Au Chip Research Articles

Optimizing the SERS activity of PS@Ag/Au chips for quantitative analysis of carcinoembryonic antigen

Tumor markers play an important role in the diagnosis, treatment, and monitoring of tumors. Carcinoembryonic antigen (CEA) is a breast and rectal cancer biomarker that plays a crucial role in the early detection of cancer. Therefore, designing a suitable and ultrasensitive method for CEA analysis is very important. In this study, we demonstrated the high surface-enhanced Raman scattering (SERS) performance, high reproducibility, and good biocompatibility of a polystyrene (PS)@Ag/Au chip. This chip was produced layer-by-layer by magnetron sputtering to generate abundant “hotspots” between the Ag and Au layers covering the PS microspheres. Interestingly, the thickness of the Au layer was easily controlled to the appropriate value. When 4-mercaptobenzoic acid (MBA) was used as a probe molecule to explore the SERS activity of the chip, the enhancement factor (EF) reached 1.12×108, with a relative standard deviation of 3.059 %. A chip labeled with 5,5’-dithiobis(succinimidyl-2-nitrobenzoic acid) (DSNB) was used for CEA immunological recognition. With a linear range of 0–10,000 ng/mL, the limit of detection (LOD) was 0.0229 ng/mL. The standard recovery of CEA in fetal bovine serum (FBS) was between 84.90 % and 103.1 %. This chip is expected to be a novel tool in the field of cancer detection.

High-Frequency Quartz Crystal Microbalance and Dual-Signaling Electrochemical Ratiometric Assays of PTP1B Activity Based on COF@Au@Fc Hybrids.

The abnormal expression of protein tyrosine phosphatase 1B (PTP1B) is highly related to several serious human diseases. Therefore, an accurate PTP1B activity assay is beneficial to the diagnosis and treatment of these diseases. In this study, a dual-mode biosensing platform that enabled the sensitive and accurate assay of PTP1B activity was constructed based on the high-frequency (100 MHz) quartz crystal microbalance (QCM) and dual-signaling electrochemical (EC) ratiometric strategy. Covalent-organic framework@gold nanoparticles@ferrocene@single-strand DNA (COF@Au@Fc-S0) was introduced onto the QCM Au chip via the chelation between Zr4+ and phosphate groups (phosphate group of the phosphopeptide (P-peptide) on the QCM Au chip and the phosphate group of thiol-labeled single-stranded DNA (S0) on COF@Au@Fc-S0) and used as a signal reporter. When PTP1B was present, the dephosphorylation of the P-peptide led to the release of COF@Au@Fc-S0 from the QCM Au chip, resulting in an increase in the frequency of the QCM. Meanwhile, the released COF@Au@Fc-S0 hybridized with thiol/methylene blue (MB)-labeled hairpin DNA (S1-MB) on the Au NPs-modified indium-tin oxide (ITO) electrode. This caused MB to be far away from the electrode surface and Fc to be close to the electrode, leading to a decrease in the oxidation peak current of MB and an increase in the oxidation peak current of Fc. Thus, PTP1B-induced dephosphorylation of the P-peptide was monitored in real time by QCM, and PTP1B activity was detected sensitively and reliably using this innovative QCM-EC dual-mode sensing platform with an ultralow detection limit. This platform is anticipated to serve as a robust tool for the analysis of protein phosphatase activity and the discovery of drugs targeting protein phosphatase.

Real-time monitoring of dephosphorylation process of phosphopeptide and rapid assay of PTP1B activity based on a 100 MHz QCM biosensing platform

The misregulation of protein phosphatases is a key factor in the development of many human diseases, notably cancers. Here, based on a 100 MHz quartz crystal microbalance (QCM) biosensing platform, the dephosphorylation process of phosphopeptide (P-peptide) caused by protein tyrosine phosphatase 1B (PTP1B) was monitored in real time for the first time and PTP1B activity was assayed rapidly and sensitively. The QCM chip, coated with a gold (Au) film, was used to immobilized thiol-labeled single-stranded 5′-phosphate-DNAs (P-DNA) through Au–S bond. The P-peptide, specific to PTP1B, was then connected to the P-DNA via chelation between Zr4+ and phosphate groups. When PTP1B was injected into the QCM flow cell where the P-peptide/Zr4+/MCH/P-DNA/Au chip was placed, the P-peptide was dephosphorylated and released from the Au chip surface, resulting in an increase in the frequency of the QCM Au chip. This allowed the real-time monitoring of the P-peptide dephosphorylation process and sensitive detection of PTP1B activity within 6 min with a linear detection range of 0.01–100 pM and a detection limit of 0.008 pM. In addition, the maximum inhibitory ratios of inhibitors were evaluated using this proposed 100 MHz QCM biosensor. The developed 100 MHz QCM biosensing platform shows immense potential for early diagnosis of diseases related to protein phosphatases and the development of drugs targeting protein phosphatases.

Label-free and early detection of HER2 breast cancer biomarker based on UiO-66-NH2 modified gold chip (Au/UiO-66-NH2) using surface plasmon resonance technique

Breast cancer is one of the leading causes of cancer death for women worldwide. This cancer occurs when the breast cells grow abnormally and spread uncontrolled. Although there are several treatments, including chemotherapy, radiation, and surgery in a clinical setting to cure cancer, these treatments cannot provide a 100 % success rate in eliminating cancer, mainly due to the late diagnosis of the disease. Thus, early detection is the key to provide better breast cancer treatment and a higher chance for survival. Herein, simple and sensitive biosensor by combining the emerging multifunctional materials of metal-organic frameworks (MOFs) with a label-free surface plasmon resonance (SPR) instrument was developed. Two types of stable Zirconium (Zr)-based MOFs, namely Zr benzene dicarboxylic acid (Zr-BDC or UiO-66) and Zr 2-amino-benzene dicarboxylic acid (Zr-BDC-NH2 or UiO-66-NH2) were synthesized using the solvothermal method. X-ray diffractometer (XRD) and fourier transform infra red (FTIR) confirmed the formation of the prepared UiO-66 and UiO-66-NH2. The electron microscopy and nitrogen adsorption desorption isotherm characterization reveal that the MOFs have a cubic crystal structure with a high surface area of 672.4 m2/g for UiO-66 and 286.1 m2/g for UiO-66-NH2. The MOFs are then functionalized on the SPR gold (Au) chip surface to serve as a matrix of Human Epidermal Growth Factor Receptor 2(HER2) antibody receptors. Interestingly, the functionalized SPR biosensors could detect the HER2 protein target with high sensitivity in the ng/mL range and a remarkable detection limit, which is 0.457 ng/mL for UiO-66-NH2. This LOD value is significantly lower than clinical concentrations of HER2 proteins in human blood (∼15 ng/mL), which indicate that the biosensor can offer the capability of early detection test.

Two-dimensional material-enhanced surface plasmon resonance for antibiotic sensing

Two-dimensional (2D) materials attract attention from the academic community due to their excellent properties, and their wide application in sensing is expected to revolutionize environmental monitoring, medical diagnostics, and food safety. In this work, we systematically evaluate the effects of 2D materials on the Au chip surface plasmon resonance (SPR) sensor. The results reveal that 2D materials cannot improve the sensitivity of intensity-modulated SPR sensors. However, there exists an optimal real part of RI of 3.5–4.0 and optimal thickness when choosing nanomaterials for sensitivity enhancement of SPR sensors in angular modulation. In addition, the smaller the imaginary part of the nanomaterial RI, the higher the sensitivity of the proposed Au SPR sensor. The 2D material’s thickness needed for the highest sensitivity decreases with increasing real part and imaginary part of the RI. As a case study, we developed a 5 nm-thickness MoS2-enhanced SPR biosensor, which exhibited a low sulfonamides (SAs) detection limit of 0.05 μg/L based on a group-targeting indirect competitive immunoassay, nearly 12-fold lower than that of the bare Au SPR system. The proposed criteria help to shed light on the 2D material-Au surface interaction, which has greatly promoted the development of novel SPR biosensing with outstanding sensitivity.

Detection of β-amyloid peptide aggregates by quartz crystal microbalance based on dual-aptamer assisted signal amplification

β-amyloid peptide (Aβ) aggregates are regarded as a typical neuropathology hallmark for the diagnosis of Alzheimer's disease (AD). Aβ40 aggregates include soluble oligomers (Aβ40O) and insoluble fibrils (Aβ40F). Both of them can simultaneously bind to two different kinds of its aptamer (Apt1 and Apt2). As a mass-sensitive sensing platform, quartz crystal microbalance (QCM) converts changes in mass on the Au chip surface into frequency shift. Here, a dual-aptamer assisted Aβ40 aggregates assay was developed. Taking Aβ40O detection as an example, Apt2 was modified on the surface of Au chip by Au–S bond. Subsequently, the solution consisted of Aβ40O and gold nanoparticles-Apt1 (AuNPs-Apt1) were injected into the QCM chamber. As a result, Aβ40O was specifically recognized and captured by Apt2. AuNPs-Apt1 were also combined on the surface of the Au chip because Aβ40O can simultaneously bind to Apt1. Then, a significant frequency shift occurred because of the large weight of AuNPs. Similarly, this procedure can be used to detect Aβ40F. This QCM biosensor was able to detect Aβ40O with a range of 0.2–10 pM with a detection limit of 0.11 pM, while the linear range for Aβ40F was 0.1–10 pM with a detection limit of 0.02 pM. This QCM biosensor was simple and highly sensitive, which provided a new method for Aβ40 aggregates detection.

Tailor-made mesoporous SiO2/Au thin film with a substitutable interface for highly sensitive and selective room-temperature gas detection of VOCs

Trace amounts of volatile organic compounds (VOCs) were detected in Au chip interfaces modified with mesoporous SiO2 nanomaterials by using a surface plasmon resonance (SPR) technique. With Kretchmann-configuration SPR, it was possible to detect interactive and specific signal changes between a SiO2/Au gas-sensor surface and acetone, formaldehyde, and methane gases at room temperature. A dielectric spacing layer on Au was expanded and SPR signals were amplified by the mesoporous SiO2 nanoparticles with a large surface area and surface properties that were easily modified with specific ligands and became highly sensitive to, and selective for, the target gas molecules. A phosphonitrilic chloride trimer (PNCT), a universal self-assembled monolayer (SAM), and post-treatment for simple substitutions of ligands equipped the surfaces of SiO2 nanoparticles with targeted receptors, which resulted in the sensitive and selective detection of acetone to CH3-, formaldehyde to NH2-, and methane to Cl-functional groups. The chips modified with each functional group had a response time of about 2 s for concentrations of each gas that ranged from 0.2 to 3.0 ppm. The sensors modified with the functional groups showed limit of detection (LOD) values of 0.3, 0.6, and 0.5 ppm, respectively, which exceeded the Occupational Safety and Health Administration (OSHA) regulations, and limit of quantification (LOQ) values of 0.9, 1.8, and 1.6 ppm. Relative humidity of 45 ∼ 84 % under ambient air had negligible influence on the baseline signals in this SPR gas-sensing system. These sensors have the potential to monitor VOCs in both environmental and indoor settings.

Bifunctional Magnetic Fe3O4@Cu2O@TiO2 Nanosphere-Mediated Dual-Mode Assay of PTP1B Activity Based on Photocurrent Polarity Switching and Nanozyme-Engineered Biocatalytic Precipitation Strategies.

Dysregulation of protein phosphatases is associated with the progression of various human diseases and cancers. Herein, a photoelectrochemical (PEC)-quartz crystal microbalance (QCM) dual-mode sensing platform was developed for protein tyrosine phosphatase 1B (PTP1B) activity assay based on bifunctional magnetic Fe3O4@Cu2O@TiO2 nanosphere-mediated PEC photocurrent polarity switching and QCM signal amplification strategies. The PTP1B-specific phosphopeptide (P-peptide) with a cysteine end was designed and immobilized onto the QCM Au chip via the Au-S bond. Subsequently, the Fe3O4@Cu2O@TiO2 nanosphere was connected to the P-peptide via the specific interaction between the phosphate group on the P-peptide and TiO2. After incubation with PTP1B, the dephosphorylation of the P-peptide occurred, causing some Fe3O4@Cu2O@TiO2 nanospheres to be released from the chip surface. The released magnetic Fe3O4@Cu2O@TiO2 nanospheres (labeled as R-Fe3O4@Cu2O@TiO2) were quickly separated via magnetic separation technology and attached to the Bi2S3-decorated magnetic indium-tin oxide (Bi2S3/MITO) electrode by magnetic force, inducing the switch of the photocurrent polarity of the electrode from anodic current (the Bi2S3/MITO electrode) to cathodic current (the R-Fe3O4@Cu2O@TiO2/Bi2S3/MITO electrode). Also, the nondephosphorylated P-peptide linked Fe3O4@Cu2O@TiO2 nanospheres as nanozymes with horseradish peroxidase activity to catalyze the formation of precipitation on the surface of the Au chip, leading to a frequency change of the QCM. Thus, the proposed PEC-QCM dual-mode sensing platform achieved accurate and reliable assay of PTP1B activity because of the different mechanisms and independent signal transductions. In addition, this dual-mode sensing platform can be easily extended for other protein phosphatase activity analysis and shows great potential in the early diagnosis of the protein phosphatase-related diseases and the protein phosphatase-targeted drug discovery.

Electrical SPR biosensor with thermal annealed graphene oxide: Concept of highly sensitive biomolecule detection

(Reduced) graphene oxides as promising 2D materials have been explored extensively to improve the performance characteristics of SPR sensors. Herein, we demonstrate the tuning optical properties of SPR biochips by the combination of two strategies: (i) using gold/reduced graphene oxide (Au/rGO) interfaces prepared by thermal annealing of Au/GO, and (ii) applying external electrical bias via the solid-liquid interface during SPR measurements. We investigated this novel approach by studying a model biological interaction of prostate-specific antigen (PSA) with lectin Concanavalin A (Con A) based on glycan recognition, as the glycan motifs detection is increasingly requested due to the growing knowledge of the importance of glycans in various biological processes and their use as biomarkers. The thermally annealed Au/rGO as a functional layer of SPR chips provides higher signals and 10 times better LOD (limit of detection) compared to Au/GO case. This experimental finding was cross-verified by SPR simulations based on a model combining the optical indices (dielectric parameters) and thicknesses of the GO and rGO thin films obtained from ellipsometry characterizations. In addition, the unique optoelectrical properties of rGO thin films allowed for efficient tuning of the plasmonic intensities by applying an electrical bias at the Au/rGO interface, exploited here to improve the Con A LOD down to 10 ng/ml, what is by 1 order of magnitude better compared to the classic Au chip. The electrical SPR biosensor approach presents a proof-of-concept for future ultrasensitive SPR biosensor platforms.

Хавчуу Ам Ордын Судалгаанд Геофизикийн Аргуудыг Хэрэглэсэн Байдал

When comparing the exploration results thus far from Khavchuu with those of known mineralisation and mineral deposits in the region. The occurrence of north to north-east trending, low angle, thrust faults which also coincide with resistivity and chargeability highs, magnetic lows, As anomalies and positive Au chip samples, issimilar to that observed and documented at Boroo. The resistivity anomalies generated have been interpreted as being associated with an area of silicification or quartz veining and from the dipole-dipole results these seem to occur as shallowly dipping structures similar to those hosting the Boroo mineralisation. The chargeability highs could be interpreted as regions of sulphide mineralisation and coincide with many of the anomalous areas again as with Boroo, although in the southern area the near surface chargeability low becomes a chargeability high with depth suggesting a degree of sulphide destruction during weathering in the upper regions. Magnetic lows could be interpreted again as zones of weathering and associated destruction of magnetite in granites or sulphides in mineralised regions. Assuming that any mineralisation at Khavchuu will exhibit a similar refractory component, this broad weathering could be of significant economic importance.

Detection of 5-hydroxymethylfurfural based on split-DNAzyme assisted signal amplification via quartz crystal microbalance

5-hydroxymethylfurfural (HMF) is one of the food contaminants mainly formed by Maillard and caramelization reaction. Here, we developed a simple method to detect HMF based on split-DNAzyme assisted signal amplification via Quartz crystal microbalance. Firstly, two fragments of the split-DNAzyme (ESΙ and ESII) and AuNPs-ssDNA were prepared. In the absence of HMF, the amino group of ESΙ reacted with the aldehyde group of ESΙΙ by Schiff base condensation，which linked ESΙ and ESII as DNAzyme. With the help of Mg2+, this DNAzyme cleaved AuNPs-ssDNA, freeing the complementary sequence of capture DNA from the ssDNA. In the presence of the target HMF, the aldehyde group in its molecular structure preferred to react with ESΙ, which prevented the link of ESΙ and ESII. In this case, DNAzyme cannot be formed effectively and the ssDNA modified on AuNPs cannot be cleaved. Secondly, the capture DNA was immobilized on Au chip in the QCM chamber. Then, the intact AuNPs-ssDNA was introduced to hybridize with the capture DNA, resulted in a large frequency change (ΔF) of the QCM biosensor because of the huge increased mass of AuNPs. So, HMF can be detected based on the frequency change (ΔF) of the QCM biosensor. This QCM biosensor is more sensitive than previously reported methods, which provide a new direction for the analytical detection of HMF and other food contaminants.

Highly Sensitive and Stable Copper-Based SERS Chips Prepared by a Chemical Reduction Method.

Cu chips are cheaper than Ag and Au chips for practical SERS applications. However, copper substrates generally have weak SERS enhancement effects and poor stability. In the present work, Cu-based SERS chips with high sensitivity and stability were developed by a chemical reduction method. In the preparation process, Cu NPs were densely deposited onto fabric supports. The as-prepared Cu-coated fabric was hydrophobic with fairly good SERS performance. The Cu-coated fabric was able to be used as a SERS chip to detect crystal violet, and it exhibited an enhancement factor of 2.0 × 106 and gave a limit of detection (LOD) as low as 10–8 M. The hydrophobicity of the Cu membrane on the fabric is favorable to cleaning background interference signals and promoting the stability of Cu NPs to environment oxidation. However, this Cu SERS chip was still poor in its long-term stability. The SERS intensity on the chip was decreased to 18% of the original one after it was stored in air for 60 days. A simple introduction of Ag onto the clean Cu surface was achieved by a replacement reaction to further enhance the SERS performances of the Cu chips. The Ag-modified Cu chips showed an increase of the enhancement factor to 7.6 × 106 due to the plasmonic coupling between Cu and Ag in nanoscale, and decreased the LOD of CV to 10–11 M by three orders of magnitude. Owing to the additional protection of Ag shell, the SERS intensity of the Cu-Ag chip after a two-month storing maintained 80% of the original intensity. The Cu-Ag SERS chips were also applied to detect other organics, and showing wide linearity range and low LOD values for the quantitative detection.

An Immunosensor for the Determination of Cathepsin S in Blood Plasma by Array SPRi-A Comparison of Analytical Properties of Silver-Gold and Pure Gold Chips.

The array SPR imaging (SPRi) technique is well suited to the determination of biomarkers in body fluids, called liquid biopsy. No signal enhancement or analyte preconcentration is required. With the aim of achieving signal enhancement and lowering the cost of a single determination, the replacement of gold-covered chips by silver–gold chips was investigated. The aim of this work was to investigate the analytical characteristics of a biosensor formed on a Ag/Au chip and to compare them with those of a biosensor formed on a gold chip. A biosensor for the determination of cathepsin S (Cath S) was chosen as an example. The biosensor consisted of the linker cysteamine and an immobilized rat monoclonal antibody specific for cathepsin S. Both biosensors exhibited a Langmuirian response to Cath S concentration, with linear response ranging from LOQ to 1.5 ng mL−1. The LOQ is 0.1 ng mL−1 for the biosensor formed on the Ag/Au chip, and 0.22 ng mL−1 for that formed on the gold chip. Recoveries and precision for medium and high Cath S concentrations were acceptable for both biosensors, i.e., precision better than 10% and recoveries within the range 102–105%. However, the results for the lowest Cath S concentration were better for the biosensor formed on the Ag/Au chip (9.4 and 106% for precision and recovery, respectively). Generally, no significant differences in analytical characteristics were observed between the Ag/Au and Au chips. The two biosensors were also compared in the determination of Cath S in real samples. Nine plasma samples from healthy donors and nine from patients with ovarian cancer were analyzed for Cath S concentration with the biosensors formed on Ag/Au and Au chips. The results obtained with the two biosensors were very similar and show no significant differences on the Bland–Altman plot. The Cath S concentration in the blood plasma of ovarian cancer patients was elevated by one order of magnitude as compared with the control (12.6 ± 3.6 vs. 1.6 ± 1.2 ng mL−1).

Interaction of donepezil with tau protein: Insights from surface plasmon resonance and molecular modeling methods

Alzheimer's is a progressive neurodegenerative disease in which extracellular precipitation of amyloid fibrils of the β peptides and the accumulation of phosphorylated tau in neurofibrillary tangles play major roles. There is some indirect evidence indicating the potential of donepezil to interact with tau protein. In the present study, various aspects of donepezil binding to tau protein have been investigated using surface plasmon resonance (SPR) and molecular modeling methods. Tau protein was immobilized on Au chip using 11-mercaptoundecanoic acid (MUA) and the interaction of various concentrations of donepezil with the immobilized tau was evaluated by SPR at different temperatures. Besides, to have a better understanding of this interaction, molecular docking approach was also performed. The equilibrium constant decreased following increasing the temperature in the presence of various concentrations of donepezil, which indicates that donepezil binding to tau protein increases upon rising temperature. The calculated thermodynamic parameters showed that the main force involved in the interaction is van der Waals and hydrogen bonding. Finally, the molecular modeling analysis showed that donepezil bind to a cavity on R2 region- microtubule binding domain of tau monomer.

Graphene‐Coated Gold Chips for Enhanced Goos–Hanchen Shift Plasmonic Sensing

Plasmon‐based sensing relies on the interaction of photons with nanostructured materials. Surface plasmon resonance (SPR) biological and chemical sensors offer unique advantages of real‐time and label‐free detection techniques and therefore, they have been around in the commercial market for many decades. The principle of the Goos–Hanchen (GH) shift, whereby linearly polarized light undergoes a small lateral shift upon total internal reflection at a dielectric surface, is highly sensitive to refractive index (RI) changes in the sensing medium and can thus be utilized for plasmonic sensing. 2D materials such as graphene can boost the plasmonic efficiency of these sensors because of their excellent optical properties. Herein, a customized GH shift–based SPR sensor is devised using graphene‐coated Au chips. With the help of experimental results, it is shown that graphene can enhance the sensitivity of the conventional Au‐only configuration 2.35 times.

Chitosan-Based Nanocomposites for Glyphosate Detection Using Surface Plasmon Resonance Sensor.

This article describes an optical method based on the association of surface plasmon resonance (SPR) with chitosan (CS) film and its nanocomposites, including zinc oxide (ZnO) or graphene oxide (GO) for glyphosate detection. CS and CS/ZnO or CS/GO thin films were deposited on an Au chip using the spin coating technique. The characterization, morphology, and composition of these films were performed by Fourier-transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), and contact angle technique. Sensor preparation conditions including the cross-linking and mobile phase (pH and salinity) were investigated and thoroughly optimized. Results showed that the CS/ZnO thin-film composite provides the highest sensitivity for glyphosate sensing with a low detection limit of 8 nM and with high reproducibility. From the Langmuir-type adsorption model and the effect of ionic strength, the adsorption mechanisms of glyphosate could be controlled by electrostatic and steric interaction with possible formation of 1:1 outer-sphere surface complexes. The selectivity of the optical method was investigated with respect to the sorption of glyphosate metabolite (aminomethylphosphonic acid) (AMPA), glufosinate, and one of the glufonisate metabolites (3-methyl-phosphinico-propionic acid) (MPPA). Results showed that the SPR sensor offers a very good selectivity for glyphosate, but the competition of other molecules could still occur in aqueous systems.

SPR immunosensor combined with Ti4+@TiP nanoparticles for the evaluation of phosphorylated alpha-synuclein level.

A highly sensitive and specific surface plasmon resonance (SPR) method using one anti-alpha-synuclein antibody (anti-αS) and titanium phosphate nanoparticles (Ti4+@TiP) was developed for quantitative evaluation of phosphorylated αS level which was defined by the ratio of p-αS to total alpha-synuclein (t-αS) (p-αS/t-αS). The close affinities of anti-αS to αS (0.975pM-1) and p-αS (0.938pM-1) were obtained. Based on this fact, both αS forms were simultaneously captured and the t-αS was quantified using the anti-αS immobilized Au chip. With the selective recognition of Ti4+@TiP nanoparticles, the p-αS was quantified. The dynamic ranges of our method were 1.0~20.0pgmL-1 for the detection of t-αS and 0.1~10.0pgmL-1 for that of p-αS. The analysis of αS- and p-αS-spiked artificial cerebrospinal fluid samples revealed the high accuracy of the method. Furthermore, the concentrations of αS and p-αS in clinical CSF samples collected from three healthy donors were determined and displayed a high correlation with the results from acommercial ELISA kit, confirming the viability and of the proposedmethod. The method is convenient, economical, and practical for the evaluation of phosphorylated αS level with high sensitivity and selectivity. It is of great significance for the early diagnosis of PD and the evaluation of PD progression.Graphical abstract.

Phase-Sensitive Pulse Sensor Using 2-D Active Plasmonics on Conformal Substrates

Real-time monitoring of the vital signals using flexible and portable biosensors plays an important role in future human life. However, there is most often a tradeoff between the improvement of the mechanical properties of these sensing chips and their sensitivity. In this study, we proposed 2-D polydimethylsiloxane (PDMS)–Au and silk–Au chips with microhole and microparticle patterns performing in an integrated platform of plasmonic ellipsometry. Under an external sinusoidal signal, we observed the regular dependence of the optical responses and plasmonic resonances on the frequency and not on the current. Using integrated plasmonic-ellipsometry technique and the phenomenon of active plasmonics, PDMS–Au microhole chip has demonstrated that $\Delta $ and $\Psi $ parameters became lesser by increasing the frequency and the resonance wavelength underwent a redshift. However, for silk–Au chip with inverse pattern of microparticle bumps, $\Delta $ and $\Psi $ had augmentation trend with respect to the frequency and the resonance wavelength shifted to shorter wavelengths. By optical and thermal analyses, we have demonstrated that this study can provide new insights into fabricating optically phase and amplitude sensitive biosensors based on conformal substrates with thermo-optical properties that can behave in redshift and blueshift regimes.

Hollow molecularly imprinted polymer based quartz crystal microbalance sensor for rapid detection of methimazole in food samples

In this study, a novel detection method of methimazole was proposed based on the hollow molecularly imprinted quartz crystal microbalance (QCM) sensor, in which the hollow imprinted polymers (H-MIPs) were firstly prepared through the surface imprinted techniques, using hollow silica spheres as matrix supporting material and methimazole as template molecule. The characterizations of H-MIPs were carefully studied. Compared with traditional MIPs, H-MIPs exhibited faster mass transfer rate and higher adsorption capacity. After coating onto the surface of Au chip, the H-MIPs QCM sensor was fabricated. Based on the frequency shift, good linear behavior in the range of 5–70 μg L–1, limit of detection of 3 μg L–1, and good recoveries of 88.32%–107.96% in the spiked pork, beef and milk were obtained. The analysis process could complete within 8 min. The developed sensor provided an effective, fast and accurate method for the methimazole detection in food samples.

Cu-nanoflower decorated gold nanoparticles-graphene oxide nanofiber as electrochemical biosensor for glucose detection.

A novel electrospinning approach is proposed for the fabrication of copper (Cu)-nanoflower decorated gold nanoparticles (AuNPs)-graphene oxide (GO) nanofiber (NF) as an electrochemical biosensor for the glucose detection. In this study, GO was mixed with poly(vinyl alcohol) (PVA) and used as a fiber precursor, which greatly improves the electrochemical properties. The above solution was uniformly coated onto the surfaces of gold chip to form GO NFs via electrospinning. AuNPs were coated onto the surface of GO NFs and then incorporated organic-inorganic hybrid nanoflower [Cu nanoflower-glucose oxidase (GOx) and horseradish peroxidase (HRP)]. The electrochemical experiments revealed that Cu-nanoflower@AuNPs-GO NFs exhibited outstanding electrochemical catalytic nature, and selectivity for the conversion of glucose to gluconic acid in the presence of GOx-HRP-Cu nanoflower. The Cu-nanoflower@AuNPs-GO NFs coated Au chip exhibited good linear range 0.001-0.1 mM, with a detection limit of 0.018 μM. The Cu-nanoflower@AuNPs-GO NFs modified Au chip exhibited higher catalytic properties, which are attributed to the coating of unique organic-inorganic nanostructured materials on the surfaces of Au chip. These results indicate that the nano-bio hybrid materials can be applied as a promising electrochemical biosensor to monitor glucose levels in biofluids.