Multiple reaction monitoring for the detection of disease-related synaptic proteins

Synaptic dysfunction occurs early in Alzheimer＇s disease （AD） and is acknowledged as a primary pathologic target for treatment. Synaptic degeneration is the pathological feature most strongly correlated with loss of cognitive function ante mortern （Terry et al., 1991）. Synapses are heavily damaged in hippocampal and neocortical regions of AD brain, whereas motor and occipital cortices are relatively spared （Honer et al., 1992）. Despite extensive work, the molecular mechanisms underlying synaptic degeneration are largely unknown.

Gold Nanoparticles/Thermochromic Composite Film on Screen-Printed Electrodes for Simultaneous Detection of Protein and Temperature

In this study, gold nanoparticles and thermochromic composite films modified screen-printed carbon electrodes (TM-AuNPsSPCEs) were developed as a platform for the simultaneous detection of protein and temperature. The TM-AuNPs composited film had better sensitivity resulting from the gold nanoparticles amplification effect. A phase transition model analysis of TM-AuNPs films found that the TM-AuNPs films had three-phase transition intervals (<45℃, 45℃ to 80℃ and >80℃) which accommodated the temperature requirements for protein denaturation. When used to detect different concentrations of haemoglobin (Hb) solution, the TM-AuNPs modified SPCEs had a better sensitivity in detecting the different concentrations in comparison to TM and AuNP modified SPCEs which showed no clear sensitivity towards the different Hb concentrations. The dual detection and excellent sensitivity show a good application prospect for the study of the TM-AuNPs composite film.

Comparison between Two Methods for Detecting Gene Flow and Analysis on the Influencing Factors

[Objective] The aim was to test the consistency between two commonly used methods PCR detection and protein detection for detecting gene flow,and investigate the factors influencing the consistency.[Method] 1 769 samples of three varieties under three treatments（wind,bee and control）were detected with both methods.[Result] There was phenomenon in field that Bt gene was transferred into F1 generations but couldn＇t express,that meant,the result of PCR detection was not consistent with that of protein detection.By comparing environmental factors,it was proved that wind and bee treatments didn＇t significantly affect the expression of gene flow.However,the Bt gene expression rate in bee treatment was higher than that in wind treatment.[Conclusion] The paper will provide reference for accurate detection of gene flow.

Aptamer-based cell-free detection system to detect target protein

Biomarkers of disease,especially protein,show great potential for diagnosis and prognosis.For detecting a certain protein,a binding assay implementing antibodies is commonly performed.However,antibodies are not thermally stable and may cause false-positive when the sample composition is complicated.In recent years,a functional nucleic acid named aptamer has been used in many biochemical analysis cases,which is commonly selected from random sequence libraries by using the systematic evolution of ligands by exponential enrichment(SELEX)techniques.Compared to antibodies,the aptamer is more thermal stable,easier to be modified,conjugated,and amplified.Herein,an Aptamer-Based Cell-free Detection(ABCD)system was proposed to detect target protein,using epithelial cell adhesion molecule(EpCAM)as an example.We combined the robustness of aptamer in binding specificity with the signal amplification ability of CRISPR-Cas12a′s trans-cleavage activity in the ABCD system.We also demonstrated that the ABCD system could work well to detect target protein in a relatively low limit of detection(50-100 nM),which lay a foundation for the development of portable detection devices.This work highlights the superiority of the ABCD system in detecting target protein with low abundance and offers new enlightenment for future design and development.

Electrochemical aptasensor for the detection of vascular endothelial growth factor(VEGF) based on DNA-templated Ag/Pt bimetallic nanoclusters

In this paper, the DNA-templated Ag/Pt bimetallic nanoclusters were successfully synthesized using an optimized synthetic scheme. The obtained DNA-Ag/Pt NCs have an ultrasmall particle size and excellent distribution. The DNA-Ag/Pt NCs show intrinsic peroxidase-mimicking activity and can effectively catalyze the H2O2-mediated oxidation of a substrate, 3,30,5,50-tetramethylbenzidine（TMB）, to produce a blue colored product. Based on this specific property, we employed the aptamer of VEGF to design a label-free electrochemical biosensor for VEGF detection. Under the optimized experimental conditions, a linear range from 6.0 pmol/L to 20 pmol/L was obtained with a detection limit of 4.6 pmol/L. The proposed biosensor demonstrated its high specificity for VEGF and could directly detect the VEGF concentration in human serum samples of breast cancer patients with satisfactory results. This novel electrochemical aptasensor was simple and convenient to use and was cost-effective and label-free in design, and would hold potential applications in medical diagnosis and treatment.

Highly Sensitive Protein Sensor Based on Thermally-Reduced Graphene Oxide Field-Effect Transistor

We report the fabrication of a highly sensitive field-effect transistor （FET） biosensor using thermally-reduced graphene oxide （TRGO） sheets functionalized with gold nanoparticle （NP）-antibody conjugates. Probe antibody was labeled on the surface of TRGO sheets through Au NPs and electrical detection of protein binding （Immunoglobulin G/IgG and anti-lmmunoglobulin G/anti-lgG） was accomplished by FET and direct current （dc） measurements. The protein binding events induced significant changes in the resistance of the TRGO sheet, which is referred to as the sensor response. The dependence of the sensor response on the TRGO base resistance in the sensor and the antibody areal density on the TRGO sheet was systematically studied, from which a correlation of the sensor response with sensor parameters was found： the sensor response was more significant with larger TRGO base resistance and higher antibody areal density. The detection limit of the novel biosensor was around the 0.2 ng/rnL level, which is among the best of,＇eported carbon nanomaterial-based protein sensors and can be further optimized by tuning the sensor structure.

Electrochemical detection of human ferritin based on gold nanorod reporter probe and cotton thread immunoassay device

In this study,a natural cotton thread immunoassay device combined with gold nanorod（GNR） reporter probe is developed for the rapid,sensitive and quantitative electrochemical determination of human ferritin,a lung cancer related biomarker.Human ferritin as an analyte and a pair of monoclonal antibodies are used to demonstrate the proof-of-concept on the cotton thread immunoassay device.An enhancement of the sensitivity is achieved by using gold nanorod as an electroactive report probe compared with a traditional gold nanoparticle（GNP） report probe.The device was capable of measuring 1.58 ng/mL ferritin in 30 min by anodic stripping voltammetry（ASV） testing,which meet the requirement for clinical diagnosis.

Crosstalk-free colloidosomes for high throughput single-molecule protein analysis

Droplet microfluidics is a powerful platform for high-throughput single-molecule protein analysis.However,the issues of coalescence and crosstalk of droplets compromise the accuracy of detection and hinder its wide application.To address these limitations,a novel colloidosome-based method was presented by combining a Pickering emulsion with droplet microfluidics for single-molecule protein analysis.Utilizing the self-assembly of easily synthesized colloidal surfactant F-SiO2 NPs at the water/oil interface,the colloidosomes are rigidly stabilized and can effectively avoid the leakage of fluorescent molecules.The crosstalk-free colloidosomes enable high-throughput single-molecule protein analysis,including heterogenous dynamic studies and digital detection.As a robust and accurate method,colloidosome-based microfluidics is promising as a powerful tool for a wide variety of applications,such as directed enzyme evolution,digital enzyme-linked immunosorbent assay(ELISA),and screening of antibiotics.

CPL:Detecting Protein Complexes by Propagating Labels on Protein-Protein Interaction Network

Proteins usually bind together to form complexes, which play an important role in cellular activities. Many graph clustering methods have been proposed to identify protein complexes by finding dense regions in protein-protein interaction networks. We present a novel framework （CPL） that detects protein complexes by propagating labels through interactions in a network, in which labels denote complex identifiers. With proper propagation in CPL, proteins in the same complex will be assigned with the same labels. CPL does not make any strong assumptions about the topological structures of the complexes, as in previous methods. Tile CPL algorithm is tested on several publicly available yeast protein-protein interaction networks and compared with several state-of-the-art methods. The results suggest that CPL performs better than the existing methods. An analysis of the functional homogeneity based on a gene ontology analysis shows that the detected complexes of CPL are highly biologically relevant.

Enzyme-catalyzed deposition of polydopamine for amplifying the signal inhibition to a novel Prussian blue-nanocomposite and ultrasensitive electrochemical immunosensing

The uncontrollable synthesis of Prussian blue (PB) and its weak stability toward OH -are great challenges affecting its electrochemical biosensing application. Herein we utilize the unique properties of chitosan (CS) to realize the facile and controllable synthesis of a CS-PB nanocomposite and combine it with the urease-catalyzed deposition of polydopamine (PDA) for amplifying the electrochemical signal inhibition of PB to develop a novel immunosensing method for protein detection. The immunosensor was constructed on a CS-PB modified electrode, and a urease-functionalized silica nanoprobe was prepared for tracing its sandwich immunoassay toward the model analyte of carcinoembryonic antigen. Besides the electrochem- ical impedance effect of the quantitatively captured nanoprobes, their enzymatic reaction can release numerous OH -to destroy the PB crystals and also induce the PDA deposition onto the immunosensor. These caused drastic electrochemical signal inhibition to PB. Based on the above multi-signal amplification mechanism, the method exhibits a very low detection limit of 0.042 pg mL^(-1) along with a very wide linear range of six-order of magnitude. In addition, the CS-PB based immunosensor has excellent specificity, repeatability, stability and reliability. Thus this PB nanocomposite and the proposed electrochemical immunosensing method reveal a promising potential for future applications.

Phase-sensitive plasmonic biosensor using a portable and large field-of-view interferometric microarray imager

Nanophotonics,and more specifically plasmonics,provides a rich toolbox for biomolecular sensing,since the engineered metasurfaces can enhance light–matter interactions to unprecedented levels.So far,biosensing associated with high-quality factor plasmonic resonances has almost exclusively relied on detection of spectral shifts and their associated intensity changes.However,the phase response of the plasmonic resonances have rarely been exploited,mainly because this requires a more sophisticated optical arrangement.Here we present a new phase-sensitive platform for high-throughput and label-free biosensing enhanced by plasmonics.It employs specifically designed Au nanohole arrays and a large field-of-view interferometric lens-free imaging reader operating in a collinear optical path configuration.This unique combination allows the detection of atomically thin(angstrom-level)topographical features over large areas,enabling simultaneous reading of thousands of microarray elements.As the plasmonic chips are fabricated using scalable techniques and the imaging reader is built with low-cost off-the-shelf consumer electronic and optical components,the proposed platform is ideal for point-of-care ultrasensitive biomarker detection from small sample volumes.Our research opens new horizons for on-site disease diagnostics and remote health monitoring.