Rapid signal enhancement method for nanoprobe-based biosensing

The use of nanoprobes such as gold, silver, silica or iron-oxide nanoparticles as detection reagents in bioanalytical assays can enable high sensitivity and convenient colorimetric readout. However, high densities of nanoparticles are typically needed for detection. The available synthesis-based enhancement protocols are either limited to gold and silver nanoparticles or rely on precise enzymatic control and optimization. Here, we present a protocol to enhance the colorimetric readout of gold, silver, silica, and iron oxide nanoprobes. It was observed that the colorimetric signal can be improved by up to a 10000-fold factor. The basis for such signal enhancement strategies is the chemical reduction of Au3+ to Au0. There are several chemical reactions that enable the reduction of Au3+ to Au0. In the protocol, Good's buffers and H2O2 are used and it is possible to favor the deposition of Au0 onto the surface of existing nanoprobes, in detriment of the formation of new gold nanoparticles. The protocol consists of the incubation of the microarray with a solution consisting of chloroauric acid and H2O2 in 2-(N-morpholino)ethanesulfonic acid pH 6 buffer following the nanoprobe-based detection assay. The enhancement solution can be applied to paper and glass-based sensors. Moreover, it can be used in commercially available immunoassays as demonstrated by the application of the method to a commercial allergen microarray. The signal development requires less than 5 min of incubation with the enhancement solution and the readout can be assessed by naked eye or low-end image acquisition devices such as a table-top scanner or a digital camera.

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“…This figure has been adapted from Dias et al . 20 Please click here to view a larger version of this figure.…”

Section: Representative Resultsmentioning

confidence: 99%

“…Previous to enhancement, the visible spots with the lowest number of AuNPs were where approximately 10000 nanoparticles were printed, after enhancement the spots harboring less than 10 nanoparticles became visible. 20 …”

Section: Discussionmentioning

confidence: 99%

Rapid Nanoprobe Signal Enhancement by <em>In Situ</em> Gold Nanoparticle Synthesis

Dias

Svedberg

Nystrand

et al. 2018

JoVE

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“…At the same time, the approaches that are promising and deserve special attention are based on increasing the size of the label immediately after the formation of a specific immune complex in the test zone. The realization of such signal amplification should start with the use of reagents specifically bound in the test zone: nanoparticles as seeds for growth [10], nanozymes with catalytic properties [11], or conjugated enzymes [12,13]. Below are examples of the use of gold nanoparticles (GNPs) as labels that combine catalytic properties with seed growth.…”

Section: Introductionmentioning

confidence: 99%

“…This approach was used to reduce the detection limit of pesticides in multiplex LFIA [27], potato virus X [28], and Salmonella enteritidis [29]. Moreover, Dias et al illustrated that the gold enhancement method can be used to lower the LOD of bioanalytical systems with various markers—silver, magnetic particles, and particles of silicon dioxide [10]. After optimizing the concentrations of reagents and the amplification time, the detection limit was reduced by 100 times [10].…”

Section: Introductionmentioning

confidence: 99%

Enlargement of Gold Nanoparticles for Sensitive Immunochromatographic Diagnostics of Potato Brown Rot

Razo

Panferova

Panferov

et al. 2019

Sensors

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Lateral flow immunoassay (LFIA) is a convenient tool for rapid field-based control of various bacterial targets. However, for many applications, the detection limits obtained by LFIA are not sufficient. In this paper, we propose enlarging gold nanoparticles’ (GNPs) size to develop a sensitive lateral flow immunoassay to detect Ralstonia solanacearum. This bacterium is a quarantine organism that causes potato brown rot. We fabricated lateral flow test strips using gold nanoparticles (17.4 ± 1.0 nm) as a label and their conjugates with antibodies specific to R. solanacearum. We proposed a signal enhancement in the test strips’ test zone due to the tetrachloroauric (III) anion reduction on the GNP surface, and the increase in size of the gold nanoparticles on the test strips was approximately up to 100 nm, as confirmed by scanning electron microscopy. Overall, the gold enhancement approach decreased the detection limit of R. solanacearum by 33 times, to as low as 3 × 104 cells∙mL–1 in the potato tuber extract. The achieved detection limit allows the diagnosis of latent infection in potato tubers. The developed approach based on gold enhancement does not complicate analyses and requires only 3 min. The developed assay together with the sample preparation and gold enlargement requires 15 min. Thus, the developed approach is promising for the development of lateral flow test strips and their subsequent introduction into diagnostic practice.

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“…First, a high detection limit is related to the limitations of label detection, such as gold nanoparticles. In this case, the task can be solved using various amplification tools, such as a pre-concentration of the sample, the aggregation or catalytic increase of the label size on the test strip, or the use of new types of labels [ 10 , 11 , 12 , 13 ]. Second, the incomplete binding of antibodies with the antigen under the kinetic conditions of the LFIA causes a high detection limit.…”

Section: Introductionmentioning

confidence: 99%

How to Improve Sensitivity of Sandwich Lateral Flow Immunoassay for Corpuscular Antigens on the Example of Potato Virus Y?

Razo

Panferov

Safenkova

et al. 2018

Sensors

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A simple approach was proposed to decrease the detection limit of sandwich lateral flow immunoassay (LFIA) by changing the conditions for binding between a polyvalent antigen and a conjugate of gold nanoparticles (GNPs) with antibodies. In this study, the potato virus Y (PVY) was used as the polyvalent antigen, which affects economically important plants in the Solanaceae family. The obtained polyclonal antibodies that are specific to PVY were characterized using a sandwich enzyme-linked immunosorbent assay (ELISA) and surface plasmon resonance (SPR). For LFIA, the antibodies were conjugated with GNPs with a diameter of 17.4 ± 1.0 nm. We conducted LFIAs using GNP conjugates in a dried state on the test strip and after pre-incubation with a sample. Pre-incubating the GNP conjugates and sample for 30 s was found to decrease the detection limit by 60-fold from 330 ng∙mL−1 to 5.4 ng∙mL−1 in comparison with conventional LFIA. The developed method was successfully tested for its ability to detect PVY in infected and uninfected potato leaves. The quantitative results of the proposed LFIA with pre-incubation were confirmed by ELISA, and resulted in a correlation coefficient of 0.891. The proposed approach is rapid, simple, and preserves the main advantages of LFIA as a non-laboratory diagnostic method.

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Rapid signal enhancement method for nanoprobe-based biosensing

Cited by 18 publications

References 31 publications

Rapid Nanoprobe Signal Enhancement by <em>In Situ</em> Gold Nanoparticle Synthesis

Rapid Nanoprobe Signal Enhancement by <em>In Situ</em> Gold Nanoparticle Synthesis

Enlargement of Gold Nanoparticles for Sensitive Immunochromatographic Diagnostics of Potato Brown Rot

How to Improve Sensitivity of Sandwich Lateral Flow Immunoassay for Corpuscular Antigens on the Example of Potato Virus Y?

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