Bimetallic nanoparticles with sulfated galactan eliminate Vibrio parahaemolyticus in shrimp Penaeus vannamei.

Bimetallic (Au/Ag) nanoparticles (BNPs) have shown enhanced antibacterial activity compared to their monometallic counterparts. Sulfated galactans (SG) are a naturally occurring polymer commonly found in red seaweed Gracilaria fisheri. They are biocompatible and biodegradable and environmentally friendly. In this study, we utilized SG in combination with BNPs to develop composite materials that potentially enhance antibacterial activity against shrimp pathogens Vibrio parahaemolyticus and Vibrio harveyi, compared to BNPs or SG alone. BNPs were coated with sulfated galactan (SGBNPs) and characterized using UV-vis spectroscopy, Fourier transform infrared (FTIR) spectroscopy, zeta potential, and transmission electron microscopy (TEM). UV-vis spectroscopy analysis revealed that the surface plasmon peaks of BNPs and SGBNPs appeared at 530 nm and 532 nm, respectively. Zeta potential measurements showed that SGBNPs had a negative charge of -32.4 mV, while the BNPs solution had a positive charge of 38.7 mV. TEM images demonstrated the spherical morphology of both BNPs and SGBNPs with narrow size distributions (3-10 nm). Analysis of the FTIR spectra indicated that SG maintained its backbone structure in SGBNPs, but some functional groups were altered. Notably, SGBNPs showed superior antimicrobial and antibiofilm activities against V. parahaemolyticus and V. harveyi compared to SG and BNPs. Furthermore, treatment with SGBNPs significantly down-regulated the expression of virulence-related genes (toxR, cpsQ, and mfpA) for V. parahaemolyticus 3HP compared to the respective control, bacteria treated with BNPs or SG. Diets supplemented with SGBNPs, BNPs, or SG showed no detrimental impact on the growth of shrimp Penaeus vannamei. Shrimp fed with SGBNPs-supplemented feed showed significantly higher survival rates than those fed with BNPs-supplemented feed when infected with 3HP after being on the supplemented feed for seven days and a subsequent number of fifteen days. These findings collectively demonstrate the benefit of using SG capped Au-Ag BNPs as an antibacterial agent for the prevention and control of Vibrio sp. Infection in shrimp while reducing the risk of environmental contamination.

Synthesis of Au@Ag core-shell nanorods with tunable optical properties.

The synthesis of noble metal nanostructures with adjustable optical properties is essential due to their potential applications in various fields such as imaging, (bio) sensors, and catalysis. In this study, Au@Ag core-shell nanorods were synthesized with tunable optical properties. The synthesis process includes a two-stage approach: first, gold nanorods were synthesized through seed-mediated growth, and in the second stage, these gold nanorods were used as seeds to synthesize Au@Ag core-shell nanorods through the silver deposition process. Tunable core-shell nanorods were produced by changing the concentration of silver ions, reducing agent, stabilizing agent, seeds, and buffer as well as pH and the reaction time. Transmission electron microscopy images demonstrated the formation of the Au@Ag core-shell nanorod structure. In addition, UV-visible spectroscopy revealed the peak height and its shift towards shorter wavelengths, demonstrating the tunable optical properties of the synthesized nanorods. Overall, in this study, we demonstrated the synthesis of Au@Ag core-shell nanorods with adjustable plasmonic optical properties that could be changed by precisely controlling the thickness of the silver shell on the surface of the gold core.

Highly luminescent, fast switching electro-optical device based on core-shell bimetallic nanoparticles/ ferroelectric liquid crystal composites.

Owing to the passive nature of liquid crystal (LC) materials, achieving luminous displays using pure LC materials is challenging. In addition, it is difficult to achieve a fast switching time using pristine ferroelectric LC devices without compromising their cell thickness. Herein, we have developed a fast switching and highly luminescent electro-optical device by dispersing a minute concentration of bimetallic nanoparticles (Au@Ag NPs) having a spherical gold core and a silver shell within a ferroelectric liquid crystal (FLC) host matrix, ZLI3654. Au@Ag core-shell NPs having synergic attributes of both counterparts were successfully synthesized by a facile seed-mediated route. The Au core helps to tune the shape of the Ag shell and provides enhanced electron density as well as improved stability against oxidation. Introducing nanoparticles induces little structural modifications to the host FLC, resulting in an improvement in the mesogenic alignment. Interestingly, ∼29-fold enhancement in the photoluminescence (PL) intensity is observed on dispersing 0.25 wt% of Au@Ag NPs into the FLC host matrix. The enhanced electromagnetic field in the FLC-nanocomposite is attributed to the Localized Surface Plasmon Resonance of Au@Ag NPs, which strengthens the photon absorption rates by the FLC molecules, culminating in the massive enrichment of the PL intensity. In addition, the improved localized electric field inside the FLC device led to a noticeable enhancement in the spontaneous polarization, dielectric permittivity, and, most interestingly, ∼53% fastening in the switching time at an optimum concentration (0.25 wt%) of Au@Ag NPs. The improved electro-optical parameters of the Au@Ag NPs/FLC composite have been compared with the performance of both pristine Au NPs/FLC and Ag NPs/FLC composites, respectively, for the comprehensiveness of the study. The present study paves a systematic way to develop FLC-based advanced electro-optical devices with faster switching and higher luminescence properties.

Development of a SERS aptasensor for the determination of L-theanine using a noble metal nanoparticle-magnetic nanospheres composite.

An ultrasensitive surface-enhanced Raman spectroscopy (SERS) aptamer sensor (aptasensor) using a noble metal nanoparticle-magnetic nanospheres composite was developed for L-theanine detection. It makes use of Fe3O4@Au MNPs and Au@Ag NPs embedded with the Raman reporter 4-mercaptobenzoic acid (4MBA). Au@4MBA@Ag NPs modified by aptamer and Fe3O4@Au MNPs modified by cDNA created the aptasensor with the strongest Raman signal of 4MBA through the specific binding of the aptamer. With the preferred binding of L-theanine aptamer to L-theanine, Au@4MBA@Ag NPs were released from Fe3O4@Au MNPs, causing a linear decrease in SERS intensity to achieve the SERS detection of the L-theanine. The SERS peak of 4MBA at 1078 cm-1 was used for quantitative determination. SERS intensity showed a good log-linear relationship within the range 10-10 to 10-6 M of L-theanine. The aptasensor has a high selectivity for L-theanine compared with other twelve tested analytes. Hence, this aptasensor is a promising analytical tool for L-theanine detection. The developed method was applied to the analysis of real samples, demonstrating excellent performance. The comparison with the standard liquid chromatography mass spectrometry method showed an error within 20%.

Au@Ag Nanopencil with Au Tip and Au@Ag Rod: Multimodality Plasmonic Nanoprobe based on Asymmetric Etching for the Detection of SCN- and ClO.

In this paper, Au@Ag nanopencil is designed as a multimodality plasmonic nanoprobe based on asymmetric etching for the detection of SCN- and ClO- . Au@Ag nanopencil with Au tip and Au@Ag rod is prepared by asymmetric tailoring of uniformly grown silver-covered gold nanopyramids under the combined effect of partial galvanic replacement and redox reaction. By asymmetric etching in different systems, Au@Ag nanopencil exhibits diversified changes in the plasmonic absorption band: O2 •- facilitated by SCN- etches Au@Ag rod from the end to the tip, causing a blue shift of the localized surface plasmon resonance (LSPR) peak as the aspect ratio decreases; while the ClO- can retain Au@Ag shell and etch Ag within rod from the tip to the end, causing a redshift of the LSPR peak as the coupling resonance weakens. Based on peak shifts in different directions, a multimodality detection of SCN- and ClO- has been established. The results demonstrate the detection limits of SCN- and ClO- are 160 and 6.7 nm, and the linear ranges are 1-600 µm and 0.05-13 µm, respectively. The finely designed Au@Ag nanopencil not only broadens the horizon of designing heterogeneous structures, but also enriches the strategy of constructing multimodality sensing platform.

An electrochemiluminescence resonance energy transfer biosensor based on CDs/PAMAM/rGO nanocomposites and Au@Ag2S nanoparticles for PML/RARα fusion gene detection.

In recent years, electrochemiluminescence resonance energy transfer (ECL-RET) with low background signal and high specificity has attracted much attention among researchers. Herein, we established a novel ECL-RET biosensor for PML/RARα fusion gene detection. In this ECL-RET system, carbon dots (CDs) with low toxicity and prominent electrochemical activity were used as donor and Au@Ag2S core-shell nanoparticles (Au@Ag2S NPs) were employed as ECL acceptor. The Au@Ag2S NPs possessed a wide ultraviolet-visible (UV-vis) absorption spectrum between 500 nm and 700 nm, which completely overlapped with the ECL spectrum of CDs. Furthermore, the CDs-decorated poly-amidoamine/reduced graphene oxide (CDs/PAMAM/rGO) nanocomposites were prepared to improve the ECL signals and served as a substrate to stably load capture probe deoxyribonucleic acid (DNA). Based on the ECL-RET biosensing strategy, the Au@Ag2S NPs-labeled assistant probes and target DNA could pair with capture probes to form the sandwich-type DNA structure and the distance between donor and accepter was closed, leading to quenching of the ECL signal of CDs. The ECL-RET biosensor represented eminent analytical performance for PML/RARα fusion gene detection with a wide linear relationship from 5 fM to 500 pM and a low detection limit of 0.72 fM, which provided a novel technical means and theoretical basis for detection and diagnosis of acute promyelocytic leukemia.

Enhancing the Extinction Efficiency and Plasmonic Response of Bimetallic Nanoparticles of Au-Ag in Robust Thin Film Sensing Platforms.

The extinction efficiency of noble metal nanoparticles (NPs), namely gold (Au) and silver (Ag), are dependent on their size and surrounding dielectric. Exploiting the Localized Surface Plasmon Resonance (LSPR) phenomenon, the composition and structure of the NPs might be tailored to achieve a configuration that optimizes their response (sensitivity) to environmental changes. This can be done by preparing a bimetallic system, benefiting from the chemical stability of Au NPs and the higher scattering efficiency of Ag NPs. To enhance the LSPR sensing robustness, incorporating solid supports in the form of nanocomposite thin films is a suitable alternative. In this context, the NPs composed of gold (Au), silver (Ag), and their mixture in bimetallic Au-Ag NPs, were grown in a titanium dioxide (TiO2) matrix using reactive DC magnetron sputtering. Thermal treatment at different temperatures (up to 700 °C) tuned the LSPR response of the films and, consequently, their sensitivity. Notably, the bimetallic film with Au/Ag atomic ratio 1 exhibited the highest refractive index sensitivity (RIS), with a value of 181 nm/RIU, almost one order of magnitude higher than monometallic Au-TiO2. The nanostructural analysis revealed a wide NP size distribution of bimetallic NPs with an average size of 31 nm, covering about 20% of the overall surface area. These findings underscore the significant potential of bimetallic film systems, namely AuAg-TiO2, in LSPR sensing enhancement.

Surface-enhanced Raman Scattering of Au-Ag bimetallic nanopillars fabricated using surface-plasmon lithography.

Arrays of gold-silver (Au-Ag) bimetallic nanopillars were fabricated by a newly developed surface-plasmon lithography (SPL) and their enhancement properties as surface-enhanced Raman scattering (SERS) substrates have been studied. We demonstrated that the SPL is a low-cost and high efficiency method for the fabrication of SERS substrates with both high sensitivity and reproducibility. The nanopillars showed a good response in the detection of methylene blue molecules at a low concentration of 1.0 × 10-11mol· l-1. The SERS enhancement factors (EFs) are on the orders of 107and the relative standard deviation of SERS intensity is <8% over an area of 50µm × 50µm. The EFs increase fast with the height increasing from 200 to 530 nm, then increase slowly when further increase the height of the nanopillars to 1100 nm. In addition, the Au-Ag bimetallic coating has shown much higher SERS enhancement than the coatings of either the pure Au or Ag. The excellent SERS enhancement and reproducibility of the Au-Ag coated nanopillars indicated that the fabricated SERS substrates can be used for the detection of biochemical molecules at trace level and the SPL is a promising method for fabrication of SERS substrates.

DNAzyme signal amplification based on Au@Ag core-shell nanorods for highly sensitive SERS sensing miRNA-21.

Here, we developed a surface-enhanced Raman scattering (SERS) sensor based on functionalized Au@Ag core-shell nanorods (Au@Ag NRs) and cascade DNAzyme amplifier (CSA) for sensitive and accurate determination of microRNA-21 (miRNA-21). The as-prepared SERS nanoprobes were composed of a thiol-modification hairpin probe (HP2)-functionalized Au@Ag NRs and hairpin DNAzyme (HP1-Dz). Compared with original gold nanorods, the silver shell caused an enhancement of plasmonic properties, resulting in a significant enhancement of Raman signals. In the presence of target miRNAs, the hairpin construction of HP1-Dz changed due to DNA/RNA hybridization; subsequently, the DNAzyme-catalyzed cleaving process changed, and the Raman signals of the SERS nanoprobes gradually "turned off" with time elapse because of the dissociation of the Raman reporter from the surface of Au@Ag NRs. Hence, based on this principle, the proposed SERS sensor exhibited good linearity in the range 0.5 fM to 10 nM for miRNA-21 detection with a detection limit (LOD) of 0.5 fM. The proposed SERS platform has potential application in quantitative and precise detection of miRNA-21 in human serum.

A novel electrochemical aptasensor based on layer-by-layer assembly of DNA-Au@Ag conjugates for rapid detection of aflatoxin M1 in milk samples.

Aflatoxin M1 (AFM1) is a common toxin in dairy products that causes acute and chronic human health disorders. Thus, the development of a rapid and accurate AFM1 detection method is of vital importance for food safety monitoring. This work was to develop a novel electrochemical aptasensor for sensitive and specific determination of AFM1. The dendritic-like nanostructure was formed on the gold electrode surface by layer-by-layer assembly of gold-silver core-shell nanoparticles modified with DNA conjugates. In the presence of AFM1, the specific recognition between AFM1 and Apt caused the disassociation of the DNA controlled dual Au@Ag conjugates from the surface of the electrode, causing less methylene blue to bind to the surface and weakening the electrochemical signal. The more AFM1 there is, the weaker the electrochemical signal. Transmission electron microscope results showed that the successfully synthesized Au@Ag nanoparticles exhibited a core-shell structure with Au as core and Ag as shell, and their average diameter was about 30 nm. Under optimal conditions, the electrochemical aptasensor showed a wide detection ranging from 0.05 ng mL-1 to 200 ng mL-1, and a low detection limit of 0.02 ng mL-1. Moreover, the proposed strategy has been successfully applied to the detection of AFM1 in cow, goat, and sheep milk samples with satisfactory recoveries ranging from 91.10% to 104.05%. This work can provide a novel rapid detection method for AFM1, and also provide a new sensing platform for the detection of other toxins.

Ultrasensitive multiplex SERS immunoassay based on porous Au-Ag alloy nanoparticle-amplified Raman signal probe and encoded photonic crystal beads.

An ultrasensitive multiplex surface-enhanced Raman scattering (SERS) immunoassay was developed using porous Au-Ag alloy nanoparticles (p-AuAg NPs) as Raman signal amplification probe coupling with encoded photonic crystal microsphere. p-AuAg NPs were synthesized and modified with the second antibody (Ab2) and Raman tag (mercaptobenzoic acid, MBA) to prepare a Raman signal-amplified probe. The high porosity of the p-AuAg NPs enables significant coupling of the localized surface plasmon resonance and thus abundant inherent hotspots for Raman signal enhancement. 3D-ordered silver nanoparticles-coated silica photonic crystal beads (Ag/SPCBs) were prepared as encoded SERS substrate for multiplex detection using their reflection peaks. The signal-amplified probe was used for multiplex detection of tumor markers carcinoembryonic antigen (CEA) and alpha fetoprotein (AFP). The wide linear ranges of 10-7-103 ng/mL for CEA and 10-4-103 ng/mL for AFP with detection limits of 1.22 × 10-8 ng/mL and 2.47 × 10-5 ng/mL for CEA and AFP at a signal-to-noise ratio of 3 were obtained. The proposed multiplex SERS immunoassay method displays ultrahigh sensitivity, wide linear range, and excellent specificity, which can be successfully applied to measure clinical serum samples with satisfactory results. The research provides a novel SERS signal enhancement strategy for the multiplex bioassay.

SERS and Indicator Paper Sensing of Hydrogen Peroxide Using Au@Ag Nanorods.

The detection of hydrogen peroxide and the control of its concentration are important tasks in the biological and chemical sciences. In this paper, we developed a simple and quantitative method for the non-enzymatic detection of H2O2 based on the selective etching of Au@Ag nanorods with embedded Raman active molecules. The transfer of electrons between silver atoms and hydrogen peroxide enhances the oxidation reaction, and the Ag shell around the Au nanorod gradually dissolves. This leads to a change in the color of the nanoparticle colloid, a shift in LSPR, and a decrease in the SERS response from molecules embedded between the Au core and Ag shell. In our study, we compared the sensitivity of these readouts for nanoparticles with different Ag shell morphology. We found that triangle core-shell nanoparticles exhibited the highest sensitivity, with a detection limit of 10-4 M, and the SERS detection range of 1 × 10-4 to 2 × 10-2 M. In addition, a colorimetric strategy was applied to fabricate a simple indicator paper sensor for fast detection of hydrogen peroxide in liquids. In this case, the concentration of hydrogen peroxide was qualitatively determined by the change in the color of the nanoparticles deposited on the nitrocellulose membrane.

Naked-Eye Detection of Morphine by Au@Ag Nanoparticles-Based Colorimetric Chemosensors.

In this study, we report a novel and facile colorimetric assay based on silver citrate-coated Au@Ag nanoparticles (Au@AgNPs) as a chemosensor for the naked-eye detection of morphine (MOR). The developed optical sensing approach relied on the aggregation of Au@Ag NPs upon exposure to morphine, which led to an evident color variation from light-yellow to brown. Au@Ag NPs have been prepared by two different protocols, using high- and low-power ultrasonic irradiation. The sonochemical method was essential for the sensing properties of the resulting nanoparticles. This facile sensing method has several advantages including excellent stability, selectivity, prompt detection, and cost-effectiveness.

Progress in Laser Ablation and Biological Synthesis Processes: "Top-Down" and "Bottom-Up" Approaches for the Green Synthesis of Au/Ag Nanoparticles.

Because of their small size and large specific surface area, nanoparticles (NPs) have special properties that are different from bulk materials. In particular, Au/Ag NPs have been intensively studied for a long time, especially for biomedical applications. Thereafter, they played a significant role in the fields of biology, medical testing, optical imaging, energy and catalysis, MRI contrast agents, tumor diagnosis and treatment, environmental protection, and so on. When synthesizing Au/Ag NPs, the laser ablation and biosynthesis methods are very promising green processes. Therefore, this review focuses on the progress in the laser ablation and biological synthesis processes for Au/Ag NP generation, especially in their fabrication fundamentals and potential applications. First, the fundamentals of the laser ablation method are critically reviewed, including the laser ablation mechanism for Au/Ag NPs and the controlling of their size and shape during fabrication using laser ablation. Second, the fundamentals of the biological method are comprehensively discussed, involving the synthesis principle and the process of controlling the size and shape and preparing Au/Ag NPs using biological methods. Third, the applications in biology, tumor diagnosis and treatment, and other fields are reviewed to demonstrate the potential value of Au/Ag NPs. Finally, a discussion surrounding three aspects (similarity, individuality, and complementarity) of the two green synthesis processes is presented, and the necessary outlook, including the current limitations and challenges, is suggested, which provides a reference for the low-cost and sustainable production of Au/Ag NPs in the future.

Metal Cluster Triggered-Assembling Heterogeneous Au-Ag Nanoclusters with Highly Loading Performance and Biocompatible Capability.

In this work, we firstly report the preparation of heterogeneously assembled structures Au-Ag nanoclusters (NCs) as good drug carriers with high loading performance and biocompatible capability. As glutathione-protected Au and Ag clusters self-assembled into porous Au-Ag NCs, the size value is about 1.358 (±0.05) nm. The morphology characterization revealed that the diameter of Au-Ag NCs is approximately 120 nm, as well as the corresponding potential ability in loading performance of the metal cluster triggered-assembling process. Compared with individual components, the stability and loading performance of heterogeneous Au-Ag NCs were improved and exhibit that the relative biocompatibility was enhanced. The exact information about this is that cell viability was approximately to 98% when cells were incubated with 100 µg mL-1 particle solution for 3 days. The drug release of Adriamycin from Au-Ag NCs was carried out in PBS at pH = 7.4 and 5.8, respectively. By simulating in vivo and tumor microenvironment, the release efficiency could reach over 65% at pH = 5.8 but less than 30% at pH = 7.2. Using an ultrasound field as external environment can accelerate the assembling process while metal clusters triggered assembling Au-Ag NCs. The size and morphology of the assembled Au-Ag NCs can be controlled by using different power parameters (8 W, 13 W, 18 W) under ambient atmosphere. Overall, a novel approach is exhibited, which conveys assembling work for metal clusters triggers into heterogeneous structures with porous characteristic. Its existing properties such as water-solubility, stability, low toxicity and capsulation can be considered as dependable agents in various biomedical applications and drug carriers in immunotherapies.

Golden and Silver-Golden Chitosan Hydrogels and Fabrics Modified with Golden Chitosan Hydrogels.

Golden and silver-golden chitosan hydrogels and hydrogel-modified textiles of potential biomedical applications are investigated in this work. The hydrogels are formed by reactions of chitosan with HAuCl4·xH2O. For above the critical concentration of chitosan (c*), chitosan-Au hydrogels were prepared. For chitosan concentrations lower than c*, chitosan-Au nano- and microgels were formed. To characterise chitosan-Au structures, sol-gel analysis, UV-Vis spectrophotometry and dynamic light scattering were performed. Au concentration in the hydrogels was determined by the flame atomic absorption spectrophotometry. Colloidal chitosan-Au solutions were used for the modification of fabrics. The Au content in the modified fabrics was quantified by inductively coupled plasma mass spectrometry technique. Scanning electron microscopy with energy dispersion X-ray spectrometer was used to analyse the samples. Reflectance spectrophotometry was applied to examine the colour of the fabrics. The formation of chitosan-Au-Ag hydrogels by the competitive reaction of Au and Ag ions with the chitosan macromolecules is reported.

DNA-Origami-Based Assembly of Au@Ag Nanostar Dimer Nanoantennas for Label-Free Sensing of Pyocyanin.

Early-stage detection of diseases caused by pathogens is a prerequisite for expedient patient care. Due to the limited signal-to-noise ratio, molecular diagnostics needs molecular signal amplification after recognition of the target molecule. In this present study, we demonstrate the design of plasmonically coupled bimetallic Ag coated Au nanostar dimers with controlled nanogap using rectangular DNA origami. We further report the utility of the designed nanostar dimer structures as efficient SERS substrate for the ultrasensitive and label-free detection of the pyocyanin molecule, which is a biomarker of the opportunistic pathogenic bacteria, Pseudomonas aeruginosa. The experimental results showed that the detection limit of pyocyanin with such nanoantenna based biosensor was 335 pM, which is much lower than the clinical range of detection. Thus, fast, sensitive and label-free detection of pyocyanin at ultralow concentration in an infected human body can pave a facile route for early stage warning for severe bacterial infections.

Rapid synthesis of monodispersed Au-Ag alloy nanosponges using selective laser melting and dealloying for sensitive near-infrared surface-enhanced Raman scattering.

We developed a rapid synthesis method for monodispersed Au-Ag alloy nanosponges (NSs) with high density of 'hotspots' for near-infrared surface enhanced Raman scattering (NIR-SERS) by a selective laser-irradiation melting and chemical dealloying process. Au@Ag core-shell nanocubes were firstin situconverted into solid alloyed Au-Ag nanospheres by a rapid laser irradiation igniting quick fusion and quenching process within two minutes. The alloyed Au-Ag nanospheres transformed into Au-Ag alloy NSs after treated by a chemical dealloying process. Different from traditional thermal annealing, it thus can effectively avoid the heat fusion between nanoparticles, and maintain the alloyed Au-Ag nanospheres and NSs in high monodispersity. Importantly, due to the strong plasmonic coupling in nanopores (pore size less than 10 nm), the obtained Au-Ag alloy NSs show a broad and intense localized surface plasmon resonances absorption ranging from visible to near-Infrared region (500-1200 nm). The accessibly open structures for absorbing targets and high-density of 'NIR-hotspots' endow the Au-Ag alloy NSs substrate with superior sensitivity in NIR-SERS detection of 4-aminothiophenol with an enhancement factor of ∼107. This work not only provides a simple pathway for rapid preparation of NIR-SERS substrate for biosensing, but also might open up a new horizon for fabricating spongy nanostructures with other elements.

A SERS-LFA biosensor combined with aptamer recognition for simultaneous detection of thrombin and PDGF-BB in prostate cancer plasma.

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-1and 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.

Au/Ag composite-based SERS nanoprobe of Cr3.

Quantitative characterization of Cr3+, an important element revealing human metabolism and biological environmental variation, is still difficult to achieve by conventional biochemical methods due to the lack of high-sensitivity, real-time techniques with rapid response detection. Using surface-enhanced Raman scattering (SERS), we construct an Au/Ag composite-based SERS nanoprobe for the quantitative characterization of Cr3+ content in solution, in which DL-mercaptosuccinic acid (DL-MSA) is employed for Raman signal enhancement, and 4-mercaptobenzoic acid (4-MBA) is chosen as the Raman reporter. The achieved result demonstrates obvious advantages of the synthesized Au/Ag composite-based SERS nanoprobe in sensitivity and response speed. Importantly, this Au/Ag composite-based SERS nanoprobe might provide a new strategy for dynamic monitoring of Cr3+ content in human metabolism.