Gold Nanoparticle Amplification Research Articles

Tapered optical fiber LRSPR biosensor based on gold nanoparticle amplification for label-free BSA detection

Surface plasmon resonance (SPR)-based fiber optic sensors are widely used in biosensing and associated analysis of biomolecular interactions. However, the limited penetration depths of conventional SPR (CSPR, <300 nm) and localized SPR (LSPR, <200 nm) restrict their applications in specific biosensing as the surface immobilized biomolecules, i. e. antibody or aptamer, will shield the plasma wave from the target. To solve the problem, an optical fiber long range SPR (LRSPR) biosensor based on Au nanoparticles (AuNPs) amplification is developed for bovine serum albumin (BSA) detection. The single mode fiber spliced between two multimode fibers is firstly tapered for the enhancement of evanescent field, then deposited with Al2O3-Ag-Au multilayers to stimulate LRSPR and realize micron-scale larger penetration depth, finally modified with the BSA antibody by covalent bonding to specifically recognize the target biomolecule. AuNPs are introduced to improve the sensitivity after the BSA antigen-antibody combination is accomplished, taking advantage of the plasma hybridization with LRSPR and their high mass ratio. A good log-linear spectral response is obtained at the BSA concentration range of 1 ng/mL-10 mg/mL, with high sensitivity of 19.46 nm/log(ng/mL) and low limit of detection (LOD) of 0.3 ng/mL. The sensitivity of LRSPR is improved 5.6-fold and the minimum detectable BSA concentration is reduced 4 orders of magnitude by introducing AuNPs amplification. Moreover, the designed sensor shows the merits of high specificity, good stability and fast response, making it of great potential for trace biosensing applications.

Imprinted limited domain aptamer electrochemical sensors based on dual signal amplification of GOCS composites and gold nanoparticles for specifically detecting of Cd2+

An ultra-sensitive electrochemical sensor based on glassy carbon electrode (GCE) modified with carbon disulfide functionalized graphene oxide (GOCS)/gold nanoparticles (AuNPs) and dual recognition of aptamer/ion imprinting polymer (IIP) is proposed for the detection of Cd2+. The inherent layered structure of GOCS composites is convenient to provide high specific surface area, AuNP can improve electrode activity and the synergistic effect between the two materials contributes to further modification and signal amplification. The IIP cadmium ion imprinted cavities on the surface of electrode by electropolymerization can achieve the specific detection of Cd2+. Owing to the dual specific recognition provided by IIP and aptamer and the multiple signal amplification provided by GOCS and AuNPs, the sensor exhibits high detection response toward target Cd2+ with a detection limit of 0.15 μg/L in the linear range of 0.4–30 μg / L. The sensor had outstanding selectivity, excellent reproducibility, long-term stability and good reusability. Furthermore, this method can realize the detection of Cd2+ in real water samples with recovery rate of 86.5 % − 104.70 % (RSD=0.07 % − 9.65 %). This electrochemical strategy opens up more possibilities for the construction of trace detection of Cd2+ with record-high selectivity and sensitivity in water samples.

Label-free electrochemical biosensor based on dual amplification of gold nanoparticles and polycaprolactones for CEA detection

Carcinoembryonic Antigen (CEA), an acidic glycoprotein with human embryonic antigen properties, is found on the surface of cancer cells that have differentiated from endodermal cells. This paper presents a label-free electrochemical immunoassay for the dual amplification detection of CEA using gold nanoparticles loaded with polypyrrole polydopamine (Au/PPy-PDA) and polymerized polycaprolactone (Ng-PCL) prepared by ring-opening polymerization (ROP). First, the composite Au/PPy-PDA was adhered to the electrode surface. Then, gold nanoparticles form a Au–S bond with the sulfhydryl group in Apt1 to secure it on the electrode surface. Subsequently, the non-specific binding sites on the electrodes surface are closed by bovine serum albumin (BSA). Next, CEA is dropped onto the electrode surface, which is immobilized by antigen-antibody specific recognition, and the carboxyl-functionalized Apt2 forms a "sandwich structure" of antibody-antigen-antibody by specific recognition. Polymeric Ng-PCL is adhered to the electrode surface, leading to an increase in the electrochemical impedance signal, resulting in a complete chain of signal analysis. Finally, the response signal is detected by electrochemical impedance spectroscopy (EIS). Under optimal experimental conditions, the method has the advantages of high sensitivity and wide linear range (1 pg mL−1∼100 ng mL−1), and the lower limit of detection (LOD) is 0.234 pg mL−1. And it has the same high sensitivity, selectivity and interference resistance for the real samples detection. Thus, it provides a new way of thinking about biomedical and clinical diagnosis.

Determination of Menthol by a Quartz Crystal Microbalance (QCM) Using Gold Nanoparticle Amplification

Menthol is a monocyclic monoterpene with a distinct flavor that is frequently utilized in a variety of food and medicinal items. In this study, a sensitive method based on quartz crystal microbalance (QCM) with gold nanoparticles amplification was developed. A gold chip was initially modified with mono(6-mercapto-6-deoxy)-β-cyclodextrin (SH-β-CD) through Au-S affinity binding. When menthol is absent, the host–guest interaction brings ferrocene (Fc) labeled-ssDNA (Fc-ssDNA) to enter the SH-β-CD cavity. The hybridization between Au nanoparticles functionalized-ssDNA (AuNPs-ssDNA) and Fc-ssDNA produces a significant frequency shift. However, in the presence of menthol, the inclusion competition between Fc and menthol reduces AuNPs-ssDNA modification on the chip surface. In this case, the change of QCM frequency is greatly reduced by menthol. Thus, menthol determination is accomplished by measuring the change in QCM frequency with a linear range from 10−8 M to 10−2 M and a limit of detection of 7.81 nM, which is superior to previously reported results. The method has also been applied in real samples such as mint and essential oil with satisfactory results.

Wash-free electrochemical aptasensor for the detection of aflatoxins by the signal amplification of ferrocene-capped gold nanoparticles

Wash-free electrochemical aptasensor for the detection of aflatoxins by the signal amplification of ferrocene-capped gold nanoparticles

Optical fiber SPR biosensor based on gold nanoparticle amplification for DNA hybridization detection

An optical fiber SPR biosensor based on multimode fiber (MMF)- hollow core fiber (HCF)-MMF is proposed and experimentally confirmed for in situ DNA hybridization analysis. In order to improve the sensitivity of DNA hybridization detection, a sandwich model based on gold nanoparticles (AuNPs) amplification is proposed. In this model, the probe DNA (pDNA) is first modified on the optical fiber sensing area by covalent bonding, and then the biotinylated target DNA (tDNA) is modified on the AuNPs by the high affinity between biotin and streptavidin. Finally, the tDNA on the surface of the AuNPs specifically hybridizes with the pDNA on the optical fiber to form a sandwich model. The near field coupling enhancement between AuNPs and gold film and the high mass ratio of AuNPs give high sensitivity to DNA hybridization detection. Experimental results show that the sandwich-type fiber SPR sensor has a log-linear response in the DNA concentration range of 1 pM–10 nM, and the sensitivity and detection limit are 4.04 nm/log(μM) and 1pM, respectively. This is 1.44 times more sensitive than that without sandwich assay. In addition, the DNA sensor has good specificity and stability, which foreshadows its great application potential in the fields of disease diagnosis, microbial detection and environmental science.

Electrochemical detection of omethoate and acetamiprid in vegetable and fruit with high sensitivity and selectivity based on pomegranate-like gold nanoparticle and double target-induced DNA cycle signal amplification

The study reports synthesis of gold-graphene quantum dot nanohybrid via reduction of chloroauric acid with arginine and aspartic acid-functionalized graphene quantum dot (Arg/Asp-GQD). The Arg/Asp-GQD-Au offers pomegranate-like architecture and Schottky heterojunction and was used for construction of electrochemical sensor for detection of omethoate and acetamiprid coupled with double target-induced DNA cycles. Target molecule hybridizes with aptamer DNA in duplex DNA to release auxiliary strand DNA. This triggers the DNA cycle and brings one redox probe to electrode surface. By the DNA cycle, one target molecule can transfer many redox probes to electrode surface and produces a significant signal amplification. The detection signal was enhanced by catalysis of Arg/Asp-GQD-Au toward redox of these probes due to its excellent catalytic activity. Differential pulse voltammetric peak current linearly increases with increasing target concentration between 5 × 10−14 and 5 × 10−10 M with detection limit of 1.67 × 10−14 Μ (S/N = 3) for omethoate and between 1 × 10−14 and 5 × 10−10 M with detection limit of 3.33 × 10−15 M (S/N = 3) for acetamiprid. The proposed method provides a much better sensitivity and selectivity and was successfully applied to detection of omethoate and acetamiprid in vegetable and fruit.

Piezoelectric aptasensor with gold nanoparticle amplification for the label-free detection of okadaic acid

Okadaic acid (OA) is one of the most common marine biological toxins, which can cause human poisoning or even death. It is desirable and essential to develop novel approaches for OA detection in a convenient, practical and low-cost manner. In this study, a novel piezoelectric aptasensor was designed for the detection of OA. The aptamers specifically binding with OA were used as the sensing elements. Quartz crystal microbalance (QCM) device was used as the transducer for responsive signal detection. Gold nanoparticles (AuNPs) were used to amplify the detection signals. The results showed that the linear detection range of OA was 0.5 ∼ 200 nM with a detection limit of 0.32 nM. This biosensor provides a novel approach for inexpensive, ultrasensitive, well-specific and label-free detection of OA as well as other marine biological toxins with minor modifications.

A novel colorimetric aptasensor for ultrasensitive detection of aflatoxin M1 based on the combination of CRISPR-Cas12a, rolling circle amplification and catalytic activity of gold nanoparticles

Colorimetric approaches have received noticeable attention among sensing methods in view of simplicity and watching the color change of sample by the naked eyes. However, developing colorimetric sensing methods which show high sensitivity is still problematic. Herein, based on CRISPR-Cas12a, rolling circle amplification (RCA) and catalytic activity of gold nanoparticles (AuNPs), a colorimetric aptasensor was introduced for highly sensitive detection of aflatoxin M1 (AFM1). In the presence of AFM1, the CRISPR-Cas12a is inactivated and large single-stranded DNA (ssDNA) structures are formed on the surface of AuNPs following the addition of T4 DNA ligase and phi29 DNA polymerase. So, the sample color remains yellow after addition of 4-nitrophenol. However, no huge DNA structure is observed on the surface of AuNPs in the absence of target because of activation of CRISPR-Cas12a and digestion of primer. So, the color of sample switches to colorless. The results indicated that the biosensor had high selectivity toward AFM1 and the approach achieved a detection limit as low as 0.05 ng/L. In addition, it could sensitively identify AFM1 in the spiked milk samples. Overall, this approach is highly sensitive and does not require sophisticated equipment. Therefore, it maintains promising potential for other mycotoxins detection in real samples by simply replacing the applied sequences.

Gold nanoparticles amplified microcantilever biosensor for detecting protein biomarkers with high sensitivity

This work reported a microcantilever biosensor based on gold nanoparticles (AuNPs) amplification, which is applied to detect the protein biomarker Alpha fetoprotein (AFP) with high sensitivity. The detection limit of the AuNPs amplified biosensor is 21 pg/mL, about 70 times of magnitude smaller than that without AuNPs amplification. Linear dependence of the relative frequency shift on the AFP concentration between 0 ng/mL and 70 ng/mL were achieved. the sensitivity was dramatically enhanced from 7.68 Hz/nM to 412 Hz/nM by the signal amplification immunoassay, and the good detection reproducibility was obtained.

Electrochemical Detection of Omethoate and Acetamiprid In Cabbage With Ultrahigh Sensitivity and Selectivity Based on Pomegranate-Like Gold Nanoparticle and Double Target-Induced DNA Cycle Signal Amplification

Electrochemical Detection of Omethoate and Acetamiprid In Cabbage With Ultrahigh Sensitivity and Selectivity Based on Pomegranate-Like Gold Nanoparticle and Double Target-Induced DNA Cycle Signal Amplification

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 (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.

Fluorescence immunoassay for multiplex detection of organophosphate pesticides in agro-products based on signal amplification of gold nanoparticles and oligonucleotides

Herein, we developed a multi-analyte fluorescence immunoassay for detection of three organophosphate pesticides (triazophos, parathion, and chlorpyrifos) in various agro-products (rice, wheat, cucumber, cabbage, and apple) using fluorescently labeled oligonucleotide and gold nanoparticle (AuNP) signal amplification technology. The AuNP probes for the three analytes were constructed by simultaneously modifying the corresponding antibodies and fluorescently labeled oligonucleotides on the probe surface. Three fluorophores (6-FAM, Cy3, and Texas red) with high fluorescence intensity and little overlap of excitation/emission wavelengths were selected. The method showed satisfactory linearity for triazophos, parathion, and chlorpyrifos in the ranges of 0.01–20, 0.05–50, and 0.5–1000 μg/L, respectively. For the 3 analytes, the limits of detection (LODs) were 0.007, 0.009, and 0.087 μg/L, respectively. The average recoveries were 77.7–113.6%, with relative standard deviations (RSDs) of 7.1–17.1% in various food matrices. The proposed method offers great potential in food safety surveillance, and could be used as well as a reference for multi-residue analysis of other small-molecule contaminants.

A highly sensitive assay of DNA based on inductively coupled plasma mass spectrometry detection with gold nanoparticle amplification and isothermal circular strand-displacement polymerization reaction

In this work, a simple, sensitive and specific assay for DNA was proposed by combining inductively coupled plasma mass spectrometry (ICP-MS) detection with gold nanoparticle (AuNPs) amplification and isothermal circular strand-displacement polymerization reaction (ICSDPR). First, AuNPs were decorated with hairpin-structured DNA (HP-DNA) through Au–S bond to form the AuNPs probe. The ICSDPR was conducted on AuNPs probe in a homogeneous phase to realize the dual amplification and simplify the analytical process at the same time. By using a biotin modified primer, AuNPs were connected with biotins after the ICSDPR, then captured by the streptavidin modified magnetic beads (SA-MBs), and finally detected by ICP-MS. Many key factors including probe volume, hybridization time, polymerase amount, primer concentration, enzyme reaction time, SA-MBs capture time and desorption time were optimized. Under the optimized condition, the proposed method could detect target DNA as low as 45 zmol (8.9 fM in 5 μL) in a relative short time (about 4.5 h) with good specificity, and the linear range of this method is 0.1–10000 pM, the relative standard deviations are in the range of 3.6–6.4%. The proposed method was applied for determination of target DNA in human serum samples, the recovery for the spiked human serum samples is in the range of 84–120%. It demonstrates a good application potential of the developed method for biological studies and clinical diagnosis of human pathogenic diseases.

Colorimetric and visual mercury(II) assay based on target-induced cyclic enzymatic amplification, thymine-Hg(II)-thymine interaction, and aggregation of gold nanoparticles.

A colorimetric biosensor and visual test is described for the determination of mercury(II). It relies on the specific thymine-Hg(II)-thymine (T-Hg2+-T) interaction which induces a cyclic amplification process (caused by the enzyme exonuclease III) and the aggregation of gold nanoparticles. These results in a color change from red to violet. Under optimized conditions, this colorimetric assay (best performed at 524nm) has a detection limit as low as 0.9nM with a detection range over 4 orders of magnitude (from 1nM to 10μM). Graphical abstract Schematic of a colorimetric method for determination ofmercury ions (Hg2+) based on the thymine-Hg2+-thymine interaction-triggered cyclic enzymatic amplification and aggregation of gold nanoparticles with the aid of exonuclease III(Exo III).

Colorimetric and fluorescent dual-mode detection of microRNA based on duplex-specific nuclease assisted gold nanoparticle amplification.

MicroRNAs (miRNAs) are attractive candidates for biomarkers for early cancer diagnosis, and play vital roles in physiological and pathological processes. In this work, we developed a colorimetric and fluorescent dual-mode sensor for miRNA detection based on the optical properties of gold nanoparticles (AuNPs) and the duplex-specific nuclease (DSN)-assisted signal amplification technique. In brief, FAM labelled hairpin probes (HPs) were immobilized on AuNPs, and fluorescence was efficiently quenched by the vicinity of the fluorophores to the AuNPs surface. In the presence of target miRNAs, the HPs could specifically hybridize with miRNAs and the DNA strand in the DNA/RNA heteroduplexes could be subsequently hydrolyzed by DSN. As a result, numbers of fluorophores were released into the solution, resulting in obvious fluorescence signal recovery. Meanwhile, the target miRNAs were able to participate in other hybridization reactions. With the DSN-assisted signal amplification technique, lots of gold nanoparticles were produced with short-chain DNA on their surface, which could aggregate in salt solution and result in a colorimetric detection. The proposed dual-mode strategy offers a sensitive, accurate and selective detection method for miRNAs. One reason is that the stem of the HPs was elaborately designed to avoid hydrolyzation by DSN under optimal conditions, which ensures a relatively low background and high sensitivity. The other is that the dual-mode strategy is more beneficial for enhancing the accuracy and reproducibility of the measurements. Moreover, the unique selective-cutting ability and single-base mismatch differentiation capability of the DSN also give rise to a satisfactory selectivity. This demonstrated that the developed method could quantitatively detect miR-21 down to 50 pM with a linear calibration range from 50 pM to 1 nM, and the analytical assay of target miRNAs in cell lysate samples revealed its great potential for application in biomedical research and clinical diagnostics.

Colorimetric adenosine aptasensor based on DNA cycling amplification and salt-induced aggregation of gold nanoparticles

An aptamer based assay is described for the colorimetric detection of adenosine. The presence of adenosine triggers the deformation of hairpin DNA oligonucleotide (HP1) containing adenosine aptamer and then hybridizes another unlabeled hairpin DNA oligonucleotide (HP2). This leads to the formation of a double strand with a blunt 3' terminal. After exonuclease III (Exo III)-assisted degradation, the guanine-rich strand (GRS) is released from HP2. Hence, the adenosine-HP1 complex is released to the solution where it can hybridize another HP2 and initiate many cycles of the digestion reaction with the assistance of Exo III. This leads to the generation of a large number of GRS strands after multiple cycles. The GRS stabilize the red AuNPs against aggregation in the presence of potassium ions. If, however, GRS forms a G-quadruplex, it loses its ability to protect gold nanoparticles (AuNPs) from salt-induced AuNP aggregation. Therefore, the color of the solution changes from red to blue which can be visually observed. This colorimetric assay has a 0.13nM detection limit and a wide linear range that extends from 5nM to 1μM. Graphical abstract Schematic presentation of acolorimetric aptamer biosensor for adenosine detection based on DNA cycling amplification and salt-induced aggregation of gold nanoparticles.

Photoelectrochemical biosensor for microRNA detection based on multiple amplification strategies.

A photoelectrochemical biosensor is described for sensitive detection of microRNA-162a. A multiple amplification strategy is employed that involves (a) isothermal strand displacement polymerase reaction; (b) terminal deoxynucleotidyl transferase-mediated extension, (c) amplification of streptavidin-coated gold nanoparticles, and (d) biotin functionalized alkaline phosphatase. Graphite-like C3N4 (g-C3N4) nanosheets were used as photoactive material. By using these amplification strategies, the detection limit is as low as 0.18fM of microRNA, and the photocurrent increases linearly with the concentration of microRNA-162a in the range from 0.5fM to 1pM. The method was successfully applied to quantify the expression level of microRNA-162a in total RNA extracted from the leaves of maize seedlings after incubation with the chemical mutagen ethyl methanesulfonate. The results confirmed the applicability of the method to the analysis of practical biological samples. Graphical Abstract Schematic of a photoelectrochemical microRNA assay based on a multiple amplification strategy involving (a) isothermal strand displacement polymerase reaction; (b) terminal deoxynucleotidyl transferase-mediated extension,

Construction of a probe-immobilized molecularly imprinted electrochemical sensor with dual signal amplification of thiol graphene and gold nanoparticles for selective detection of tebuconazole in vegetable and fruit samples

A probe-immobilized molecularly imprinted electrochemical sensor was constructed for selective determination of tebuconazole in vegetable and fruit samples. Thiol graphene was introduced onto a glassy carbon electrode modified with gold nanoparticles to increase its specific surface area. Prussian blue was co-deposited with gold nanoparticles on the modified electrode and served as the immobilized probe, followed by electro-polymerization of the molecularly imprinted polymer film as the recognition element. Systematic validation and characterization were performed to verify the successful preparation and mechanisms of the Prussian blue and molecularly imprinted polymers in the electrode. Several important parameters, including monomer concentration, scan cycles and pH, were systematically varied to elucidate their influence on the performance of the sensor. Meanwhile, the surface features of the modified electrode were characterized using scanning electron microscopy, atomic force microscopy, cyclic voltammetry and electrochemical impedance spectroscopy. The optimized sensor demonstrated a wide linear range from 5.0 × 10−8 mol L−1 to 4.0 × 10−4 mol L−1 with a detection limit of 1.25 × 10−8 mol L−1. The proposed sensor exhibited specific recognition of tebuconazole in selectivity experiments and contrast tests. Furthermore, the sensor can be used for detection of tebuconazole in real samples with satisfactory recoveries.

Radial Flow Assay Using Gold Nanoparticles and Rolling Circle Amplification to Detect Mercuric Ions.

A novel colorimetric assay employing oligonucleotide-conjugated gold nanoparticle (AuNP probes) and rolling circle amplification (RCA) was developed for simple detection of mercuric ions (Hg2+). The thymine-Hg2+-thymine (T-Hg2+-T) coordination chemistry makes our detection system selective for Hg2+. In the presence of Hg2+, the thymine 12-mer oligonucleotide is unable to act as a primer for RCA due to the formation of T-Hg2+-T before the RCA reaction. However, in the absence of Hg2+, DNA coils as RCA products are generated during the RCA reaction, and is further labeled with AuNP probes. Colorimetric signals that depend on the amount of DNA coil-AuNP probe complexes were generated by drop-drying the reaction solution on nitrocellulose-based paper. As the reaction solution spread radially because of capillary action, the complexes formed a concentric red spot on the paper. The colorimetric signals of the red spots were rapidly measured with a portable spectrophotometer and determined as the ΔE value, which indicates the calculated color intensity. Our assay displays great linearity (detection limit: 22.4 nM), precision, and reproducibility, thus demonstrating its utility for Hg2+ quantification in real samples. We suggest that our simple, portable, and cost-effective method could be used for on-site Hg2+ detections.