Signal Amplification Strategy For Detection Research Articles

Ultrasensitive electrochemical biosensor based on triple signal amplification strategy for detection of serum cf-miR-181b: A possible biomarker related to osteosarcoma’s early diagnosis and chemotherapy monitoring

Osteosarcoma is one of the most common primary malignant bone tumors, however, the current diagnostic methods based on tissue biopsy suffers from invasive operation, high heterogeneity and non-early diagnosis. Herein, we proposed a new liquid biopsy method using triple signal amplification-based electrochemical biosensor (E-sensor) in detection of serum cf-miR-181b closely related to osteosarcoma. The E-sensor adopted an enzyme-linked DNA magnetic microbead (MMB), in which the miR-181b-triggered ligase chain reaction products were immobilized onto the surface of MMB followed by the attraction of horseradish peroxidase, to produce a catalytic current on the electrode surface. The E-sensor could detect miR-181b as low as 6.70 aM with a single-base resolution. Finally, the E-sensor was applied to detect serum cf-miR-181b in different individuals, which exhibited excellent performance in discriminating serum miR-181b between control group (healthy people/non-osteosarcoma patients) and osteosarcoma patients. Also, this assay could be used to distinguish the osteosarcoma patients before and after effective chemotherapy. In parallel, all results were in good agreement with that obtained by qRT-PCR. Therefore, the proposed E-sensor, due to its low cost, easy miniaturization and generalization, holds a huge application potential in the early auxiliary diagnosis and therapeutic monitoring of osteosarcoma and is of great value in clinical translation.

A Novel SPR Immunosensor Based on Dual Signal Amplification Strategy for Detection of SARS-CoV-2 Nucleocapsid Protein

Since the global outbreak of coronavirus disease 2019 (COVID-19), it has spread rapidly around the world. The nucleocapsid (N) protein is one of the most abundant SARS-CoV-2 proteins. Therefore, a sensitive and effective detection method for SARS-CoV-2 N protein is the focus of research. Here, we developed a surface plasmon resonance (SPR) biosensor based on the dual signal-amplification strategy of Au@Ag@Au nanoparticles (NPs) and graphene oxide (GO). Additionally, a sandwich immunoassay was utilized to sensitively and efficiently detect SARS-CoV-2 N protein. On the one hand, Au@Ag@Au NPs have a high refractive index and the capability to electromagnetically couple with the plasma waves propagating on the surface of gold film, which are harnessed for amplifying the SPR response signal. On the other hand, GO, which has the large specific surface area and the abundant oxygen-containing functional groups, could provide unique light absorption bands that can enhance plasmonic coupling to further amplify the SPR response signal. The proposed biosensor could efficiently detect SARS-CoV-2 N protein for 15 min and the detection limit for SARS-CoV-2 N protein was 0.083 ng/mL, with a linear range of 0.1 ng/mL~1000 ng/mL. This novel method can meet the analytical requirements of artificial saliva simulated samples, and the developed biosensor had a good anti-interference capability.

Highly sensitive host-guest mode homogenous electrochemical thrombin signal amplification aptasensor based on tetraferrocene label

The development of sensitive and convenient detection methods to monitor thrombin without the use of enzymes or complex nanomaterials is highly desirable for the diagnosis of cardiovascular diseases. In this article, tetraferrocene was first synthesized and then a sensitive and homogeneous electrochemical aptasensor was developed for thrombin detection based on host-guest recognition between tetraferrocene and β-cyclodextrin (β-CD). In the absence of thrombin, the double stem-loop of thrombin aptamer (TBA) prevented tetraferrocenes labeled at both ends from entering the cavity of β-CD deposited on gold electrode surface. After binding with thrombin, the stem-loop structure of TBA opened and transformed into special G-quarter structure, forcing tetraferrocene into the cavity of β-CD. As a result, thrombin allowed eight ferrocene molecules to reach the gold electrode surface, greatly amplifying the response signal. The obtained aptasensors showed dynamic detection range from 4 pM to 12.5 nM with detection limit around 1.2 pM. Overall, the results indicate that the proposed aptasensors are promising for future rapid clinical detection of thrombin and development of signal amplification strategies for detection of various proteins.

Novel electrochemical aptasensor with dual signal amplification strategy for detection of acetamiprid

In this work, a novel dual signal amplification strategy for aptasensor employing reduced graphene with silver nanoparticles and prussian blue-gold nanocomposites was developed for detection of acetamiprid. To improve the sensitivity of aptasensors, reduced graphene oxide-silver nanoparticles (rGo-AgNPs) were modified on a bare glassy carbon electrode surface, which provided a large specific surface area for subsequent material immobilization and amplified current signal. The electrical signal output and sensitivity of the aptasensor was significantly improved after the immobilization of prussian blue-gold nanoparticles (PB-AuNPs) as a catalyst for the redox reaction. The analysis experiment exhibited that it had super-high sensitivity with a detection limit of 0.30 pM (S/N = 3), which met the requirements of the vast majority of daily leaf vegetable testing. Under optimized conditions, the proposed aptasensor showed a wide linear detection range from 1 pM to 1 μM. This aptasensor also had good stability and high selectivity for acetamiprid detection without an interfering effect of some other pesticides. The proposed aptasensor displayed good recovery rates in real samples, which proposed a new method for constructing electrochemical sensors and provided a novel tool for rapid, sensitive analysis of pesticides with low cost.

Paper-based electrochemiluminescence origami device for protein detection using assembled cascade DNA–carbon dots nanotags based on rolling circle amplification

In this work, we developed a cascade signal amplification strategy for detection of IgG antigen by combining the rolling circle amplification (RCA) technique with oligonucleotide functionalized carbon dots (CDs), based on a paper-based electrochemiluminescence (ECL) origami device (PECLOD) for the first time. In this PECLOD, three-dimensional (3D) macroporous Au-paper electrode was fabricated and employed as the working electrode for specific and efficient antibodies capture. The RCA product containing tandem-repeat sequences could serve as an excellent template for periodic assembly of CDs, which presented per protein recognition event to numerous CDs tags for ECL readout. Under the optimal conditions, the proposed strategy showed remarkable amplification efficiency, very little nonspecific adsorption with good stability, reproducibility, and accuracy. Using human IgG (H-IgG) as a model protein, the designed strategy was successfully demonstrated for the ultrasensitive detection of protein target. The results revealed that the strategy exhibited a dynamic response to H-IgG range from 1.0fM to 25pM with a limit of detection as low as 0.15fM. Importantly, the methodology can be further extended to the detection of other proteins or biomarkers.

Dual signal amplification of surface plasmon resonance imaging for sensitive immunoassay of tumor marker

Surface plasmon resonance imaging (SPRi) is an intriguing technique for immunoassay with the inherent advantages of being high throughput, real time, and label free, but its sensitivity needs essential improvement for practical applications. Here, we report a dual signal amplification strategy using functional gold nanoparticles (AuNPs) followed by on-chip atom transfer radical polymerization (ATRP) for sensitive SPRi immunoassay of tumor biomarker in human serum. The AuNPs are grafted with an initiator of ATRP as well as a recognition antibody, where the antibody directs the specific binding of functional AuNPs onto the SPRi sensing surface to form immunocomplexes for first signal amplification and the initiator allows for on-chip ATRP of 2-hydroxyethyl methacrylate (HEMA) from the AuNPs to further enhance the SPRi signal. High sensitivity and broad dynamic range are achieved with this dual signal amplification strategy for detection of a model tumor marker, α-fetoprotein (AFP), in 10% human serum.

A chronocoulometric aptasensor based on gold nanoparticles as a signal amplification strategy for detection of thrombin

A sensitive chronocoulometric aptasensor for the detection of thrombin has been developed based on gold nanoparticle amplification. The functional gold nanoparticles, loaded with link DNA (LDNA) and report DNA (RDNA), were immobilized on an electrode by thrombin aptamers performing as a recognition element and capture probe. LDNA was complementary to the thrombin aptamers and RDNA was noncomplementary, but could combine with [Ru(NH3)6]3+ (RuHex) cations. Electrochemical signals obtained by RuHex that bound quantitatively to the negatively charged phosphate backbone of DNA via electrostatic interactions were measured by chronocoulometry. In the presence of thrombin, the combination of thrombin and thrombin aptamers and the release of the functional gold nanoparticles could induce a significant decrease in chronocoulometric signal. The incorporation of gold nanoparticles in the chronocoulometric aptasensor significantly enhanced the sensitivity. The performance of the aptasensor was further increased by the optimization of the surface density of aptamers. Under optimum conditions, the chronocoulometric aptasensor exhibited a wide linear response range of 0.1–18.5nM with a detection limit of 30pM. The results demonstrated that this nanoparticle-based amplification strategy offers a simple and effective approach to detect thrombin.