Search

After optimizing the original aptamer sequence by truncation strategy, a magnetic separation-assisted DNAzyme-driven 3D DNA walker fluorescent aptasensor was developed for detecting the food-borne pathogen Cronobacter species. Iron oxide magnetic nanoparticles (MNPs) modified with a hybrid of truncated aptamer probe and DNAzyme strand (AP-E1) denoted as MNPs@AP-E1, were employed as capture probes. Simultaneously, a DNAzyme-driven 3D-DNA walker was utilized as the signal amplification element. The substrate strand (Sub) was conjugated with the gold nanoparticles (AuNPs), resulting in the formation of AuNPs@Sub, which served as a 3D walking track. In the presence of the target bacteria and Mg2+, E1-DNAzyme was activated and moved along AuNPs@Sub, continuously releasing the signal probe. Under optimized conditions, a strong linear correlation was observed for Cronobacter sakazakii (C. sakazakii) in the concentration range 101 to 106 CFU mL−1, with a low detection limit of 2 CFU mL−1. The fluorescence signal responses for different Cronobacter species exhibited insignificant differences, with a relative standard deviation of 3.6%. Moreover, the aptasensor was successfully applied to determine C. sakazakii in real samples with recoveries of 92.86%—108.33%. Therefore, the novel method could be a good candidate for ultra-sensitive and selective detection of Cronobacter species without complex manipulation. [ABSTRACT FROM AUTHOR]

Dynamic DNA nanodevices have gained tremendous attention due to their extraordinary inherent functionality and advantages, however, dynamic DNA nanodevices-based biosensors are still challenging due to their high reliance on proteases and limited amplification capabilities. Herein, exploiting bispecific aptamer as initiators for the first time, we developed a three-dimensional (3D) DNA nanomotor biosensor powered by DNAzyme and entropy-driven circuit for sensitive and specific detection of lysozyme, in which walking and rolling strategies are efficiently integrated to achieve excellent signal amplification capability. Benefiting from the high selectivity of bispecific aptamer, the 3D DNA nanomotor biosensor can respond to lysozyme with high specificity and operate at high speed to release signals. The whole process is independent of protease, avoiding the influence of adverse environment on the operation stability. Under optimal conditions, it can achieve a limit of detection as low as 0.01 pg/mL with an excellent linear range of 0.05 pg/mL–500 ng/mL for lysozyme. Furthermore, the proposed strategy revealed high accuracy in the analysis of real samples, indicating a great potential for the application of nanomotor biosensors to the detection of non-nucleic acid targets. [ABSTRACT FROM AUTHOR]

In recent years, food safety issues have become more serious, which caused extensive study on various methods for detecting food hazards. Gold nanoparticles (AuNPs) have drawn significant attention in nanoscience for the construction of biosensors because of their good biocompatibility, excellent quenching effect, unique surface plasmon resonance (SPR) properties, and high surface-to-volume ratio. Owing to the rapidly increasing demand for technologies, aptamers have widely emerged as biorecognition elements which can bind to targets with high specificity and affinity. Several AuNPs and aptamer-based biosensors have been developed for the detection of different molecules. In this review, we mainly introduce the principles and applications in food hazards detection of optical biosensors, including colorimetric aptasensor, fluorescence aptasensor, surface-enhanced Raman spectroscopy (SERS)-based aptasensor, and chemiluminescence-based aptasensor. This feature article highlights the recent advances of AuNPs and aptamers for their potential applications of the optical biosensor. Finally, the prospects on improving the convenience of aptamer screening technology and the stability of AuNPs application achieving the combination with other technologies to realize large-scale applications are put forward. [ABSTRACT FROM AUTHOR]

Acyclic guanosine analogues, a class of widely used antiviral drugs, can cause chronic toxicity and virus resistance. Therefore, it is essential to establish rapid and accurate methods to detect acyclic guanosine analogues. In this study, five acyclic guanosine analogues (acyclovir, famciclovir, ganciclovir, penciclovir, and valaciclovir) were used as positive targets to obtain broad-spectrum aptamers through Capture-SELEX technology. Real-time quantitative PCR (Q-PCR) was used to monitor the aptamer SELEX process. After the sixteen rounds of selection against mixed targets, sequences were obtained by high-throughput sequencing (HTS). Furthermore, a broad-spectrum aptamer, named CIV6, was found as the higher performance aptamer that was suitable for five acyclic guanosine analogues by graphene oxide (GO) polarization and fluorescence assay. Finally, the aptamer CIV6 was used to construct GO fluorescence assay to detect five acyclic guanosine analogues. The limits of detection (LOD) of acyclovir, famciclovir, ganciclovir, penciclovir, and valaciclovir were 0.48 ng·mL−1, 0.53 ng·mL−1, 0.50 ng·mL−1, 0.56 ng·mL−1, and 0.38 ng·mL−1, respectively. [ABSTRACT FROM AUTHOR]

Herein, we report the fabrication of Fe3O4@TiO2 nanosheet/Ag/g-C3N4 (Fe3O4@ns-TiO2/Ag/g-C3N4) composite photocatalysts with well-designed hierarchical yolk-shell structure. To endow the composites with fascinating features, multiple functional components are perfectly integrated into the definite structure. The photodegradation experiments of organic pollutants revealed a significant enhancement in photocatalytic activity of developed composites as compared to P25, which is mainly due to the synergetic interaction of the tailored three-dimensional (3D) yolk-shell porous nanostructure, extended sunlight response range, and retarded the recombination probability of photogenerated electrons-holes. More importantly, the hybrid samples exhibited superior magnetic properties due to the magnetic component. The excellent magnetic recyclability and reusability of the photocatalysts are verified by the magnetic hysteresis loop and cyclic photocatalytic degradation experiments, which is significant for the green and sustainable applications of photocatalysts. Considering its remarkable photocatalytic performance and expectant magnetic recyclability, the composite photocatalysts are expected to be a promising candidate to dispose of future environmental issues. [ABSTRACT FROM AUTHOR]

A rapid and highly sensitive time-resolved fluorescence (TRF)-based aptasensor for simultaneous recognition of mycotoxins ochratoxin A (OTA) and fumonisin B1 (FB1) was developed using multi-color, Ln3+-doped time-resolved fluorescence nanoparticles (TRF-NPs) (NaYF4: Ce, Tb and NH2-Eu/DPA@SiO2 NPs) coupled with complementary strand DNA (cDNA) as luminescence probe and aptamers-conjugated amine-functionalized Fe3O4 magnetic nanoparticles (MNPs) act as a capture probe. Under the optimized conditions, the time-resolved fluorescence intensities at 544 and 618 nm corresponded with Tb3+ and Eu3+, respectively, were used to measure FB1 (Y = 19,177.1 + (− 12,054.4)x, R2 = 0.9917) and OTA (Y = 4138.8 + (− 11,182.6)x, R2 = 0.9924), respectively. The limits of detection (LODs) for FB1 and OTA were 0.019 pg mL−1 and 0.015 pg mL−1, respectively, which were much lower than previously described methods for simultaneous recognition of mycotoxins OTA and FB1 while detection range varied from 0.0001–0.5 ng mL−1. This aptasensor was effectively applied to quantity FB1 and OTA in maize samples and results were compared with ELISA method. This is the first reported time-resolved fluorescence (TRF)-based aptasensor to detect two agriculturally important toxins in the maize. The developed aptasensor has potential to be used for detection of toxins in food safety fields. Graphical abstract [ABSTRACT FROM AUTHOR]

The performance of chloramphenicol aptamer, including binding thermodynamics, structure switching, and binding domain, was investigated by isothermal titration calorimetry, circular dichroism, and molecular docking. Then, a new fluorescence aptasensor was developed with signal amplification mediated by exonuclease I-catalyzed reaction and hybridization chain reaction (HCR) for chloramphenicol detection. In this system, the aptamer-binding domain is blocked by the initiator of HCR, the aptamer undergoes structure switching in the presence of chloramphenicol, and DNA dissociation occurs. The released aptamer is subsequently recognized and cleaved by Exo I to set free chloramphenicol. With the Exo I-assisted chloramphenicol recycling, an increasing number of initiators were exposed from the digestion of the initiator-aptamer complex. Then, the chain-like assembly of FAM labeled H1 and H2 through HCR was triggered by the initiator, generating a long DNA polymer. Under optimum conditions, the aptasensor exhibited a log-linear range from 0.001 to 100 nM of chloramphenicol and a detection limit of 0.3 pM. Additionally, the designed biosensing platform was applied to determine chloramphenicol in milk and lake water with high accuracy. The current approach provides a new avenue to develop sensitive aptasensors with the assistance of binding mechanism between aptamer and target compounds. [ABSTRACT FROM AUTHOR]

A "turn on" time-resolved fluorometric aptasensor is described for the simultaneous detection of zearalenone (ZEN), trichothecenes A (T-2), and aflatoxin B1 (AFB1). Multicolor-emissive nanoparticles doped with lanthanide ions (Dy3+, Tb3+, Eu3+) were functionalized with respective aptamers and applied as a bioprobe, and tungsten disulfide (WS2) nanosheets are used as a quencher of time-resolved fluorescence. The assay exploits the quenching efficiency of WS2 and the interactions between WS2 and the respective DNA aptamers. The simultaneous recognition of the three mycotoxins can be performed in a single solution. In the absence of targets, WS2 is easily adsorbed by the mixed bioprobes via van der Waals forces between nucleobases and the WS2 basal plane. This brings the bioprobe and WS2 into close proximity and results in quenched fluorescence. In the presence of targets, the fluorescence of the bioprobes is restored because the analytes react with DNA probe and modify their molecular conformation to weaken the interaction between the DNAs and WS2. Under the optimum conditions and at an excitation wavelength of 273 nm, the time-resolved fluorescence intensities (peaking at 488, 544 and 618 nm and corresponding to emissions of Dy3+, Tb3+ and Eu3+) were used to quantify ZEN, T-2 and AFB1, respectively, with detection limits of 0.51, 0.33 and 0.40 pg mL−1 and a linear range from 0.001 to 100 ng mL−1. The three mycotoxins can be detected simultaneously without mutual interference. The assay was applied to the quantification of ZEN, T-2 and AFB1 in (spiked) maize samples. This homogeneous aptamer based assay can be performed within 1 h. Conceivably, it can become an alternative to other heterogeneous methods such as the respective enzyme-linked immunosorbent assays. [ABSTRACT FROM AUTHOR]