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We designed and prepared a novel anemone-like array substrate (ALAS) integrated pump-free microfluidic sensor based on surface-enhanced Raman spectroscopy (SERS). ALAS substrate forms ordered nanoantenna arrays on polystyrene (PS) nanospheres, which can improve the light-capturing efficiency of the substrate and induce surface plasmon resonance. It successfully achieved multi-dimensional enhancement of electric field coupling and further enhanced the Raman scattering signals of the Raman reporter molecules. Driven by a capillary pump, the seawater containing Hg2+ can be loaded in 100 s without the need for cumbersome syringe pumps. Our results demonstrated that the integrated sensor exhibits excellent responsiveness in detecting Hg2+ within the concentration range of 10−7 to 10−12 mol L−1. The detection limit can reach 1 pmol L−1. Therefore, we believe that this ALAS integrated microfluidic sensor provides a promising solution for the rapid and sensitive detection of Hg2+. [Display omitted] • The newly anemone-like array substrate (ALAS) showed multi-dimensional synergistically coupled SERS enhancement. • The ALAS contained nanospheres and nanoantennas to provide large surface area and improved the ssDNA modification. • The capillary force from comb-like structural channels and hydrophilic inner surface eliminates the need of syringe pump. [ABSTRACT FROM AUTHOR]

[Display omitted] • A bio-derived dynamic hydrogel substrate (DDHS) was proposed to identify exosomes. • DDHS has robust electromagnetic enhancement and dynamically controllable hot spots. • DNA self-assembly produces abundant reporters while 'lock' them into hot spot area. • Microfluidic chip acts as an integrated platform and accelerates DNA self-assembly. In the context of surface-enhanced Raman scattering (SERS) applications, an effective active substrate is supposed to exhibit a high enhancement factor, long-term stability, and excellent repeatability, as well as allow target molecules to enter the hot spot area with adequate quantity and affinity. The electromagnetic field in hot spots can be drastically amplified and results in an extraordinary large signal enhancement. However, uncontrolled formation of hot spots has hampered the realization of this intention. Here, we reported an innovative SERS active substrate, named as DNA-derived dynamic hydrogel scaffold (DDHS), which is endowed with the robust electromagnetic enhancement and exceptional target affinity. Based on this integrated microfluidic chip, rationally designed DNA oligonucleotides were introduced to recognize exosome indicator-CD63, which achieved a limit of 2.63 particles μL−1. Taken together, we believed that the proposed strategy would be possible to accelerate SERS applied to trace detection of tumor biomarkers, thus offering a promising route toward screening test and early diagnostic of cancer diseases. [ABSTRACT FROM AUTHOR]

Hepatocellular carcinoma (HCC) is a harmful malady that truly debilitates human health, and hence it is of significance to isolate and on-line profile the phenotype of HCC cells for further diagnosis and therapy. We developed a novel strategy for efficient capture and in situ heterogeneous phenotype analysis of circulating tumor cells (CTCs) at the single-cell level based on surface-enhanced Raman scattering (SERS) fingerprint characteristics. Herein, a new microfluidic chip with lantern-like bypass structure was designed to capture CTCs by their large size from whole blood. Furthermore, two types of SERS-aptamer nanotags were fabricated, realizing spectral recognition of single CTCs in accordance with the surface membrane protein expression. Up to 84% of CTCs with a purity of 95% were captured from whole blood samples using the present SERS-aptamer based microfluidic chip at 20 μL min−1. The results showed that the proposed strategy can successfully identify HCC cell subtypes by SERS measurements, which was related to the clinical surface biomarkers. This may open a new avenue for serving as a powerful tool of cancer diagnosis and prognosis evaluation. [ABSTRACT FROM AUTHOR]

The simultaneous detection of multiple biomarkers plays an important role in the accurate diagnosis of cancer. In this study, we developed a novel, surface-enhanced Raman scattering (SERS)-based microfluidic device for the simultaneous detection of free prostate-specific antigen (f-PSA) and total PSA (t-PSA) markers. A fully automatic droplet-based microfluidic platform for the rapid and sensitive detection of f-PSA and t-PSA was designed. Magnetic immunocomplexes were aligned on one side of the channel using a permanent magnet embedded in the microfluidic device, and parent microdroplets containing magnetic immunocomplexes and supernatant solutions were split into two smaller daughter droplets at the Y-shaped junction of the channel. Then, Raman signals of sequential droplets including supernatant solutions were measured for the quantitative analysis of the PSA markers. Two parallel microfluidic channels were designed and fabricated for the simultaneous detection of f-PSA and t-PSA. Our results showed a good linear response for both PSA markers in the range from 0.05 to 100 ng mL −1 . The limits of detection were estimated to be below 0.1 ng mL −1 for both the f-PSA and t-PSA. This SERS-based assay in a microfluidic channel was completed in 10 min without any manual incubation and washing steps. Our method is a very promising clinical tool for PSA-based screening test of prostate cancer. [ABSTRACT FROM AUTHOR]

Acute myocardial infarction (AMI) is a serious disease with high mortality that afflicts many people around the world. The main cause of death from AMI was the inaccurate early diagnosis, which resulted from the medical treatment might be a delay. Therefore, it is crucial to achieve the rapid detection of AMI. The cardiac troponin I (cTnI) level in human serum may significantly increase as the myocardial membrane ruptured, and the creatine kinase-MB (CK-MB) was also associated with the AMI recurrence and the infarct size of myocardial infarction. Both of them are regarded as important cardiac biomarkers for the early diagnosis of AMI. Therefore, we chose these two cardiac biomarkers as indicators for simultaneous detection. We proposed a single-track finger-pump microfluidic chip for simultaneous surface-enhanced Raman scattering (SERS) detection of cTnI and CK-MB. The entire detection process takes only 5 min without the cumbersome syringe pump. Meanwhile, it enables multiple reagent additions and removals of the unbonded reactants. This microfluidic sensor employed "sandwich" immunoassays based on SERS nanoprobes, AMI biomarkers, and magnetic beads. It is possible to detect two cardiac biomarkers simultaneously in a single measurement, greatly simplifying the detection process and reducing the detection time. Magnetic beads with SERS nanoprobes were separated and captured in the microchamber by a round magnet integrated into the chip. Our results showed that the detection limits of cTnI and CK-MB could reach to 0.01 ng mL−1, respectively. The limit of detections (LODs) match with the clinical threshold values for AMI biomarkers. It is believed that the proposed single-track finger-pump microfluidic chip can be used as an effective tool for determining early AMI. [Display omitted] • A SERS-based finger-pump microfluidic chip is demonstrated to achieve the detection of dual AMI biomarkers. • The integration of two check microvalves can ensure single-track flow for multiple reagent additions on chip. • The simultaneous detections were conducted in single measurement by identifying dual SERS nanoprobes. • The cTnI and CK-MB biomarkers were detected by SERS and the detection limit could reach to 0.01 ng mL−1. [ABSTRACT FROM AUTHOR]

We report the application of a fully automated surface-enhanced Raman scattering (SERS)-based solenoid-embedded microfluidic device to the quantitative and sensitive detection of anthrax biomarker poly-γ- d -glutamic acid (PGA) in solution. Analysis is based on the competitive reaction between PGA and PGA-conjugated gold nanoparticles with anti-PGA-immobilized magnetic beads within a microfluidic environment. Magnetic immunocomplexes are trapped by yoke-type solenoids embedded within the device, and their SERS signals were directly measured and analyzed. To improve the acccuracy of measurement process, external standard values for PGA-free serum were also measured through use of a control channel. This additional measurement greatly improves the reliability of the assay by minimizing the influence of extraneous experimental variables. The limit of detection (LOD) of PGA in serum, determined by our SERS-based microfluidic sensor, is estimated to be 100 pg/mL. We believe that the defined method represents a valuable analytical tool for the detection of anthrax-related aqueous samples. [ABSTRACT FROM AUTHOR]

In this study, we reported a novel highly ordered nano-micro hierarchical structure on flexible polydimethylsiloxane (PDMS) layer as a SERS stamp for ultrasensitive detection, which can generate huge SERS signals with silver nanoparticles (AgNPs) owing to a multiscale coupling electromagnetic enhancement mechanism. Highly ordered nanowrinkles were prepared by oxygen plasma and stretching treatment of PDMS. Indeed, a tactfully designed zigzag micropattern can efficiently reduce the fracture defects of nanowrinkles because the contraction force can be lessened at releasing step. This proposed substrate has high reproducibility and uniformity that the relative standard deviation (RSD) was below 7 %. With uniform hot spots on this novel flexible SERS substrate, 2, 4, 6-trinitrotoluene (TNT) residues can be detected on coarse surfaces of target item. A molecule interaction mechanism of Meisenheimer complex was applied to combine AgNPs and nanowrinkles for highly sensitive detecting TNT. The detection sensitivity of TNT molecules can achieve a limit of 10−13 mol L−1. Additionally, a practical application was proceeded by wiping the cloth bag to detect the TNT residues with a limit of 10−9 mol L−1. This demonstrated stamp-like flexible substrate showed unique SERS activity and non-invasive sampling, it is expected to be a promising tool for the explosive, drug and environmental pollutant in field-detection. [ABSTRACT FROM AUTHOR]

We fabricate a novel light trapping induced wrinkled nanocone SERS substrate on flexible and transparent PET film for highly sensitive TNT detection based on Meisenheimer complex. • We report a novel light trapping induced wrinkled nanocone SERS substrate on flexible and transparent PET film. • Highly sensitive TNT detection employed the electromagnetic coupling effect based on Meisenheimer complex. • This flexible substrate can be widely used to detect analytes on irregular or rough surface of the suspicious items. We reported an ultrasensitive TNT detection method via a novel light trapping induced wrinkled nanocone flexible SERS substrate, which was fabricated by colloidal lithography and oxygen plasma etching on transparent PET film. Especially, a set of nanowrinkles with 50−60 nm was found on the sidewall of nanocone after etching. By coating 30 nm gold film, this flexible SERS substrate provided uniform hot spots, which demonstrated high reproducibility and sensitivity. 4-ATP molecules based Meisenheimer complex, which is a well-known charge-transfer interaction between electron-poor TNT and electron-rich amino group, was taken to detect ultra-low concentration of TNT explosive. The Raman signal of TNT was significantly enhanced by charge-transfer, light trapping effect and coupled electromagnetic field. The detection sensitivity of TNT molecules was as low as 10−13mol/L, and show a good linear response in the range from 10−8 to 10−13mol/L. Consequently, by brushing this flexible SERS substrate onto a cloth bag, trace amount of TNT residues with concentration as low as 10-10mol/L can be easily analyzed. It is believed that the proposed highly sensitive and uniform flexible substrate provides a significant solution for trace analysis of TNT residue in criminal forensic, military and security check. [ABSTRACT FROM AUTHOR]

Precise and specific miRNA detection plays a vital role in exploring development mechanisms of cancer disease, thereby it can significantly improve relevant prevention and treatment strategies. In this work, a surface-enhanced Raman spectroscopy (SERS)-based microfluidic chip has been devised with a microcone array SERS substrate (MCASS) for the miR-141 detection. This substrate excels in unique SERS activity and large surface area for DNA oligonucleotide modification. As the presence of miR-141, the DNAzyme walker induced cleavage reaction took place on the finely designed and prepared dual DNA conjugated SERS nanoprobes. The SERS nanoprobes can anchor on MCASS by the DNA hybridization that achieved an impressive detection limit in the femtomolar level. With this integrated SERS-based microfluidic chip, we provided a miRNA detection strategy using DNAzyme walker amplification technology. It is believed that this strategy could be a powerful tool for miRNA detection and related cancer screening test. [Display omitted] • DNAzyme walker induced SERS nanoprobes in microfluidic channel was firstly demonstrated for miRNA detection. • The newly fabricated MCASS featured as SERS substrate and its large surface area that can improve DNA modifications. • The Raman signals of the target were enhanced by MCASS substrates and SERS nanoprobes together. • The miR-141 was successfully detected with high sensitivity and selectivity. [ABSTRACT FROM AUTHOR]

We reported a novel multifunctional nanocone array as solid immunoassay plate and surface-enhanced Raman scattering (SERS) substrate for the simultaneous immunoassay of prostate-specific antigen (PSA) and thrombin based on microfluidic chip. In traditional immunoassays, microtiter plates are often used as solid capture plates to form immunocomplexes. However, the two-dimensional surface of the microtiter plate limits the efficiency of target antigen capture due to its steric inhibition. To solve this problem, a nanocone array covered with deposited gold film was successfully fabricated on glass slides that could be directly sealed with PDMS microfluidic chip. As a SERS active substrate, it can also provide a large surface area for capture aptamer conjugation to form a "sandwich" immunocomplex. On the strength of this integrated microfluidic chip, we could detect PSA and thrombin simultaneously with the detection limits of 0.01 ng mL−1 and 0.01 nM. Compared to previous reports, this detection strategy demonstrated the rapid and automatic performance with comparable detection limits. It is believed that the proposed microfluidic sensor has great potential for the early diagnosis of prostate cancer. • A novel SERS-based microfluidic sensor was proposed to achieve the detection of dual prostate cancer markers. • The unique nanocone array with nanoscale wrinkles acted as the solid capture plate and SERS substrate for immunoassay. • The SERS substrate can further enhance the Raman signal of SERS nanotags by the link of "sandwich" immunocomplexes. [ABSTRACT FROM AUTHOR]