Optical fiber surface plasmon resonance sensor using electroless-plated gold film for thrombin detection.

This paper describes the simple and label-free detection of thrombin using optical fiber surface plasmon resonance (SPR) sensors based on gold films prepared by the cost-effective method of electroless plating. The plating conditions for simultaneously obtaining gold film on cylindrical core and end surfaces of an optical fiber suitable for measurement were optimized. The fabricated sensor exhibited a linear refractive index sensitivity of 2150 nm/RIU and 7.136 (a.u.)/RIU in the refractive index of 1.3329-1.3605 interrogated by resonance wavelength and amplitude methods respectively and a single wavelength monitoring method was proposed to investigate the sensing performance of this sensor. Polyadenine diblock and thiolated thrombin aptamers were immobilized on gold nanoparticles and gold films respectively to implement a sandwich optical fiber assay for thrombin. The developed optical fiber SPR sensors were successfully used in the determination of thrombin down to 0.56 nM over a wide range from 2 to 100 nM and showed good selectivity for thrombin, which indicated their potential clinical applications for biomedical samples.

Data mining and spatio-temporal characteristics of urban road traffic emissions: A case study in Shijiazhuang, China.

Accurate estimation of traffic emissions and analysis of spatio-temporal distribution on urban roads play a crucial role in the development of low-carbon transportation system. Traditionally, a region's emission characteristics have been studied using numerous emission models with GPS-based spatio-temporal data. Due to the heavy data processing needs of GPS-based data, emission characteristics for a large region have been studied by dividing the region into a limited number of smaller areas or units. Additionally, GPS data are based on a few vehicles in the traffic which does not fully reflect road conditions. This paper proposed an approach that can be used to study and calculate the spatio-temporal emission pattern of a region at a roadway section level by using Baidu's online traffic data and COPERT model. The proposed method can be used to estimate road-level emission patterns while avoiding the impact of redundant data in large datasets, making the dataset more reliable, applicable, and scalable. The proposed approach has been demonstrated through a study of spatio-temporal emission patterns in the Qiaoxi district within city of Shijiazhuang, China. Online data crawling technology was used to obtain data on urban road traffic speed and driving distance. The linear reference technology was used to construct a two-layer road network model to conduct the coupling and matching of traffic data with the road network data. The COPERT model was implemented to calculate the average traffic emissions on each road in the road network, and a traffic emission intensity index was proposed to quantify the CO, VOC, NOx and CO2 emissions on urban roads in the study area. The analysis results show that the traffic emission intensity of the expressway, trunk road, secondary road, and branch road is high during the morning peak (7 AM-9 AM) and evening peak (5 PM-7 PM). The sections with higher traffic emission intensity are mainly concentrated on the main roads and secondary roads such as Jiefang South Street, Shitong Road and Xinhua Road. Nearly one-third of 2nd Ring and 3rd Ring roads also have relatively high emission intensity. The research results provide new ideas for estimating traffic emissions in urban road networks and analyzing the spatio-temporal distribution of traffic emissions. The research results can also provide a decision-making basis for traffic management departments to formulate energy-saving and emission-reduction measures and promote the development of urban green and low-carbon transportation.

Series or parallel toehold-mediated strand displacement and its application in circular RNA detection and logic gates.

Toehold-mediated strand displacement (TMSD) is widely employed in constructing a wide range of chemical reaction networks. In TMSD, single-stranded DNA or RNA can fold back upon itself to form a local short double-strand structure often hindering bimolecular hybridization. Here, based on series and parallel circuits, we introduce two mechanisms: series toehold-mediated strand displacement (STMSD) and parallel toehold-mediated strand displacement (PTMSD). These mechanisms can be highly effective when the target area is blocked by a secondary structure. In addition, these systems allow regulating the reaction rates spanning three to five orders of magnitude by adjusting the length of the two toeholds with the added advantage of multifunctional regulation and selectivity. To demonstrate the impressive function of this approach, a logic operation system based on STMSD was constructed to simulate the signal processing of a half-adder. We believe that the introduction of series and parallel toeholds will provide design flexibility contributing to the development of molecular computers, molecular robotics, and DNA-based biosensors.

CPA-Cas12a-based lateral flow strip for portable assay of Methicillin-resistant Staphylococcus aureus in clinical sample.

The rapid and accurate identification of methicillin-resistant Staphylococcus aureus at an early antibiotic therapy stage would be benefit to disease diagnosis and antibiotic selection. Herein, we integrated cross-priming amplification (CPA) and CRISPR/Cas 12a (designated as CPA-Cas 12a) systems to establish a sensitive and efficient lateral flow assay to detect methicillin-resistant Staphylococcus aureus. This assay relies on the CPA isothermal nucleic acid amplification strategy which can amplify the DNA extracted from Staphylococcus aureus and accompanying the indiscriminately trans-cleavage process of Cas 12a/CrRNA duplex after recognizing specific sequence. Taking the advantage of reporter and high turnover Cas 12a activity, a dramatic change in response was achieved to produce a significant increase in the analytical sensitivity. The signal conversion and output were realized using a lateral flow strip to achieve field-deployable detection. Furthermore, this bioassay was accommodated with a microfluidic device to realize automatically portable detection. This proposed assay completed within 30 min with the detection limit of 5 CFU mL-1, was verified by testing bacterial suspension and 202 clinical samples. Given the high sensitivity, specificity and efficiency, this colorimetric readout assay through strip could be further promoted to the clinical diagnosis, clinical medication of multidrug-resistant bacteria.

Electrochemical Biosensor for Detection of the CYP2C19*2 Allele Based on Exonuclease â ¢.

Currently, the therapeutic effect of clopidogrel differs considerably among individuals and is thought to be closely related to the genetic polymorphism of CYP2C19. The CYP2C19*2 gene can reduce the antiplatelet aggregation effect of clopidogrel, which increases the risk of major cardiovascular adverse events in patients. In this research, we report a new type of biosensor for the highly sensitive detection of the CYP2C19*2 gene based on exonuclease III assisted electric signal amplification and the use of calixarene to enrich electrical signal substances. Specifically, under the best conditions, the logarithmic concentrations of the analytes have a good linear relationship with the peak current in the range of 0.01 fM to 100 pM and the detection limit is 13.49 aM. The results have also shown that this method has good selectivity, high sensitivity, and stability, etc., and will provide a very promising application for the detection of the CYP2C19*2 gene and other biological molecules by replacing corresponding nucleic acid sequences.

Detection of carcinoembryonic antigens using a wavy gold-silver alloy nanoplate enhanced surface plasmon resonance imaging biosensor.

Carcinoembryonic antigen (CEA) is regarded as a promising broad spectrum tumor biomarker for clinical diagnosis, progression, and prognosis. Surface plasmon resonance imaging (SPRi) was considered as one of the powerful tools for immunoassay with advantages of label-free, real-time detection with high-throughput. Herein, wavy gold-silver alloy nanoplates functionalized with anti-CEA antibodies providing high protein loading capacity and high mass are used as signal enhancers for CEA detection through SPRi sandwich assay. The present method exhibits a dynamic range for CEA determination from 0.1 to 312.5 ng mL-1 and a detection limit of 0.55 ng mL-1, well below normal physiological levels. This biosensing approach demonstrates the advantages of wavy gold-silver alloy nanoplates compared to conventional gold nanoparticles as a signal amplifier to enhance the SPRi signal, which is expected to become a new prospect for detection of cancer markers in biomedical research and clinical diagnosis.

An exploratory study on the checkout rate of circulating tumor cells and the prediction of efficacy of neoadjuvant therapy and prognosis in patients with HER-2-positive early breast cancer.

Background: Neoadjuvant therapy is a standard treatment for patients with large, nonmetastatic breast cancer and may allow breast-conserving surgery after tumor downsizing while decreasing the risk of subsequent relapse. Dynamic changes of circulation tumor cells (CTCs) have a role in predicting treatment efficacy of breast cancer. However, the relationship between CTC enumeration before neoadjuvant therapy and pathologic complete response rate is still uncertain. Methods: The study was exploratory. A total of 50 breast cancer patients were enrolled in a phase II clinical study of neoadjuvant therapy for HER-2-positive early breast cancer. They were enrolled for blood draws before and after neoadjuvant therapy. We used two methods (CellSearch and TUMORFISH) to detect CTCs. We compared the sensitivity of the two systems and investigated the correlation of the enumeration on baseline CTCs with the diagnosis, prognosis, and efficacy of neoadjuvant therapy of the patients with HER-2-positive early breast cancer. We also explored the dynamic change of CTCs after neoadjuvant therapy. Results: The sensitivity of TUMORFISHER (27/50) method was significantly higher than that of the CellSearch system (15/50, p=0.008). The CTC numbers detected by the two detection systems were not significantly correlated with lymph node status, clinical stage, ki-67 level and hormone receptor status. Patients with ≥1 CTC before neoadjuvant therapy measured by the TUMORFISHER system had a significant high pCR rate (74.1% vs. 39.1%, p = 0.013); whereas, there was no predictive effect on pCR by CellSearch system (73.3% vs. 51.4%, p = 0.15). Patients with a decrease in CTCs enumeration after neoadjuvant therapy were more likely to achieve pCR than those with no change or increase in CTCs enumeration (87.5% vs 50.0%, p = 0.015) by the TUMORFISHER method. Unfortunately, there was no predictive value of CTCs enumeration for EFS before and after neoadjuvant therapy by two methods. Conclusions: Our study demonstrates that the new CTCs detection method TUMORFISHER system has a higher checkout rate in early breast cancer than the CellSearch system, and shows the opportunity of CTC enumeration as a novel assistant biomarker to predict the response of neoadjuvant therapy in patients with HER-2-positive early breast cancer.

Functionalized Mn3 O4 Nanosheets with Photothermal, Photodynamic, and Oxidase-Like Activities Triggered by Low-Powered Near-Infrared Light for Synergetic Combating Multidrug-Resistant Bacterial Infections.

Multidrug-resistant (MDR) pathogenic bacterial infections have become a major danger to public health. Synergetic therapy through multiple approaches is more powerful than the respective one alone, but has been rarely achieved in defeating MDR bacterial infections so far. Herein, indocyanine green-functionalized Mn3 O4 nanosheets are engineered as an efficient and safe antibacterial agent with photothermal, photodynamic, and oxidase-like activities, which display powerful ability in treating MDR bacterial infections. Therein, photothermal and photodynamic activities can be triggered by a single low-powered near-infrared laser (808 nm, 0.33 W cm-2 ), resulting in the generation of localized hyperthermia (photothermal conversion efficiency, 67.5%) and singlet oxygen. Meanwhile, oxidase-like activity of this material further leads to the generation of hydroxyl radical as well as superoxide radical. Sheet-like structure with rough surfaces make them tends to adhere on bacterial surface and thus damage membrane system as well as influence bacterial metabolism. As a result, Gram-positive and Gram-negative bacteria can both be eradicated. Animal experiments further indicate that the functionalized Mn3 O4 nanosheets can effectively treat methicillin-resistant Staphylococcus aureus-infected wounds through the triple synergetic therapy. Moreover, toxicity evaluation in vitro and in vivo has proved the superior biosafety of this material, which is promising to apply in clinical anti-infective therapy.

Negatively Charged Sulfur Quantum Dots for Treatment of Drug-Resistant Pathogenic Bacterial Infections.

Drug-resistant pathogenic bacteria as a worldwide health threat calls for valid antimicrobial agents and tactics in clinical practice. Positively charged materials usually achieve antibacteria through binding and disrupting bacterial membranes via electrostatic interaction, however, they also usually cause hemolysis and cytotoxicity. Herein, we engineered negatively charged sulfur quantum dots (SQDs) as an efficient broad-spectrum antibiotic to kill drug-resistant bacteria in vitro and in vivo. The SQDs can destroy the bacterial membrane system and affect their metabolism due to the intrinsic antibacterial activity of elemental sulfur and catalytic generation of reactive oxygen species, which exhibit effective therapeutic effect on subcutaneously implanted infection model induced by representative pathogenic Methicillin-resistant Staphylococcus aureus and Pseudomonas aeruginosa. Plus, the negatively charged surface makes the SQDs have excellent hemocompatibility and low toxicity, which all highlight the critical prospect of the SQDs as a potent biocompatible antibacterial agent in clinical infection therapy.

A simple signal-on strategy for fluorescent detection of tuberculostatic drug isoniazid based on Ag clusters-MnO2 sheets nanoplatform.

As a first-line tuberculostatic drug, isoniazid (INH) plays effective and irreplaceable role in prevention and treatment of tuberculosis. In this work, a rapid and simple signal-on fluorescence approach is established for INH assay by employing a platform composed of silver nanoclusters (AgNCs) and MnO2 nanosheets. In the proposed sensing system, strong red fluorescence of poly (methacrylic acid)-stabilized AgNCs can be greatly quenched after they attach to the surfaces of MnO2 nanosheets. With the addition of INH, MnO2 nanosheets are reduced to Mn2+ and subsequently release the AgNCs, which leads to obvious fluorescence recovery again. Based on this mechanism, highly sensitive detection of INH in the range of 0.8-200 µM is realized (detection limit: 476 nM). The present strategy shows remarkable advantages including simplicity, rapidness, high sensitivity and wide detectable range. This method is also practical and comparable to high-performance liquid chromatography, which can be applied to detect INH in human urine and serum samples as well as pharmaceutical products.

Surface plasmon resonance imaging-based biosensor for multiplex and ultrasensitive detection of NSCLC-associated exosomal miRNAs using DNA programmed heterostructure of Au-on-Ag.

Exosomal miRNAs are potential tumor biomarkers for early diagnosis of non-small cell lung cancer (NSCLC). Herein, a surface plasmon resonance imaging (SPRi)-based biosensor was developed for simultaneous detection of multiplex NSCLC-associated exosomal miRNAs in a clinical sample using Au-on-Ag heterostructure and DNA tetrahedral framework (DTF). Exosomal miRNAs are captured by various DTF probes immobilized on the gold array chip. Subsequently, single-stranded DNA (ssDNA) functionalized silver nanocube (AgNC) hybridizes with the captured exosomal miRNAs and then the ssDNA-coated Au nanoparticles assembled on the surface of AgNC, forming Au-on-Ag heterostructures as essential labels to realize amplified SPR response. With the aid of DNA programmed Au-on-Ag heterostructure and DTF, the SPRi-based biosensor exhibits wide detection range from 2 fM to 20 nM, ultralow limit of detection of 1.68 fM, enhanced capture efficiency, and improved antifouling capability. Furthermore, the biosensor enables accurate discrimination of NSCLC patients based on detection results of exosomal miRNAs. Overall, this developed biosensor is a promising tool for multiplex exosomal miRNAs detection, providing a new possibility for early diagnosis of NSCLC.

Etching-controlled suppression of fluorescence resonance energy transfer between nitrogen-doped carbon dots and Ag nanoprisms for glucose assay and diabetes diagnosis.

Numerous methods have been developed for glucose detection, only few cases can be really applied in clinical diagnosis. Herein, we report a new approach to achieve the detection of glucose in clinical samples and distinguishing the diabetic patients with healthy ones. Specifically, a fluorescence resonance energy transfer (FRET) system is established first, where nitrogen-doped carbon dots (N-CDs) and Ag nanoprisms (AgNPRs) with good spectral overlap act as energy donor and acceptor, respectively. Then, the FRET can be inhibited through oxidative etching of the energy acceptor in the presence of glucose and glucose oxidase, where hydrogen peroxide is generated to transform AgNPRs into Ag+ ions. Based on the turn-on fluorescent signal versus glucose concentration, a new method for quantitative detection of glucose is developed. This etching-induced analytical method is simple, reliable, robust and cost-effective, which is promising to assist the doctors to clinically diagnose diabetes and other diseases related to metabolic disorders.

High-sensitive and multiplex biosensing assay of NSCLC-derived exosomes via different recognition sites based on SPRi array.

Non-small cell lung cancer (NSCLC) have been reported to secret a high concentration of exosomes into blood circulatory system, which is one of sensitive and non-invasive biomarkers for NSCLC's early-stage diagnosis. But it is still lack of feasible and accurate methods to analyze the different NSCLC cells-derived exosomes. Herein, we built a SPRi biosensing assay for high-sensitive and multiplex characterizations of NSCLC-derived exosomes by bioaffinity interactions of antibodies and different recognition sites. By this way, the exosomes derived from normal lung and NSCLC cells can be effectively distinguished through precise identification of the exosomal protein pattern. And the multiplex characterizations of NSCLC-related exosomes are also achieved by anti-CD63, anti-EGFR and anti-EpCAM modified SPRi array. The limit of detection (LOD) of this SPRi-based biosensor approaches to the level of 104 particles/µL with the help of functionalized gold nanoparticles. Besides, the developed biosensing assay was successfully applied in the determination of exosomes purified from clinical plasma samples. This SPRi biosensing strategy might offer a potential alternative for massive high-throughput screening for NSCLC in clinical specimens.

A multifunctional DNA nano-scorpion for highly efficient targeted delivery of mRNA therapeutics.

The highly efficient cancer cell targeted delivery plays an important role in precise targeted therapies. Herein, a multifunctional DNA nano-scorpion nanostructure (termed AptDzy-DNS) functioned with aptamers and DNAzyme is developed for highly efficient targeted delivery of mRNA therapeutics in gene therapy. The designed AptDzy-DNS is self-assembled with specific aptamers as "scorpion stingers" for targeting tumor cell and DNAzymes as "scorpion pincers" for targeted gene therapy by cleaving mRNA into fragments. The as-prepared AptDzy-DNS can effectively distinguish cancer cells from normal cells by specific cross-talking between aptamers on AptDzy-DNS and overexpressed cell-surface receptors. In the process of gene therapy, by reacting with Mg2+-dependent DNAzyme on AptDzy-DNS, the mRNA oligonucleotide in cancer cell is auto-cleaved into broken strand, failing to be translated into corresponding protein. Following, the downregulation protein can block cancer cell growth and realize highly efficient targeted therapies. The results demonstrate that the multifunctional AptDzy-DNS shows promise for targeted cancer cell discrimination, highly efficient targeted delivery of mRNA therapeutics in gene therapy. Thus, this developed strategy provides impressive improvement on gene targeted therapy and paves the way for application of AptDzy-DNS in human cancer targeted therapies.

A highly sensitive SPRi biosensing strategy for simultaneous detection of multiplex miRNAs based on strand displacement amplification and AuNP signal enhancement.

Herein, a dual channel surface plasmon resonance imaging (SPRi) biosensor has been developed for the simultaneous and highly sensitive detection of multiplex miRNAs based on strand displacement amplification (SDA) and DNA-functionalized AuNP signal enhancement. In the presence of target miRNAs (miR-21 or miR-192), the miRNAs could specifically hybridize with the corresponding hairpin probes (H) and initiate the SDA, resulting in massive triggers. Subsequently, the two parts of the released triggers could hybridize with capture probes (CP) and DNA-functionalized AuNPs, assembling DNA sandwiches with great mass on the chip surface. A significantly amplified SPR signal readout was achieved. This established biosensing method was capable of simultaneously detecting multiplex miRNAs with a limit of detection down to 0.15 pM for miR-21 and 0.22 pM for miR-192. This method exhibited good specificity and acceptable reproducibility. Moreover, the developed method was applied to the determination of target miRNAs in a complex matrix. Thus, this developed SPRi biosensing method may present a potential alternative tool for miRNA detection in biomedical research and clinical diagnosis.

Mixed-solvent liquid exfoliated MoS2 NPs as peroxidase mimetics for colorimetric detection of H2O2 and glucose.

Ultra-small molybdenum disulfide nanoparticles (MoS2 NPs) were prepared by a facile liquid exfoliation method with ethanol/water as the solvent. The produced MoS2 NPs were of high purity due to the easily removable ethanol/water solution. The prepared MoS2 NPs exhibited an intrinsic peroxidase-like activity in analogy to that of horseradish peroxidase (HRP). A custom-made spectrometer was employed to investigate the peroxidase-like activity of MoS2 NPs in the presence of H2O2 and glucose. The change in absorption detected from MoS2 NPs is proportional to the amount of target. The calibration curve of H2O2 and glucose shows a good relationship between the concentration of target and the change in the absorption of MoS2 NPs. The limit of detection of H2O2 and glucose achieved by this method could approach 1.25 µM and 7 µM respectively. This method has been applied for the detection of glucose in serum from humans. Therefore, these produced MoS2 NPs offer an alternative high-efficiency and economic way to detect diabetes.

An enzyme-free surface plasmon resonance biosensing strategy for detection of DNA and small molecule based on nonlinear hybridization chain reaction.

A label-free and enzyme-free surface plasmon resonance (SPR) biosensing strategy has been developed for highly sensitive and specific detection of target DNA by employing the nonlinear hybridization chain reaction (HCR) amplification. Nonlinear HCR is a hairpin-free system in which double-stranded DNA monomers could dendritically assemble into highly branched nanostructure upon introducing a trigger sequence. The target DNA partly hybridizes with capture probe on the gold sensing chip and the unpaired fragment of target DNA works as a trigger to initiate the nonlinear HCR, forming a chain-branching growth of DNA dendrimer by self-assembly. Real-time amplified SPR response is observed upon the introduction of nonlinear HCR system. The method is capable of detecting target DNA at the concentration down to 0.85 pM in 60min with a dynamic range from 1 pM to 1000 pM, and could discriminate target DNA from mismatched sequences. This biosensing strategy exhibits good reproducibility and precision, and has been successfully applied for detection of target DNA in complex sample matrices. In addition, the nonlinear HCR based SPR biosensing methodology is extended to the detection of adenosine triphosphate (ATP) by aptamer recognition. Thus, the versatile method might become a potential alternative tool for biomolecule detection in medical research and early clinical diagnosis.

A novel surface plasmon resonance biosensor for enzyme-free and highly sensitive detection of microRNA based on multi component nucleic acid enzyme (MNAzyme)-mediated catalyzed hairpin assembly.

MicroRNAs (miRNAs) are potentially useful biomarkers for early diagnosis of human diseases. Here, a simple surface plasmon resonance (SPR) biosensor has been developed for highly sensitive detection of miRNA by designing a new enzyme-free and isothermal amplification strategy, named multi component nucleic acid enzyme-mediated mismatched catalyzed hairpin assembly (MNAzyme-CHA). The partial MNAzymes co-recognized the target to form a stable active MNAzyme, which continued to digest multiple hairpin H0 substrates, concomitantly generating a lot of fragments. The H0 fragments could initiate the mismatched CHA cycles, resulting in the generation of massive hairpin H1-H2 complexes. As a result, the H1-H2 complexes and streptavidin were attached to the sensor surface, leading to a significantly amplified SPR signal readout. The established biosensor showed high sensitivity and selectivity with a wide dynamic range from 1 pM to 100 nM. It was also successfully applied to the determination of target miRNA spiked into human total RNA samples. Thus, this developed biosensing strategy presents a simple and stable platform toward sensitive and convenient miRNA detection, and has great potential in assays of many other nucleic acids analytes for biomedical research and early clinical diagnosis.