation was strongly dependent on a large number of "hot spots" at the tips and between the nanogaps of aggregated GNUs. Alkyl ketene dimer (AKD) was used to make the filter paper modify its property from hydrophilic to hydrophobic, which consequently increased the density of GNUs and extended the retention time of the analyte. SERS biosensors based on hydrophobic paper exhibited prominent reproducibility and selectivity. The detection limit of Cyt c in PBS was 1.148 pg/mL, while the detection limit in human serum was 1.79 pg/mL. Moreover, the analysis of the serum samples of healthy subjects and NSCLC patients confirmed the feasibility of its clinical application. The results were consistent with enzyme-linked immunosorbent assay results. This method can be a powerful strategy for quantitative detection of extracellular Cyt c, and it is expected that the SERS-based biosensors could be applied in the practical clinical diagnoses of NSCLC., Competing Interests: The authors declare that there are no conflicts of interest related to this article., (© 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement.)

Cisplatin, as one of the front-line chemotherapeutic drugs, is employed for the treatment of esophageal squamous cell carcinoma (ESCC). However, the occurrence of cisplatin resistance and metastasis remain as challenges in clinical therapy. To investigate the mechanism involved in cisplatin resistance, in this study, we established cisplatin resistant cell lines (Res) from Eca109 and TE-1 parental cells (Par), and we observed that fibronectin (FN)-mediated cell migration and spreading abilities are significantly increased in Res cells when compared to Par cells. Furthermore, we found that the integrin α5 expression is remarkably upregulated in Res cells, and inhibition of α5 results in more apoptosis and endows the Res cells resensitize to cisplatin in vitro and in vivo . In a mechanistic manner, we identified the expression of BARD1 is significantly increased in Res cells, and silencing of BARD1 reverse the effects of α5 on cisplatin resistance. Moreover, we found that the α5/FAK/PI3K/AKT signal axis is activated in Res cells, which mediates the increased expression of BARD1, as well as the cisplatin resistance and cell survival. Thus, our results demonstrate that α5 is required for cisplatin resistance through the promotion of FAK/PI3K/AKT/BARD1 signaling to prevent cells from apoptosis and enhance the DNA damage repair ability. Taken together, our study provides plausible mechanisms of α5-mediated cisplatin resistance in ESCC cells, highlighting that inhibition of α5 may be a potential target for improving efficacy in cisplatin-based chemotherapy., Competing Interests: None., (AJCR Copyright © 2019.)

Ultra high frequency radio frequency identification (UHF RFID)-based indoor localization technology has been a competitive candidate for context-awareness services. Previous works mainly utilize a simplified Friis transmission equation for simulating/rectifying received signal strength indicator (RSSI) values, in which the directional radiation of tag antenna and reader antenna was not fully considered, leading to unfavorable performance degradation. Moreover, a k -nearest neighbor ( k NN) algorithm is widely used in existing systems, whereas the selection of an appropriate k value remains a critical issue. To solve such problems, this paper presents an improved k NN-based indoor localization algorithm for a directional radiation scenario, IKULDAS. Based on the gain features of dipole antenna and patch antenna, a novel RSSI estimation model is first established. By introducing the inclination angle and rotation angle to characterize the antenna postures, the gains of tag antenna and reader antenna referring to direct path and reflection paths are re-expressed. Then, three strategies are proposed and embedded into typical k NN for improving the localization performance. In IKULDAS, the optimal single fixed rotation angle is introduced for filtering a superior measurement and an NJW-based algorithm is advised for extracting nearest-neighbor reference tags. Furthermore, a dynamic mapping mechanism is proposed to accelerate the tracking process. Simulation results show that IKULDAS achieves a higher positioning accuracy and lower time consumption compared to other typical algorithms.

In this article, for the first time, a novel, high-yield and template-free method for the synthesis of Ag nanoparticle decorated thionine/infinite coordination polymer (AgNP/THI/ICP) fibres is proposed. The thionine can be adsorbed to the AgNP/THI/ICP fibres by π-conjugation and act as the redox probe. The AgNP/THI/ICP fibres not only favor the immobilization of antibody but also facilitate the electron transfer. It is found that the AgNP/THI/ICP fibres can be designed to act as a sensitive label-free electrochemical immunosensor for carcinoembryonic antigen (CEA) determination. Under the optimized conditions, the linear range of the proposed immunosensor is estimated to be from 50 fg/mL to 100 ng/mL and the detection limit is estimated to be 0.5 fg/mL at a signal-to-noise ratio of 3, respectively. The prepared immunosensor for detection of CEA shows high sensitivity, reproducibility and stability. Our study demonstrates that the proposed immunosensor has also been used to determine CEA successfully in diluted blood samples., (Copyright © 2014 Elsevier B.V. All rights reserved.)