An amplified fluorescent biosensor for Ag+ detection through the hybridization chain reactions

A multifunctional fluorescent sensor for Ag+ and Hg2+ detection in seawater

In order to detect Ag+ and Hg2+ in seawater, we explored a multifunctional fluorescence sensor. A multifunctional Ag+ and Hg2+ sensor was designed by using gold nanoparticles (AuNPs) as quenching agent, PicoGreen dye as fluorescent probe of base pairing double-stranded deoxyribonucleic acid (DNA), and combining the characteristics of Ag+ making C base mismatch and Hg2+ making T base mismatch. Meanwhile, the DNA logic gate was constructed by establishing logic circuit, truth table, and logic formula. The relevant performances of the sensor were investigated. The results revealed that the sensor can detect Ag+ in the range of 100 to 700 nM with R2 = 0.98129, and its detection limit is 16.88 nM (3σ/slope). The detection range of Hg2+is 100-900 nM with R2 = 0.99725, and the detection limit is 5.59 nM (3σ/slope). An AND-AND-NOR-AND molecular logic gate has been successfully designed. With the characteristics of high sensitivity, multifunction, and low cost, the recommended detection method has the potential to be applied to the detection of Ag+ and Hg2+ in seawater.

Dual-Channel Fluorescent/Colorimetric-Based OPD-Pd/Pt NFs Sensor for High-Sensitivity Detection of Silver Ions

Silver ions (Ag+) exist widely in various areas of human life, and the food contamination caused by them poses a serious threat to human health. Among the numerous methods used for the detection of Ag+, fluorescence and colorimetric analysis have attracted much attention due to their inherent advantages, such as high sensitivity, simple operation, short time, low cost and visualized detection. In this work, Pd/Pt nanoflowers (NFs) specifically responsive to Ag+ were synthesized in a simple way to oxidize o-phenylenediamine (OPD) into 2,3-diaminophenazine (DAP). The interaction of Ag+ with the surface of Pd/Pt NFs inhibits the catalytic activity of Pd/Pt NFs towards the substrate OPD. A novel dual-channel nanosensor was constructed for the detection of Ag+, using the fluorescence intensity and UV-vis absorption intensity of DAP as output signals. This dual-mode analysis combines their respective advantages to significantly improve the sensitivity and accuracy of Ag+ detection. The results showed that the limit of detection was 5.8 nM for the fluorescence channel and 46.9 nM for the colorimetric channel, respectively. Moreover, the developed platform has been successfully used for the detection of Ag+ in real samples with satisfactory recoveries, which is promising for the application in the point-of-care testing of Ag+ in the field of food safety.

A ratiometric fluorescent nanoprobe based on CdSe quantum dots for the detection of Ag+ in environmental samples and living cells

With the widespread application of Ag⁺ in modern life and industry, the potential hazardous effects of Ag⁺ to environment and humans have attracted great concerns. Thus, effective and rapid strategies for Ag⁺ detection are highly desirable. In this paper, a novel ratiometric fluorescence sensor using CdSe quantum dots (QDs) has been constructed for sensitive and selective detection of Ag⁺, which is based on the formation of Ag₂Se QDs. CdSe QDs were initially prepared and showed single wavelength emission at 510 nm. When Ag⁺ exists, a rising peak appeared at 650 nm and the emission at 510 nm declined, exhibiting distinct ratiometric fluorescence emission (I₆₅₀/I₅₁₀) characteristic with a linear response over the Ag⁺ concentration range of 0.01-4 μM. Significantly, the fluorescence changed from green to red. The detection limit of the constructed sensor is 1.4 nM. Furthermore, the sensing assay can be successfully applied to detect Ag⁺ in real water samples and living cells.

Highly sensitive and specific detection of silver ions using a dual-color fluorescence co-localization strategy

Ag⁺ ions are widely used in various fields of human life due to their unique properties and they threaten the environment and human health. The traditional methods for Ag⁺ detection commonly suffer from disadvantages including limited sensitivity, expensive equipment and complicated operating steps. Herein, we developed a highly specific dual-color fluorescence co-localization (DFC) strategy based on the C-Ag⁺-C structure for Ag⁺ detection. In this strategy, Ag⁺ ions can be captured to form C-Ag⁺-C base pairs, and these ions enable single-stranded DNAs to form double strands. The DFC strategy can exclude nonspecific interaction sites and greatly improve the sensitivity and specificity. By DFC of the QDs and Cy5 linked to the DNA strands, highly sensitive Ag⁺ detection was achieved in the concentration range from 0.14 pM to 200 nM, with a limit of detection (LOD) of 0.14 pM. Moreover, this method has been applied for the detection of Ag⁺ ions in real environmental samples with satisfactory recoveries. We believe that the DFC strategy is promising for Ag⁺ detection.

Unraveling the hazardous impact of diverse contaminants in the marine environment: Detection and remedial approach through nanomaterials and nano-biosensors

Marine pollution is one of the most underlooked forms of pollution as it affects most aquatic lives and public health in the coastal area. The diverse form of the hazardous pollutant in the marine ecosystem leads the serious genetic level disorders and diseases which include cancer, diabetes, arthritis, reproductive, and neurological diseases such as Parkinson's, Alzheimer's, and several microbial infections. Therefore, a recent alarming study on these pollutants, the microplastics have been voiced out in many countries worldwide, it was even found to be in the human placenta. In recent times, nanomaterials have demonstrated their potential in the detection and remediation of sensitive contaminants. In this review, we presented a comprehensive overview of the source, and distribution of diverse marine pollution on both aquatic and human health by summarizing the concentration of diverse pollutions (heavy metals, pesticides, microbial toxins, and micro/nano plastics) in marine samples such as soil, water, and seafood. Followed by emphasizing its ecotoxicological impact on aquatic animal life and coastal public health. Also discussed are the applicability and advancements of nanomaterials and nano-based biosensors in the detection, prevention, and remediation of diverse pollution in the marine ecosystem.

A reliable fluorescent and colorimetric dual-readout assay for Ag+ tracing

Silver ion pollution is a great threat to global environment and public healthcare today. Thus, quick, portable and sensitive assays for Ag⁺ tracing are highly needed. Herein, a reliable fluorescent and colorimetric dual-channel assay has been constructed for Ag⁺ detection by utilizing a terbium-based fluorescent nanomaterial (named as Tb-DPA) and a Pt/Pd nanoflower (Pt/Pd NF)-triggered reaction between N-ethyl-N-(3-sulfopropyl)-3-methylaniline sodium salt (TOPS) and 4-amino-antipyrine (4-AAP). Initially, in the sensing system containing 4-AAP, TOPS, Tb-DPA and Pt/Pd NF, TOPS and 4-AAP is catalyzed by Pt/Pd NF to produce a purple compound (called as PC1), which endows a broad UV absorption that can fully cover the emission band of Tb-DPA. Thus, the system exhibits a high UV absorption (originating from PC1) and a low fluorescence intensity (originating from Tb-DPA) which has been quenched by PC1 through a filtering effect. However, when the system meets Ag⁺, the oxidase-like activity of Pt/Pd NF will be inhibited, leading less amount of PC1. As a result, the system exhibits a decreased UV absorption and a recovered fluorescence intensity, both of which can be used for Ag⁺ detection, reporting low detection limits of 3.63 nM and 1.63 nM, respectively. Specially, results from the dual-channel assay can mutually validate each other, improving the detection reliability. Moreover, this dual-mode assay shows good capability toward Ag⁺ detection in real samples, illustrating the potential for practical applications.

Versatile Sensing Platform of Innovative Copper Oxide Assisted Cu-Phenolic Coordination Nanosheet mediated Fluorophore tagged GT-rich SSA based Fluorescence ON-OFF Biosensor for Subsequent Detection of Cd2+ and S2− Ions

Increased levels of toxic metal/non-metal ions Cadmium (Cd2+) and Sulfide (S2−) in the environment can be detrimental to human health. Given the circumstances, the detection and measurement of Cd2+ and...

Rapid and sensitive detection of Salmonella in milk based on hybridization chain reaction and graphene oxide fluorescence platform

Salmonella is a foodborne pathogen that has contributed to numerous food safety accidents worldwide, making it necessary to detect contamination at an early stage. A pair of specific primers based on the invA gene of Salmonella was designed for PCR. Target double-stranded DNA (dsDNA) from PCR was purified and denatured at high temperature to obtain target single-stranded DNA (ssDNA). Two carboxyfluorescein-labeled hairpin probes (H1-FAM and H2-FAM) were designed with complementary portions to the ssDNA sequence so that binding could trigger H1-FAM and H2-FAM hybridization chain reaction (HCR) to produce a long dsDNA complex. In this study, graphene oxide (GO) was used in the development of a homogeneous fluorescence detection platform for Salmonella. Using this HCR-GO assay platform, Salmonella detection was completed in 3.5 h. Salmonella was reliably and specifically detected with a limit of detection (LOD) of 4.2 × 10¹ cfu/mL in pure culture. Moreover, this new HCR-GO assay platform was successfully applied to the detection of Salmonella in artificially contaminated milk with a LOD of 4.2 × 10² cfu/mL.